Engineering and Communications in Antarctica: Enabling Technologies in Antarctica [1st ed.] 9789811557316, 9789811557323

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Springer Transactions in Civil and Environmental Engineering

Neloy Khare   Editor

Engineering and Communications in Antarctica Enabling Technologies in Antarctica

Springer Transactions in Civil and Environmental Engineering Editor-in-Chief T. G. Sitharam, Indian Institute of Technology Guwahati, Guwahati, Assam, India

Springer Transactions in Civil and Environmental Engineering (STICEE) publishes the latest developments in Civil and Environmental Engineering. The intent is to cover all the main branches of Civil and Environmental Engineering, both theoretical and applied, including, but not limited to: Structural Mechanics, Steel Structures, Concrete Structures, Reinforced Cement Concrete, Civil Engineering Materials, Soil Mechanics, Ground Improvement, Geotechnical Engineering, Foundation Engineering, Earthquake Engineering, Structural Health and Monitoring, Water Resources Engineering, Engineering Hydrology, Solid Waste Engineering, Environmental Engineering, Wastewater Management, Transportation Engineering, Sustainable Civil Infrastructure, Fluid Mechanics, Pavement Engineering, Soil Dynamics, Rock Mechanics, Timber Engineering, Hazardous Waste Disposal Instrumentation and Monitoring, Construction Management, Civil Engineering Construction, Surveying and GIS Strength of Materials (Mechanics of Materials), Environmental Geotechnics, Concrete Engineering, Timber Structures. Within the scopes of the series are monographs, professional books, graduate and undergraduate textbooks, edited volumes and handbooks devoted to the above subject areas.

More information about this series at http://www.springer.com/series/13593

Neloy Khare Editor

Engineering and Communications in Antarctica Enabling Technologies in Antarctica

123

Editor Neloy Khare Ministry of Earth Sciences Delhi, India

ISSN 2363-7633 ISSN 2363-7641 (electronic) Springer Transactions in Civil and Environmental Engineering ISBN 978-981-15-5731-6 ISBN 978-981-15-5732-3 (eBook) https://doi.org/10.1007/978-981-15-5732-3 © Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Foreword

Antarctica is the coldest continent on earth with extreme winds. The continent is snow- and ice-covered, with round the year freezing temperatures. The ‘Catabian winds’ over the icy continent of Antarctica cause violent snowstorms that can last for days, and sometimes even weeks, making it a very dangerous place not only to humans but also to any engineering structures required to host people or scientific equipment to do scientific research in the Antarctic region. To mitigate the risk of snow and ice disasters, including snowstorms, the dedicated efforts are needed to create technologies that could withstand the extreme environmental conditions in Antarctica and make the stay of people comfortable in the isolated and inhospitable environment of Antarctica. A successful cost-effective and sustainable operation in a remote, harsh (cold) climate is largely dependent upon the attention given to logistics management and planning. However, being a pristine environment, these technologies need to be nonpolluting. Logistics in this environment is a big challenge. The National Centre for Polar and Ocean Research at Goa has been continuously putting efforts to adopt such technologies and complex logistics. During the last forty years, India has systematically evolved its cold engineering and green technologies and logistics operations and demonstrated the capability for maintaining year-round two research bases ‘Maitri’ at Schirmacher Oasis and ‘Bharti’ at the Larsemann Hills region, with a commitment to preserve the pristine Antarctic environment. With the establishment of the third Indian research station at Larsemann Hills, Indian scientific activities have not only got diversified manifold but also ably covering geographically distinct localities having their own unique scientific significance. Though we have made reasonable progress in the field of non-conventional energy generation in the Antarctic region through windmills, we have to move further ahead and excel in this highly specialized field. As far as communication is concerned, we have demonstrated our capabilities by establishing a direct 24X7 connectivity with Antarctica using Earth station including video conferencing and transmission of TV channel to Indian research bases in Antarctica. We also support

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Foreword

remote sensing satellite data collection from polar orbiting satellites and transfer the data at high speed to India through geostationary satellites. The present book, Engineering and Communications in Antarctica—Enabling Technologies has ably covered most of the relevant engineering, communication, environmental Impact assessment and non-conventional energy generation aspects of Antarctica. I am sure this book will provide a good reference material and encourage the development of newer technologies to support scientific research in the polar region. Bangalore, India

Prem Shankar Goel

Preface

Since the discovery of oil and other mineral resources in the polar regions, significant interest has been generated in exploring these regions in the interest of seeking knowledge and potential resources. To create areas and environments that are essential for human habitat in harsh Antarctic regions that are safe, comfortable and well developed, it is necessary to properly manage various facilities that serve as infrastructure in cold regions, from planning, construction and maintenance to demolition stages. This requires a comprehensive evaluation system that should be capable of centrally managing them all. Polar regions offer unique opportunities and challenges to face with regard to any engineering structure as, these regions remain below-freezing temperatures regularly occur for months at a time necessitates regular dealing with freeze-thaw effects on building materials or the exchange of moisture through walls of dwellings or any buildings. We need to use proper materials, proper design methods and proper construction methods to have something that can function and last in the unique and harsh polar environment. There is the issue of melting permafrost, which is basically soil with ice particles mixed into its pores, is a pretty good foundation to build on as long as it stays frozen. But when it thaws and the ice in the pores of the soil turns to water, very often the remaining soil will no longer be able to support heavy buildings, pipelines, etc. Many structures built on permafrost were designed with the notion that the permafrost would stay frozen. But now a large number of research bases at Antarctica are being affected with the permafrost thawing due to global warming impacting polar regions coupled with the issue of having a greater number of freeze-thaw cycles as a result of the changing climate. For this purpose, the establishment of engineering methodologies for technical policies on infrastructure, as well as the introduction of consensus-building support to the formulation of technical-policy processes, is essential. Though India has ably constructed Maitri station indigenously and set up third research base ‘Bharti’ at Larsemann Hills region, yet the challenges ahead are to foster expertise which can provide solutions to complex environmental and engineering problems common in cold regions like Antarctica. Concerted efforts should be aimed at standardizing the transition of infrastructure policies and internationally promoting infrastructure vii

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Preface

improvement evaluation methods, as well as their application. We must emphasize on the establishment of environmental policies and waste-management systems, development of methods for planning transportation systems in cold regions, development of technologies and establishment of methodologies for infrastructure systems in cold regions that are safe and reliable. National Centre for Polar and Ocean Research (NCPOR), as the nodal agency for Indian Antarctic programme, is to support research and development within the field of cold region engineering Various participating organizations like Research and Development Establishment (Engineers), Pune, Defence Electronics Application Laboratory (DEAL), Dehradun, Snow and Avalanche Study Establishment (SASE), Chandigarh, National Aerospace Laboratories (NAL), Bangalore have always been focusing on research and development in cold climate engineering to cater the demands imposed by the Antarctic climate. Many Indian researchers are involved in research projects concerning cold climate technology/Engineering. Icing is a well-known phenomenon for polar regions. A big problem is the icing of water intakes at power stations, radio masts, power lines and aeroplanes, etc. used for various logistics purposes in Antarctica. De-icing is an expensive process. Therefore, our efforts should be focused on the phenomenon of atmospheric icing to increase understanding as to how ice builds up on different surfaces and how we, through proper choice of materials, can reduce the adhesiveness of the ice. Having spent more than twenty-five years in a cold region, it is most appropriate to collate and evaluate the engineering and technological status from the country’s point of view. Similarly, Antarctica is one of the few remaining nearly pristine sites in the world and is certainly by far the largest such site. Antarctica is particularly vulnerable to some types of environmental change, notably those that would require biological activity for reversal or amelioration. Pollutants that would be readily biodegradable elsewhere can have very long lifetimes in the Antarctic environment, increasing the possibility of long-term alteration through human activities. Its preservation and well-being is, therefore, vital to the health of the rest of the planet, and impacts to Antarctica's environment could have global effects. To enhance protection of the Antarctic environment, the Antarctic Treaty parties in 1991 adopted the Protocol on Environmental Protection to the Antarctic Treaty, designating Antarctica as a natural reserve and setting forth environmental protection principles to be applied to all human activities in Antarctica, including the conduct of science, regulated tourism and fishing concerns, but also a position of leadership in the international stewardship of the Antarctic environment. The protection of the Antarctic continent, and the great Southern Ocean surrounding it, is important for every mankind. The discovery of the ozone hole above the Antarctic in 1985 alerted the world to the potentially dangerous changes in the environment caused by human activities. This discovery led to the first measures to control pollution on a global scale. India is committed to preserve the pristine nature of the icy continent, and therefore, undertake regular environmental Impact assessment.

Preface

ix

The present book Engineering and Communications in Antarctica—Enabling Technologies discusses, in one volume, a wide array of topics that have entered the mainstream of Geotechnical and Geoenvironmental Engineering in the past especially during the initial phase of Indian Antarctic Expeditions, while at the same time not losing sight of the lessons we have learnt in cold engineering technologies during our initial efforts in the contemporary fields of Polar Engineering and communications. It also covers various articles on diversified aspects of environmental science and collates the overall achievements during the last many decades in the fascinating field of Antarctic Engineering and Environmental Impact Assessment. Accordingly, the present book covers articles on wind energy by Ramesh et al. While Rai discussed the Engineering aspects in Antarctica, Pathak has ably reviewed the engineering details of Dakshin Gangotri and Maitri. An interesting history about Dakshin Gangotri station and its establishment process has ably been provided by Sharma. Similarly, communication aspects have been highlighted by Dhaka and commercial polymers and their utility in cold region have been discussed by Dabholker et al. Besides, Tiwari and Khare have reviewed the environmental studies carried out in the past over Indian Antarctic research base ‘Maitri’. On the contrary, Ramchandran and Sathe have studied the natural radioactivity in Antarctica and fire safety in Antarctica has been ably touched upon by Chatterjee. Details on the environmental management services at ‘Maitri’ station have been provided by Veerbhadraiah and Jain. On the other hand, Tiwari and Da Lima Leitao have provided a detailed account of the third Indian research station ‘Bharti’ at Larsemann Hills region. Additionally, the Structural assessment of the second Indian station ‘Maitri’ in Antarctica is provided by Raghava and Murthy. It is hoped that the present book will serve as a useful reference for young researchers who are fascinated towards cold region engineering and environmental research. New Delhi, India January 2020

Neloy Khare

Acknowledgements

Dr. M. N. Rajeevan, Secretary to the Government of India, Ministry of Earth Sciences, who has shown keen interest and provided valuable guidance and encouragement for reviewing the studies carried out pertaining to Antarctic Engineering and technologies in this book, is gratefully acknowledged. All contributing authors are deeply acknowledged for their significant scientific inputs which they provided to this book. Without their support and cooperation, this book would never have materialized in time. I gratefully appreciate the valuable technical expertise and guidance of various reviewers who have contributed significantly in improving the quality of various papers considered in this book through their critical review on various manuscripts. The officers and staff of the Ministry of Earth Sciences, New Delhi and Director, of the National Centre for Polar and Ocean Research, Goa deserve appreciation for their direct or indirect involvement in the preparation of this book. Special thanks are due to, Dr. Debishree Khan, Dr. Shabnam Chowdhury, Shri. Haridas Sharma from the Ministry of Earth Sciences, New Delhi for the assistance and support rendered in the preparation of this book.

xi

Contents

1

Utilization of Wind Energy at Indian Antarctic Station: Near-Term and Long-Term Objectives . . . . . . . . . . . . . . . . . . . . . . M. P. Ramesh, Kanaka Muthu, T. Ramesh, A. P. Chandran, B. S. Ashoka, I. Rajashekar, N. Jayaraman, G. Nanjunda, and T. K. Lokesh

2

Engineering in Antarctica: Assessment Status Report . . . . . . . . . . . Kulbhushan Rai

3

Review of the Status of Engineering Aspects of Dakshin Gangotri and Maitri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R. C. Pathak

1

25

35

4

Dakshin Gangotri Station: The Pride of India . . . . . . . . . . . . . . . . S. S. Sharma

51

5

Communication from Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . . M. K. Dhaka

77

6

Commercial Polymers and Their Utility in Polar Regions . . . . . . . Bhupesh Sharma, Pawan K. Bharti, D. A. Dabholkar, U. K. Saroop, A. K. Aggarwal, V. K. Verma, and K. M. Chacko

83

7

Antarctic Environmental Studies over the Last 35 Years of the Indian Antarctic Expedition . . . . . . . . . . . . . . . . . . . . . . . . . 123 A. K. Tiwari, Tara Megan da Lima Leitao, and N. Khare

8

Natural Radioactivity Heavy Metal Concentration in the Antarctic Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 T. V. Ramachandran and A. P. Sathe

9

Environmental Management Services at Maitri, Antarctica . . . . . . 143 G. Veerabhadraiah and A. Jain

xiii

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Contents

10 Fire Safety at Maitri Station: A Brief Report . . . . . . . . . . . . . . . . . 175 P. Chatterjee 11 Establishment of India’s Third Research Station in Antarctica—A Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 A. K. Tiwari and Tara Megan da Lima Leitao 12 Structural Assessment of the Second Indian Station ‘Maitri’ in Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 G. Raghava and S. G. N. Murthy

Editors and Contributors

About the Editor Dr. Neloy Khare presently scientist ‘G’/adviser to the Government of India at the Ministry of Earth Sciences, has a distinctive acumen of not only handling administration but also quality science. His area of research covers large spectrum of geographically distinct locations like Antarctic, Arctic, Southern Ocean, Bay of Bengal, Arabian Sea, Indian Ocean, etc. He has more than 30 years of experience in the field of paleoclimatic research using paleobiology (Paleontology). Having completed his Ph.D. on tropical marine region and D.Sc. on southern high latitude marine regions towards environmental/climatic implications using various proxies including foraminifera (micro-fossil), he has made significant contributions in the field of paleoclimatology of southern high latitude regions (Antarctic and Southern Ocean) using micropaleontology as a tool. He has been conferred honorary and adjunct professorship by many Indian Universities. He has a very impressive list of publications to his credit (123 research articles in national and international scientific journals; 23 popular science articles). He has authored/edited many books published by international and national publishers. He was awarded the Rajiv Gandhi National Award in 2013 by the President of India. He has made tremendous efforts to popularize ocean and polar science across the country by way of delivering many invited lectures, radio talks and publishing popular science articles. He has sailed in Arctic Ocean as a part of “Science PUB” in 2008 during the International Polar Year campaign for scientific exploration in Arctic Ocean and became the first Indian to sail in the Arctic Ocean.

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Editors and Contributors

Contributors A. K. Aggarwal Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India B. S. Ashoka National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India Pawan K. Bharti Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India K. M. Chacko Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India A. P. Chandran National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India P. Chatterjee Centre for Fire, Explosive and Environment Safety, Research and Development Organisation, Delhi, India M. K. Dhaka Defence Electronics Applications Laboratory, Raipur Road, Dehradun 248 001, Uttarakhand, India D. A. Dabholkar Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India A. Jain Environment Division, Engineers India Limited, Engineers India Bhavan, 1, Bhikaiji Cama Place, New Delhi 110066, India N. Jayaraman National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India N. Khare ESSO-Ministry of Earth Sciences, Lodhi Road, New Delhi 110003, India Tara Megan da Lima Leitao National Centre for Polar and Ocean Research, Vasco-da-Gama, Goa, India T. K. Lokesh National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India S. G. N. Murthy Senior Principal Scientist, CSIR - Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai 600113, India Kanaka Muthu National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India G. Nanjunda National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India R. C. Pathak Bharti Vidyapeeth Lal Bahadur Shastri Marg, Pune 411 030, Maharashtra, India

Editors and Contributors

xvii

G. Raghava Former Chief Scientist, CSIR - Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai 600113, India; Professor in Civil Engineering, Nitte Meenakshi Institute of Technology, Yelahanka, Bengaluru 560064, India Kulbhushan Rai Research and Development Establishment (Engineers), Defence Research and Development Organisation, Dighi, Pune, Maharashtra, India I. Rajashekar National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India T. V. Ramachandran Bhabha Atomic Research Center, Mumbai 400085, Maharashtra, India T. Ramesh National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India M. P. Ramesh Formerly from Centre for Wind Energy Technology, Velachery-Tambaram Main Road, Pallikaranai, Chennai 600 100, Tamil Nadu, India A. P. Sathe Bhabha Atomic Research Center, Mumbai 400085, Maharashtra, India U. K. Saroop Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India Bhupesh Sharma Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India S. S. Sharma 703, Cordia, Nyati Estate, Mohammad Wadi, Pune 411060, Maharashtra, India A. K. Tiwari National Centre for Polar and Ocean Research, Vasco-da-Gama, Goa, India G. Veerabhadraiah Environment Division, Engineers India Limited, Engineers India Bhavan, 1, Bhikaiji Cama Place, New Delhi 110066, India V. K. Verma Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India

Chapter 1

Utilization of Wind Energy at Indian Antarctic Station: Near-Term and Long-Term Objectives M. P. Ramesh, Kanaka Muthu, T. Ramesh, A. P. Chandran, B. S. Ashoka, I. Rajashekar, N. Jayaraman, G. Nanjunda, and T. K. Lokesh

1.1 Introduction Winds in the coastal Antarctic region are notorious. As a matter of fact, the instantaneous peaks are known to cross 300 kmph, and with blizzards, the structures built in the Antarctic region must be designs that can withstand extraordinary loads. At the same time, it would make sense to use the winds in Antarctica for a variety of applications. The first experiments with wind power were made by Indian Scientific Antarctic expeditions in 1984 by Bharat Heavy Electricals Limited. R & D E, Pune, also made some rudimentary trials. However, due to the lack of concentrated efforts, these attempts did not make any headway. Based on the recommendations of the U R Rao’s committee (1996), National Aerospace Laboratories, Bangalore, took up the study of the possibilities of using wind as an alternate source of energy at Maitri and other locations used by Indian Antarctic Expedition members for the conduct of scientific experiments. NAL collected invaluable information over the 16th to 21st Antarctic Expeditions and conducted several experiments. A detailed program addressing the following aspects was prepared and implemented: • Quantification of Wind energy as a usable resource • Study of energy consumption patterns

M. P. Ramesh (B) · I. Rajashekar Formerly from Centre for Wind Energy Technology, Velachery-Tambaram Main Road, Pallikaranai, Chennai 600 100, Tamil Nadu, India e-mail: [email protected] K. Muthu · T. Ramesh · A. P. Chandran · B. S. Ashoka · N. Jayaraman · G. Nanjunda · T. K. Lokesh National Aerospace Laboratories, Wind Energy Division, Post Bag. no. 1779, Bangalore 560 017, Karnataka, India © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_1

1

2

M. P. Ramesh et al.

• Identification of available infrastructure facilities available at Maitri for wind turbine installations • Addressing the energy needs at Maitri.

1.2 Wind Power Potential Antarctica was able to maintain a pristine environment for so long with the help of unbearable winds that makes living in the Antarctic environment an extremely difficult proposition. In fact, it is the most often quoted difficulty by the early explorers, as well as present-day scientists, involved in the out-door work at Antarctica. Some estimates of peak winds have crossed 250 km/h in the coastal regions. Inland regions, on the continental ice and oases, where stations have been in place have not shown very high values when compared to the coastal regions. The phenomenon of very high winds is generally explained by the occurrence of very frequent cyclones and anti-cyclones that are formed around 55° to 60° South around the continent. This happens very frequently and with great intensities. Apart from this, the presence of strong and sustained Katabatic winds has also been experienced in the coastal zones and glaciers.

1.3 Meteorological Measurements at Indian Stations Wind speed and Directions were measured at Dakshin Gangotri, as well as at Maitri, as a part of the meteorological measurements that were undertaken by the India Meteorological Department. The readings were taken at Synoptic hours. Apart from this, wind speeds were kept track of using strip chart recorders. Dakshin Gangotri showed exceptionally high average wind speeds. This is understandable, as Dakshin Gangotri was located on the shelf ice. The averages at Maitri were relatively lower and strongly influenced by the time of the year. This is an important point that should be noted as the successful integration of wind energy conversion devices with the existing energy supply system would very largely depend upon a clear understanding of the nature of wind energy availability in the given region. Figure 1.1 shows the measured monthly averages at Maitri over a five-year period. The pattern of winds is somewhat different from the monsoon-based wind system. Summer months show relatively light winds, which is quite consistent over the years. Mid-winter shows a relatively high wind season, but inter-annual variation is also somewhat high during this period. The wind speeds collected at Maitri by IMD is a part of Synoptic weather observations. The data is being collected as per the standards set by the World Meteorological Organization. But this could not be employed for quantification of wind energy availability for two reasons. First was that the information between two observations was not directly available. The second point was that the sensors are located on the top of Maitri station. In wind energy work,

1 Utilization of Wind Energy …

3

Fig. 1.1 Monthly mean wind speeds and standard deviations (IMD)

it is important to measure the free stream velocities at several elevations from the ground to be able to describe wind energy potential with a good degree of accuracy. There are several other installations on the building, and the building itself can cause difficulty to model type of perturbations into the flow field. It was, therefore, decided to set up an independent microprocessor-based three-level wind-monitoring system. Ice-free wind speed and direction sensors rated at 90 m/s survival speed were fixed on an already existing 28 m tall mast at three levels. Data loggers were housed in summer huts where experiments related to SODAR, Geomagnetism, and other sciences were set up. Data loggers were programmed to store hourly averages of wind speed, direction, and standard deviation. The data collection was initiated in January 1997. Monthly average wind speeds at two levels are shown in Fig. 1.2. Mid-level wind speed sensor was damaged while being serviced. Although readings were obtained after the repair, the readings could not be taken with much confidence. The wind rose and frequency distribution of winds are given in Fig. 1.3.

