Dow's Fire & Explosion Index Hazard Classification Guide [7 ed.] 0816906238

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DOW'S FIRE & EXPLOSION INDEX HAZARD CLASSIFICATION GUIDE

SEVENTH EDITION

DOW'S FIRE & EXPLOSION INDEX HAZARD CLASSIFICATION GUIDE SEVENTH EDlTION

a AIChE technical manual published by the American Institute of Chemical Engineers 345 East 47th Street, New York, NY 10017 © 1994

ACKNOWLEDGMENT The American Institute of Chemical Engineers wishes lO acknowlcdgc the cooperation of Thc Dow Chemical Company in releasing their 7th edition of the Fire amI Explosion JI/de:! Hazard CJassification Guide for publication. Speciallhanks to N. E. Schcrner, W. R. Heitzig. J. F. Murphy. S. M. Hartnagle. N. H. Humphrey. B. H. Seortiehini and T. O. Gibson of The Dow Chemical Company, whose carcful evaluation and review of Lhi s materi al provided sorne important innovations lo make the Guide more use[ul to the chemica! industry.

Copyright In U.S.A. © 1994 LC 80-29237 ISBN 0-8169-0623-8

TABLE OF CONTENTS Preface .......................................... .......................................................... ................ .......................... . Introduction: The Fire & Explosion Index Syslem ........ ..... ..................... ..... ............. .. ........ ..... .............. Procedure for Risk AnaIysis Calculations ....................................... .... .................... .. ....... .... ... ..... .... ... . Selection ofPertinent Process UnilS ............................... ... ..... .... .. ... ... ..... ....... ... .................................... Detennination oC M aterial Factor .. ............................................. ...... ... ... .. ....... .... .. .... .. ........................ . Process Unit Hazaros Factors .............. ... .... .... .... ....... ................. .. .. .............. ....... ......... ........ ...... ......... General Process H azards ........... .... ...... ..... ........ ..... .. .... ..... ..... ... ... ..... .. ................................................. . Special Process Hazards .......................................... ................................................ ..... .......... .... .. .... ... Determination of Process Unit Hazards Factor .. .. ... .. ... ........... .... .. ....................................................... . Determination of Fire and Explosion Index .............................................. .. .... .. ..... .... ... ......................... Loss Control Credit Factors ............................................................ ....... ....... .. .... .. ...... ......................... Process Unit Risk Analysis Swnmary ... ..... ... ............ .. ..... ...... .... ..... .. .................................................... Discussion ofMPPD, 81 and Plant Layout .......................................................... .. ... .. ...... .. .. .. .............. Manufacturing Unit Risk Analysis Swnmary ..... ..... ......... ...... ... ........... .. ... ................................... ......... Risk Analysis Package .................................................................................................. ...... .... .. ...........

1

2 3 8 10 15

16 20 37 38 39 47 57 58 59

TABLES 1 2 3 4 5 6

-

Material Factor Determination Guide .... ...... ......... ............................. .. ........ .. ........................... Material Factor Temperature Adjustment ........ ........... .... .. ..... .. ............................................ .... . Dust Explosion Penalty .. ................... .... .............. ........... ................... ..................... .. .. ....... ...... High Pressure Penalty forFlammable and Combustible Liquids ............................................. .. HOl Oil Heat Exchange System Penalty .............................. ............. ... ..................................... Degree of Hazard for F&EI ............. .................... ........ ....... ........................ .............. ... ... . ...... ..

13 14 21 22 36 38

FIGURES 1234 56789-

Procedure for Calculating F&EI and Olher Risk Analysis lnfollllation ............... ........ .... .. ........ Prcssure Penalty for Flammable and Combustible Liquids ......................... .... .. .... ...... ............ ... Liquids or Gases in Process .. ..... .. .... ... ... ... ... ...... .. ........ .. ..................................... ... .................. Liquids or Gases in Storage ....... .................................. .. ....................... .... ...... ......................... Combustible Solids in Storage/Dust in Process ....................................................... ... .............. Fuewer plants. TI1e system can also be used for risk evaluations oC small processes wilh modest inventaries of potentiaUy hazardous materials; its application 10 pilot plants is strongly recommended. The system can be applied if handling a minimum of approximatel)' 1,(XX) lb (454 kg) of a flarnmable or reactive material. A Mlord 01 coution is in arder for those planning 10 use thc F&EI system for the risk evaluation of facilities. Common sense and good judgment must be used during lhe actual calculatioR and in the interpretation of its rcsults. Process hazards that contribute to thc magnitude and probability oC losses have been quantified as "penalties" to provide factors for computation. Not cvery penalty may be applicable 10 a specific situation and pemaps sorne may have to be adjusted.

2

PROCEDURE FOR RISK ANALYSIS CALCULA TIONS To develop an F&EI and Risk Analysis Swnmary. the following are needcd: a. An accurate plot plan of the plant (manufacturing unit) b. A process flow sheet c. A Firt &: Explosion Inda Hazard Classificatjon Guide. Seventh &titiao d An Fll'e & Explosion lndex Fono (page 5 - F&EI. Seventh Edition) e. A Loss Control Credit Factors Fonn (page 6 - F&EI, Sevcnth Edition) f. A Process Unit Analysis Summary Fonn (page 6 - F&EI. Seventh Edition) g. A Manufacturing Unit Risk Ana1ysis Swnmary Fonn (page 7 - F&EI, Seventh Edition) h. Replacement cost data for the instaUed process equipment under study. 1be procedure 10 be followed is listed below. Figure 1, page 4, presents a flowchart outlining the procedure for risk analysis calculations. J. Selection shoold re made on thc pIOl plan oC thc Pertinent Proccss UnilS that are comidered of key importance ro the process and that would have the greatest impact on the magnitude of a potential tire

or explosiono 2. Detennination is 10 be made of the Material Factor (MF) for eaeh Process Unil The MF for a particular material in the Process Unit is 10 be obtained frem Table 1, page 13 or Appendiccs A or B, pages 60 to 73. 3. Calculatioo is 10 be completed Cor the General Process Hazards Factor with application of the appropriate penalties according to the F&EI Fonn, page 5. 4. Calculation is to be completed Cor the Special Process Hazards Factor with application oC the appropriate penalties according 10 the F&EI Fonn, page 5. 5. Detennination oC the Process Unit Hazaros Factor is 10 be done by calculating the product oC the General and Special Process Hazards Factors. 6. Detennination of the F&EI is to be done by calculating the product oC the Process Urot Hazards Factor and the Material Factor. 7. Detennination oC the Area of Exposure surrowx:ling the Process Unit being evaluated is 10 be perfonned based on Radius ofExposure from Figure 7, page 48, and pagcs 47 10 SO. 8. Detennination oC the replacement value of all equipment within the Area of Exposure and me inven10ry is 10 be done. 9. Detennination ofthe Damage Factor, wruch represents the degree ofloss exposure, is to be done using Figure 8, page 53, based on the MF and the Process Unit Hazards Factor (F3). 10. Oetennination of the Base Maximum Probable Property Damage (Base MPPD) is 10 be made by multiplying thc Yalue of the Arca of Exposure by the Damage Factor. 11. Application of the Loss Control Credit Factor to the Base MPPD allows for the determination of the Actual MPPD. 12. Dctennination of the Maximum Probable Days Outage (MPDO) is perfonned by using Figure 9, page 55, knowing the Actual MPPD. 13. Detennination of the Business Interruption (BI) is done by using the equation given on page 56 whcre the MPOO is multiplled by the Yalue ofProduction for the Month (VPM) and by 0.70/30. Each of the steps given above is outlined and explained in the following pages of this guide. Appendix C, Basic Preventive and Protective Features, and Appendix D. Loss Prevention Olecklisl, are atso provided for use in assessing the important 10ss control arcas in a plan[ or manufacluring uniL WhcrJ. developing the F&EI. it is recommended that people with a working knowledge of the plant's hislOry/experiences be contacted to discuss probable incident scenanos 10 assure thc mos! viable F&EIs are

developed.

3

FIGURE! PROCEDURE FOR CALCULATING FIRE & EXPLOSION INDEX AND OTHER RISK ANALYSIS INFORMATION Select Pertinent Process U nil

.¡. Dell:n nme Material Factor

I

,¡,

,¡,

CalcuIate F I

CaJculale Fl

General Process Hazards Factor

Special Process Hazards Factor

I Determine Process Unil Hazards Factor FJ ::: FI X Fl

.¡. Calculate l..oss Control Credit Factor = el x el x el ~

Detrnnine F&EI F&EI :::: Fl x Mataial Factor

.

Determine Area ofExposure

... Determine Replacement Value in Exposure A tea

+ Determine Base MPPD

... Determine Actual MPPD

... Determine MPOO

... Determine Br

4

...

Detennine Damage Factor

FIRE & EXPLOSION INDEX

I DAn

A.REAICOUNTAY

DlVISION

lOCATlON

"'"

..... NUF... CTUAINQ UNIT

PROCESS UNrT

PREPARED IY:

APPROYU) IV : (S~I~1l

REVlEWEO 'Y :{~l

REVlEWED IIY: (Teehnology

IIUIU!lNO

CenI...,

AEVlEWED BY : (5."1}' & Lo.. P,.ventlon)

MATERIALS IN PROCf.SS Ut,¡rr

STATE OF OPERATION

-

"""" -

ITARTUP

....SIC MATERIAl(S) FOA MATERIAL FACTOR

-

-

_WJ.OPERAnoH

lHUTOOWH

MATERIAL FACTOR ¡Sea TabIe 1 or Appendioes A Of 8) Nota reqtkements when lI'Iill9lTlperature over 140 °F (60 oC)

lo

General Procesa Hazards Base Factor ....................................................... A. Exothermic Chemical Reactions B. Endothermic Processes C.

...................................................

Penalty Factor Range

Penalty fac-

1.00

1.00

tor

USed(l)

0.30 lo 1.25 0.20 lo 0.40 0.25 lo 1.05 0.25100.90 0.20 lo 0.35

Material Handling and Transfer

D. Enclosad or Jndaor Process Units

E. Aocoss F. Drainage and Spill Control

galorcu.m.

0.25100.50

General Procesa Hazards Factor (F , ) ............................................................... ........................ ..

2. Speclal Process Hazards Base Factor .................................................. A. Toxlc Malerlal(s) B. C.

........................................................

Sub-Almospheric Pressure « 500 mm Hg) Operalion In or Near Flammable Range

,.

0.50 Inerted

Nollnert&d

Tank Farms Slorage Flammabla Uqulds

0.50

2. Process U sel or Purga Failure 3.

0.30

A1ways in Flammabla Ranga

0.80

D. Ousl Explosion (Sea Table 3)

0.25 lo 2.00

E.

Prassura (Saa Figura 2)

F.

l ow Tefll)9ralUre Ouantity of FlammablaAJnslabla Matarial:

G.

1.00 0.20 lo 0.80

pslg or kPa gauga psig or kPa gauga

Operating Prassura Relial Saning

0.20 l O 0.30

He

-

Quanlily _ _ lb or kg BTU/ lb or kcallkg

1.

llqulds or Gases in Process (Sea Figure 3)

2. 3.

Uqulds or Gases in Slorage (Sea Figura 4) Combuslible Sollds In Sloraga. Ousl in Process (Saa Figura 5)

H.

Corrosion and Eroslon

0.10 lo 0.75 0.10101 .50

1.

laakaga - Jolnls and Packing

J.

Use 01 Flrad EQulpment (See Figure 6)

K.

Ho! Oil Heat Exchange System (See Tabla 5)

L

Rotatlng Equipmenl

0.15101.15 0.50

................................ ... .................. ....... ................ ..... = ~ ...•..•.•....• _.................................................

Speclal Process Hazards Factor (F2) .. ...... Process Unit Hazards Factor (F1 Fire 800 Explosion Index (F3

x

x MF

F2)

= ~~ ........... ... .......................................... ...................... (1) For no pona ~y use 0.00.

5

1.00

LOSS CONTROL CREDlT FACTORS 1, Process Control eredit Factor (Ct)

Fealura

,.

Emergency Power

eredit Factor

Factor

Ranae

Used(2)

Credit

eredit

Feature

Ranae f.

0,98

Factor 0.94 lo 0.96

Inert Gas

0.97 lO 0.99

g. Operating InstructionSlProcedures

0.91 lo 0.99

c. E)(plosion Control

0.84100.98

h. Reactive Chemical Aeview

0.91 lo 0.98

d. Emergency Shutdown

0.96 to 0.99

f. Other Process Hazard Analysls

0.91 lo 0.98

e. Computer Control

0.93100.99

b. Cooling

eredit Factor Used :21

el VahJe(3) 2.

Materlal1solatlon Credit Factor (e 2)

feature

eredit

CradH

factor

factor

Ranae

Credit

fealure

Factor

Ranae

Usedf21

a. Ramole Control Valvas

0.96 lo 0.98

c. Drainage

0.91 lo 0.97

b. OumpIBlowdown

0.96100.98

d. Interlock

0.98

eradit Factor Usedf21

e2 Value(3) 3.