1.4 Extreme Winds The data logger was also recording 2 s gusts and Table 1.1 gives measured gusts during the measurement period. There were two data loggers for data storage. First data logger recorded data from 12 and 28 m level instruments and the second data logger from the 22 m level. The data obtained on peak speeds appear to be reasonable for the 12 m level. As indicated earlier, data from the 22 m level anemometer was somewhat doubtful.

4

Fig. 1.2 Sensors on 28 m mast and monthly average wind speeds

M. P. Ramesh et al.

1 Utilization of Wind Energy …

5

Fig. 1.3 Wind rose and frequency distribution at Maitri (1998)

There were some breaks in the data for various reasons. From among the data that became available, it was feasible to get continuous records for nearly two years. The Survey of India has published a contour map of Maitri environs. Based on this map a Digital Terrain Model of the area was prepared (Fig. 1.4). This, in combination with the wind speed and direction information, was used to determine effective wind power availability around Maitri. The calculations were carried out on a 25 m × 25 m grid, and possible energy production levels were determined. To be able to get a good understanding of how this wind potential gets translated into energy production, the annual energy outputs (normalized) from a typical wind turbine has been calculated for the entire region around Maitri and presented in Fig. 1.5. Slightly elevated regions can give better outputs than sheltered regions. This will be one of the important factors to be considered while setting wind turbines. Depending upon where the new summer facilities would be set up, the location of future wind turbines would be determined. For the existing station, a suitable location could be to the South of the station at about 300 m. The energy that could be expected would be in the range of 4000 to 4500 KWH/year/kW installed. Other locations could be considered as by and large, the area has possible production levels at about 3500 to 4000 KWH/year/kW. Wind turbines are normally designed for withstanding speeds up to 75 m/s which is inadequate in Antarctica. Further, due to sustained higher wind speeds, fatigue damages would result in wind turbines often

11.37

17.88

18.69

24.82

21.73

17

Feb-97

Mar-97

Apr-97

May-97

Jun-97

24.41

19.87

22

14.95

Sep-97

Oct-97

Nov-97

Dec-97

20.88

24.01

16.94

19.61

25.01

Feb-98

Mar-98

Apr-98

May-98

Jun-98

Jan-98

24.2

Aug-97

Jul-97

Date

Time

12

27

30

3

12

2

13

2

26

19

2

18

18

20

12

30

21:00

23:00

07:00

05:00

23:00

18:00

18:00

09:00

02:00

04:00

16:00

21:00

22:00

08:00

23:00

05:00

88

82

98

93

76

1

1

1

3

22

17:00

00:23

01:00

05:00

00:00

26.27

19.98

17.25

24.63

21.6

19.18

32.25

22.94

26.58

19.42

19.48

12.19

Avg

Hourly

Gust

Time

Hourly

Date

Max

Max

Avg

22 m Max

12 m

Jan-97

Month and year

Table 1.1 Peak wind speeds (m/s) at Maitri, Antarctica

12

28

30

3

12

6

16

18

18

20

12

30

Date

22:00

00:00

07:00

05:00

23:00

03:00

23:00

16:00

23:00

09:00

23:00

05:00

Time

126

138

122

107

79

Gust

Max

1

5

3

7

22

Date

23:00

07:00

04:00

22:00

23:00

Time

28.26

21.54

18.53

26.43

22.97

16.59

26.19

22.64

27.59

27.63

19.35

24.33

28.37

20.76

20.66

12.79

Avg

Hourly

Max

28 m

12

27

30

3

12

2

13

2

26

19

2

17

18

20

13

30

Date

(continued)

22:00

23:00

07:00

05:00

23:00

18:00

18:00

11:00

02:00

04:00

16:00

21:00

22:00

08:00

01:00

05:00

Time

6 M. P. Ramesh et al.

20.49

18.45

21.57

23.39

19.07

17.38

Aug-98

Sep-98

Oct-98

Nov-98

Dec-98

Jan-99

Date

Time

7

7

24

25

8

18

04:00

10:00

10:00

00:00

08:00

07:00

97

10

08:00 19.97

17.59

16.69

26.43

22.2

19.49

21.36

Avg

Hourly

Gust

Time

Hourly

Date

Max

Max

Avg

22 m Max

12 m

Jul-98

Month and year

Table 1.1 (continued)

27

7

22

25

8

18

7

Date

05:00

10:00

06:00

01:00

08:00

07:00

04:00

Time

104

136

Gust

Max

10

7

Date

08:00

03:00

Time

18.55

21.02

29.54

23.82

21.74

23.58

Avg

Hourly

Max

28 m

7

24

25

8

18

9

Date

10:00

10:00

01:00

08:00

07:00

22:00

Time

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Fig. 1.4 Digital terrain model of Maitri and surroundings

suffering damages. These aspects must be essentially kept in view while proposing wind turbines for use in Indian stations.

1.5 Energy Consumption Patterns The station plan is shown in Fig. 1.6. The building consists of a specially designed structure with living quarters located at the ground floor. There is a mezzanine floor which houses the communication room, as well as stores. Summer huts are located to the North of the station around the lake. The station is designed to house 25 persons during winter and, with several “Summer huts”, can accommodate up to 50 persons during the Antarctic summer. Electrical power is provided using Aviation Turbine Fuel driven engines with three-phase alternators. The main station has a provision for the space of heating using hot water circulation and hotplates.

1.6 Electrical Power Station has ten alternators rated at 62.5 KVA in three independent clusters to cater for electrical power requirements. At any point of time, two generators are kept operational. The two generators are not synchronized and cater for independent

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Fig. 1.5 Potential areas around Maitri

loads. Summer huts also get the electrical power requirements supplied from the main station. Recently two used 100 kVA alternators were added to the station’s electrical generation capacity, but no scheduled loads were earmarked for this additional back up capacity. The total energy consumption pattern based on data available at the station has been calculated and is presented in Fig. 1.7. The hourly records from the generator rooms have been used to determine daily average power requirements. The average power requirement during summer falls slightly. During winter the power consumption gradually increases. The latter part of winter, that is, after September, the power consumption falls slightly. Fuel requirement for power generation is estimated using a linear model. The model was established using specific fuel consumptions as indicated by the engine manufacturers. Except for a few perturbations, the fuel consumption patterns and power requirements have been in the range of 30–50 kW, and an average fuel consumption of 300–400 L per day is to be expected. Over a year, the estimated fuel requirement is in the range of 150,000 L for power generation. There is a separate automotive workshop with its own 30-kVA alternator. This independent generator separately caters for the electrical power requirements of this workshop. The automotive workshop has a few power tools, lathe, drilling machines, and welding sets. Automotive Battery charging is another load that needs to be met from this generator. Frequently the alternator would be pressed into service for battery charging purposes.

10

Fig. 1.6 Maitri building and energy flow paths

Fig. 1.7 Electrical power requirement at Maitri

M. P. Ramesh et al.

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Fig. 1.8 Heating fuel consumption patterns

1.7 Heating System at Maitri The station is equipped with four oil-fired furnaces placed in the Boiler room. The heating of the living quarters is manually controlled. Normally only one burner will suffice to maintain the station temperature above 10 °C. The boiler room also houses the water pumping controls to pump water from the lake to the station. Each room and living area are equipped with heat exchangers with recirculating hot water systems. All the heat exchangers are connected in parallel. The burners consume about 10 L of fuel per hour, and based on the number of hours, the burners are kept operational fuel requirement is estimated daily. The average daily consumptions monthly are presented in Fig. 1.8. In the same graph, the monthly mean wind speeds are plotted. In general, higher wind speed months show higher fuel for heating consumption. There are exceptions during the Months of March and latter parts of the year. This could be since the wintering team would have just taken over by March and acclimatization to Antarctic Winter would take some time. On an average, fuel consumption for station heating is in the range of 100–350 L per day, and during winters, the monthly consumption can reach 8000–9000 L.

1.8 Infrastructure at Maitri The Indian station has most of the installation equipment that are necessary for the installation of medium-sized wind power equipment. There is one track-mounted crane (Fig. 1.9) with a capacity of 18 tons with a boom height of 70 feet. It is feasible

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Fig. 1.9 Mobile crane in operation

to move the crane to any desired location without any difficulty. Apart from this, the station has welding, machining, and other workshop facilities. There are crab winches of 10 to 20 tons pulling and lifting capacity. At the station, during summer, there are sixty to sixty-five persons available and installation of wind power equipment up to 50 kW capacity range would present no serious problem. For bigger machines, some preparations would be necessary. However, under the present and immediate future load levels, machines of larger capacity may not be required.

1.9 Addressing Energy Needs at Maitri The energy consumption pattern at the station is well documented and reported earlier. Maitri also serves as a base station for field camps run by scientists working on Geology, Biology, Geomagnetism, and other disciplines. Over six expeditions, it was tried to address the stand-alone electrical power requirements using small but effective wind electric generators. Several proposals for setting up larger wind generators for meeting part of energy requirements at the station have been submitted to NCAOR, Goa. The energy needs have been discussed in the previous section. To meet the energy demands, at least partly a two-pronged approach was suggested. The first was to look at the near-term requirements, which would give relief to some of the logistic

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13

problems. The other is to look at the possibilities of using wind power for meeting a considerable portion of the energy requirements for heating and other needs. This would require higher investments and forward planning.

1.10 Stand-Alone Requirements To address the immediate requirements of small stand-alone applications, small machines were procured from foreign sources. Figures 1.10, 1.11 and 1.12 show installation at the automotive workshop and Vittiah peak and on a field camp cabin used by scientists for their field work. It was found that the machines had extraordinary application possibilities in most cases. At Maitri automotive workshop, again a 30-kVA alternator would have to be started and run mostly for battery charging purposes. Therefore, the savings affected would be enormous in terms of manpower and logistics. Further point is that the frequent disconnection and connection with battery terminals will result in wear and tear over a short period of time. This would, in turn, result in loose contact and other related problems. Another significant place where it made good sense was to install a battery charger to keep the microwave repeater station batteries fully charged at all times. The normal practice was to have a battery sortie every day to bring fully charged batteries from the station to the repeater station and replace drained batteries. This required a three

Fig. 1.10 72 W charger at workshop

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Fig. 1.11 72 W charger at Vittiah peak

hundred horse power vehicle with two persons travelling every day for this task for about 70 kilometers. The battery chargers functioned very well for a few years. The operating conditions at the station require that the systems perform trouble free for at least five years. The standard machines, contrary to the claims made by the manufacturers, were found to have very short service lives, and there are several environmental, electrical, and electronic system requirements that can lead to a system failure. In the ordinary circumstances, these problems might appear simple enough to tackle, but from the expedition team leader and members’ point of view, these could become complex problems that they would prefer to avoid. Therefore, the systems deployed were reengineered to address the above constraints. The system already used needs to be strengthened and alternative-bearing mounting arrangements would have to be designed. Electronics that goes with the system requires to be carefully redesigned to suit the load conditions. Considering the limitations cited above, NAL’s Wind Energy Division developed a simple windmill of 250 W size with very few components and subassemblies. This machine was tested during the XX ISAE. Based on the experience gained, the alternator was redesigned and is presently under detailed testing (Figs. 1.12, 1.13, and 1.14). This machine employs a specially designed low-speed alternator using rare earth magnets and has been found to possess very good load matching properties.

1 Utilization of Wind Energy …

Fig. 1.12 Battery charger installed on Sankalp used for charging instrument batteries

Fig. 1.13 360 W wind charger opposite to NPL hut

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Fig. 1.14 NAL developed wind battery charger at Vittiah peak and measured performance

The idea behind this machine development was that there are very few components and all critical components were oversized in terms of the service loads. This was especially important because of the very harsh operating conditions in Antarctica. The necessary charge controller was also developed at NAL. Three years of experience gained by most of the groups initial fears of windmills not being effective in the Antarctic has been dispelled. Presently there is a demand for small machines from

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the laboratories engaged in fieldwork. Logistic groups have an expressed requirement for such portable machines.

1.11 Station’s Energy Requirements As explained earlier the fuel consumption at the station has been estimated. Considerable fuel is also required to transport fuel from the ship to the station. Apart from the convoy movements for scientific and other logistic requirements, quite a lot of logistic effort needs to be provided just for fuel movement. Therefore, the idea should be to consume as less fuel as is feasible. Looking at the need to ensure the safety and continuity in energy supply systems at the station, the introduction of wind power systems should be such that it does not alter the basic way the logistics are handled. This can be quite easily implemented by taking on space heating at the station. Figure 1.15 shows the present space heating arrangement at the station. The present scheme of heating is simple. The ambient temperature in the living quarters is kept track of 24 h a day around the year. When the temperature goes below a preset value, the boiler would fire up. Figure 1.8 shows the monthly fuel consumption. It was, therefore, suggested to introduce a heating element in the hot water tank. A wind turbine would energize the electrical heater. This will minimize the frequency of starting the boiler operation, which would automatically reduce the

Fig. 1.15 Possible introduction of wind power in space heating system at Maitri

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fuel consumption. The importance of this approach is that any breakdown of service from the wind machine will not jeopardize the station’s requirements. Contrary to the popular perception that wind power or solar power should always go with an expensive storage system, here the energy is stored as heat energy. Further, the control system required will be simple. Once the personnel operating services at Maitri get used to the idea of wind turbines supplying part of energy requirement more systems could be introduced. Most of the wind turbines are expected to have a service life of about 20 years. But at Antarctica, most of these systems have developed one snag or the other, and active service life has been in the range of 2–3 years. Generally, designers do claim longer service life expectancy, while inspectors and end users indicate a more cautious approach.

1.12 A Wind Turbine for Space Heating Some of the salient design constraints of this special windmill are as follows: The windmill shall be of simplest possible design yet carrying with it all the sophistication needed in a place like Antarctica. Winds at Maitri station have been studied, and with this as a basis, a study of possible energy production and consequent fuel saving that can be anticipated has been worked out to about 35,000 kWH per year from a typical 10 kW wind turbine. During blizzards, when heat input to the station must be highest, the power generation will also be at its peak. It may be noted that for this study an idealized wind turbine that cuts in at 4 m/s, delivers rated power at 16 m/s and continues to work at rated power until 25 m/s has been assumed. After 25 m/s the machine would be shut down by the control system. A practicable machine would have somewhat better characteristic, and it makes the system even more attractive. There are many companies in the United States and Europe manufacturing and marketing machines in this capacity range. Most of the machines are designed to operate in a normal environment. The typical cut-in wind speeds are in the range of 4–5 m/s and rated power would be delivered at 12–16 m/s. Almost all the machines have two safety shut down features. One would be based on aerodynamics and the other one would be either mechanical or electrical engineering based. Except for two machines, none of the machines studied have envisaged being set up in environments with +75 m/s as would be encountered in Antarctica. This point should be carefully noted. There are quite a few wind turbines of capacities from few watts to 30 kW developed for remote area use. They are generally manufactured in small batches. The cost per kW cannot be generally taken as a criterion, and there will always be some further development required to suit a given application.

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1.13 Approach to the Design Problem The wind machine to be used in Antarctica requires to be designed with the following additional constraints as compared to the normal situations: 1. The wind conditions can be extremely severe (+90 m/s) in addition to being colder than −20 °C. 2. There are lull periods during certain portions of the year and even on a diurnal basis. There will be a new set of personnel every year manning the life support systems, which include energy supply systems. Therefore, the maintenance schedules should be as simple as is feasible and should be able to accommodate the common sense approach that armed forces engineers generally adopt. With the above considerations, there are three approaches that could be followed: 1. Design and develop an entirely new machine specifically tailored for Antarctic operating conditions. 2. Procure one of the state-of-the-art machines designed for sufficiently high survival speeds and install. 3. Procure one of the state- of-the-art machines with all the features of safety and control systems and incorporate additional safety features as required in Antarctic conditions.

1.14 Approach I 1.14.1 Design and Development of an Entirely New Machine Wind electric generator consists of a set of blades, a speed matching transmission, a synchronous or asynchronous generator, a yaw mechanism in case of a horizontal axis machine and a support structure. Invariably these machines have a µP based control system. A decision must be made regarding the axis of rotation of the wind machine to be designed. A vertical axis machine appeals as the best choice for the extraordinarily varying wind speeds at Antarctica. But a vertical axis machine suffers on several counts. They are not self-starting which makes it difficult to accommodate in a place like Antarctica. They generally have a vibration problem that cannot be avoided because of the unavoidable design constraints of a tall rotating structure. These designs have been known to get into early fatigue failure. The structural design of blades also presents a serious challenge because of very large slenderness ratios. Balancing of the rotor would also be an additional problem because of the very low solidity and the consequent inability of the blade profile to keep the shape intact over a wide range incident wind speed. With these constraints in the background, it may be a good idea to consider a horizontal axis machine of the following specifications:

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1.14.2 Possible Specifications of Wind Turbine for Antarctic Applications

a.

Rotor diameter

7.5 m

b.

Tower height

12/14 m

c.

Weight

< 5 Tones

d.

Cut-in WS

4 m/s

e.

Cut-out WS

16 m/s

f.

Shut down

25 m/s

g.

Control

µ processor-based Active pitch control

h.

Yaw system

Tail vane control

i.

Generator

Self-excited synchronous

j.

Safety during storms

Rotor on brake, rotor turned away from wind

This Antarctic wind machine would be designed for heating loads only. This implies that there would be no frequency-related constraints. Therefore, the rotor can be designed for a constant tip speed ratio resulting in variable rotor speed. The rotor must be pitch regulated, with a feathering feature. There would have to be additional features of disc brakes to have the first level of safety. Table 1.2 shows the rough specifications of the machine. For a rotor of 7–8 M diameter, the cheapest and most effective orientation mechanism would be a passive hinged and inclined tail system. This forms the third safety feature.

1.14.3 Rotor Design A three-bladed fast running rotor with full airfoil sections (LS 101, aerodynamically efficient and structurally strong) has been chosen with a design tip speed ratio of 5. A tapering blade with a twist of about 18° from tip to root has been arrived at. With the design wind speed at 12 m/s, the rotor would have an RPM of 150 and at the shutdown wind speeds the rotor would be fully feathered using an active control. The blades are subjected to centrifugal forces, bending stresses in both out of the plane and in the plane. The blades would have to contend with the problems of ice accumulation during blizzards and during low wind periods. Extreme low temperature will be other material-related constraint that has to be addressed. The extreme conditions of wind and high fatigue are aspects that need to be kept track of. Due to the triple redundant architecture of safety devices, it is essential that the blades should have pitch regulation.

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1.14.4 Transmission It is proposed to design and develop a slow speed permanent magnet-based multipole alternator that can be shaft mounted so that the need to step up or step down the speed of rotation is avoided.

1.14.5 Generator The generator shall be a three-phase alternator using a rotating magnet fixed armature design. It would be designed with multiple poles such that the rated rotational speed would be under 150 rpm. Special care would be taken to work under very low ambient temperatures. The windings shall be rated to withstand 200% of rated current for short intervals of time so that momentary overloads will not result in catastrophic failures. The generator shall be a three-phase alternator using a rotating magnet fixed armature design. It would be designed with multiple poles such that the rated rotational speed would be under 150 rpm. Special care would be taken to work under very low ambient temperatures. The windings shall be rated to withstand 200% of rated current for short intervals of time so that momentary overloads will not result in catastrophic failures.

1.14.6 Yaw Mechanism The vertical bearing would be of enough oversize and shall be provided with adjustable damping. A hinged tail vane would take the rotor out of wind beyond operating wind speeds. Power output would be taken out through slip rings obviating the need to have cable untwisting sequences. A remote manual furling arrangement would be incorporated to carry out emergency shut down procedures.

1.14.7 Support Structure A tubular steel structure of adequate structural stability shall be designed. Foundation shall be of a simple pile design. This type of foundation idea has already been tested and found to be feasible.

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1.14.8 Control System The safety of the personnel and other equipment takes precedence over machine safety. Therefore, a three-tiered safety system should be developed and incorporated. The First level is to have a very reliable monitoring system that would consider the dangerous gusts and start appropriate control action in advance. Second level is to have a fail-safe control system in such a manner that in case pitching fails, the blades would automatically be feathered. If the yaw mechanism fails, the machine would be turned away from the wind. In case the load is suddenly “thrown off”, emergency braking would be initiated. Such precautions shall be built into the system design so that unanticipated problems would be addressed adequately. The third level of safety is provided for a manual shutdown of the machine so that with advanced knowledge of a very serious weather disturbance or when the machine is not required to supply load a manual shutdown option shall be available to the user. Approximate time schedules for executing the work is given in the chart. It may be noted that about 2 years has been indicated. Partly this is due to the intervals between the expedition timings. It is also essential to completely establish the credentials of the machines to be deployed at Antarctica before. It is, of course, feasible to reduce the lead time by nearly six months if the testing itself can be taken up at Antarctica.

1.15 Approach II 1.15.1 Modifications on Machine/S Procured from the Market There are several companies engaged in design, development and manufacture of small wind turbines. Table 1.2 gives a sample list of such turbines. In this approach, one can take advantage of several subsystems developed for use with wind energy systems such as slow speed alternator, power electronics, control systems, and other essential components of wind turbines. This would reduce the cost of development and lead time to the final product. Several options are available from around the world. Most of these machines are used either in combination with other renewable energy devices or in stand-alone mode. The American experiments with North Wind turbines (1 kW) are in association with SPV panels. Russians use wind turbines almost exclusively for space heating. Keeping in view the complexities of this special requirements and keeping in view a small concept to deployment time frame, it becomes necessary to look at existing wind turbine options, their specifications, survival capabilities, and make some possible choices. There are quite a few small turbines deployed in various antarctic stations. Information must be gathered about such deployment and performance studied. Subsequently, it will be necessary to approach the manufacturers

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Table 1.2 The following table gives a sample list of machines and their salient features Make

Power (kW)

Hub height (m)

Rotor area (m2 )

List price (lacs)

Furlander, Germany

30

18

133

32

Jacobs, Germany

33

23

172

38

Kano Rotor, Germany

30

30.5

141

36

Sudwind, Germany

30

18.5

123

30

Vergnet GEV, France

10

18

38

20

Vergenet GEV, France

25

18

79

30

3

12

20

10

NorthWind, USA

and seek redesign for site-specific constraints. It is a niche market that they would be interested in looking at. A few models could be chosen, tested, and certified by accredited certification bodies. This is normally done by the manufacturers, and it is possible to discuss this aspect with the manufacturer. Such models can be deployed at Indian Antarctic station.