Fire Protectlon Credlt Factor (e3) Feature

a. leak Delection

eredit

Cradl! Factor Ranga

Credit

factor

Fealure

Factor Used{21

Ranga

0.94 lo 0.98

f.

b. Slructura! Stee!

0.95 lo 0.98

g. Foam

0.92 lO 0.97

C. Fire Waler Supply

0.94 lo 0.97

h. Hand ExlinguisherslMonitors

0.93 to 0.98

1. Cable Prolectlon

0.94100.98

d. Special Syslems e. Sprinkler Syslems

0.91

Waler Curtains

eredi. Factor Used{21

0.97100.98

0.74 to 0.97

C. Valuel') loss COntrol Credit Factor

= C1

L.I_ _ _- - '

X C2 X C3(3)

=

.Jl

L-_ _ _

(Enter on line 7 below)

PROCESS UNIT RISK ANAL YSIS SUMMARY f.

Fire & Explosion Inclex (F&EI) .. ....................... (Sea Fronl)

2.

Radius 01 Exposure ....... ............ .. .. .. ................. (Flgure 7)

ft or m

3.

Area 01 Exposure ... ...... .... .. ... .... .... .. .... ... .. .

.......................

ft2 or m2

4.

Value 01 Area 01 Exposure ......................... ..................................... .... ... .... .... ... ... ........ .......

5.

Damage Factor ..... ............. ........ ....................... (Flgure 8)

6.

Base Maxlmum Probable Propeny Oamage

7.

Loss Control Credit Factor... ......... ......... ........ (See Above)

8.

Actual Maximum Probable Property Damaga - (Actual MPPD) [6

9.

Maximum Probable Days OUlage - (MPDO) .. .. .. (Figure 9)

10. Business InlerrupUon

$MM

I

x 51 ···································

$MM

1

..............

$MM

I

$MM

1

I

(Base MPPD) [4

I I

x 71···

.... ... .....

days

(BI) ...................... .. .. .. ... ...................... ......... .. ... ............ .... ....

.........

(2) For no creditlactor enler 1.00. (3) Product 01 all lactors used. Reler lo Fire & Explosion Index Hazard Classificalion GukJe lor details.

6

MANUFACTURING UNIT RISK ANALYSIS SUMMARY AREA J COUNTAY

DlVISION

LOCATlOH

SlTE

MANJFACruRINO UNIT

TYPE Of OPERAnoN

PREPAREDBY

TOTAL UFO. UNlT REPLACEMENT VAWE

DATE

Value O,

Process Unft

Area 01

Exposure

Material

Ma·or Material

Factor

F&EI

$MM

Maximum Probable Property Damage 2 Maximum Probable Days Oulage

1 3

Business Interruption

REV!OI-IM

7

S ... MPP01 $MM

Actual MPP01 $MM

Days Outage MPD02

813 Loss $MM

SELECTION OF PERTINENT PROCESS UNITS

-----~~~~~~~~~~~~~~------

1he F&EI calculation is a 001 10 hclp determine the arcas of greate.~lloss potcntiaJ in a particular process. It also enables one to predict the physical damage and business intcnuption mal would occur in lile event oC

an incidcnL The first stcp in making

me F&EI calculation requires using an cfficicnt and lagica! procedure to determine

which proccss units should be studied. A proccss unit is defined as any majar itcm of process equipment. 'Thc foUowing process units could be idcntified in a furnace/quench seelion of a vinyl chIoride moromerl ethylene dichIoride plam: elhylene dichloride preheater, ethylene dichIoride evaporator, fumace, quench coturno, clhylene dichIoride absorber and tarpot A designadon oC me Proccss Unit must be entered in thc appropriatc spacc on thc F&EI formo pagc 5. Thc Manufacturing Unit designarlon must also be entered on the F&EI formo A Manufacturing Unit is the cntire production facility including chemical processes, mechanical processes, warehouse, packaging lines, etc. For cxample, manufacturing units may be a latex planto DOW ANOL® plant or DowElanco Fonnulations plant. 1be process area of a latex plant could have the following process units: raw material storage tanlc/s, process stream storage lank/S. aqueous tank, reactor feed pumps, reaclor, stripper, recovery tank/s, lalex storagc tank/s.

A warehouse may also be treated as a process unit. Thc matcrials stored within a fire-walled area, or within !he total storagc area wherc firc walls are not provided, would constitute a Process Unit. It is quite clcar that most manufacluring unilS have many process unilS. To calculate the Fire and Explosion Index, however, only process units that could havc an impact from a loss prevcntion slandpoint should be evaluated. Thcse are known as Pert1ncnt Process Units.

Important factors for selecting Pcrtincnt Proccss UnilS include: a. o.cmical energy potential (Material Factor) b. Quantity of hazardous material in the Process Unit c. Capital density (dollars per square foot) d. Process pressurc and process temperature e. Past history of problcms that rcsulted in a firc and expIosion incident f. Units critieal 10 plant operation, Lc., thennal oxidizer Generally. the greater the magnitude of any of these faclors, thc greatcr thc lik:elihood that the process unit nceds to be evaluated. Thc dcstruction of scarcc. critieal or one-of-a-kind equipment in or ncar a process area couId produce many days of downtimc. Even with minimal fire and explosion damage. this could create large losscs due 10 business interruption. The loss of such criticaI cquipment is a valid reason for selecting a Pertinent Process

Unit.

1llere are no hard and fast rules governing the choice of Process Units for evaluation. For hcIp in dctermining which pieces of equipment have Ihe greatest potential for tire and explosion, consult with Technology Centers. cxpcricnccd plant enginccrs. process safety and Ioss prevention specialists or othcrs wilh process expericncc.

8

Important Considerations A.

1be Fire and Explosion Index system assumes that a process unit handles a minimurn of 5. lb (2,268 kg). or about 600 gal (2.27 ml) of a flammable. combustible or reactive material. If less material is involved, genera11y thc risk wUl be overstaJed. However. F&EI calculations can providc meaningful results for pilot plants if they handle at least 1, lb (454 kg) or about 120 gal (0.454 ml) of combustible or reactive material.

B.

Careful consideration is needed when equipment is arranged in series and the items are not effcctively isolated from each otber. An example would be a reaction train without an intermediate purnp. In such situations. the type of process determines whether severa! vessels or just a single vessel should te considercd as thc Process Unil In a poIystyrene train, for example, where the main hazard is from unreacted material in the first stage reactor, it is inappropriate 10 apply any penalties for vacuum operadon in the flash tank or devolatilizer (wruch is effectively the third or rOUM stage) because it is inconceivable lo have both hazards occurring al the same point in Ihe process. In this case, it would be reasonable to carry out two separate F&EI calcuJations, treating the first stage and founh stage reactors as separate Proccss Units. It should rarely be necessary lO calculate the F&EI for more man three or four Process Units in a single process arca of a Manufacturing Unil The number ofProcess Units will vary according 10 thc type of process and the configuration of the Manufacturing Unit.