1.16 Approach III 1.16.1 Deployment of Commercially Available Machine It is also possible to procure some of the machines that have been tested elsewhere in Antarctica and trial install them in a suitable place within the country for trials during the ensuing monsoons. Once the systems are understood, they can be tried out in Antarctica. In all the three cases it is essential that a considerable study of existing wind energy systems will make the project more viable.

1.17 Conclusions A decision to go for an approach would have to be arrived at after such a study. It must be noted that indigenous development, though might appear to be rather elaborate, has certain advantages. In the long run, the cost of such systems when used in large numbers would come down, and in the process, a workable technology would have been developed. This itself would be an asset. It must be recognized that there are many Antarctic stations without any wind energy devices, and what is developed in India would have a good cost advantage over other sources. The next important advantage would be that since the product is developed from within the country, spare parts as may be required would never be a problem, which is a perennial problem

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with imported systems. This is particularly true in the small machine sector. Besides, apart from a small and apparent initial cost and time advantage the options II or III may give, in the long run, it is always a disadvantage to depend upon sources beyond Indian borders. It may be noted that even information on such deployment does not become available easily except commercial details. MoES/NCAOR may also consider the deployment of wind machines of larger capacities (>10 kW) to gain operational experience. This can be considered as a viable option as it is possible to import, modify, and build additional controls to take care of the extraordinary conditions prevailing at Maitri. In this case, the machine cost would be added to the above project cost. The fact is that in the long run, it is not feasible to source these machines from abroad. The spare parts availability from these companies becomes a very difficult situation to handle. The experience gained so far indicates that notwithstanding the warranty clauses, the companies fail to respond to technical and other queries regarding the failures.

Chapter 2

Engineering in Antarctica: Assessment Status Report Kulbhushan Rai

2.1 Introduction Antarctic expedition is a major scientific activity for the nation, and DRDO obviously, cannot be out of such premier scientific endeavours. To prove this point, right from the third expedition, engineers and scientists of R&DE (E), Pune have been participating practically in every expedition. During the initial phase, it was an experience to get exposed to the new environment with a certain spirit of adventure. As the base was being established for a permanent station, the efforts started getting converted into design, technologies, and missions to be accomplished. R&DE (E) took the initiative not only to construct the first wintering station at Dakshin Gangotri but also to collect data enough to plan the next station as a permanent habitat. These efforts culminated in the new station, “Maitri” which came up in 1988 and has been acknowledged as one of the well designed and constructed sites in Antarctica. Maitri is a modern comfortable station with living accommodation for 25 persons and good scientific amenities for research work. It also has facilities for summer camps to accommodate about 35 scientists.

2.2 Scientific Importance Since pioneering days of the initial polar adventures, men have lived and survived in the inhospitable terrain of Antarctica. Explorers have lived in summer and winter in tents and in the caves scooped out of the mass of snow and ice. Large-scale K. Rai (B) Research and Development Establishment (Engineers), Defence Research and Development Organisation, Dighi, Pune, Maharashtra, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_2

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building activity in Antarctica began in the International Geophysical year 1956– 1957. Expeditions at the National level were conducted by some of the countries and habitats constructed for their permanent stations in Antarctica. Most of the stations were constructed on an ice shelf or on the land free of ice nearer the Antarctica coastline during the initial expeditions. Subsequently, the expedition teams of the USA and the then USSR went deep inside the continent and constructed their stations near the South Pole also. Different types of habitats were constructed to suit the geographical and environmental conditions of Antarctica. The main factors that affect habitat construction in Antarctica are: a. b. c. d. e. f.

low-temperature High wind Snow accumulation and snowdrift Regional surface characteristics Visibility Accessibility

Of all the above factors the special considerations which govern the construction of habitat are the problems of snow accumulation and snowdrift. Solutions exist for constructing buildings to cater for very low-temperature (−50 to −60 °C) and structures can withstand the severe gale conditions of over 200 Kmph wind speed. But it is the snow accumulation for which special solutions must be found in designing an accommodation. Though the precipitation is not high, there is a net accumulation of snow year after year because of drifting snow. The drift snow renders any surface structure untenable after two or three years. The Indian Permanent Station has survived for more than 15 years as a key factor of IAE even after the expiry of its design life. This could be achieved due to scientific studies carried out from time to time for health monitoring of structure and allied systems.

2.3 Role of R&DE (E) in Antarctic Engineering R&DE (Engrs), a premier DRDO Laboratory is actively associated with Indian Antarctic participation since the third expedition mainly for providing logistic and scientific support. The first permanent Indian Station at Antarctica named ‘Dakshin Gangotri’ was constructed during the third expedition (1983–84). Situated at 70° 053, 12° OOE, ‘Dakshin Gangotri’ was the first ever Indian station established at the icy continent. Although the Dakshin Gangotri structure was imported, three living containers mounted on sledges were indigenously made and erected there. R&DE (Engrs) played a pivotal role in the commissioning of this station. During fourth, fifth and sixth expeditions new habitats based on insulated enclosures, knockdown containers, etc. were provided for living in addition to regular maintenance of DG Station. The DG Station located about 15 kms from the shore and constructed on about 300 m thick ice-shelf was expected to provide service for three years initially but was used for

2 Engineering in Antarctica: Assessment Status Report

27

about seven years. Due to continuous snow/ice accumulation, the DG Station got buried under snow/ice over a period and by 1987–88 it was completely covered by more than one metre of ice. DG was finally abandoned in 1990. With the continuous association with Antarctic expeditions year after year, scientists and engineers of R&DE (Engrs) attained enough know-how and confidence to design an indigenous permanent station at Antarctica. This culminated into the development of a new station MAITRI which came up in 1988 and has been acknowledged as one of the well designed and constructed sites in Antarctica. ‘Maitri’ the Second Permanent Indian Station at Antarctica designed and developed by R&DE (Engrs) was realised using completely indigenous resources. It was constructed by Scientists, Engineers, Army and Navy during 1988–89.

2.4 Scientific Aims During the past many expeditions, the following scientific aims were kept in mind while formulating various research proposals. a. b. c. d. e. f.

Surveying of area for foundation Surveying of Priyadarshini Lake for Water Supply Structural Health Monitoring of 28 m Mast Health monitoring of gensets Monitoring of Central Heating System and Water Supply Experiments on Fuel Cells.

The above is in addition to design, development and construction of Maitri Station and other logistic activities from time to time.

2.5 Regular Investigation Maitri station, being totally indigenous, was the first attempt to set up a permanent station by India. The problems connected with foundation, structure, materials and equipment were constantly monitored and corrective measures essential have been attended to from time to time. The following aspects were monitored in various expeditions. a. b. c. d. e.

Structural health Services such as Central Heating, Power and Water Supply, etc. Fire Hazards Environmental Control Health Monitoring of Gensets.

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2.6 The Site Maitri is situated at Schirmacher Hills-an ice-free boulderous terrain at 70° 46 S and 11° 44 E. The nearby Priyadarshini lake ensures vital water supply to the station throughout the year. For the most part of the winters, this lake is frozen and covered up to 2 m of ice. This site remains free from ice and snow accumulation for the most part of the year. The terrain is undulating, and the lowest temperature reaches up to −40 °C in winters.

2.7 Salient Factors Governing the Design Following factors were considered for design: Extreme low-temperature up to −40 °C High Wind Velocity up to 200 kmph Snow accumulation up to 2 m Limited available manpower Simple construction Easy repairability, maintenance and replacement of components Restriction on individual component size and weight for transportability by MI-8 helicopter. viii. Limited resources like fuel, food and water ix. Easy handling of individual components by available crane and transport resources x. Selection of suitable material of construction to withstand low-temperatures and fire hazards xi. Interchangeability of components xii. Construction with the help of trained as well as untrained manpower and completion of complete station structure within the stipulated time frame. i. ii. iii. iv. v. vi. vii.

2.8 Maitri Station Keeping all the above factors in mind, the station was designed and developed by R & DE (Engrs). The following paras cover a brief account of various components of the station and as well as additional facilities designed and developed from time to time to support various scientific activities related to Indian Antarctic research programmes. Plate I show the schematic arrangement of Maitri Station. The Maitri station is mainly divided into four blocks, namely Main Block, ‘A’ Block, ‘B’ Block and ‘C’ Block catering to different services.

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2.9 Foundation All the blocks of ‘MAITRI’ except ‘A’ Block is built on steel stilts having adjustable telescopic columns joined by cross beams. ‘A’ Block rests on the ground to comply even level of the building. A thorough survey was carried out and then the levelling of complete foundation columns was achieved. Plate I1 shows the schematic arrangement of the telescopic columns used along with cross beams and as well as the superstructure. The foundation is designed to withstand wind speeds up to 200 kmph and as well as self-weight of the superstructure. The adjustable stilts cater for the undulations of the rocky terrain.

2.10 Superstructure MAITRI Station comprises of four blocks. The main block houses living accommodation, communication control room, library, IMD laboratory, pooja room, deep freezers and storage space, etc. Block ‘A’ accommodates the MI room facility and health club. Block ‘B’ houses central heating system, water storage tanks and distribution, snow-melt plant, kitchen, dining hall, common room, laundry, urinals and bathing modules. Block ‘C’ provides accommodation for incinerator type toilets. Keeping in mind the logistic limitations, the modular construction method is used. Prefabricated panels made from timber framework with marine plywood on both sides and polyurethane as insulation material sandwiched between them are the main building blocks of the complete station. These panels are interconnected by wooden connectors. Fire retardant gypsum board lining is provided from inside while the external finish is provided by plastisol coated GI sheets. Adequate fire safety equipment along with smoke detector system is provided covering every part of the building. Plate III shows the typical cross-section of MAITRI and plate IV shows a photograph of the completed station.

2.11 Life Support Systems 2.11.1 Water Supply System Water supply to the MAITRI Station is ensured by pumping water from nearby Priyadarshini lake about 260 m away from the station. A steel support structure, about 200 m on land and about 60 m in water supports the insulated ducts carrying water supply pipelines. The pump house is erected at about 60 m from the edge of the lake and a submersible pump is lowered into the water. The pump is enclosed in two concentric SS jackets which are electrically heated to ensure continuous pumping of water even at −40 °C ambient temperature. The entire copper pipeline from the pump

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house to the boiler room in ‘B’ block is encased in a rectangular airtight insulated duct supported out of marine plywood and 100 mrn rigid polyurethane foam. Plate V shows the schematic of a typical duct assembly. Initially, a 40 mm dia copper pipe for water supply surrounded by 25 mm dia copper pipes from both sides carrying hot water mixed with anti-freeze media (monoethylene glycol (MEG)) to maintain the duct temperature was catering for the water needs of the station. To avoid any accidental pilferage of MEG into the lake due to leakage, a new pipeline was installed employing trace heating of the copper pipe throughout the length of the pipeline and the support 25 mm hot water and MEG carrying pipes were removed. Self-Limiting Self-Regulating type (SLSR) of electrical trace heaters are employed for heating. Temperature sensors are installed inside the duct to indicate the temperature on the control panel provided in the boiler room. The total pipeline is divided into three equal lengths and fitted with SLSR trace heaters to balance the three phases of the genset. One stand by pipeline is also catered. The water from the lake is pumped into two stainless steel tanks of 2500 lit capacity located in the boiler room and further distributed to utility points. A control panel with temperature indicators and safety system is installed in the boiler room for observation and operation. After every pumping operation, leftover water in the pipeline is drained back using blowers. A stand by centrifugal pump is also installed in the pump house. The system has worked for almost 12 years now and due to wear, tear and also due to extensive weathering of the support structure, pump house structure and support jetty type structure, the complete water supply line is tilted and needs to be replaced by alternative arrangement. Plate VI shows the water supply scheme and a typical photograph.

2.11.2 Power Supply and Electrical System Initially, 4 × 62.5 KVA Gensets were installed in ‘A’ Block to cater power supply of the station. After some time, these gensets having outlived their lives were discarded. Later to avoid sound pollution and for more safety, ‘Aditya’ powerhouse, little away on the rear side of the station has been constructed in 1992–93. ‘Aditya’ is constructed with three knocks down containers made from prefabricated modular panels. Four specially designed 62.5 KVA gen sets are housed in two containers and the third container caters for the control panel. Two more 62.5 KVA gensets housed in Standard IS0 containers with insulation panels were also installed later and a powerhouse named ‘Bhaskara’ was commissioned in 1994. Stand by sets were added during later expeditions. Special anti-vibration mountings, cold start devices, control panels, diesel engines and alternators employed for the last 12 years as basic units have ensured the continuous power needs of MAITRI. Plate VII shows a typical view of ‘Aditya’ powerhouse.

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2.11.3 Central Heating System A central heating system maintains the comfortable 20 °C+ or −4 °C temperature of ‘MAITRI’ throughout the year. It consists of hot water generators (boilers), radiators and closed loop piping through which hot water and anti-freeze is circulated at about 80 °C. Hot water radiators of 1000 K. CaVh capacity have been installed at appropriate places to maintain the desired temperature. Four hot water generators of 2 lakh K. CaVh capacity installed in the boiler room of ‘B’ Block and connected to radiators meet the entire heat load of the station. At a time only one boiler serves the needs of the entire station and the others act as stand by. Two fuel tanks of 2500 L each connected in parallel provide a feed to 500 L capacity fuel tank for daily needs. Appropriate safety features have been provided with the boilers and fuel tanks. Plate VIII shows the photograph of the boiler room.

2.11.4 Waste Disposal Solid and liquid waste disposal in sub-zero conditions is a challenging task and possess several problems. For disposal of human waste, five incinerator type toilets have been installed in ‘C’ Block of the station. The toilet ash, ash collected from the incinerator, plastics, metal fins, grates and leftover food waste, etc. are segregated, sealed in barrels and backloaded for disposal following strict norms. Wastewater from kitchen and bathrooms, etc. is directed to two bio-disc treatment plants. The effluent after treatment in both these plants is collected into a pond of about one lakh litre capacity. This water is periodically pumped out to an uphill location about 300 m away from the pond where the water is soaked into the ground.

2.12 Other Facilities 2.12.1 28 m Mast A 28 m mast was erected at MAITRI to facilitate the mounting of various sensors and equipment by various participating agencies. It is still functioning fine and has withstood many blizzards sometimes exceeding 200 kmph wind speeds. The mast consists of modular components namely base frame, mother truss, standard trusses, central truss, top truss, tilting frame and a top movable platform with the mounting arrangement. The anchorage system consists of hand winch assembly with worm reduction gearbox, Op holdfast Op spikes and TI3 trifor with 20 m rope, etc. Plate IX shows the schematic of the mast and plate X shows the photograph of the same

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2.12.2 Aluminium Helipads Two 10 m × 10 m helipads are used for landing and take-off of helicopters. Two types of modular panels of size 235 mm × 31.6 mm × 2500 mm and 5000 mm are joined together in a brickwork pattern to form a set. Special aluminium alloy extrusion, HE-30 WP (933 kg/cm2 ) with deodar timber insulation at the bottom is used as basic building blocks of the helipads. Plate XI shows the photograph of the helipad.

2.12.3 Seismological Vault This is an underground shelter providing permanent seismological observatory at MAITRI. The shelter is in modular construction built using timber panels 125 mm thick with PU foam insulation. Siporex floor panels are used for flooring. The Seismometers which record 2, N–S and E–W signals are placed inside the shelter whereas the seismogram is placed at nearby Tirumala Hut. A 500 W bulb is fitted in the shelter with a digital temperature controller to maintain the inside temperature of shelter at +15 °C. Plate XI1 shows the schematic arrangement of the shelter and Plate XIII shows the photographs of the same.

2.12.4 Shelter for Brewer Spectrophotometer This is an aluminium shelter which houses Brewer Ozone Spectrophotometer for continuous ozone measurement experiment at MAITRI. The shelter is designed in RDE-40 welded construction with PU foam insulation and FRP lining of 2.5 rnrn from inside. Special provision is made for fixing of the spectrophotometre. Zebra weblift nylon anchorages with concrete foundation provide stability to the shelter against blizzards and high winds. Plate XIV shows the photograph of the shelter. In addition to the above, vehicle repair shelter (plate XV), dome shelter for greenhouse, walk-in type of cold storages, electrical earthing of the complete station, bathing modules (plate XVI)) and other facilities have been provided from time to time.

2.12.5 Major Findings/Outcome From the experience gained on structures, I equipment developed for Antarctica R&DE (Engrs) was able to design and develop a full-fledged indigenous station in Antarctica. As such, the second Indian Station with all services was developed by R &

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DE (Engrs) in 1987 and was commissioned during seventh and eighth expeditions at a new location in Antarctica, which was named “MAITRI”. The existing DG station, which was buried completely due to snowdrift, I accumulation has been abandoned in 1989. Since 1988 onwards the Indian Wintering teams have been continuously staying at MAITRI Station to peruse their scientific studies.

2.13 Overall Contributions Following major logistic support and activities for the Indian Expedition to Antarctica have been provided right from the beginning of the Antarctic programmes. a. b. c. d. e. f. g. h. i. j. k. l. m. n. o. p. q. r. s. t.

Indian Permanent Station “Dakshin Gangotri” Indian Permanent Station “Maitri” Central Heating System Water Supply System Power Generation 28 m Mast Seismological Vault Dobson Hut. Shelter for Spectrophotometer Helipads Balloon launching Shelter Containerised shelters for Power House Sledge Mounted Containerised Modules Sledge Mounted Fuel Tanks Fuel Cell Technology HF Link/ Communication/ email hut Condition Monitoring of Maitri Foundation Trace Heating System for the new water supply system Static Charge Control System Condition Monitoring of Gensets.

All the above systems were developed successfully and still serving satisfactorily even after their designated life cycle.

2.14 Significant Achievements Design and Development of Indian Antarctic Station “Maitri” and allied engineering systems has been successfully completed. The station was totally indigenous, and it has saved a substantial amount of foreign exchange. Although the station was designed for 10 years, it is still playing a key role in the Indian Antarctic Expedition for Wintering tasks.

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Since Antarctica is the virgin scientific laboratory of the world; our scientists got direct exposure to this laboratory. This has helped Engineers and Scientists of this establishment to gain deeper knowledge and exposure on the design and development of various equipment and structure for the polar region, in turn, giving a stronger technology base pertaining to cold region engineering.

2.15 Conclusions Because of the exposure of our Scientists to Siachen and Antarctica, this establishment could indigenously develop Maitri Station. With further studies in Cold Region Engineering and collection of information from other countries, the team is geared up to take up the more challenging task to carry out scientific studies and evolve better methods of construction and provide engineering support to the future missions to Antarctica. Having been identified as a nodal agency, this establishment now can effectively implement a long-term plan by involving eminent engineering units of the country. The next target is to take up or help in the design and development of alternative Indian Permanent Station at Antarctica.

Chapter 3

Review of the Status of Engineering Aspects of Dakshin Gangotri and Maitri R. C. Pathak

3.1 Introduction At the two ends of the Earth lie the Antarctic and Arctic. Into these icy worlds came sealers and whalers looking for new hunting grounds, explorers searching for new trade routes and scientists/engineers and seamen on voyage of discovery. At one of these very ends of the earth is the coldest, windiest, highest cleanest loneliest and pristine, emptiest, place, Antarctica also called ‘Bottom of the world’ though on average, it has the highest relief (Sugden 1982; Pathak 2013). The Indian Antarctic Expedition started in 1981 over two decades back when the first Expedition was launched for its summer tenure under the guidance of its leader Dr. S. Z. Qasim, an eminent Oceanographer. The first wintering, the Antarctic expedition was launched in 1983. Since then the Indian expeditions have been wintering every year for carrying out scientific and logistic activities. The Ministry of Earth Sciences (erstwhile Department of Ocean Development) is the nodal agency for organizing and coordinating this expedition every year. Under the collaboration with the Department of Ocean Development (DOD) and later National Centre for Antarctic and Ocean Research (NCAOR) with many scientific and other institutions of the country have established first Indian Antarctic Station ‘Dakshin Gangotri’ (DG) on ice shelves and permanent station, Maitri on ice-free hills named as ‘Schirmacher Hills’ DG was constructed during the Third Indian Antarctic Expedition (1983–84) and later MAITRI, was constructed during the period of 1988–89 7th and 8th ISEA. Since then, MAITRI has been in use around the year for all wintering expeditions. The DG station was closed during 26 February 1990 and converted into a supply base.

R. C. Pathak (B) Bharti Vidyapeeth Lal Bahadur Shastri Marg, Pune 411 030, Maharashtra, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_3

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3.2 Review of Constructional Aspects Dakshin Gangotri (DG) The first manned station of India in Antarctica is Dakshin Gangotri, which is located on ice-shelf on Princess Astrid Coast. The load of the station is borne by a raft foundation to effect even distribution. The station consists of two double story blocks linked by a narrow passage. Timber is the basic building material and prefabricated panels consist of two plywood sheets of 9 mm thick, attached to the two sides of a timber load-bearing frame. The space between the two faces is filled by thermally insulated material. The outside face is protected by cladding material of 25 mm thick layers of material over which metallic sheets are bolted. The kitchen and bathroom have melamine faced plywood. Internal finishing in all other rooms is provided by hardboard (Fig. 3.1a, b) (Scientific report of VIII and IX ISEA, 1994, Sharma 1986) Due to the accumulation of approximately 1 m of snow every year the station was finally closed on 26 February 1990 and was converted into the supply base. For such ice-shelf construction jack-up platform type of construction is suggested/recommended (Figs. 3.2 and 3.3) which shows HALLEY BAY-V (UK) and Dew line station, Greenland, DYE-3). Herein we can clearly observe that the stations can initially be raised at some desired heights and further the height of the whole superstructure can be raised depending on the yearly snow accumulation. It can also be seen from Fig. 3.3a, b that the station can be moved horizontally on rail girders for safeguarding against the earlier stressed foundation.

3.3 Maitri This a full-fledged indigenous station fully designed by R&DE (E), a DRDO organization and was constructed during the 1988–89 (8th expedition). Maitri station was constructed by Scientists, Engineers and Logistic Support from Army/Navy/Air Force. It is modular construction and houses 25 persons round the year and accommodates about 35 scientists during summer periods (Scientific report of VIII and IX ISEA). Maitri station is built on Schirmacher Hills, which is an ice-free boulderous terrain (Fig. 3.4a–d). Its water supply comes from Priyadarshini Lake. Russian station, Novolazreskaya which is about 5 kms away from Maitri. The station is constructed by prefabricated marine ply sandwiched panels, 100 mm thick with all the Life Support System. Polyurethane foam in between the marine plywood fills and works as insulating material. Fire retardant Gypsum board lining is provided from inside while external finishing is provided by the plastisol coated metallic sheet. The station has been designed keeping in mind the wind velocity and foundation, which is on telescopic steel adjustable columns which cater for boulderous/undulated topography of the ground. The foundation is laced with steel bracing and by guy

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Fig. 3.1 a Dakshin Gangotri (DG). b Design of service life of building

ropes anchoring to the ground to safeguard the station from higher hazards of wind (Fig. 3.5). The main lifeline of water is supplied from Priyadarshini Lake and a submersible pump through a 40 mm diameter pipe. In later expeditions, the Methylethyl glycol (MEG)-based heating of pipe ducting has been replaced and a Self-Limiting SelfRegulating (SLSR) trace heating tape is duly put over these pipes (Fig. 3.6a, b), which ensures heating of water during the continuous pumping supply operation of water. As a stand by arrangement one snow-melt tank of 1000 L capacity also is housed in the boiler room for the severe winter, if any mishap occurs (XVII ISEA, Sivan 2000).

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Fig. 3.2 a and b Halley Bay-V station (UK) on jacked up platform

Fig. 3.3 a and b Dew line station Dye-3 green land (Another view) (on jack-up platform)

3.4 Environmental Management An efficient system of waste disposal has been incorporated in the station. Incinerator type of toilet, toilet ash, plastic metal tins, grates scraps and left out food waste are collected, segregated sealed in barrels and backloaded for disposal as per laid down

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Fig. 3.4 a Front view of Indian permanent station ‘Maitri’. b Rear view of Indian permanent station ‘Maitri’. c Winter view of Indian permanent station ‘Maitri’. d Pump house near Priyadarshini lake for water supply to Indian permanent station ‘Maitri’

standard norms while on the return journey. Waste water or effluent water is collected from the kitchen bath to a pond via two bio-disc digester types of plants that have been imported from the UK. The effluent water after treatment in both these plants is periodically disposed of by pumping during summer months on the other side of a distant hill feature located about 300 m from the main station, where the water is soaked into the ground as a natural recourse ensuring no seepage action. An

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Fig. 3.4 (continued)

experimental greenhouse was added during IX ISEA (Pathak and Gangadhar 1994; Pathak 2013).

3.5 Miscellaneous Facilities Efficient communication systems (HF Link, VHF communication, satellite communication INMARSAT, telephone facilities) all provide excellent communication with the mainland. Fax is also available since 14th expedition R & DE (Engineers) has installed an electronic mail system on ERNET in Antarctica. Other miscellaneous items are 28 MAST, Fuel cells, Dobson Hut, Seismological vault, etc.

3.6 Critical Review Status of Maitri 3.6.1 Rehabilitation/Residual Life of Permanent Station Maitri Passage of time age of the building, its design considerations, its functional aspect, utility, etc. determines the obsolescence of the building. Later, it requires either

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Fig. 3.5 Details of foundation, panel and joints

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Fig. 3.6 a Existing water supply. b Modified water supply with trace heating

replacement after demolition due to enhanced recurring maintenance costs. Some main factors are (a) (b) (c) (d)

Rehabilitation due to location hazards Replacement Protection—maintenance for prolonging life Modernization

Also, modern thinking/concepts may be vitally essential for its functional aspects. These are (i) (ii) (iii) (iv) (v) (vi) (vii) (viii) (ix)

Breakthrough technology factors Modular concept Spatial and temporal utilization New physical architectural design Any other improvement in service life Backlog/cost of maintenance New design Stresses/distress developed to the old building Efficacy of various waterproofing treatments and other locational hazards degree of fire hazards, wind hazard, etc.

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3.7 Obsolescence/Depreciation The obsolescence and depreciation are due to physical conditions or utility of the building and also reduction in the value of the property or building (Jha 2012; goo gle.co.in). (i) Residual Life of building = Designed Life of the Building + Safety factor (ii) Some depreciation techniques used for buildings are (a) Straight line method Annual depreciation D = ((C − Sc)/N) (Original cost − Scrap value)/ (Life in years)

(3.1)

where C = Original cost Sc = Scrap value (value of the building when it becomes useless except for sale or junk) N = life of building in years and D = Annual Depreciation (b) Constant Percent Method If P is the percentage rate of annual depreciation then, P = 1 − (Sc/C) ∗ 1/n

(3.2)

where annotation has the same values. Other methods are (c) (d) (e) (f)

Sinking fund Method Quantity survey Method Direct observation Method Declining Balance Method

At Antarctica, we must also take into consideration of allied resources around the station such as recurrent source of water supply, ground conditions, topographical and geomorphological changes and so on. Some other techniques are enclosed at Appendix 1.

3.8 Suggested Recommendations As will be observed, the permanent station Maitri was designed for 10–12 years, and now it is on the brink of residual life. It is high time that we should design a new infrastructure with modern technological programmers including the latest smart materials available in the world market.

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3.9 Service Life Index The concept of remaining service life could be better communicated to interested parties if it could be described in a single numeric parameter. The Service Reserves Factor (SRF) serves this function by stating the simple ratio of the remaining service life to the required service life as follows: SRF = t/T, where t = Time to failure (years), and T = Required remaining time in service (years) A lower SRF indicates a more severe or deteriorated condition. The main structural components of the panel/wharf or even the same component in different exposure zones may have different SRFs. This means that several SRFs may need to be determined for the structure, and the lowest should be used as an evaluation parameter.

3.10 Time to Failure The simplest and generally acceptable failure mode is that when the structural reserves of the component are exhausted. The structural reserves are defined as the difference between the total remaining capacity of a component and that which corresponds to its structural limit condition. However, proper maintenance practice would generally not allow a structure to reach this point of structural failure or even the point where its repairs become prohibitive. The most common scenario in ports is to take the structure out of operation for major repairs when attempts to keep it in service by regular small-scale maintenance repairs fail. Hence the term ‘maintenance failure’ is used to describe the condition when regular maintenance of the structure becomes either economically prohibitive or operationally impossible. To calculate the time to maintenance failure (t), first, an associated failure mode must be defined. For example, for steel sheet piles it is multiple perforations occurring over a short period of time at many locations along the wharf/panel. For steel pipe pile corrosion this may be a critical diameter to wall thickness ratio. For prestressed concrete piles—a maximum number of corroded strands; for shotcrete repairs—a percent of failed repair patches, etc. Once the failure mode and the service reserves are defined, the corresponding inspection parameters and criteria for calculation of time to failure are to be determined. In the most general case, the main parameter is the rate of deterioration. For instance, for corrosion perforation of steel, this is the rate of pitting, while for the critical wall thickness, this is the mean rate of the area corrosion. To calculate the

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time for the maintenance failure, the remaining service reserves should be divided by the rate of deterioration.

3.11 Required Remaining Time in Service For a marine wharf/panel, the required remaining time in service is either established directly, as a management/operational decision, or it is assumed based on the required total (design) life. It should be noted that even when the structure is at the end of its design life, it may not be taken out of service (again because of the management/operational decision). Consequently, in a repair/maintenance decision based on the total required (design) service life, this parameter should be used only as a benchmark. The basic assumption is that the required remaining time in service is the difference between the design life and the actual time the structure has already been in service. Since the latter is usually a known value, the only parameter to be determined (or assumed) is the total required (design) service life. Design life of 50 years was for a long time the value of choice in marine engineering. Today, however, ports around the world keep in operation (possibly with modifications and repairs) structures which are much older than 50 years. In lieu of owner-specified service life expectations, it is recommended to use a required service life of at least 80 years for decisions related to maintenance and repairs of wharves/panels. With this value set as an evaluation parameter: T (Required Remaining Time in Service) = 80 − Time Since Construction Example for Calculation of SRF: The sheet pile bulkhead has been in service for 15 years. The results of ultrasonic testing indicated that the average value of the minimum flange thicknesses measured on the bulkhead sheet piles is 6.0 mm, while the original thickness was 15 mm. 1. Mean value of maximum thickness loss is 15.0 mm − 6.0 mm = 9.0 mm 2. Pitting 2. Perforation Rate is 9.0 mm/15 years = 0.6 mm/ year 3. Time to widespread perforation: 6.0 mm/ 0.6 mm/year = t = 10 years 4. Required Remaining Time in Service: 80 years − 15 years = 65 years (T) 5. Service Reserves Factor (t/T): 10 years/65 years = 0.153. Service reserves factors calculated in this or similar way may be efficiently used for maintenance/rehabilitation planning in the ports, and particularly for the prioritization of these activities

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3.12 Proposed New Station It is ripe time that a modern new station should be designed and erected with all the recurring support systems and the latest breakthrough technology materials with modular concepts. In the above depreciation method Eq. (3.1), i.e. from straight-line method, we have, D = (C − Sc)/N If we take Sc = Scrap Value tending to zero. The Annual depreciation, D = (C − O)/N = C/N, which will infer that if we take N = 10 years. The building infrastructure of Maitri Station has lived its total useful life. This also infers that now the recurring maintenance cost like wind, leak proofness, panels maintenance, heat load, etc. should go higher towards non-economical range or so. Till such time the building/support facilities and their maintenance are dire essential on a regular basis.

3.13 Maintenance Management System It is heartening to observe that due to the efficient maintenance on regular basis by MoES/NCPOR our engineers/scientists and concerned personnel, the station has been functioning and performing its functions well. Primarily maintenance management system comprises the following: (a) (b) (c) (d) (e) (f) (g) (h)

Technical factors Organizational considerations Financial factors Economic and Environmental criteria Policy considerations Time-Life Residual life Modern Thinking—lean/mean maintenance programme Futuristic maintenance Programmes like (i) Evolving regular maintenance programmes (ii) Special inspection/monitoring programmes (iii) Appropriate database for implementation function, planning/programme function, etc. (iv) Constructional and other Mechanical, electrical, plumbing and civil engineering aspects (v) Stresses/desire measuring technical aspects like Non-Destructive Techniques (NDT) or (vi) Prompt repair/rehabilitation techniques

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3.14 Conclusions It is observed that Maitri is under its residual life period and apart from its constructive/ well-programmed maintenance scheduled, a new station/ infrastructure must be designed and erected at suitably studied, selected site at Antarctica. The present station may be converted into a summer station or any other useful functions. A reduced maintenance or maintenance-free station with modern infrastructure is dire essential in the present scenario (see Appendix 1).

Appendix 1 Durability and whole service life of building 1. Designing and service-life requirement • Early assessment of durability of building components • Designing for acceptable probability remain fit Optimization of performance • Seeing/ examining life of worst/weakest component material. 2. Service life assessment factorial-based methodology (a) Reference service life ‘RSL is defined as period of time that the component or assembly can normally be expected to last under specified service conditions’. It may be derived from • • • •

Modelling Experience Accelerated testing Data from manufacturers

(b) Estimated service life. ‘ESL is expected life of particular component in its specific environment allowing for factors given below: • • • • • • •

Quality of materials—timber and steel. Design level Work execution (quality of workmanship) Environmental condition (internal/external) In-use conditions Maintenance conditions Structural detailing

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• Modular/technological changes. 3. Service life planning: It can be carried out in the following steps: • • • • • • •

Assessment of client’s requirements Assessment of client’s brief (benchmarking) Assessment of conceptual design Assessment of detailed design Assessment of operations and maintenance (o & m) Assessment of construction Assessment of maintenance plan.

4. Probabilistic failure-based methodology for building components Software-based information (a) method (1) • After 50 years brick wall pointing of mortar becoming loose • Cracking > 15 mm after 60 years. Partial collapse after 70 years. (b) method (2) • • • • •

Physical deterioration models Material properties under specified Environmental conditions (herein cold region conditions of Antarctica) Past performance data Laboratory test under simulations conditions.

5. Minimizing deterioration of materials used (A) Concrete • • • •

Physical process: freeze thaw, abrasion thermally cracking, drainage Carbonation—ingress of chlorides—leading to reinforcement corrosion Chemical attack Study of environment—avoid alkali-aggregate reaction.

(B) Timber • • • • • • •

Use of dry timber (exterior < 18% moistures and interior < 12% moisture) Protective/adequate ventilation Protection form wetting Separation from wet materials Avoidance of water traps/condensation Details to accommodate timber movement Choice of naturally durable timber/wood species

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• Appropriate preservation treatment • Moisture control and maintenance. (C) Steel • • • • • •

Surface treatment form corrosion by paints/coating, etc. Keep steel dry Avoid steel air movements (e.g. Lofts, etc.) Keep steel warm—warm frame constr. Weathering steels Stainless steel (galvanizing, etc.).

6. Maintenance • • • • •

Whole life costing maintenance Lean, mean, maintenance programmes Special/periodical regular maintenance Stresses/distress measuring techniques Prompt repair/rehabilitation techniques.

References Jha NK (2012) Construction project management—theory and practical. M/S Dorling Kindersley (India), Pvt. Ltd., Delhi Ninth Indian expedition to Antarctica, Scientific report, 1994. Department of Ocean Development, Technical publication no. 6, 1–120 Pathak RC (2013) Antarctic geocryology. Global Book Organisation, Delhi Pathak RC, Gangadhar RS (1994) IX ISEA. Some constructional aspects of green house and plant growth aspects. DOD publication, New Delhi Sharma SS (1986) A study of Dakshin Gangotri ice shelf. DOD Publication, New Delhi and Centre for Earth Science Studies, Trivandrum Sivan KR (2000) Scientific report of ISEA XVII, DOD, New Delhi, India Sugden D (1982) Arctic and Antarctic. M/S Basil Blackwell Publisher, Oxford, England UK Google.co.in

Chapter 4

Dakshin Gangotri Station: The Pride of India S. S. Sharma

4.1 Introduction Indian scientists made the history of establishing a permanent base and carrying out year around research activities in the icy continent of Antarctica in 1983–85 by constructing the first Indian permanent station Dakshin Gangotri at 70o 05 S 12o E on the ice shelf located in Queen Maud Land in East Antarctica. The station was established by the third Indian Scientific Antarctic Expedition (ISAE), which sailed from Goa on 3 December 1983. This could be termed as a unique achievement as the entire work on establishing the station including site selection, construction and commissioning of various systems, the trial of various systems, etc. was completed in a record time of 60 days, which included many bad weather days. Not only that, to fulfil the obligation of being conferred the consultative status and making a bid for membership of Scientific Committee of Antarctic Research (SCAR), a wintering party of twelve personnel comprising three scientists and the supporting staff was positioned in the station, which successfully went through its first winter in the station and gathered valuable scientific and other data for furthering the Indian Antarctic programme. The paper describes, in brief, the technical appreciation which had gone through in selecting the site of the station, the outline design, and layout of the station, some details about the life support systems and the efforts put in to establish them, and brings out some salient points about their performance during the first winter.

S. S. Sharma (B) 703, Cordia, Nyati Estate, Mohammad Wadi, Pune 411060, Maharashtra, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_4

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4.2 Background As mentioned above, the station was established by the Third ISAE in 1983–84 which was launched with this primary aim. Prior to that India had sent two expeditions, viz, First ISAE in 1981–82 led by Dr. S. Z. Qasim with the primary task of reaching Antarctica and gathering the first-hand information about the continent and making a base for launching the Antarctic programme in the later years. The Second ISAE led by Sh. V. K. Raina was launched in 1982–83 with the aim of selecting a suitable site for the permanent station and drawing out a concrete plan for year-round Antarctic research. This expedition was also required to make recommendations for the design of the station and drawing out a plan for its construction and commissioning in the Antarctic summer of 1983–84 by the Third ISAE. The name Dakshin Gangotri (DG) was suggested by Dr. S. Z. Qasim after he saw a small stream taking off from the snout of the glacier on Schirmacher Oasis where India had established a summer camp during the First ISAE. The suggestion of Dr. S. Z. Qasim was accepted by the then Prime Minister of India Smt. Indira Gandhi who was personally interested in this programme and was also in charge of the Department of Environment and Department of Ocean Development (DOD). Based on the recommendation of the second ISAE that the first station should be established on the ice shelf close to the seashore, the design of the station was conceptualized and bids for procurement of the same through indigenous means, as well as import, were invited. Since no agency in India had any experience of the polar region, especially with respect to construction technology and other allied areas, the emphasis was laid on considering the offer from the agency from abroad having experience of similar work in Antarctica. Accordingly, after careful considerations the offer of M/S Structaply of the UK for the main structure was accepted. This company had supplied a similar station to the British Antarctic Survey for their station Halley IV on an ice shelf in East Antarctica. Based on the recommendations of the company, some life support systems were procured from the UK and some from the erstwhile West Germany. The Corps of Engineers of the Indian Army and Defence Research Development Organization (DRDO) were associated with various activities like outline design of the station and the allied systems, acceptance of the technical offer for the items from various agencies from abroad as well as India, etc. A construction party from the Corps of Engineers and Corps of Electrical and Mechanical Engineers (EME) was sent to West Germany and the UK in the summer of 1983 for training on construction of the structure and commissioning of various allied life support systems. The construction party was closely associated with the preparation of the packaging and transportation plan, loading of the items in ship MV Finnpolaris at the port in the UK and other related activities with a view to avoid any confusion and delay during construction and commissioning of the systems.

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4.3 Dakshin Gangotri (DG) Ice Shelf As mentioned earlier that based on the recommendations of the first two ISAE the station was to be constructed on DG ice shelf. It would, therefore, be pertinent to describe the outline details of the DG ice shelf before proceeding further. The area where Dakshin Gangotri is located forms part of an unnamed ice shelf. Some snow studies pertaining to this ice shelf have been carried out in the past (Korotkevivich 1978; Richter and Strauch 1982). To understand further this shelf for planning future explorations, snow studies pertaining to this shelf were taken up by the author during 1983–85 (Sharma 1986).

4.4 Geographical Layout The study area extends from 69o 50 S to 70o 45 S and 08o 30 E to 13o E within Queen Maud Land. It has a Fiambul ice shelf on the west and an unnamed ice shelf on the east. The complete ice shelf, 150 km long with an average width of 70 km, runs along the Princess Astrid coast in a zigzag manner. It is flat-topped having a gradual southward ascent from sea-edge to its point of origin at the foot of the Schirmacher Oasis. The total area of the shelf is about 10,000 km2 . There is no station functioning at present on this shelf, except the Indian station Dakshin Gangotri which was established in 1983–84 and remained functional till 1989–90. The other station, which earlier operated in this region is the USSR station Lazarev (69o 59 S: 12o 55 E) which was abandoned in the early sixties.

4.5 Topography The shelf originates from Schirmacher Oasis which extends from 11o 49 E to 11o 26 E with a total area of about 35 km2 . This includes 27 km2 of bedrock, 3 km2 of lagoons, 3 km2 of firm/ice-fields and 2 km2 lakes. Due to the presence of many freshwater lakes, the area of Schirmacher Oasis has been named as Schirmacher lake district (Richter and Strauch 1982). The depth of lakes in the region varies from 5 to 13 m with water availability practically throughout the year. The Soviet station Novolazarevskaya is located on the Oasis at an altitude of 105 m at the foot of a glacier. The ice shelf understudy starts from the foot of the north wall of Schimacher Oasis, which can rightly be termed as the hinge point or the strand crack area of the shelf. All along the southern edge of this shelf, there are large lakes having depths as much as 100 m. Prominent among these are lake Ozhidaniya with a maximum depth of 105 m and lake Zigzag with a maximum depth of 122 m. These lakes are permanently covered with ice (Richter and Strauch 1982). In this region, there are also some shallow freshwater seasonal streams running from west to east, which make this area inaccessible for

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Table 4.1 Measurements of ice thickness in different locations No. of hole

Location

Date of drilling

(b) Depth observed (in m) (c) Remarks

1.

69o 59 S

Jan. Aug. 1975

374

2.

69o 59 S

(ii) Oct. 1975

357

3.

69o 59 S

Aug. 1976

447

Depth of sea under the glacier 203 m

snow vehicles during summer months. In addition, there are several crevasses covered by snow bridges during most of the year. The crevasses are surface fractures caused by the movement of the shelf due to tidal waves about the hinge point of the strand crack region and warming and cooling of the ice mass around the year. In the lower region of this shelf, near the coast, there are two high grounds permanently covered with snow/ice which are named as Kurklaken and Leningrad kollen. The height of these features varies from 50 to 100 m. The general layout of the shelf is shown in Fig. 4.1.