A separate F&EI form (pages 5 and 6) must be completed for each process unit evaluated. The results of each calculation must also be listed on the Manufacturing Unit Risk Analysis Surnmary (page 7). C.

It is also important 10 give careful consideration to the state or point in time of the operation. By their nature, such normal stages as start-up, steady-state opcration, shutdown. filling. emptying. adding catalyst. etc.• ofien create unique conditions having an impact en the F&EI. Generally, good judgment will enable selection of the point in time of operation 10 peñorm the F&EI calculation. OccasionalIy more than one point in time will have lO be studied lO determine the significant risk.

9

DETERMINATION OF MATERIAL FACTOR 'Ole Material Factor (MF) i5 the basic starting vaJuc in the computalion of thc F&EI and other risk analysis valucs. 'The MF i5 a rncasure of thc intrinsic rate of potential cnergy release from fire Of cxplosion produced by combustion Of cheroical reaction. 11lc MF i5 obtaincd from N F and N R. 11le N p and NR are NFPA ratings Of "signals" exprcssing bilily and reactivity (Of instability) respectively, as discussed below undcr "Unlisted Substances."

Oamma-

GeneraUy, NF and NR are foc arobient temperaturcs. It is recognizcd thal the tire and reaction hazards of a material increase markedly with temperalure. 11le tire hazard from a combustible liquid al a tcmperature aboye its flash point i5 equivalent to that from a flammable liquid al ambient temperature. Reaction ratcs also inercase very markedly with temperature. If the temperature of the material on which the MF is bascd i8 over 140 °F (60 OC), a certain adjusttncnt may be required, as discusscd below under C. "Temperature Adjusunent oC Material Factor," Appcndix A providcs a listing of MFs for a number of chemical compounds and materials, and these values will be used in mOSl cases. If Appendix A does oot list thc material, N F and NR may possibly be found in NFP A 325M or NFPA 49 adjusted for temperature, if appropriate, and used with Table 1 to detennine the MF. If the material is a combustible dust, use thc Dust Hazard Class Number (Sl number) rather than the NF· A.

Unlisted Substances lf neither Appcndix A, NFPA 49, flOr NFPA 325M contains values for the substance, mixture or compound in question, lhese values will have 10 be detennincd fmm thc flammability value (NF) or dust class (St) (sec Table 1, page 13.). First, the parame1ers shown in lhe lefi column of thc table 00 page 13 will have lO be detennincd. 'The NF of liquids and gases is obtained fmm flash point data, and the Sr of dusts or mists is delenoined by dusl explosion tcsting. 1be NF of combustible solids depends on the nature of the material as categorizcd in the len column.

The reactivity value (NRJ ean be obtained fmm a qualitative deseription of the instability (or reactivity wilh water) of thc substance, mixture or compound al ambiem temperature, as follows bascd ro NFPA 704: NR

=O

NR

= 1

Matcrials that in lhemselves are nonnally stable, cvcn undcr fire conditions. lbis dcgrcc usually includes: • Matcrials tha1 do nOl reae1 with water, • Malcrials that exhibit an exotherm al tempcralurcs >300 oC (572 0F) but S500 oC (932°F) when tcstcd by Differential Scanning Calorirnetcr (OSC); • Malcrials that do nol exrubit in exotherm al tempcratures $500 oC (932°F) whcn teSlcd by DSC. Materials thal in lhemselves are nonnally stablc but that can bccomc unstable al clevatcd tcmperatures and prcssurcs. lbis degree usually includcs: • Matcrials that changc or decompose on exposure lo air, lighl or moisture; • Malerials that exhibit an exOlhenn al tcmperatures > 150 oC (302°F), bU1 S300 oC (572 "F).

10

Na = 2

Na

=3

Na = 4

Matcrials that rcadily undergo violent chemica1 change al elcvated tcmpera[Urcs and prcssures. This degree usually includcs: • Materials that exhibit an exotherm at temperaturcs S ISO oC (302 0F) whcn tcsted by DSe; • Matcrials that may react violcntly with water or form JXltcntiaUy explosive mixtures with water. Materials that in themselves are capable oC detonation oC cxplosive decomposition or explosive reaction but that rcquire a strong initiating sourcc or that must be heatcd under confmement beCore initiation. This degree usually includes: • Materials mat are sensitivc 10 thermal or mechanical shock al elevated tcmpcralures and pressures; • Malerials that react explosively with waler without requiring heat or confinement. Materials thal in themselves are readily capable oC delonation of explosive decomJXlsition or explosive reaction al normallempcralurcs and pressures. This degrce usually includes materials that are scnsjtive lo localized therma! or mechanica! shock at normal tempcraturcs and pressures.

Note that reactivity includes selC·reactivily (inslabilily) and reactivity with walCr. A guidelinc Cor thc reactivity value (NJ0 is looking at thc peak lempcrature oC the lowest Differcntial 'Thermal Analysis (DTA) or Differential Scaruting Calorimeter (DSC) exotherm value as follows: Exothenn, oC

Exotherm, °F

N.

>300 lO 5500

>572 10 :::;932

O

>150 to 5::300

>302 to 5572

I

~150

~302

2,3, &4

A couple of additional qualifiers are:

1. If the substance or campound is an oxidizer. inerease NR by one (bul nol over NR =4). 2. Any shock·sensitive material shou1d be NR = 3 or 4. 3. lf the NR oblained seems inconsistent with known propenies of the substance. mixture or com· JXlund. additional reactive chemicals lesting shou1d be done. 4. Assistance in interpreting thc significancc of ose or DTA data can be obtained from the sitc Reactive Olemicals cantact persono Once the NF or St has becn obtained and determined. the NR. the resulting NF (or SI) and NR are uscd with Tablc 1 to determine the MF. Make the nccessary adjusunents as discussed below undcr "Temperature Adjusunent ofMaterial Factor."

B.

Mixtures Mixtures of various kinds can be uoublesome unde r cenain conditions. Nonnally. matcrials thal react violcntly - Cor example, fuel and air or hydrogen and chlorine - are mixcd undcr controlled eonditiollS. The reactiollS gcncrally takc place continuously and rapidIy, producing nonflammable. stable produc ts mal are safcly contained wilhin a process unit such as a reactor. 11lc combustion of fuel and air in a

11

fumace is a good exarnple of lhis son of controlled reaction. However, sinee "flarne-outs" and other breakdowns can still occur, the MF should be based on lhe initial reactive mixture, which fits the description of "most hazardous material present during a realistic operating scenario." For additional infonnation see Appendix. B, page 72. Mixtures of solvents or of a solvent witlt a reactive material can also create troublesome situations.