4.6 Thickness of the Shelf Measurements of ice thickness of the shelf taken in 1984–85 indicate that the thickness on the seaward edge varies from 100 to 200 m, out of which about 10 to 30 m is exposed above sea level. Korotkevivich (1978) carried out measurements of ice thickness towards the interior of the shelf in 1975 which is presented in Table 4.1. Verma and Mittal of NGRI, Hyderabad (1985, personal communication) carried out measurements of ice thickness in the region of Dakshin Gangotri by seismic studies. Preliminary analysis of their studies suggests an average thickness of 300 m.

4.7 Movement of the Shelf No factual data on the rate of flow of the shelf are available. However, from the coastline of the shelf, it is observed that the shelf movement is not very significant, though several icebergs of small size are formed every year. The slow movement is attributed to its limited size, with its origin from the foot of the Schirmacher Oasis, and presence of high grounds on the northward edge, which restrict the movement of the central part of the shelf. On the other hand, in the shelves located to the east and west of the two high grounds, the movement is reported at the rate of 1–30 m/year (Personal communication, lgor Simonov, 1984 leader USSR team at Novolazrevaskaya station during 1983–84).

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4.8 Craters on the Shelf The Norwegian scientists have reported crater formation in the general area of this shelf. According to them, large areas of the shelf have been seen sinking into the sea in the past and as such the shelf is not suitable for occupation. However, during reconnaissance before construction of DG station and later, no evidence of such craters was found.

4.9 Snow Accumulation on the Shelf The pattern of snow accumulation in the central part of this shelf was studied during 1984–85 by erecting wooden poles. Depths of fresh snow accumulation and depletion on these stakes were measured from time to time. A preliminary analysis of this data suggests the following pattern. (a) There is no accumulation or negligible accumulation on the stakes in the region 5–6 km from the shelf edge. (b) In the rest of the area, the maximum and minimum accumulations are 120 and 60 cm/year, respectively. (c) The maximum accumulation is seen during blizzards in Feb–Mar and Sept–Oct. (d) From Feb. to Oct., the average accumulation is 90 cm. The accumulated snow suffers a depletion of 10–15 cm during Nov–Dec. Thus, for the planning of structures, the average yearly accumulation may be taken as 70 cm in the areas having a smooth surface without any obstruction. However, in the region having any exposed obstruction, natural or man-made, the drift accumulation was observed to be significant. Density profiles of the shelf during 1984–85 indicate the following pattern. (a) The density of newly accumulated snow on stakes during a blizzard varies from 0.4 to 0.43 gm/cc. (b) The top layer exposed to the sun at the end of the winter transforms into sun crust, which after freezing gives an average density of 0.7 to 0.8 gm/cc. This layer later forms the foundation for the snow, in succeeding years. (c) The density profile during summer indicates a top layer (50–60 cm thick) with an average density of 0.42 gm/cc. The layer of the hard-buried ice sheet is underlain by snow (40–50 cm thick) of density 0.42–0.5 gm/cc. Typical representative density profiles taken during summer and winter 1984 in the close vicinity of the station on the shelf, are shown in Fig. 4.2.

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Table 4.2 Values of average Ram Hardness (R) during 1984 Month

Ram Hardness in Kg

(c)

Maximum

Minimum

(2) Average

(a) Remarks

Jan

328

110

207

Feb

395

55

172

Mar

434

50

256

(i) Fresh snowfall observed (ii) Fresh snowfall observed Only one profile recorded Coldest month

Apr

307

197

205

May

229

89

168

Jun

304

304

304

July

380

89

219

Aug

489

167

293

Sep

455

192

247

Oct

300

190

242

Nov

220

151

180

(ii) Dec

254

49

133

4.9.1 Strength Profile The strength profiles of 1 m depth of snow are taken with Ramsonde during 1984 indicate the following pattern: (a) Strength of snow increases rapidly with the onset of winter in March and attains very high values during the peak winter period between June and October. The strength decreases rapidly in November with the onset of summer. (b) The highest average value of 304 kg corresponding to 8.56 kg/cm2 of unconfined compressive strength is obtained in June 84. The lowest average value of 133 kg corresponding to 5.20 kg/cm2 of unconfined compressive strength is obtained in December 84. These values give a fair indication of trafficability of the shelf snow. (c) The top surface of ice shelf has high average strength from March to October and below-average strength during the remaining period. The average values are presented in Table 4.2 and Fig. 4.3.

4.9.2 Snow Precipitation a. Snow precipitation measurements before construction of the station were not available, and also they could not be carried out during 1984 due to non-availability of proper instruments. However, most of the precipitation takes place during blizzards, though some snow precipitation was observed during non-blizzard days also. Taking into account an average accumulation

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of 70 cm of snow on the stakes with an average density of 0.4 gm/cc, the precipitation in terms of equivalent water works out to approximately 28 cm. However, this figure may be very deceptive for realistic estimates as most of the snow is carried to coastal regions by katabatic winds. A large part of the information given above was gathered through various sources while sighting the DG station and some was obtained later while wintering in the DG station.

4.10 Site Selection of DG Station The most important and the foremost task before the Third ISAE was to select a suitable site for the station prior to reaching Antarctica so that minimum time is spent between reconnaissance for the suitable site and other preparations. Keeping this in mind a thorough study of the general area was taken up with the help of maps, aerial photographs and other information available through various sources. During this study, those members who had participated in the past two ISAEs were consulted and their views considered. Since no guidelines for sighting the Antarctic station on an ice shelf were available, the Third ISAE drew their own guidelines after a thorough discussion with all members and with the ship crew. The guidelines drawn are as under (a) The site should have accessibility from the seashore as well as from the Russian winter convoy route throughout the year, (b) It should preferably be on a level patch so that it does not attract excessive snow accumulation (drift snow) during blizzards. (c) The area should not have crevasses in the general area. (d) It should have enough dispersal area for dumping of construction stores and other logistic items like fuel barrels, food dump, etc., as well as parking of snowmobiles like Pisten Bully, cranes, etc. (e) It should have all-round unobstructed vision to avoid any monotony to the wintering party who would be staying in the station during winter months, which experience two months of polar night. The sites identified and considered, with their merits and demerits, are described below.

4.10.1 Sites A and B Near the Shelf Edge and Ski-Way Hut (Refer Sketch) The sites were just 5 km and 1 km, respectively, from the edge of the ice shelf. The general area had hard ice on its surface with some intermittent cracks. The snow

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which had got accumulated during blizzards was getting eroded due to severe wind activities, which were more intense in this area than in any other place away from the coast. Consideration of the site being so close to the edge of the shelf was considered as a negative point as it would present higher chances of it becoming an iceberg. Also, there was a higher probability of crack formation in the foundation structure due to its being on hard ice instead of on snow. The other technical ground for their rejection was that this area being the farthest point from the Strandcrack region, would experience maximum movements during the movement of the shelf during swells in the sea underneath.

4.11 Sites C and D on the High Grounds Covered with Ice These two high grounds were very closely observed from the air. It was seen that the high grounds on the top and on slopes had a broken texture. In daylight, by reflection of the sunlight, one could clearly notice the long wind-swept slopes of blue ice having intermittent patches of white freshly accumulated snow as well as the old snow. This indicated that gaps between the blue ice which were 1–2 m wide were the crevasses and covered by the snow accumulated by the wind. This snow further got compacted by melting and freezing due to radiation and freezing by the wind. There was a possibility of these blind crevasses opening in peak summer. It was felt that team members’ movements throughout the year would be totally confined to the high feature due to crevasses and fierce wind activity, and the snow on the convex slopes is in the tension zone and hence more prone to cracks would severely affect the stability of the building structure.

4.12 Site E Between the Shelf Edge and Strand Crack Region This site was on a flat piece of the ice shelf and had an open area around. It was 20 km south of the shelf edge, and 20 km north of the riverside area. The surface in the top strata had an accumulation of freshly accumulated snow of up to 40–50 cm, then a hard-icy layer of 5–10 cm and then a medium-hard snow layer of 15–20 cm. This indicated an ideal surface for a building foundation as well as presented less possibility of crack formation due to shelf movements caused by swells in the seawater below the shelf. There were no apparent crevasses since the area was generally flat. Another important plus feature was that from this site one could see the icebergs in the north, Schirmacher hill and Wohlthat ranges and ice-free rocky peaks in the south, and the high features on north–east and north–west, which broke the monotony of an isolated observer. From the physical fitness point of view, the general area provided enough

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place to move around for work as well as for exercise. The last site which, after some discussion and prodding by avalanche/crevasse probing rods, was accepted by all. All the points mentioned above were discussed while sailing, and the site selection was finalized before we touched the ship berthing point. After reaching the shelf edge, we had a confirmatory reconnaissance by air and later on ground and we noticed that the points deliberated, and inferences drawn were logical and accordingly the site E selected was approved. During ground reconnaissance, the station building was sited in the east–west direction, with the front of the building facing the east which was the windward side, and the length of the building oriented along the wind direction.

4.13 Dakshin Gangotri Station The station was planned with two double-storey blocks A and B, linked by a narrow single-storeyed passage which was termed as C block. The total floor area was approximately 800 m2 , which was based on a raft type of foundation, to ensure even distribution of the load and to avoid unequal sinking in the snow. Timber was the basic material used for the prefabricated panels. The A and B blocks each had 11 portal frames made of wooden panels as the main structural members, which were 6 m high and suitably attached to the foundation beams. The foundation raft with the 60 cm and 30 cm deep beams placed in a grid type arrangement was placed on a hard ice layer which was obtained by digging 1 m deep trenches in ice. To further ensure a proper levelling of the ice surface as well as a higher bearing capacity, the ice layer was required to be covered with Corrugated Galvanized Iron (CGI) sheets, of which a large number had been lost during the helicopter accident. The side walls also consisted of 100 mm thick timber prefabricated panels of marine plywood sheets of 9 mm thick, attached to the two sides of a timber load-bearing frame. The space between the two faces was filled up by a timber load-bearing frame. The outside face of the structure was protected by cladding, consisting of a 25 mm thick layer of insulation material over which metallic sheets were bolted. Internal finishing varied from area to area, depending on the utility. The radio room had acoustic tiles, while the generator and boiler rooms were provided with asbestos lining. The kitchen and the bathrooms had melamine faced plywood. Internal finishing in all other rooms was provided with hardboard. Out of the two blocks, block A housed essential services including generators, the fuel supply system and various workshops on the ground floor, and storage space on the first floor. Block B had laboratories, kitchen, dining room and lounge on the ground floor, while the first floor had two-man bunk rooms, radio rooms and toilets. In all, there were six bunk rooms to accommodate twelve members of the wintering party. An office provided for the base commander was later modified to serve as office cum living accommodation for the base commander. In addition, some space was left for provisioning of additional bunk rooms as and when required. The station was energized by electrical power generated by three 62.5 kva threephase generators, of which one was for running, one for maintenance and one as

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a standby. The peak load of the entire station was 40 kva initially at the time of commissioning the station, and later got increased to over 50 kva. In addition to the main generators, there were two 12 kva generators of M/s Kirloskar make, six 1.5 kva Honda generators to assist the construction party. A weekly fuel storage tank of 4,500 L capacity was provided within the station from which the fuel was pumped to daily storage tanks for the generators and boilers. Boilers were provided for central heating as well as for the snowmelt plant for melting ice for providing water supply for various purposes. Heating to maintain a steady temperature of 15 o C was done through close-circuit hot water pipes and radiators. All wastewater was discharged into the underground twin drains. Arrangements were also made for the circulation of fresh hot air in living spaces, and exhausts of the same were provided at suitable locations. A modern kitchen was provided, having facilities for cooking on power and gas. The station was also provided with a small operation theatre and a medical room with adequate storage of drugs. The water supply was through snow melting plant of capacity 1000 L installed on one side of the B block, which had a hatch from which snow could be shovelled from outside. After shovelling one had to wait for about half an hour for snow to melt. Melting of snow was through the circulation of hot water mixed with anti-freeze from the boilers. After the snowmelt tank was full, the water had to be pumped in the storage tank provided in the bathrooms. The toilets were Humus type toilets, where night soil got converted to air and some negligible quantity of soil waste, which could be taken out once in a fortnight. After each use one had to add some humus in the toilets and churn the night soil through a handle provided for the purpose above the seats. Continuous circulation of hot air was essential for the smooth operation of the toilet system. It was provided with a satellite communication system with the operating terminal inside the radio room and receiving and transmitting line on the C block. This system, which was linked to INMARSAT, provided telephone and telex links on global basis and had facilities for telefax and slow scan TV transmission. The station was designed to house laboratories on the ground floor in B block, where meteorological, microbiological and glaciology labs were planned. Some facilities for atmospheric studies were also planned. Additional storage facilities were provided in the loft, which was obtained through the space between the trussed roof panels and the ceiling panels of the first floor. The entire building was designed to withstand 80 knots of wind velocity. The stability of the building against the wind was ensured by the deposition of snow on the 1 m extended foundation all around the structure. Additional safety was provided by anchoring the entire building by means of straps that were put over the roof with lower ends buried in suitable anchors in ice. The expedition was equipped with four snowmobiles (Pisten Bully) of which three were for passenger carriage and one with crane attachment. It had two German sledges known as Nansen sledges. It had two mechanically operated hand snow cutters for snow cutting. It carried 1200 barrels of Jet A1 fuel for operation of vehicles and other plants, for which a fuel dump was created close to the station.

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4.14 Chronology of Construction and Life Support System Installation The ship reached the pre-decided ship berthing point termed as Indian bay 70o S 12o 45o E, about 100 km away from the station site on 26 December. It was berthed alongside the fast sea ice at about 10 km from the shelf edge. Unloading of vehicles and essential construction items commenced immediately, with everyone assisting the construction party. On 27 December, layout of the building was done and commenced with the help of Pisten Bully blades. On 28 December foundation digging was completed and laying of the foundation was taken up and completed by 29 December morning. Meanwhile dumping of construction stores commenced through Mi8 helicopters by under slinging operation and essential stores started arriving. Transportation of stores also commenced through surface routes with the help of sledges towed by Pisten Bully vehicles and all activities were in full swing with a lot of enthusiasm and team spirit. While all this operation was on, one Mi8 helicopter with underslung load comprising some foundation structural items crashed in the sea, very close to the ship. Luckily the entire crew of five personnel comprising IAF personnel survived by managing to come out through a slit specially created in the bailey of the aircraft for observing the under slung operations. Because of this mishap all underslung operations were suspended and essential stores were carried by loading the second Mi8 helicopter in the fuselage. On 01 January 1984, the aluminium helipad sent by DRDO was made close to the construction site and all dumping of stores was commenced by landing the helicopter on the helipad. By 05 January, the foundation was completed, and work commenced on the superstructure, and by 15 January the entire superstructure of the station was completed and work on fixing the cladding was taken up. By 01 February, entire structure was completed and works on installation of life support systems were commenced and by 15 February, the station was ready except for some essential systems like water supply and power generation. On 24 February, all systems were ready and vigorous testing of all was commenced. Earlier the station was hit by a major blizzard on around February 15–16 and the ship had to go much away from the shore and had to remain there for a long time, which resulted in excess consumption of fuel. The ship crew warned the expedition about the onset of early winter and the ship running short of fuel in case of another blizzard was encountered. Keeping this in view, the date for shifting the wintering party in the station was decided as 24 February. The station was handed over to the wintering party after a systematic briefing about all systems. On 25 February the area experienced another major blizzard for two days when all outside operations had to be suspended. On 27 February all except the wintering party of 12 personnel left for the ship after briefing the wintering party about various systems. By this time all systems had been tested and found suitable for survival and sustenance of the wintering party. Due to some problem two of the three 62 kva generators for power supply were not fully operational and fault finding was in progress. The engines of the two were in working condition but the required output was not coming. To overcome the crisis the standby

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Plate 4.1 Summer camp of construction party Dec 1983–Jan 1984

generators of 12 kva and other small sets taken from India were commissioned and established at suitable locations. A plan for running the essential systems on the limited power available was drawn and rehearsed, and preparations were made to face the crisis in case the third generating set also packed up. Plates 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13, 4.14, 4.15, 4.16 and 4.17 highlight various activities/events related to the establishment of Dakshin Gangotri station.

4.15 Performance of the Station Set up During Winter 1984 The ship sailed on 01 March, with a lot of reservations in the minds of the summer party about wellbeing of the wintering party, as this was the first time when a group of 12 Indians coming from different backgrounds, with little knowledge and understanding about each other were sharing a newly and freshly commissioned accommodation at an isolated place on ice, much away from their homeland, in the most unknown hostile conditions. Immediately on 01 March work on completion and testing of the remaining systems, fixing of cladding on the outer walls, shifting of fuel barrels close to the station, retrieving and taking stock of the food container boxes buried in the blizzard snow, and many other activities commenced, and by 10 March the wintering party was able to clean up the station and instal most of the systems. On 14 March the area was hit by a very major blizzard with wind velocity in the range of 70 kts

4 Dakshin Gangotri Station: The Pride of India

Plate 4.2 Foundation laying—DG station Dec 1983

Plate 4.3 Helipad on ice for Mi 8 helicopter—Dec 1983–Jan 1984

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64

Plate 4.4 Superstructure construction DG station—16 Jan 1984

Plate 4.5 DG station after commissioning—24 Feb 1984

S. S. Sharma

4 Dakshin Gangotri Station: The Pride of India

Plate 4.6 First wintering team DG station—March 1984

Plate 4.7 Kitchen DG station March 1984

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Plate 4.8 Bunkroom DG station—March 1984

Plate 4.9 Construction party—summer 1984

S. S. Sharma

4 Dakshin Gangotri Station: The Pride of India

Plate 4.10 DG station after 15 March 1984 blizzard

Plate 4.11 Vehicles buried in drift snow—May 1984

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Plate 4.12 Scientific work on snow mechanics in progress on ice shelf DG station-June 1984

Plate 4.13 Flag hoisting—DG station 15 Aug 1984

4 Dakshin Gangotri Station: The Pride of India

Plate 4.14 After the flag hoisting 15 Aug 1984, Temp −45 °C

Plate 4.15 First wintering party left alone after sailing of Ship—01 March 1984

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Plate 4.16 First wintering party of DG station with the PM Sh Rajiv Gandhi—Jul 1985

Plate 4.17 DG station during full moon—Feb 1985

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Fig. 4.1 Layout of Indian base in Antarctica

with gusting up to 100 kts, which shook the entire structure. Since the entire structure was exposed to outside wind, there were a lot of vibrations and swing of the structure, which created a sort of panic in the minds of the wintering party. Continuous observations were made, and leakage points plugged, and the susceptible areas strengthened. Disaster management drills for various possible mishaps were evolved and rehearsed. On 14 March generator exhaust duct made of foam panels collapsed and part of the roof of A block was exposed, which was immediately repaired. On 15 March the straps holding and anchoring the station to shelf ice had to be cut as because of them there were excessive noise and vibrations in the station building which disturbed the members. On this day, the snowmelt tank had to be filled from outside by the wintering party personnel by going out in severe blizzard after tying ropes and moving very carefully close to the wall. The blizzard lasted for five days and caused a lot of disruptions and buried a lot of items that were left outside. During this period, investigations on the two generating sets were in progress with continuous dialogues with their suppliers in West Germany. The maintenance team detected the wearing out of the couplings between the engines and alternators and took suitable action by improvising the replacement by fabricating the couplings from some ordinary rubber. This improvisation worked, and the power position improved. The defect had occurred while synchronizing the running of two generating sets simultaneously for meeting the requirement of excessive load.

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Fig. 4.2 Typical density profiles taken in Dakshin Gangotri ice shelf during summer and winter, 1984

In early April, one of the biological toilets started giving foul smell as due to lack of heat inside the toilet seat, the humus was not effective and the entire night soil was in wet condition. This had to be cleaned manually and the system was re-commissioned. In May end outside temperature dropped to as low as −45 and blizzards were too frequent. Because of this, there was an excessive load on the heating system, which was obvious from the noise it was producing and also the

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Fig. 4.3 Variation of average values of Ram hardness in kg with time in Dakshin Gangotri ice-self, during 1984

station remaining generally at about 15 C. To take care of this the air heating system in both the blocks was switched on. One of the snow vehicles having crane attachment packed up in March, which became a severe handicap in lifting the fuel barrels from the fuel dump. Also, since the repair garage’s door in A block was too narrow all vehicles had to be left outside in open, which resulted in their totally getting filled up with snow due to blizzards. The polar night set in on 21 May and lasted till 21 July with outside temperatures on the shelf dropping to below −55. Nevertheless, by this time most of the things were in shape and going was generally good. On 25 June battery of one of the vehicles exploded while the EME personal working on it was tightening the terminal attachment for charging. This caused spurt of acid on the face of the person handling the operation and severely damaged his eyes. Luckily, he escaped without any major damage. This accident was because of excessive dryness inside the station. On 29 June Mrs. Indira Gandhi, the then Prime Minister of India talked to the leader of the wintering party and conveyed her appreciation and best wishes. By August end more than half of the station building was buried in snow and the team members had to use the roof hatches for their entry and exit. November brought a lot of cheer with rising temperatures and continuous sunshine and a feeling of having gone through the worst period of our stay in the newly built DG station. On 27 December the first sortie of the 4th ISAE landed close to the station and summer activities for handing over the station to the new team commenced. The station was finally handed over on 20 March 1985 after full briefing and after running all

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systems jointly. The wintering party moved to the ship on 27 March and sailed for their homeward journey in ship MV Finn Polaris.