1be best MF for mixtures should be obtained from reactive chemical LCsting data, as recommendcd in Appendix. B. Ir reactive chemical testing data is not available, an approximation can be obtained by using the MF oC the component witlt the highest MF value. This component should be ene of significant concentration such

as 5% or more.

One particularly troublesome mixture is thc "hybrid." This is a mixture of combustible dust and Oarnmable gas, which can (onn an explosive mixture in airo The Material Factor must adequately reflect tite material hazard prescnt in litis uRique siluoliotl, and reactive chcmical testing data musl be employed 10 dctennine the proper MF. It is recommended tltat a reactive chemicals specialist be

con,uHed. C.

Mists One special condition can lead 10 explosions similar 10 having a flarnmable or combustible vapor above its flash point. A suspension of fincly dividcd drops of flarnmable or combustible liquid in air can givc a flarnmable mixture tltat has many of the characteristics of a flarnmable gas/air mixture. Mists of flammable or combustible liquids al temperaturcs well below their flash points can be as explosive as flammable vapor/air mixtures. For example, for suspcnsions in which the droplet diameter is less than 0.01 mm (0.()(X)4 in), the lower flammability limil of the suspcnsion is nearly the same at ambient temperature as thal of the substance al i15 flash poim. It is important thal mists not be processed inside enclosed process slructures because flarnmable coneentrations are more easily attained and overpressures from explosions can result in structural damage. The bcst dcfense against mist explosions is 10 avoid the conditions where a mist will fonn. Ir a mist 1S possible, me malerial faclOr can be raised one step (ref. Table 1, page 13) to account for the increased risk, and it is also rccommended that a loss prevention specialist be consulted.

12

TABLEl MATERIAL FACTOR DETERMINATION GUIDE Reactivity oc Instability Liquids & Gases Flarnmability or Combustibilitv l Non-combustiblel

NFPA 325M or49 NF-O

F.P. > 200 °F (> 93.3 oC)

NF -1

F.P. > 100 °F (> 37.8 oC) NF =2 $ 200 °F ($ 93.3 oC) F.P. ~ 73 °F ~ 22.8 oC) NF~3 < 100 "F « 37.8 oC) oc F.P. < 73 °F« 22.8 OC) & BP. ~ 100 °F (~ 37.8 oC) F.P. < 73 °F« 22.8 OC) & NF -4 B.P. < 100 °F« 37.8 oC) Combustible Dust or Mistl SI-l (K,;, $ 200 bar m/sec) SI-2 (K,;, = 201 -300 bar m/sec) St-3 (!Cs. > 300 bar m/sec) Combustible Solids Dense> 40 mm thick4 Np= 1 Open < 40 mm lhick' NF~2 Foam, fiber. powder, etc.' Np=3 F.P. =Flash Poinl, closed cup

NR~O

NR~

1

NR =2

NR~3

NR =4

1

14

24

29

40

4

14

24

29

40

10

14

24

29

40

16

16

24

29

40

21

21

24

29

40

16 21 24

16 21 24

24 24 24

29 29 29

40 40 40

4

14 14 16

24 24 24

29 29 29

40 40 40

10 16

B.P. =Boiling Point at Standard Temperatures and Pressure (STP)

Notes: I Includes volatile solids. 2Will not bum in aje when exposed to a temperature oC 1500 °F (816 oC) Coc a period oC five minutes. JICst values are Coc a 16litcr oc larger closed test vesscl with Slrong ignition sourcc. Sce NFPA 68. Guide

lor Venting 01 Dejlagralions. 41ncludes wood - 2 inches nominal thic.k.ress, magnesiwn ingots, tight stacks af solids and tight m Us of

papee oc plastic film. Example: SARAN ~. 51ncludes coarse granular material such as plastic pellets. rack slOrage, wood pallets and non~usting ground material such as polystyrene. 'Includes rubber goods such as tires and boots, STYROFOAM ~ brand plastic roam and fine material such as METHOCEL~ cellulUt or sudden cooling of the tank. The penalty is O.SO. Open vent or non·inert gas padded opcrating pressure·vacuum relief system would rcquire a penalty of 0.50. Storage of combustible liquids at temperatures aboye their c10sed cup flash points without inerting would also require a penalty oC 0.50. If an inened. closed vapor recovery systcm is used and its aiNightness can be assured, no penalty is applied. Sce next paragraph. Process equipment or process storage tanks that could be in or near the flarnmable range onIy in the event oC instrument or equipment failure wou1d require a penalty of 0.30. Any process unit that relies on inert purge 10 keep it out of the Oarnmable range rcquires a penalty oC 0 ..30. This penalty also applies 10 paddcd barges or tank cars. No penally is awlied bere ifthe penalty specified in B., "Sub·Atmospheric Prcssure" has already been taken Processes or operaLions thal are by nature always in or near the flarnmable range, eithcr bccause purging is not practical or bccause it was elected not lo purge, receive a penalty oC 0.80.

Dust Explosion The maximum rate oC pressure rise and maximum pressure generated by a dust are largely influenced by the particle size. In general. the finer the dUS1. the greater the hazard because of the rapid rate of pressure rise and maximum pressures anained. The penalties listed in this section are intended 10 apply 10 any Process Unit involving dust handling operations: transfening. blending, grinding. bagging, etc.

Al! dusts have a partic1c size range. For delennination of the penalty, use the 10% size; that ¡s. the partic1e size al which 90% of the dust is coarser and 10% is finer. Scc Tablc 3 for appropriate penalties. Unless dust explosion testing has shown that no dust explosion hazard exists, dust penalties should be applied.

TABLE3 DUST EXPLOSION PENALTY ParticJe Size

Tyler Mesh Si ..

Microns

Penalty (Use 1/2 ifin an inert gas)

175+

60 to 80

0.25

150'0175

80 'o 100

0.50

l00to 150

100 to 150

0.75

75 to 100

15010200

1.25

200

2.00

21

E.

Rel ter Pressure

Whcre operating pressures are aboye atmospheric, a penalty is applied for thc higher release rates causcd by higher pressure in the event of a leak. 1be concem is lhe IX)ssibility of failure oC sorne comlxment in the Process Unit causing tite release oC flammable materials.