4.16 DG in the Following Years In the following years, in 1985–86 the station was completely buried in ice and no part was visible. The later expeditions had to erect hatches in the roof at various points for accessing the station. The vision outside was totally obstructed and there was always a fear of the structure collapsing because of excessive snow load. In 1988–89 the second permanent station Maitri, indigenously designed by R&D E (E), Pune (DRDO), was commissioned at Schirmacher Oasis, and the DG station was finally abandoned and closed in 1989–90. The point to note is that at the time of abandoning the station all systems were fully functional and a lot of items could be retrieved for use at other places in Antarctica. In the opinion of the author, it speaks very high of the personnel who planned and commissioned the station and the maintenance personnel from the Corps of Engineers and EME who were in charge of the station in the following years.

4.17 Conclusions Establishing the first Indian station and commissioning the systems was a unique experience and the achievement of the Third ISAE. Spending the first winter in its midst and running the station successfully without any mishap, while carrying out research in the respective fields can be termed as a giant step in elevating the prestige of the nation in the world’s scientific community. It would not be wrong if the above is termed as an unparallel historical step of a very major programme of Indian scientific exploration, with participation of a large scientific community coming from various laboratories, and active involvement of the Armed Forces. Though DG station does not exist today in its functional form, but it served the purpose for which it was planned and established. The present station Maitri is fully functional and planning for the third station is in an advanced stage by the NCAOR. And in due course many more Indian stations with state-of-the-art facilities will come up, but it will not be an exaggeration to say that the aim of constructing the Indian Station Dakshin Gangotri as a first step and the contributions made by it will always be appreciated and remembered.

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References Korotkevivich VS (1978) Drilling through the ice shelf in the vicinity of Novolazrevskaya. Annual scientific report on Antarctica studies of USSR, p 50 Richter W, Strauch E (1982) Deutorium and 18 O variations in lakes of the Scirmacher Oasis (East Antarctica). Scientific report on Antarctic studies of GDR, pp 56–58 Sharma SS (1986) A study of Dakshin Gangotri ice-shelf. Third Indian expedition to Antarctica, scientific report scientific, 1986. Department of Ocean Development, Technical Publication No. 3, pp 243–248

Chapter 5

Communication from Antarctica M. K. Dhaka

5.1 Introduction Defence Electronics Applications Laboratory (DEAL), Dehradun began participating in Indian Antarctic Expeditions (IAEs) from 11th IAE (1991–92) by conducting experiments on HF communication between India and Antarctica. HF propagation studies using HF beacon, voice and packet data exchange were carried out till 13th IAE. Thereafter, in 15th IAE (1995–96), DEAL was assigned the larger responsibility by erstwhile Department of Ocean Development (now Ministry of Earth Sciences) to take over and improve the total communication at Antarctica apart from carrying out its research interest. This included long-range and short-range communication. The long range of approximately 12,000 kms could be negotiated using satellite and HF media, whereas short-range communication could be provided using several means like VHF/UHF or even HF and satellite media (as shown in the Fig. 5.1). DEAL has been providing voice, fax, telex, email and weather fax data services to the expedition members.

5.2 Salient Achievements Ever since 15th IAE till date, DEAL has been improving communication facilities at Maitri. Few of the DEAL team achievements are summarized below:

M. K. Dhaka (B) Defence Electronics Applications Laboratory, Raipur Road, Dehradun 248 001, Uttarakhand, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_5

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Fig. 5.1 Communications in Antarctica

1. Replacement of 5 kW and 1 kW HF transmitters by 100-W HF transmitter and directional Log periodic antenna for HF communication (15th IAE) removed electrical interference within Maitri station; lowered power taxation on Gen sets; vacated one living room without losing out on the quality of HF communication. 2. Installation of bust of father of the nation, Mahatma Gandhi in the icy continent dedicated to global peace and science on 26 January 1997, to mark the 50th anniversary of independence—DEAL provided near real-time picture transmission of the event between PM residence, New Delhi and Maitri, Antarctica. 3. GPS mapping of the convoy route. 4. Introduction of new services like email, Internet. 5. Indian station Maitri was placed on the global amateur net with special call signs VU3AXA and AT3D. 6. Introduction of smaller INMARSAT terminals with digital modulation and compressed speech. 7. Installation of unmanned VHF repeater station at Vetttaiah hill for shadow-free communication between India bay and Maitri for the entire convoy route. 8. Introduction of Ground plane antenna for HF/VHF communication.

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5.3 Experiments in Antarctica DEAL Scientists also carried out some very interesting experiments in Antarctica. For example, Antarctica provided a unique platform to study multi-hop behaviour of ionosphere at high-frequency band of 3–30 MHz. Significant improvement in HF communication window was observed by employing automatic link establishment (this uses a combination of rate, FEC and modulation scheme adapting to channel conditions). Effect on HF communication was correlated with geomagnetic data and some very interesting results were reported. Interesting results in VLF signal recordings were observed but this experiment could not be repeated for some meaningful conclusion. Another experiment was to detect man-made structures in Antarctica using RADARSAT SAR satellite images using Weibull distribution and its verification with the ground truth information. A brief account of various experiments related to communication at Maitri station is provided below. HF High-Speed data with frequency management: Presently HF voice communication is used as an emergency means of communication with plain vanilla HF transceiver. The situation can be highly upgraded by using Adaptive HF communication sets installed at Maitri, NCAOR and DEAL. These sets can automatically set up the links with the best available frequency at that time. With the best channel available and advanced modem, high-speed error-free data can be transferred in HF band. During previous expeditions, this has been tried with encouraging results on an experimental basis between Maitri and DEAL. Establishing Link with HAMSAT: HAMSAT is the Indian satellite launched for the Amateur radio operations with the operating frequency of 435.25 MHz and link frequency of 145.9 MHz. HAMSAT can be very helpful, when all other means of communication fail especially at the time of the disaster, experiments are being done to establish a link with the HAMSAT at DEAL. Once the setup is developed at Maitri, it can be very useful for the team members to communicate with Antarctic stations of other countries. Transmission of image data over HF band in the form of Progressive JPEG: The advantage of progressive JPEG is that if the image is being viewed on-the-fly as it is transmitted, one can see an approximation to the whole image very quickly, with gradual improvement of the quality as one waits longer. Transmission of the progressive JPEG images will be done over HF band. Normally commercially available software supports only baseline JPEG, so in-house development of the software for encoding and decoding the progressive JPEG is done. SAR image interpretation: Verification of the results obtained by processing of RADARSAT SAR data of the Antarctic region is attempted. This includes detection of man-made features, ice segmentation and sea-ice classification. DEAL feels strongly to continue experimentation with Adaptive HF set as this serves not only a means of understanding propagation channel behaviour for high frequencies over multiple hops but also emergency communication tool. HF Adaptive communication system should be installed at Maitri, DEAL and NCAOR. With little

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training, all the three nodes can exploit the cheapest mode of communication. This would generate lot of domain knowledge about multi-hop HF communication and will help in selecting the right frequencies throughout the year. DEAL has been successfully providing the total communication requirement of this national mission since the XV expedition with the cooperation of MoES/NCAOR. The Indian base station Maitri has been made fully equipped with adequate modern communication infrastructure to meet the vital communication need. Still, there is a need to augment it with high-speed data connectivity for realtime scientific data transfer from Antarctica to mainland. Recently established video conferencing facility has been an added advantage. It is strongly recommended that the Department of space may be approached to provide an Indian satellite footprint over Antarctica so that India can have its own fat pipe for voluminous scientific data transfer. DEAL is committed to provide efficient and reliable communication service between India and Indian Scientific Expeditions at Antarctica.

5.4 Dedicated Satellite Link with Maitri To facilitate online data transaction with Maitri research base at Antarctica, communication as well as entertainment at Maitri Earth Station receptor at NCAOR, a dedicated “Satellite Communication Link” connecting Indian Research Base “Maitri” in Antarctica and National Centre for Antarctic and Ocean Research (NCAOR), Goa has been established since 2009 in collaboration with Space Applications Centre, Ahmedabad and Electronics Corporation of India Limited (ECIL), Hyderabad. The facility has been created by installing a 3 m C-band antenna enclosed in a RAYDOME at Maitri and a corresponding 7.2 m antenna at NCAOR, Goa. Both these stations are communicated through a geostationary-Intelsat IS 1002 satellite (Figs. 5.2, 5.3, 5.4 and 5.5). Satcom link will provide 24 × 7 connectivity @ 1 mbps that facilitates online collaboration, online real-time data transfer, video conferencing, email and web browsing facility and live television broadcast.

5 Communication from Antarctica

Fig. 5.2 Earth station at Maitri

Fig. 5.3 Antenna inside the dome

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Fig. 5.4 System room in Maitri Station

Fig. 5.5 Video screen installed at Maitri station

M. K. Dhaka

Chapter 6

Commercial Polymers and Their Utility in Polar Regions Bhupesh Sharma, Pawan K. Bharti, D. A. Dabholkar, U. K. Saroop, A. K. Aggarwal, V. K. Verma, and K. M. Chacko

6.1 Introduction Shriram Institute for Industrial Research (SIIR), Delhi, has been involved in the National Antarctic Mission and participated in the IV, XVII and XVIII Indian Scientific Expedition to Antarctica (ISEA) in the years 1984–1985, 2007–2008 and 2009– 2010, respectively, by sending expedition members (Dabholkar et al. 1986; Sharma 2013), and following research work was undertaken: 1. Preliminary study of some commercial polymers and their utilization in the Antarctic climatic conditions during IV and further extended in XVII and XVIII Indian Scientific Expedition to Antarctica (ISEA). 2. Development of fire-resistant paint and lead-free radiation-resistant PVC for Antarctica. 3. The weathering studies at ambient condition were carried on optimized PVC formulation during XXVII–XXVIII summer Indian scientific expedition to Antarctica. The Schirmacher Oasis is situated at about 100 km inside Princess Astrid Coast of Queen Maud Land between the ice shelf and the continental ice dome in Antarctica continent. The area is oriented approximately in the east–west direction. The northeastern and north-western corners of the area are on ice shelf, while the south-western extremity is on polar ice sheet. The south-eastern end lies on a rocky outcrop. It is about 5.5 km in maximum width and 17 km in length and covers about 70 km2 area B. Sharma · P. K. Bharti · D. A. Dabholkar · U. K. Saroop · A. K. Aggarwal · V. K. Verma · K. M. Chacko (B) Shriram Institute for Industrial Research, 19, University Road, Delhi 110 007, India e-mail: [email protected] B. Sharma e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 N. Khare (ed.), Engineering and Communications in Antarctica, Springer Transactions in Civil and Environmental Engineering, https://doi.org/10.1007/978-981-15-5732-3_6

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of low-lying hilly area. Its elevation is ranging from 0 to 228 m with an average of 100 m at sea level. The geographical co-ordinates lie between Latitudes from 70° 44.21 S–70° 46.04 S and Longitudes from 11° 26.03 E–11° 49.54 E. The average annual temperature is –30 °C, and mean wind velocity is about 10 m/s. The average snow precipitation ranges between 250 and 300 mm and relative humidity is 15– 20%. Air temperature ranges between –5 and +9.2 °C during summer months and between –12 to –60 °C during winter. During summer, the polar ice melts, and water often flows into the lakes. The valleys are ice-free because the mountains block the flow of ice from the polar plateau, and low precipitation and strong winds lead to little accumulation of snow in the area. Indian scientific base Maitri in East Antarctica was established long back in the year 1989 in the Schirmacher Oasis. Since then it has been a permanent Indian scientific base at Antarctica and is being operated throughout the year to carry out purposeful research in different scientific fields, comprising of Atmospheric Sciences, Earth Sciences, Geomagnetism, Biological and Environmental Sciences, Human Physiology and Medicines, Meteorology, Ecology, Glaciology, Geology, etc. It has facilities to conduct scientific research in several fields. About twenty-five scientists including logistic staffs stay here throughout the year. In the summer season, Indian scientists from different scientific fields reach here to carry out research in their respective fields. Antarctica with large desolate areas, snow and ice cover, few landmarks and hostile weather represents extreme conditions of low temperature and high wind velocity. A permanent Indian Station at Antarctica had a wooden structure. In view of the scarcity of water in this subcontinent, it was imperative to make the structure fireproof which could withstand the extremely low-temperature conditions (−65 to −70 °C). Shriram Institute for Industrial Research undertook the job of making the wooden structure fireproof. With this in view, a study to formulate and evaluate a suitable paint having inherent properties of resisting the flames, as well as fire retardancy, was undertaken during the IV expedition, and further study was extended on various polymeric materials for sustaining harsh weatherability of Antarctica.

6.1.1 Preliminary Study on Some Commercial Polymers and Their Utilization in Antarctic Climatic Conditions The effect of extremely low temperature and high wind velocity conditions existing in Antarctica has been investigated on various polymeric materials. The selection of polymeric materials ranged from simple polyolefinic polymers like Low-Density Polyethylene (LDPE), Polypropylene (PP) and Polyvinyl Chloride (PVC) to engineering and specialty polymers like Acrylonitrile Butadiene Copolymer (ABS), polycarbonate, PVCINBR, PVC/ABS and Polytetrafluoroethylene (PTFE). The polymeric samples were exposed to the Antarctic climate for a one-month duration during the IV expedition in 1984–1985. The one-month exposed samples

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were brought back and evaluated for thermal, mechanical and electrical properties. No significant changes were observed in the properties of the samples exposed for one month. Brittle and glassy polymers could be made useful at low temperatures by making certain modifications. Because of the superior properties of the polymers over wood and metals, these could find diverse uses in the Antarctic environment. For the practical part of the study, a methodological approach consisting of different tests and analytical methods were developed. Major changes or repetitions of tests were not possible within the available time; multiple measurements were only possible to a very limited extent. In our study, the cryogenic simulation investigations were supported by other supplementary tests and examinations such as tests on UV weatherability. Samples exposed at Antarctica were evaluated for tensile, elongation and hardness before and after exposure, and the examination of samples was carried out in the lab. These supplementary experiments were carried out in order to check the results from the propagated studies, i.e. to verify results and to identify contradictory results, and to be able to distinguish between laboratory and harsh natural conditions of Antarctica. Further, the study was extended for a longer duration of about 15 months during 2007–2008 and 2009–2010 on various polymers, and an effort was made to design lead-free, lightweight flexible radiation-shielding PVC material for Antarctica.

6.1.2 Development of Fire-Resistant Paint for Antarctica Bearing in mind the extreme conditions in Antarctica, a fire and flameproof paint was developed, evaluated and successfully applied to the wooden structure of the permanent Indian station at Antarctica. From the studies carried out, it was suggested that coating should be applied at every six months’ interval to keep the desired properties of the paint because the coating gradually degraded under extreme conditions of low temperature. Antarctica with large desolate areas, snow and ice cover, few landmarks and hostile weather represents extreme conditions of low temperature −65 to −70 °C. A permanent Indian station at Antarctica has a wooden structure. With this in view, a study to synthesize and evaluate a suitable paint which has inherent properties of resisting the flames as well as fire retardancy and at the same time can withstand extreme low temperature was undertaken. The temperature has a decisive effect on the matter and its properties; some materials which have very useful properties may be rendered useless in extreme cold or hot conditions. Hence, for the Antarctic conditions, the choice of material is very critical. As there is a scarcity of water in this subcontinent, it becomes a most important feature that the material should make wooden structure fireproof, and simultaneously, it should withstand the extreme low temperature conditions. The major causes for the loss of life in wooden fire (Baker 1981) accidents are i.

Flame and its heat

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ii. Suffocation due to toxic gas concentration iii. Suffocation due to smoke iv. Suffocation due to oxygen shortage. The major causes of the loss of life in a fire involving wood appear to be the generation of carbon monoxide through the thermal break down of cellulose and partial oxidation of carbon (Dev. India 1982; Stalker 1971). The rate of thermal degradation of wood depends upon the heat transfer through the wood, type of char formed and the rates of diffusion of the gaseous decomposition products and degradation of products during their passage through the char. If the rate of heating of wood is very high, the cellulose material nearly completely vaporizes during the pyrolysis process, leaving behind a comparatively small quantity of char material. The gases evolved on pyrolysis are highly inflammable hydrocarbon-rich mixtures. To avoid the loss of life and money from a fire burning the wood, several flame-retardant chemicals are mentioned (Pearson 1984; Lee 1980; Bhatnagar 1982; Farcnik 1977) such as tetrakis(hydroxymethyl)phosphonium chloride, boric acid, calcium chloride, sodium tetraborate, ammonium pentaborate, magnesium silicate, antimony trioxide, ammonium polyphosphate, sodium silicate, potassium silicate, dicyanadiamide, etc.

6.1.3 Development of Lead-Free Radiation-Resistant PVC for Antarctica Harmful effects of radiations were recognized very soon after the discovery of UV, X-rays and of naturally occurring radionuclides late in the nineteenth century. These harmful effects were visible externally on the earth resulting from radiation coming out from natural sources. It is well established now that the exposure to radiation, even in doses substantially lower than those producing acute effects, may cause a wide variety of harmful effects; it may not be easily distinguishable from naturally occurring conditions in some cases. There are available evidences that cell damage may occur even at the lowest levels of radiation. Therefore, all forms of radiation exposure should be minimized or avoided as low as reasonably possibly. Recently, there has been a great deal of concern about the toxicity of lead. Lead toxicity on human being is well documented. In that light, production of environmentfriendly lead-free radiation-shielding material with less weight compared to conventional lead-based shields is a challenging issue. The aim of this study was to design a lead-free, flexible radiation-shielding durable material for various health care application of harsh condition in Antarctica. The study was carried out between October 2007 and March 2009 with the objective of evaluating the environmental stress on the developed formulation after exposing at Antarctica. The focus of this study is with respect to the potential degradation impact of the harsh environmental conditions on the developed PVC formulations (Mersiowski and Stegmann 1999). In recent published studies, particular

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concern is expressed on the behaviour of PVC in harsh natural Antarctic cryogenic conditions, drawing attention to several aspects which require further study since the evidence obtained is inconclusive as well as need confirmation. For the practical analysis on how PVC products behave under the specific conditions of ambient Antarctic environment, a selected range of PVC sheets and market commodity polymer sheets such as LDPE, PP, polyester were selected in comparison, comprising both rigid and flexible, for long-life and short-life applications. The sample were exposed on a wooden pellet by properly clamping at the back side of Maitri station. A study of about one year time is extremely short for the investigation of the behaviour of PVC in such conditions. With regard to the task of technical specifications for the study, it appeared appropriate to investigate the first possible changes and the physico-mechanical characterization of developed PVC under Antarctic conditions. Initial and final studies on the selected sites were carried out, and the influence of various physico-mechanical parameters (tensile, tear strength, elongation, hardness, etc.) were assessed and evaluated. Among the various materials tested, Polyvinyl Chloride (PVC) compounded with radiopaque materials such as barium, tungsten, titanium and bismuth salts were found to be most suitable ingradient for making flexible lightweight, lead-free X-ray resistant garments and can be widely used in various harsh conditions for health care. In this research work, noble process technology has been adopted to develop a unique class of materials for use in the radiation-shielding applications. A composite structure of compounded PVC which consists of a non-woven fabric has been designed and investigated for radiation shielding and resistance properties. The research work involves the development of suitable PVC compositions which are stable to ionizing radiation up to 25 Mrad and subsequently investigated for attenuation ability of X-rays with incorporation of radiopaque materials to the polymeric matrix. The experimental work involves the development of radiation-resistant PVCbased formulations and X-ray attenuation measurements, both of which were carried out simultaneously. The PVC-based formulations were not only optimized for the purpose of radiation opaqueness but also stable against radiation. The measurements were performed with X-ray machine as irradiation source. Results of the test have revealed the improved attenuation property of PVC compound filled with radiopaque materials other than lead providing weight saving advantages. Further, thermal behaviour and weatherability of PVC compounds were also studied in detail including harsh ambient condition at the South Pole. The study work would be expected to serve as reference knowledge for various industrialists, professionals and scientists working in different areas related to excess background of radiation. The designers can adopt desired methodologies by using basic correlation between composition and mechanical behaviour of the compounds as guidelines derived from the outcome of this study. The regulators as well as consumers can adopt relevant parameters from the studies presented here for ensuring the quality of PVC-based materials. For further improvements in the practices, material scientists can take this work as a reference for further research studies in this field. In a nutshell, this study is targeted to serve as an important document that can

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be used in several ways for developing radiation-shielding materials for health care applications in harsh environment such as Antarctica.

6.1.4 Materials and Methods: Various raw materials used in the present experimentation were procured and are listed blow: I.

II.

III.

Polyvinyl Chloride (PVC): PVC were selected and procured; it was a suspension and paste grade resin suited for making PVC plastic sheet and PVC plastisols. PVC resin has a very fine particle size and high surface area. The bulk density (gm/cc) 0.57 and particle size (microns) 130–180 of PVC was used Plasticizers: The main primary plasticizer Dioctyl Phthalate (DOP) and secondary plasticizer Epoxidized Soyabean Oil (ESO) have been used in the preparation of PVC formulations. DiOctyl Phthalate (DOP): It is also known as 2-diethyl hexyl phthalate having molecular weight 390.56 and specific gravity at 27 °C (g/cm3 ) 0.983 ± 0.003 was used in making PVC compositions. It is a polar aromatic plasticizer whose particles behave like dipolar molecules and links chlorine atom to two polymer chains. C6 H4 (COOC8 H17 )2 is structurally formulated below.

IV.