Example: 1be release of hexane liquid through a one-square-inch (6.5 cm2) orifice at 75 psig (517 kPa gauge) would be a1most 600 Il>'min (272 kg/min). At 300 psig (2.069 kPa gauge). the release wouId be 2-1/2 times as great or 1,500 ltVrnin (680 kg/rnin). 1be relief pressure penalty evaluates tite specific spill hazard potential at different pressure Ievels. RelieC pressure also affects dispersion characteristics.

Since lhe spill potential greatIy increases al higher pressures, equipment design and maintenance bccome more critica! as tite operating prcssure increases. Systems operating al pressures aboye 3,000 psig (20,685 kPa gauge) are outside thc range oC standard codes (ASME Codc Cor Unfircd Pressure Vesscls, Section VIII. Division 1). Por such systems. lens ring joints. cone seals or equivalent c]()Sures must be used in flange design To detennme thc appropriate penalty. consult Figure 2, page 23, and use the opcrating pressure to detennine an initial penalty value. 1be equation below applies from O to 1,000 psig (O to 6.895 kPa gauge). y =0.16109+ 1.61503X 1000

1.42879(~)2 +0.5 172(~)' 1000

or

1000

y = 0.16109 + 1.61503·(X/lOOO) - 1.42879·(X/1000)"2 + 0.5172·(X/lOOO)A3

Por pressurcs from O to 1.000 psig (O to 6.895 kPa gauge) detennine the penalty Crom Table 4 below (a1so included in Figure 2. page 23):

TABLE4 H1GH PRESSURE PENALTY FOR FLAMMABLE & COMBUSTffiLE L1QUIDS Pressure psig

Pressure kPa gauge

Penalty

1.000

6.895

0.86

1.500

10.343

0.92

2.000

13.790

0.96

2.500

17.238

0.98

3.000 to 10.000

20.685 to 68.950

1.00

> 10.000

> 68.950

1.50

1be curve in Figure 2 can be used directly to detennine penalties for flammable and combustible liquids with a flash lX)int below 140 °F (60 oC). For other matcrials. the pena1ty providcd by the curve must be adjusted as follows:

22

/

FIGURE 2 - PRESSURE PENALTY FOR FLAMMABLE & COMBUSTIBLE LIQUIDS 0.9 y - 0. 16 1ds. + 1.61503 ' *,1000 .

1.4,i79·(X¡1000)A~ + 0.5172 · (,!¡1000)A3

0.8 0.7

0.6

'"'

w

./

~ 0.5

......

0.4 0.3

0.2

.--'

-

/

z

t!

V

.----

....-

/

/

/

0.1

o o

100

200

300

400

500 PRESSURE, PSIG

For kPa multiply by 6.895.

600

700

800

900

1000

1. For bighly viscous materials such as tarso bitumen, heavy lubricating oi1s and asphalts. muhiply !he penalty by 0.10. 2. For canpressed gases used alcre or flammable liquids pressurized wilh any gas above IS psig (103 kPa gauge), multiply!he penalty by 1.2.

,

3. Por liquefied flammable gases (mcluding all other flammable materials stored ahove thcir boiling poinl), multiply!he penalty by 1.3.

There is no penalty for extrusion arxt molding operations. To detennine the final penalty, first find the penalty associated with the operating pressure from Figure 2. Then find the penalty associated with the set pressure of the relief device. Divide the operating pressure penalty by the set pressure penalty 10 get a final pressure penalty adjustment factor. Multiply the operating pressure penalty by this adjustment factor 10 get the final pressure penalty. Thus, credit is given for having a relatively high set pressure arxI vessel design pressure. Note thal il is ofien advantageous 10 sel the relief pressure close 10 the vessel design pressure. Por example, reactions in a volatile solvent, especially if a gassy, unwanted higher temperature reaction can be avoided by sctting the relief pressure so thal the solvent can boil and remove heat before the higher temperature is reached Computer simulation is generaUy used, based on reactive chcmicals or other kinetic data, lO decide whether a low relief pressure is desirable. However, this is not always des:irable in sorne reactive systems. For scme speciaI situations, it is advantageous ro merease the design pressure of a pressure vessel te min:imize the likelihood of release and in sorne speciaI cases perbaps containment of the maxirnum cxpeeted pressure can be obtained See the foUowing example of a vessel holding a viscous material. Example:

Vessel design prcssure is 150 psig (1.034 kPa gauge) Nonnal operation is al 100 psig (690 kPa gauge) Rupture disk is sel al 125 psig (862 lePa gauge) From Figure 2, the 100 psig (690 kPa gauge) operating pressure has a penalty ofO.31 and 125 psig (862 lePa gauge) set pressure has a penalty ofO.34. Viscous matcrials receivc an adjustment orO.7. so the penalty becomes: 0.31 X 0.7 =0.22 adjusted penalty The final penalty is detemtined by multiplying this penalty by the pressure adjustment factor. 0.22 X (0.31/0.34) =0.20 =final penalty See the second examplc of an cmulsion polymerization reactor showing the differcnce between a low and a high dcsign pressure.

24

Examples: Reactor design pressure is ISO psig (1.034 ltPa gauge) Nonnal operating is al 120 psig (827 kPa gauge) RelieC device set pressure al ISO psig (1.034 kPa gauge)

A

From Figure 2. the opcrating pressure penalty is 0.34. The oot pressure penalty ofO.37. Thc prcssure adjustment Cactor is 0.34,u.37. The final penalty is:

0.34 X (0.34ft).37) = 0.312 = final penalty

B.

Reactor dcsign prcssure is 300 psig (2.068ltPa gauge) Nonnal operating is a1120 psig (8271tPa gauge) RelieC dcvice set pressure at 300 psig (2.068ItPa gauge)

From Figure 2. the operating pressure penalty is 0.34. The oot pressure penalty of 0.53. The pressure adjustment factor is 0.34/0.53. The final penalty is: 0.34 X (0.34ft).53) =0.218 =final penalty F.

Low Temperature This section makes allowances Cor the possible brittleness oC carbon steel or other metals that may be exposed lO temperatures al or hclow their ducti1e/brittle transition temperarures. If a careful cvalu· ation has becn made and 00 possibilily oC temperarures bclow the transition tempcrature exists due lO oonnal and aboonnal operating cooditions. no penalty is applied. It would be very rare 10 have a vessel designed with this potentiaJ. New vessel design would avoid the low temperature hazard. The usual method oC detennining the transition temperature is 10 test samples oC the metal used in the Cabrication of the Process Unit, using a standard Olarpy lmpact test lO detennine that the design and. thereCore. operating tempcrature i5 aboye the transition tempcrature. Proper design should avoid these

Jow tempcralUre process conditions. The foUowing penalties are applied: l.