Epoxidized Soyabean Oil (ESO): ESO has high molecular weight and provides plasticizing cum stabilizing action against degradation by heat and light of PVC compositions. It has excellent resistance to extraction by soapy water and also provides resistance to extraction by oil. It improves durability of PVC compounds towards UV light. The density of ESO used was 0.994 gm/cm3 , and the structural formula of ESO is given below.

V.

Thermal Stabilizers: In our compositions, density 1.080–1.100 g/ml at 25 °C of Octyl Tin Mercaptide (OTM) has been used as a thermal stabilizer. It is clear and yellowish liquid, effective both in colour and long-term heat

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stability of PVC compounds. The Molecular formula is C22 H44 O4 S2 Sn, and the structural formula of OTM is given below.

VI.

UV Stabilizers: The UV absorbers dissipate the absorbed light energy from UV rays as heat by reversible intramolecular proton transfer. Bisphenol A of density 1.20 g/cm3 has been used as UV stabilizer in the present study. Bisphenol A is an organic compound with the chemical formula (CH3 )2 C(C6 H4 OH)2 belonging to the group of diphenyl methane derivatives. It is a colourless solid that is soluble in organic solvents, but poorly soluble in water. Bisphenol A has boiling point 220 °C. Structural formula of Bisphenol A is given in the Figure below.

VII. Antioxidants: Antioxidants are used to terminate the oxidation reactions taking place due to different weathering conditions or to reduce the degradation of materials. The IRGANOX 1010 with melting range 110–125 °C, chemically known as Pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4hydroxyphenyl) propionate) HO(CH2 )2 C OOCH2 C4 has been used in the present study. It is a sterically hindered phenolic antioxidant, non-discolouring stabilizer for organic substrates such as plastics, synthetic fibres, elastomers, etc. It protects the PVC substrates against thermo-oxidative degradation. It has good compatibility, high resistance to extraction, low volatility, odourless and tasteless. The product can be used in combination with other additives such as co-stabilizers, light stabilizers and other functional stabilizers. Structural formula of IRGANOX 1010 is given below.

VIII. Lubricants: Lubricants are used for controlled release of PVC during processing from mill or calender rolls from the injection, compression or plastic moulds and also from the injection mould, extruder screws, cylinders and also in forming dies. In this study, stearic acid having boiling point 183 °C and butyl stearate of melting point 179 °C were used as lubricants in making PVC formulations. The Structural formulas of stearic acid and butyl stearate are given below.

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IX. Cross-linking Agents—Trimethylolpropane Triacrylate (TMPTPA): The use of poly functional monomers as an additive enhances the chemical crosslinking of PVC under certain radiation conditions. TMPTMA (C18 H26 O6) , a clear liquid with density at 25 °C 1.06 g/cm3 , was used as a cross-linking agent in PVC formulations in the present study, whose properties are given below.

X. Benzoyl Peroxide: Peroxides are used for crosslinking PVC. The crosslinking of PVC by peroxide enhances the penetration resistance and shelf life of PVC. Its molecular formula is [C6 H5 C(O)]2 O2 . It was used as a peroxide initiator in the present study. Structural formula of the chemical is given below.

6.1.5 Methods Various methods used in the present experimentation were explored and are listed below. I. Procedures for physico-mechanical property evaluation. II. Procedure for assessments of commercial polymers for evaluating the stability to simulate against long-term exposure to cold condition. III. Procedures for weathering study, weatherability in ambient conditions and TGA.

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Table 6.1 Composition of PVC plastisol formulations without cross-linking agent S. no.

Ingredients

Batch 1 Batch 2 Batch 3 Batch 4 Batch 5 Batch 6 Batch 7 (phr) (phr) (phr) (phr) (phr) (phr) (phr)

1

PVC

100

100

100

100

100

100

100

2

DOP

60

70

80

70

70

70

70

3

ESO

10

10

10

10

10

10

10

4

OTM

4

4

4

4

4

4

4

5

Al–04

0.5

0.5

0.5

0.1

0.1

0.1

0.1

6

Bisphenol A

0.5

0.5

0.5

0.5

0.5

0.5

0.5

7

Stearic acid

0.5

0.5

0.5

0.5

0.5

0.5

0.5

8

IRGNOX-1010 0.5

0.5

0.5

0.5

0.5

0.5

0.5

9

TMPTMA

–

–

–

1

3

5

10

10

Benzoyl peroxide

–

–

–

0.2

0.2

0.2

0.2

6.2 Preparation of PVC Plastisol and Casting of Sheet PVC plastisol composition was prepared by varying the content of DOP, ESO, TMPTMA along with performance additive. The required amount of PVC, DOP and other additives was properly weighed and mixed properly in a planetary mixer for about one hour at 600 rpm. Details of raw materials and their quantities are given in Table 6.1.

6.2.1 Casting of PVC Sheet Thin sheets of size 20 × 20 cms were casted on a glass plate of thickness 2 mm. It was kept in an oven at 180 °C for 45 min to facilitate proper curing of the material. The prepared sheet of the each composition has been evaluated for the physicomechanical properties. Effect of weathering on developed formulations was also studied from the artificial weathering chamber. The flow diagram adopted for making plastic sheet is shown in Fig. 6.1.

6.3 Characterization of Developed PVC Sheets The PVC formulations prepared were characterized before and after radiation for various properties such as I. Tensile strength and elongation II. Hardness

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Fig. 6.1 Process for making PVC sheet

III. IV. V. VI. I.

Tear strength Weatherability Radiation shielding Thermal stability. Tensile Strength and Elongation % of Samples: The tensile strength and elongation % of the different samples were determined as per ASTM D-638 using a UNIVERSAL INSTRON Testing Machine. The testing machine used for evaluation is shown in Fig. 6.2. The test samples were cut into the standard size according to the specification ASTM D-638-80.

Dumbbell-shaped specimens of PVC sheets before and after radiation are shown in Fig. 6.3. II. Hardness: Shore hardness is a measure of the resistance of a material to the penetration of a needle under a defined force. It is determined as a number from 0 to 100 on the scales A or D. The higher is the number, the higher is the hardness. Thermoplastic elastomers are measured in Shore A and Shore D as per ASTM. For hard materials, Shore D is used; while for soft/flexible materials, Shore A is used.

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Fig. 6.2 Universal tensile testing machine

Fig. 6.3 Dumbbell-shaped specimens before and after radiation

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Fig. 6.4 Specimens before and after radiation

III. Tear Strength: This test method describes procedure for measuring the tear strength of plastics. It is the ratio of maximum force required to rupture the specimen to the thickness of the test piece. Tear strength of the sample was determined as per the guidelines of ISD 624-91. Zig-ag shaped die was used for cutting the test specimens from the compression-moulded PVC sheets. All the surfaces of the specimen were free from visible flaws and scratches. Photographs of the zig-zag shaped specimens before and after radiation are shown in Fig. 6.4. IV. UV Weatherability Test (ASTM G154) Weathering is the adverse response of a material or product for climate often causing unwanted and premature product failure. The three main factors of weathering are solar radiation, temperature and water. UV radiation emanating from solar radiation causes considerable damage to the materials. The weathering behaviour of a plastic is one of the most important factors in assessing and selecting a plastic for outdoor applications. The selection of a material by simple mechanical properties may well be sufficient in many cases, but this is ineffective if the material loses strength or discolours in service. Testing for weathering is a complex process, but it is essential that the testing be carried out on the same plastic (compounded and processed) as is intended for the application. Testing using a pure plastic resin will give unrealistic results because the reactive products produced during compounding and processing will not be present. Laboratory testing can quickly assess the relative stability of plastics but has the major disadvantage that the quicker the test the lower the correlation to real behaviour in the field. It is common for a combination of tests to be carried out to determine the real response to the actual field conditions. In the laboratory, the PVC sheet specimens were exposed to the UV rays at the wavelength of 315–400 nm. Cycles of 20 h UV at 75 ± 3 °C followed by 4 h condensation at 50 ± 3 °C were used according to the ASTM G154 and GM11. The artificial UV chamber used in the study is shown in

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fig. 6.5 uv weather resistance test chamber

Fig. 6.5. The UV ray curing was carried out for 100 h which is equivalent to 30 days of natural weathering. The specimens are periodically repositioned during the exposure period to ensure that each receives an equal amount of UV exposure. Continuous water circulation is maintained in the chamber to ensure non-increase of temperature in the chamber. After the exposure period of 100 h in the UV chamber, mechanical properties of exposed samples are tested according to the ASTM standards.

6.3.1 Weatherability in Ambient Condition at Antarctica 6.3.1.1

Materials/Compounds

Types of virgin polymers, i.e. PVC (SR–10 A—Shriram Fertilizers and Chemicals), which were commonly used in industries for various purposes were processed. The polymer had melt flow indexes of 10 and bulk density close to (gm/cc). Two different

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Table 6.2 PVC compositions Material

PVC resins

DOP

CPW

ESO

Ba/Cd (ALA-180)

CaCO3

Stearic acid

PVC-I (Flexible)

100

40

–

4

4

–

1

PVC-II (Gloves)

100

20

16

2

4

50

0.5

compositions for PVC have been compounded for different types of purpose, i.e. flexible film. The composition of PVC is listed in Table 6.2.

6.3.1.2

Experimental Conditions

Specimen size:

1–5 sq. ft pcs. of optimized PVC formulations with other commodity polymers Exposure conditions: Ambient (The average annual temperature is −30 °C, and mean wind velocity is about 10 m/s. The average snow precipitation ranges between 250 and 300 mm, and relative humidity is 15–20%. Air temperature ranges between –5 and +9.2 °C during summer months and between –12 and –60 °C during winter.) Exposure period: Between December 2007 and March 2009 (15 months). 6.3.1.3

Environmental Effects

The study is niether to provide a description of the detailed characteristics of additives, nor to perform details of environmental stress and assessment with respect to leaching of the substances in question from cryogenic conditions, but to give a general overview of the potential environmental stresses on physico-mechanical properties of PVC. Within the framework of evaluation and control of the risks of existing limitations, the exposure for various samples were carried out. The focus is laid on the effects of physico-mechanical properties and on behaviour of plasticised PVC in cryo-condition to a certain extent. The details of the results are reported in this study.

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6.4 Gamma Irradiator and X-ray Machine Used for the Studies Neither gamma rays nor x-rays are radioactive. They are pulses of energy that move through space at the speed of light. Once released, there is no way to tell the difference in these two types of rays or their origin. It was realized that the energies of the two types of rays are overlapped. Hence, the simulated study against the stability of radiation was carried out for the development of radiation-resistant PVC compositions and the same was extended for development of lightweight, lead-free shielding materials by incorporating radiopaque salts. Shriram Applied Radiation Centre (SARC)—irradiation facility at Shriram Institute for Industrial Research, Delhi (India), was employed for assessments of different doses of gamma radiation and x-rays on PVC composition for evaluating the stability to simulate against long-term exposure to harsh condition of Antarctica. SARC irradiator plant is a fully automated and computerized plant consists of radioactive cobalt-60 (60 Co γ-ray) as a radiation source. It has a designed capacity to house 800 Kilocurie of 60 Co.

6.5 Preparation of Radiation-Resistant PVC Formulations and Sheets After developing PVC formulations against gamma ray, the plasticized PVC formulation was further optimized by incorporating stabilizers in different loadings of 100, 200, 300 and 400 phr. They were prepared by employing two techniques: (i) using suspension grade PVC and (ii) emulsion grade PVC resin for sheet and gloves material preparation by using Dry Blending, Roll Milling, Compression Moulding, Dip Moulding, etc.

6.6 X-ray Exposure of Modified PVC Formulations The samples prepared by the above method have subsequently been exposed to xray emanated from x-ray machine (Model–Allengers 525), as shown in Fig. 6.6, for evaluating the attenuation of developed sample, which determines the effectiveness of shielding property. SRI-developed polymeric x-ray resistant formulations were exposed to x-ray at 30, 40 and 50 KVP, respectively, using x-ray machine.

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Fig. 6.6 Allengers x-ray machine

6.7 Thermal Behaviour of PVC Material by Instrumental Technique 6.7.1 Thermogravimetric Analysis (TGA) One of the most important properties of polymers is its thermal behaviour. Knowledge of this behaviour is essential not only for the selection of proper processing and fabrication condition, but also for the characterization of polymers and selection of appropriate end uses. Keeping this in view, TG analysis of polymers has been carried out in isothermal mode for assessment of thermal stability and also in dynamic mode for assessment of Initial Degradation Temperature (IDT). Thermogravimetric Analysis (TGA) is a dynamic technique in which the weight loss of a sample is measured continuously when its temperature is increased at a constant rate. On the other hand, in isothermal mode, weight loss can be measured as a function of time at constant temperature. During the studies, TG analysis of PVC was carried out for the determination of thermal decomposition and its stability. Thermogravimetric analysis of PVC polymer can also be adopted for assessing the degradation behaviour of the polymers in isothermal and dynamic modes. In the dynamic mode, weight loss of a sample is measured continuously when its temperature is increased at a constant rate, whereas in isothermal mode, weight loss can be measured as a function of time at constant temperature. Thermogravimetric analysis has been adopted for the study of thermal decomposition and its

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Fig. 6.7 TGA instrument used for experimentation

stability. Thermogravimetric analysis was carried out using (TA Instrument Lab, USA) Model–2960, which is shown in Fig. 6.7. The rate of increase in temperature through its decomposition region was monitored. The weight loss was recorded as a function of temperature for decomposition.

6.8 Results and Observations Results and discussions show the observations made during the study on flexible PVC formulation development, effect on PVC compounds due to exposure to harsh condition of Antarctica for long time duration and different doses of gamma radiation. Behaviour of optimized PVC composition for x-ray shielding has also been observed under different environmental conditions. The details are described as below: I. II.

Characterization of developed flexible PVC compositions Effect of different doses of gamma radiation on PVC compositions for simulating the stability property by long-term exposure to weathering III. Effect of cross-linking agent Trimethylolpropane Trimethacrylate (TMPTMA) and PTFE on properties of PVC compositions IV. Effect on viscosity V. Weathering studies VI. X-ray shielding property optimization by exposure measurements using x-ray machine and simulation by gamma-ray cesium-137 radiation source. VII. Physico-mechanical and x-ray shielding properties of radiopaque-impregnated PVC compositions.

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6.9 Physico-Mechanical Properties The results of tensile strength, hardness, tear strength and elongation % at break of different samples before and after irradiation were measured and presented in various tables apart from depicting them in graphical forms. PVC samples were exposed to gamma irradiation with an intensity ranging from 25 to 100 Mrad using cobalt-60 as radiation source. Various PVC compositions were prepared by varying the concentration of DOP between 60 and 80 phr, and their physico-mechanical properties were studied. The effect of DOP concentration on the developed formulations was studied.

6.10 Effect of Gamma Radiation on Properties of PVC The effect of gamma radiation on the PVC compositions prepared by varying the concentration of DOP was studied by evaluating the mechanical properties of the compositions after exposure at 25, 50, 75 and 100 Mrad. Results obtained for tensile strength, elongation at break, hardness and tear strength are shown in forthcoming subsections. Effect on Tensile Strength: The above cited specimens were also subjected to gamma radiation doses ranging from 25 to 100 Mrad. The results obtained are presented in Table 6.3, and the same is represented in graphical form in Fig. 6.8. Taking a closer look at the results obtained from the experimentation, it is established that the tensile strength initially increases and decreases later, which may be attributed to the degradation and scissioning of chlorine atoms released during degradation. Effect on Elongation at Break: The above cited specimens were also subjected to gamma radiation doses ranging from 25 to 100 Mrad. The results obtained are depicted in Table 6.4 and also in graphical form in Fig. 6.9. Taking a closer look at the results obtained from the experimentation, it is established that the elongation at break initially increases and decreases later. However, on irradiation, elongation at break decreases. Table 6.3 Variation in tensile strength with variation in DOP and gamma radiation DOP (phr)

Tensile strength (MPa) Un-irradiated (UR)

Irradiated at 25 Mrad

Irradiated at 50 Mrad

Irradiated at 75 Mrad

Irradiated at 100 Mrad

60

11.83

12.33

70

10.64

12.09

13.4

9.52

7.7

13.01

9.1

80

9.34

10.27

7.85

12.3

6.81

5.8

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Fig. 6.8 Variation in tensile strength (MPa) with variation in DOP and gamma radiation Table 6.4 Variation in elongation at break (%) with variation in DOP and gamma radiation DOP (phr)

Elongation (%) Un-irradiated (UR)

Irradiated at 25 Mrad

Irradiated at 50 Mrad

Irradiated at 75 Mrad

Irradiated at 100 Mrad

60

478.4

348.04

296.7

214.5

146

70

498

393.44

288.2

222.7

166.5

80

627.2

395.9

214.3

159

150.8

Fig. 6.9 Variation in elongation at break (%) with variation in DOP and gamma radiation

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6.11 Effect of Trimethylolpropane Trimethacrylate (TMPTMA) and PTFE on Properties of PVC Compositions 6.11.1 Effect of TMPTMA on Properties of PVC Composition DOP concentration was taken as 70 phr for studying the effect of gamma irradiation on various properties. This concentration was considered for the present experimentation/study as viscosity at this concentration was 1613 cP, which is useful in rotational and slush moulding. This composition also retains the requisite physico-mechanical properties required for moulding different medical products. As the concentration of the plasticizer increased, a sharp decrease in physico-mechanical properties is observed. Keeping DOP at 70 phr, other cross-linking agents were changed in type as well as concentration to have first-hand information on variation in properties. Wilkes et al. (2005) had also stated that DOP is recognized as the benchmark plasticiser for PVC. They had classified that a DOP of 25 phr is semi-rigid PVC; between 35 and 85 phr DOP, PVC is considered as flexible; and above 85 phr, it is called highly flexible. Effect on Tensile Strength: The effect of tensile strength with variation in concentrations of TMPTMA was studied. The quantity of cross-linking agent (TMPTMA) was varied as 1, 3, 5 and 10 per hundred resins (phr). These samples are subjected to gamma radiation with doses ranging from 25 to 100 Mrad. Results obtained are presented in Table 6.5. The variation in tensile strength with variation in TMPTMA concentration and gamma radiation is also presented in a graphical form in Figs. 6.10, 6.11. It can be seen from the graph that with increase in cross-linking agent concentration, the tensile strength has increased significantly; but at higher phr, it has shown a reduced tensile strength, which imparts brittleness to the PVC sheet due to crosslinking. Effect on Elongation at Break: DOP concentration was taken as 70 phr for studying the effect of gamma radiation on various properties. This concentration was considered for the present experimentation/study as our viscosity at this concentration was 1613 Cp, which is useful in rotational and slush moulding. Keeping DOP at 70 phr, Table 6.5 Variation in tensile strength (MPa) with variation in TMPTMA and gamma radiation TMPTMA (phr)

Tensile strength (MPa) Un-irradiated (UR)

Irradiated at 25 Mrad

Irradiated at 50 Mrad

Irradiated at 75 Mrad

Irradiated at 100 Mrad

1

12.068

14.62

12.75

8.23

7.86

3

12.208

14.85

13.9

7.56

4.25

5

11.927

13.6

13.422

7.31

6.9

10

11.342

12.61

12.35

7.21

4.7

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Fig. 6.10 Variation in tensile strength (MPa) with variation in TMPTMA and Gamma radiation

Fig. 6.11 Variation in elongation at break (%) with variation in TMPTMA and gamma radiation

other cross-linking agents were changed in type as well as concentration to have a first-hand information on variation in properties. The effect on elongation at break with variation in concentrations of TMPTMA was studied. The quantity of TMPTMA was varied as 1, 3, 5 and 10 Per Hundred Resin (phr). These samples are subjected to gamma radiation with doses ranging from 25 to 100 Mrad. Results obtained are presented in Table 6.6. The variation in elongation at break with variation in TMPTMA concentration and gamma radiation is also presented in a graphical form in the figure. It can be seen from the graph that with the increase in cross-linking agent concentration, the elongation has increased significantly; but at higher phr, it has shown a reduced elongation at break, which imparts brittleness to the PVC sheet due to excessive crosslinking.

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Table 6.6 Variation in elongation at break (%) with variation in TMPTMA and gamma radiation TMPTMA (phr)

Elongation (%) Un-irradiated (UR)

Irradiated at 25 Mrad

Irradiated at 50 Mrad

Irradiated at 75 Mrad

Irradiated at 100 Mrad

1

618.4

387.44

193.6

181.1

169.44

3

653.6

342.16

201.7

175.74

132.42

5

665.6

271.46

196.44

138.3

119.88

10

650.4

143.78

281.9

267.44

185.9

6.12 Weathering Studies The sample which has been exposed to artificial weathering has been tested for different physico-mechanical properties, and the results of these specimens are depicted in Table 6.7. The results show that 3 phr TMPTMA is the optimum concentration for the plasticized PVC composition with increase in concentration of 5–10 phr TMPTMA; the physico-mechanical properties decrease including the tensile strength. Table 6.7 Variation in artificial weatherability Batch

DOP (phr) 60

Elongation at break (%)

Tear strength (N/mm)

Hardness (Shore A)

Before

After

Before

After

Before

After

Before

After

13.00

11.00

370

315

44.7

38

84

71

12.35

10.45

440

375

37.4

31.8

76

65

TMPTMA (phr) 1

70 80 60

Tensile strength (MPa)

3

70 80

11.73

09.90

530

450

33.4

28.4

72

61

14.30

12.80

410

370

49.2

44.3

92

83

13.56

12.20

485

435

41.1

37.0

84

76

12.90

11.60

580

525

36.7

33.0

79

71

14.00

11.20

400

350

48.6

38.8

89

71

13.26 12.60

10.60 10.00

480 575

385 460

39.8 35.8

31.8 28.6

83 77

66 62

13.30

09.90

380

285

46.2

34.7

85

64

70

12.60

09.46

455

340

36.8

27.6

79

59

80

11.97

08.90

545

410

34

25.5

73

55

60

5

70 80 60

10

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a

b

Fig. 6.12 a Sample before exposed at Indian scientific base Maitri, East Antarctica during twentyseventh ISEA, b sample after exposed at Indian scientific base Maitri, East Antarctica during twenty-eighth ISEA

6.12.1 Observation of Behaviour of PVC Polymer The studies on the behaviour of PVC conditions have been carried out during XXVII and XXVIII Indian Scientific Expedition to Antarctica (ISEA). In order to identify and observe effects, PVC products were exposed along with other polymers incubated under ambient conditions over a period of one year as shown in Fig. 6.12. PVC samples were investigated and both the effects of Antarctic UV radiation and cryogenic condition were analysed.