2.

G.

For processes utilizing carbon steel construction and operated al or below the ductile¡brittle transition temperature. a penaUy of 0.30 is applied. IC no data are available. a SO °F (lO oC) transition tcmperarure should be assumed. For materiaJs other titan carbon steel where the operating temperature is at or below the uansi· tiOD temperature. use a penalty of 0.20. Remembcr that no penalty is applied ü lile material is appropriate foc the 10weSl possible opcrating tempcrature.

Quantity of Flammable!Unstable Material

This section coosiders the additional exposure to an area as quantities of flammable and unstable material in the process unit are increased. 1bere are three catcgories in this section. each evaluated by a separate penalty curve. Apply oo1y one penalty for the entire section. based on the material that was oolectcd as the Material Factor.

25

t.

Liquids or Gases in Process (Figure 3. page 27).

This scction appIies a penalty 10 a quantity of material thal might be spillcd and create a fire hazard. o r that mighl.. 00 exposure 10 fire. create a reactive chcmical evenL The penalty applies 10 any process operatioo. including pumping inlO holding tanks. and is valid for lhc following materials when they are selected as the MF: a. b.

Aammable liquids and those combustible liquids with a flash poim below 140 °F (60 oC). Aammable gases.

c.

Uquefied flammable gases.

d.

Coolbustible liquids wilh closed cup flash poinls aboye 140 ' F (60 'C) when !he process tcmperarure is aboYe the flash point of the material. Reactive materials regardless oCthcir flammability (NR = 2. 3 or 4).

e.

In using this penalty section. the first task is to detennine lhc pounds oC materia1s in process.

The penalty is based upon me amounl oC fuel for a tire that can be released Cmm the Process Unit or a connected line within 10 minutes. Cornmoo sense must be used in judging how much material might be released. Experience has shown that litis amount can be reasooably estimated by taking the larger oC the CoUowing:

i. Ü.

1be quantity oC material in me Process Unit or The quantity of material in the largest cmnected unil

Any connccted wUI that ca.l be isolated by closure valves operable Crom a remOle location in times oC emergency is removed from coosideration. BeCore accepting litis approximation of me quantity of material in process. (he quemon lO be asked is "What is lhc maximwn probable quantity that could be spilled?" If, using good engineering judgmeru and familiarity with me process. it is detennined that a number which is significaruly differenl fmm the abOYe, use (he lalter numbcr. being sure to document its validity. Remcmber. good judgment and process JamiJi.arity will always lead lO a more realistic approximatioo. Note. however. that ü instability (reactivity) is involvcd. the quantity of coocem is thc quantity ofmaterial nonnally inside the Process Unil

Example: O1arge drums. surge drums and renux vcssels are types of connect.ed equi¡:ment that migtu possibly contain more material than the Process Unir being evaluatcd. However. if such vessels :ue ¡:quipped with remote-cootrolled shut off valvcs. they should 001 be considered as "vessels connected to a Prcccss Urril" Entcr the appropriate quantily of fllUllmablC/Unstable material on thc space pn.wided, Item "G"

of Spccial Process Hazards. page 5. To estabüsh !he vaJue lO be appüed in using Figure 3. multiply the appropriate quantity of ílllTlm ablC/unstable material by a f:lclOr He (in BT1J/lb) and obtain total STU )l 109, The factor He ts thc hcal of ccmbustion of me material. This can be taken from Appcndlx A o r oblaincd from reacti .... e chemicaJ test data.

2t,

,

FIGURE 3 - LIQUIDS OR GASES IN PROCESS 10

:r.oo (Y) = 0~ 17I79: 0.429sS·l.oQ de> 'o.3~244·LOG ¡x).2 + O)7712~wG (J< )"3 ~.02 10 lblcu f

--

I

Curve B

I

/

/

I.

I

LOO (Y = -0.358311 + 0.459926*LOG (X) -O. 14 1022·L()(j (X)"2 + O.02216·LOO (X)"3 ,

,

'"

0. 1

10 TOTAL POUN OS X 10"6

For kg x 10"6 multiply by 0.45359.

100

Example: Ignoring aisle space, an area of 20,(XX) ft2 (1,860 m2) with a 15 ft (4.6 m) storagc hcight wouId cootain 300,fXX) ft3 (8,500 m 3) of stored material. Ir thc: material bcing storcd in the area (open-ceO foam and cardboard boxcs with polystyrene tubs) have an average density of 2.2ltVft3 (35.2 kglm3): 2.2 Ib./ft' x 300,000 fl'

=660,000 lb

Using Figure 5, Curve A for density < 10 Ibfft3, we detennine that the penalty should be 1.54. Now compare this with storage of polyethylene pellets or ceOulese powder in bags (average density of 28 Ib/ft' (449 kg/m 2)): 28 Ib/ft' x 300,000 ft'

=8,400,000 lb

Using Curve B for density > 10 lb/fP, we detennine that the penalty should be 0.92. While it is true that the fire load (in tenns of both Bros and pounds per cubic foot) is much lowcr for foam or boxes than for baggcd polyethylene pellets or methylcellulose powder, foam and cardboard boxes are much easier to ignite and wouId sustain flame more readily than the denser materials. In short, bccause lhese light materials pose a grcater tire hazard than the heavier ones, thcy are assessed a highcr penalty, even though fewer pounds are stored. The equations for Figure 5, page 31 t for the plots of Curves A and B of Combustible Solids versus

Penalty for Curves A and B are: Curve A: log Y = 0.280423 + 0.464559(log X) - 0.2829 I (log X)2 + 0.0662 I 8(1og X)'

or

log Y = 0.280423 + 0.464559·'og X -0.28291·10g X"2 + 0.066218·log X"3 CurveB: log Y = - 0.35831 I + 0.459926(1og X) - O. 141022(1og Xl' + 0.02276(1og X),

or

log Y =- 0.358311 + 0.459926·10g X - 0.141022·log X"2 + 0.02276·log X"3

H. Corrosion and Erosion Allhough good design malees allowances for corrosion and erosion, sorne corrosion/erosion problems may still accur in certain processcs.

1be corrosion rale is considered lo be the sum of thc external and internal corrosion rates. Be surc not to overlook the possible effects of minor impurities in the process stream that might cause grcatcr than normal intemal corrosioo and the possibility of external corrosioo duc to the chcmical breakdown of paint. Porosity ofbricks and impcrfections in plastic linings are likcly sites for accelcrated corrosion.

32

The following penalties apply: 1.

2. 3. 4.

S.

l.