6.12.2 Photo Simulating Conditions To achieve comparability between tests and the real behaviour of PVC in Antarctic condition, PVC samples after exposure from Antarctica were analysed for physicomechanical properties. This approach was chosen in order to achieve comparability

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Table 6.8 Comparison of PVC-developed samples with market samples Property

Market PVC sheet

Optimized PVC sheet

Market polyethylene sheet

Before exposure

After exposure

Before exposure

After exposure

Before exposure

After exposure

Hardness (Shore A)

80

83

80

81

78

83

Density (gm/cc)

3.24

2.80

2.20

2.20

1.70

2.10

Tensile strength (kg/cm2 )

80

63

85

83

90

65

Thickness (mm)

2.52

2.65

1.90

1.92

1.70

2.0

and confirmation between observed effects. Therefore, most of the numerous experiments were carried out only one time. Similar effects resulting from different tests increase the reliability of results. In contrast, effects which occurred only in a single investigation are easy to identify as failures. However, conclusions of the analytical programme have to be seen as hints and have to be compared with results from other studies on the behaviour of PVC in Antarctica.

6.12.3 Visible Changes to the PVC Materials During Simulation The PVC material changes were clearly visible during the study. Both optically and mechanically, they showed enormous differences to the exposed materials. Changes could be observed on other market sheet samples. However, there were certain differences in the extent of the change according to the photo examination’s exposed sample. The sample procured from market showed the strongest change. The physico-mechanical results are reported in Table 6.8.

6.12.4 Behaviour of PVC Under Simulated Conditions The influence of test conditions on exposed PVC sample was clearly recognizable. Examinations showed differences between the raw materials and the incubated materials. The extracted samples showed homogeneities in colouring and hardness between and within samples; changes of the surface structure was visually confirmed by scanning electron microscopy (SEM). Different effects between samples result from specific material composition, the history (used or new material) and the test

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107

conditions. Homogeneities within one sample are caused by the surrounding material which is in contact with the sample and by seeping water flows. This fact causes variations in the results in investigations. Therefore, certain deviations within single examinations have to be seen as normal. A general distinction can be made according to material composition and between old and new PVC samples. Used plasticised materials show a higher susceptibility to exposed processes. This could be attributed to commencement of corrosion, water uptake and stress during exposed time. Developed plasticised PVC materials show lower degradation effects. Between used and rigid PVC almost no difference was detectable.

6.12.5 Effect on the Mechanical Properties The investigations of the mechanical properties of the materials exposed show more or less obvious changes of these properties for plasticised PVC samples. • Influence of temperature • Influence of UV radiation Plastics including PVC are regarded as a considerable part of the ‘friction mooring’ of Antarctic climate being responsible for the sturdiness of the exposed sample. The PVC quantity in relation to the total synthetic material content is rather small in comparison to the mass of other plastic materials like polyethylene. Decreased steadiness can cause high wind speed, bizarded lazers, snow fall, etc. on parts of exposed situated on the back side of Maitri station slope as photographed at sites. The contribution to PVC degradation to such effects cannot be thoroughly estimated but has to be considered in future design for Antarctic investigations. There is evidence that the mechanical properties of exposed sample of PVC are decreased. Thus, it is expected that this process will need a very long time assessment which cannot be estimated at a probably steady decreasing level. The behaviour of developed plasticised PVC along with other polymers was investigated in harsh Antarctic simulation studies. Plasticised PVC was exposed at Indian scientific base Maitri under −40 to 3 °C, for a period of one year in ambient conditions. The samples were also examined at lab condition. After conducting the above study and analysing the results, conclusion can be drawn that the developed plasticized PVC thin flexible sheet has negligibly changed under harsh Antarctic environmental condition as compared to market polyethylene and PVC sheet.

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6.13 X-ray Shielding Property Optimization by Exposure Measurements Using X-ray Machine 6.13.1 X-ray Shielding of Polymeric Compositions Taking the lead from the development of radiation-resistant polymeric composition by gamma-ray irradiation, it was found that the optimized composition was effectively stable up to 50 Mrad because the ingredient does not remain stable against gamma radiation at 50 Mrad. Above 50 Mrad, the material had poor physicomechanical properties because the ingredients are not stable to gamma radiation. Based on the experiment against gamma-ray stability, the x-ray shielding compositions were optimized by incorporations of lead-free radiopaque compound in the polymer matrix. X-ray shielding PVC compositions were prepared by incorporation of radiopaque compound into PVC matrix along with performance additive. The results of x-ray shielding of PVC composition are presented in Table 6.9. The x-ray shielding of the flexible radiation-resistant sheet and plastisol was found to be dependent on the nature of radiopaque incorporated and on the quantity of radiopaque impregnated. Further, minimum and maximum x-ray shielding was found to be 10% in case of bone powder and 80% in case of Bi2 O3 and TiO2 , respectively.

6.13.2 X-ray Shielding Comparisons of PVC Composition The result of x-ray shielding of radiopaque impregnated into the PVC resin are presented in Table 6.9 and Fig. 6.13. The results show that the extent of x-ray shielding was found to be dependent on the type of radiopaque used and, of course, on the intensity of x-rays. The x-ray shielding of the PVC compositions was found to be 10% in case of bone powder and rock phosphate, 60% in BaSO4, 70% in TiO2, 70–74.5% in case of WO3, 80% in tungsten/TiO2 mixture and 80% also in case of Bi2O3. Further, x-ray shielding of lead sheet, lead glove and lead apron was found to be comparable to the lead-free PVC compositions studied. The intensity of x-ray shielding was also observed on various formations of developed PVC; the results shown in Fig. 6.14 at 30 and 40 KVP are comparable with lead compositions.

6.13.3 X-ray Shielding of Lead and Lead-Free Composition The result of x-ray shielding of lead apron, lead glove and developed lead-free glove is presented in Table 6.10. The results show that the extent of x-ray shielding were found to be dependent on the type of radiopaque incorporated. The maximum extent of x-ray shielding was found to be 80% in case of PVC. Further, the x-ray shielding

100

100

100

100

100

100

100

100

100

1

2

3

4

5

6

7

8

9

60

60

60

60

60

60

60

60

60

2

2

2

2

2

2

2

2

2

5

5

5

5

5

5

5

5

5

2

2

2

2

2

2

2

2

2

Quantity 200

200 100

300

TiO2 Tungsten dioxide

Nil 200

Nil

Bone powder 200 Rock phosphate 100

Rock phosphate 400

TiO2 Tungsten

WO3 Tungsten oxide

Bi2 O3 Bismuth 300 oxide

BaSO4 Barium sulphate

Tungsten oxide 200

S. PVC DOP OTM ESO St. Acid Radiopaque no. Name

Table 6.9 PVC compositions and % X-ray shielding

2.04

2.04

1.90

1.90

1.90

2.34

2.84

2.04

2.23

75

75

78

78

78

75

79

75

73

60

60

56

56

56

48

82

60

103

210

120

140

140

140

60

155

80

175

70

0

10

10

80

74.2

80

60

70

Density (g/CC) Hardness Tensile strength Elongation (%) X-ray shielding (Shore A) (kg/cm2 ) (%)

6 Commercial Polymers and Their Utility in Polar Regions 109

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B. Sharma et al. Comparison of X-ray Shielding of PVC Compositions

100

90

80

X-ray Shielding (%)

70

60

50

40

30

20

10

0

Lead sheet

Lead apron

Lead gloves

PVC+BaSO4

PVC+TiO2 PVC+RockPhosp. PVC+BonePowd. PVC+Bi2O3

PVC+Tung

PVC+Tung+TiO2

Compositions

Fig. 6.13 X-ray shielding of PVC compositions vis-à-vis lead sheet, lead gloves and lead apron

X-ray Shielding of PVC Composition 100 90 80

X-ray Shielding (%)

70 60 50 40 30 20 10 0 Lead sheet

Lead apron

Lead gloves PVC+BaSO4 PVC+TiO2

PVC+Rock Phosp.

PVC+Bone Powd.

PVC+Boron PVC+Bi2O3 Carbide

PVC+Tung

Compositions 30 KVP

40 KVP

Fig. 6.14 X-ray shielding of PVC compositions vis-à-vis lead sheet, lead gloves and lead apron at 30 and 40 KVP

in the lead sheet, lead apron and lead glove was found to be 90%, 85% and 85%, respectively. When the x-ray shielding property of the developed lead-free gloves was compared with the lead gloves available in the market, it was observed to have a marginally less value (80% vis-à-vis 85% of market sample). However, it is sufficient to serve the

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Table 6.10 Comparative properties of lead gloves vis-à-vis optimized lead-free composition S. no.

Properties compared

Lead gloves (market sample) Developed lead-free gloves PVC based

1

X-ray shielding (%)

85

80

2

Weight per pair (gms)

1800

450

3

Hardness (Shore A)

80

80

4

Density (gm/cc)

3.24

2.2

5

Tensile strength (kg/cm2 ) 80

85

6

Thickness (mm)

1.90

2.50

purpose of adequate shielding for medical professionals against the weight saving advantage.

6.13.4 Effect of X-ray Intensity on Various PVC Compositions The extent of x-ray shielding was found to be dependent on the nature of radiopaque incorporated and also on the applied x-ray intensity. The level of x-ray shielding in the exposed PVC composition was found to be in the range of 65–85%. The extent of x-ray shielding in lead sheet, lead apron and lead glove was found to be 78–90%. The results of x-ray shielding intensity are reported in Table 6.11 at various energy levels 30, 40 and 50 KVP (Fig. 6.15). Table 6.11 X-ray shielding of lead sheet, glove, apron and radiopaque-impregnated PVC S. no.

Polymer

Radiopaque

(%)

X-ray shielding (%) 30 KVP

40 KVP

50 KVP

1

Lead sheet

Lead

100

90

85

80

2

Lead glove

Lead

70

85

80

78

3

Lead apron

Lead

70

85

83

80

4

PVC[I]

Bismuth oxide

70

80

70

65

5

PVC[II]

Tungsten oxide

70

85

82

80

6

PVC[III]

Barium sulphate

70

80

70

65

7

PVC[IV]

Titanium dioxide

70

75

75

70

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6.14 Physico-Mechanical Properties of Radiopaque-Impregnated PVC Compositions Having established the x-ray shielding in the plasticized radiopaque PVC sheets and gloves, these were also evaluated for various properties such as density, tensile strength, elongation % and hardness. The results of tensile strength, hardness, density and elongation % are given in Table 6.10. It is observed that the hardness value of lead apron and lead glove was found to be 60–80. However, Shore A hardness of optimized lead-free gloves were in the range of 75–80. Further, Shore A hardness in case of PVC composition was found to be 75–80. It was also observed that the average tensile strength of lead apron and gloves was higher than the SRI lead-free x-ray resistant composition. The tensile strength is maximum for TiO2 impregnated with PVC resin, and the value of tensile strength decreases up to 55 kg/cm2 for TiO2 /Tungsten incorporated in PVC resin.

6.14.1 Assessment of Thermal Stability of PVC Compounds It is well known that polymers on processing at their respective processing temperatures generate no smoke and only low molecular weight compounds are released as aerosol in the work place environment by compounding, cutting, mixing, etc. Some of these compounds can be related to the initiator carrier system used in the polymerization process, mostly hydrocarbons; but at the very high temperature of the polymer melt (i.e. 280–350 °C), thermo-oxidative degradation of the polymer takes place at polymer processing with the formation of oxidized fragments of the degraded polymer. The first step in the data analysis process is the choice of level of decomposition. Typically, a value early in the decomposition profile is described since the mechanism here is more likely to be that of the actual product failure. On the other hand, taking the value too early on the curve may result in the measurement of some volatilization (e.g. moisture) which is not involved in the failure mechanism. A value of 5% decomposition level is a commonly chosen value. Other values may be selected to provide correlation with other types of processing of the polymers. From Table 6.12, it can be observed that plastics like PVC, etc. are thermally stable above processing temperatures. Initial degradation temperature of polymers in dynamic mode is definitely higher than the industrial practices of safe polymer processing. Plastics are processed at lower temperature than the temperature of initial degradation. Similarly in isothermal mode, the average stability of 20–30 min is an excellent proof of non-degradability of plastic materials at their processing temperatures, thereby not contributing to any generation of thermally degraded product in the atmosphere.

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Table 6.12 Determination of thermal behaviour and stability of polymers Name (processing range, °c)

Reported temp. of thermal oxidation (°c)

TGA in dynamic mode

TGA in iso: thermal mode

Degradation start at (°c)

99% degradation at (°c)

Temp. (°c)

Time (min.)

Stability (%)

PVC-I (140–250)

150–338

270.55

548.73

220

20

99.9

TG analysis of compounded PVC described as PVC-I and PVC-II was carried out to determine percentage loss and heat stability of material, respectively, in dynamic as well as in isothermal mode. In dynamic mode, temperature was increased at the rate of 10 °C/min. till it reached 500 °C. All the experiments were carried out in presence of air at the rate of 100 ml/min. The results of TGA are given in Table 6.12, and the thermograms of each polymer are shown in Fig. 6.16. The degradation characteristic of each PVC composition shows that the weight loss was started from 270 °C and above. And the same composition was found thermally stable at 220 °C up to 20 min (Fig. 6.16). % X-Ray Shielding 100 90 80 70 60 50 40 30 20 10 0

30 KVP 40 KVP

id ox

hi

Di

lp ni ta +T i PV C

PV C+

Ba r

iu

m

um

Su

en st ng +T u

PV C

e

de

e Ox

id Ox ut h

sm C+ Bi PV

id

e

ro n Ap ad Le

ad Le

Le ad

Sh

Gl ov e

ee

s

t

50 KVP

X-Ray Resistant Compositions Fig. 6.15 Intensity of X-ray at 30, 40 and 50 KVP against radiation-shielding compositions

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Fig. 6.16 Thermograms of flexible polyvinyl chloride (PVC) in dynamic mode

6.14.2 Summary of the studies PVC composition remains thermally stable for at least twenty minutes at their respective processing temperature within which the melt is shaped. Thermal analysis of polymers indicates that if the processing temperatures are maintained within the specified limits, the VOC, organic air pollutants, etc. would be under control. Based on this study it is recommended that the maximum processing temperature of PVC polymers should be 250 °C (rigid and flexible). If on comparison the general practices of PVC processing mainly calendaring, extrusion and injection moulding are considered, which are processed at the range of 140–250 °C, then the same are also observed through thermogravimetric analysis. Based on the above studies, it can be concluded that no degradation will occur during processing if properly compounded PVC is processed. The processing of PVC is environmentally safe if processed in the range of 140–250 °C. Further, the developed PVC composition with radiopaque material was also subjected to TGA analysis after accessing the degradation behaviour of PVC through dynamic and isothermal mode by TGA. The results of Initial Decomposition Temperature (IDT) and the temperature at which ash formation takes place for lead apron, lead gloves and optimized PVC samples determined by TGA Instrument are presented in Table 6.13. The data clearly shows lead apron and gloves are thermally stable up to 255 °C. However, the ash content of lead apron and gloves were found to be 78.32% at 751.79 °C and 73.57% at 759.36 °C, respectively. Figure 6.17 shows the variation of initial decomposition temperature and weight loss temperature with increasing temperature. The results also indicate that the initial decomposition temperature of optimized x-ray resistant compositions was found to be 246.43 °C in case of TiO2 /BaSO4 in PVC resin.

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115

Table 6.13 TGA analysis of lead apron, lead gloves vis-à-vis radiopaque impregnated in polymers composition S. no.

Sample

Initial decomposition temp. (°C)

Residue Temp. (°C)

(%)

1

Lead apron

255.36

751.79

78.32

2

Lead glove

264.29

759.36

73.57

3

PVC + Tungsten (III) oxide

203.14

653.57

65.04

200 150

(%)

100

50 0 -20 0

20

40

60

80

Time (min)

Fig. 6.17 Thermogram of PVC in isothermal mode

Figures 6.18 and 6.19 show the variation of weight loss of lead apron, lead glove and lead-free x-ray resistant composition samples with respect to temperature.

6.14.3 UV Spectra of X-ray Radiographs The results of % transmission of x-ray radiograph determined by UV spectra of lead sheet, lead apron, lead glove and SRI-developed lead-free PVC compositions are presented in Table 6.14. It shows that the % transmission of x-ray radiographs of lead sheet, lead apron and lead glove was found to be 75.9%, 73% and 74.8%, respectively. Similarly, the % transmission of PVC compositions were found to be (1) 0% for no radiopaque impregnated in PVC resin (2) 73.6% for Bi2 O3 impregnated in PVC resin (3) 73.8–74.2% for tungsten oxide impregnated in PVC resin. The results are also shown in Figs. 6.13 and 6.14, respectively (Table 6.15).

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Fig. 6.18 TGA curve of tungsten oxide impregnated in PVC resin

Fig. 6.19 TGA overlay curve of lead apron and glove vis-à-vis Bi2 O3 impregnated in PVC resin

6.15 Measurement of Transmitted Gamma Ray The gamma-ray transmission measurements are composed of two parts dealing with gamma-ray sources and radiation detection. The measurement of exposure rate was carried out by verifications of linear response using a 0.70 mCi Cs-137 source with all samples listed in the table (Table 6.16, Fig. 6.20).

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Table 6.14 Chemical resistance of X-ray radiopaque impregnated in PVC S. no.

Reagents

Weight of tungsten incorporated in PVC (in gms.)

Weight of TiO2 /Bi2 O3 incorporated in PVC (in gms.)

Before

After 48 h.

% Weight loss

Before

After 48 h.

% Weight loss

1

Sulphuric 3.7713 acid (10%)

3.7495

0.57

3.2770

3.2551

0.66

2

Sodium hydroxide (10%)

3.5836

3.5361

1.32

3.0018

2.9661

1.18

3

Sodium chloride (10%)

3.9907

3.9653

0.63

2.9307

2.9262

0.15

4

Ammonia solution (10%)

4.1862

4.1062

1.92

1.9315

1.9184

0.68

5

Water

4.1948

4.1908

0.09

2.0650

2.0550

0.48

Table 6.15 % Transmittance of X-ray radiographs using UV spectra S. no. Sample

Radiopaque Name

Qty. (%)

% Transmission of x-ray radiographs

1

Lead metal sheet

Lead

100

75.9

2

Lead apron (market)

Lead impregnated in rubber

73

73.0

3

Lead gloves (market)

Lead impregnated in rubber

73

74.8

4

Sodium meta periodate (IV) in PVC

Sodium meta periodate (IV)

54.20

0.6

5

Tungsten oxide in PVC Tungsten oxide

54.20

73.8

6

Tungsten oxide in PVC Tungsten oxide

63.96

74.2

7

Bismuth (III) oxide in PVC

Bismuth (III) oxide

63.96

73.6

8

Plasticized PVC sheet

Nil

0

0

6.15.1 Acceptance Limit for Radiation Monitoring Instruments: The percentage of linearity of the instrument with respect to distance and dose rate measurement is linear and below 20%. Therefore, the instrument was working properly. The transmitted exposure rate of gamma ray after shielding of the PVC compositions were found to be 10% in case of bone powder and rock phosphate, 60%

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Table 6.16 Measurements of exposure rate by radiation detector S. no.

Distance (cms)

Exposure rate calculated mR/hr

Radiation survey meter reading scale 0–20 mR/hr

Calibration factor

Linearity (%)

1

100

0.26

0.31

0.84

16

2

90

0.32

0.38

0.84

16

3

80

0.40

0.46

0.87

13

4

70

0.72

0.84

0.85

15

5

60

1.04

1.10

0.94

6

6

50

1.62

1.76

0.92

8

7

40

2.88

3.03

0.95

5

8

30

6.5

6.65

0.97

3

Fig. 6.20 Variation in exposure rate with increasing distance

in BaSO4 , 70% in Tungsten, 83% in tungsten/TiO2 mixture and 80% also in case of Bi2 O3 . Further, the results were found to be comparable to developed PVC formulation. Various developed PVC sheets were placed between the source and the detector at 100 cm distance. Exposure rate was monitored by radiation detector. The results of gamma-ray transmission/exposure experiment with 0.66 Mev energy from Cs-137 show the same trend of attenuation as compared to x-ray transmission. Details of all the samples with different materials are listed in Table 6.17.

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Table 6.17 Samples used in gamma-ray attenuation measurements Sample placed Dimensions of sheet L between radiation (CM) × W (CM) × source and detector at a thickness (mm) distance of 100 cm

Radiation exposure rate (μR/hr)

Percentage shielding (%)

30 × 30 × 3

20

70

PVC sheet with BaSO4 30 × 30 × 3

28

60

PVC sheet with Bi2 O3

30 × 30 × 3

14

80

PVC sheet with TiO2 + tungsten

30 × 30 × 3

12

83

PVC sheet with rock phosphate

30 × 30 × 3

60

10

PVC sheet with bone powder

30 × 30 × 3

62

10

PVC sheet (control)

30 × 30 × 3

70