For corrosion rates less than O.S mil/yr (0.005 in/yr) [0.127 mm/yr] wilh risk of piu.ing or local crosion. the penalty is 0.10. For a corrosiOl1 rale ovor O.S miI/yr (0.127 rnm/yr) and less Ihan 1.00 miVyr (0.254 mm!yr), !he penalty is 0.20. Por corrosion rates higher than 1 miVyr (0.254 rnm/yr), the penalty is 0.50. If lhere is a risk that suess-corrosim cracking miglu de:velop. apply a penalty or 0.7S . 1bis is canmon in process areas exposed lO contamination by chIorine vapor over prolonged periods. Where a lining is required 10 prevent corrosioo. a pena1ty ol 0.20 is applied. Howcver. if thc lining is simply to protect a product fran developing color, no penalty is taken.

Leakage - Joints and Packing Gaskets, seals of joints or shafts and pacldog can be sourccs of leaks of Oammable or combustible materials. particularly where lhennal and pressure cycling occurs. A penalty factor should be sclected according to me design oC the Process Unit under study and the material bcing used in the process. The following penalties should be applied: 1. Whcre (he pump and gland seals are likely 10 give scme leakage of a minor naturc, the penaUy is 0.10. 2. For processes koown to give regular leakage problcms at pumps. compressors and flangc joinls, !he penalty is 0.30. 3. For processes in which thennal and pressure cycling occurs, the penalty is 0.30. 4 Ifthe material in the Process Urot is penetrating in nature or is an abrnsive slurry which can cause intenniuent problems wilh sealing and if the Process Urot uses a rotating shaft seal or packing. the penalty is 0.40. S. Foe any Proccss Urot thal has sight glasses. bellows assemblies or expansion joints. the penalty is 1.50.

J.

U~

ofFired Equipment

1be presence of fired equipment in a process adds an additional probability oC ignition when OammabIe liquids. vapors or combustible dusts are released Thc penalty is applied in OCIe oC two ways: tiest, lO (he tired equipment itself when it is the Process Urot foc the F&EI calculation, and, second, to the various Process Units in me vicinity oC the fired equipment 1be distance in feel from a probable leak point in the Pnx:ess Unit ociog cvaluated 10 the air intake of lile fired equipment is the dislallce referenced in Figure 6. page 34.

L

CurveA-l (Figure6)isused: a) For any Process Unit in which the material oC (he Material Factor could be rc1eascd abovc its flash poinL b) For any Proccss Unit in which the material ofthe Material Factor is a combustible dust 2. Curve A-2 (Figure 6) is used: a) For any Process Urot in which the material ofthc Material Factoc could be released above its boi1ing point

me

The penalty is detennined by entering Figure 6 with!he diSlance from a potemiaI Jeak source to the inlake of!he fired equipment and reading thc penalty from the intcrsection with lhe appropriate cwve

(A-l or A-2) of Figure 6.

33

FIGURE 6 . FIREO EQUIPMENT PENALTY

~OG (Y) = 10.3745·X .2.70212;X'2 + 2.09171·X,j \

0.9

• ROvE BOlLING POINT

\ \

0.8 0.7

\

~ 0.6

"'" A- I

\

-'

~

c.. 0.5 0.4

0.3

\

"'"

~

0.2 ABOYE FLASH POINT 0.1

~A-2

'" ~ '"

~

~

-..........-.

LOO (Y) _ ·3.3243 ·X + 3.75127·X"2 ·1.42523·X"3

o

30

60

90

-...... 120

150

DIST ANCE IN FEET FROM POSSmLE LEAK SOURCE

For distante in melers multiply by 0.3048,

ISO

210

The equations for CUrves A-l and A-2 for Distance flom Possible Leak Source (X) and Penalty (Y)

are: Curve A.l: 10gY =

-3. 3243(~) + 3. 75 12.,('~21O ~)' - 1.4252.,( ~)3 210 \210

or

log Y =- 3.3243'(XI2IO) + 3.75127'(x/2IO)"2 - 1.42523'(X/2IO)"3

Curve A·2:

logY =-o.3745(~)-2.702l".,( 210

....!..)l +2.0917 1(~)' 210

\210

or

log Y = - 0.3745(X!21O) - 2.70212'(X!2IO)A2 + 2.09171'(X!2IO)A3 If the fued equipment (process side) itself is the Process Unit ooing evaluatcd. Ole distaJlCC from the possible leak source becomes zcro. If the equipment is heating a flarnmabl e o r combustible material , the penalty is 1.00. even lf lhe malerial is nol being healed abo ve itsJlash poinl. The "1" penalty is oot applied 10 the flf'C side. However. any olher silualÍon covered bylhis sudon involving a material processed below its flash point receives no penalty.

If a piece of flrcd equipment is localed within thc process arca and there is a possibility mat the material in the Process Unit selected as MF could 00 released aboye its flash pJint, a minimwn penalty or0.10 is requircd, regardress 01 lhe distance in volved. Flf'Cd equipment with "pressure bumer" design will require only 50% of the penalty spccified for standard bumer designo provided the air intake is 10 ft (3 m) or more aboye grade and is not exposed lO potential sources of spills from ovemead. However. thc 50% penalty cannot be applicd whcn the fired heater itself is the Process Unit being evaluated.

-

K. Hot Qil "eat Exchange System Since most hot oil (heat exchange) fluids will bum and are frequently uscd aboye their fla sh points or boiling points, thcy rcprcsent an additionaI hazard in any Process Unil that uses lhcm. The penal bes in this section are bascd on the quantity and temperature of the hcat exchange fluid used in me urtit bcing evaluated. No penalty is applicd if the hot oil is non-combustible or, if a combustible fluid. is always used bclow its fl ash point However, [he plSsible fonnation of mists should 00 considcrcd. (See page 12.)

1be quantity 10 be used with Table 5 10 determine the penalty is takco 10 be the Icsscr of 1. a lS-minute spiU caused by a break in the Une servicing thc Process Unit or 2. the bol oiJ inventory within the active circulating hot oiJ system .

1be portion of the bol oi1 hcat exchange system that can be classified as "slOrage" is nOl used in determining the active capacity unless it is connected much ofthe time to thc Proc:css Unil.

35

It is recanmended that thc F&EI for me hot oil circulating system itself be detennined. including the active (oot Slorage) tank. pumps and distribution/retum piping. Thcse detenninations have histoncaUy loo 10 large F&EI values. If the bot oil exchange system itself is the Process Dnit being evaluated. no penalty is taken for this section. However. ir a fired bol oil heat exchange system is actua1ly located in the arca of the Process Unit being evaluated. the penalty tor Section J wiIJ apply.

TABLES HOT OIL HEAT EXCHANGE SYSTEM PENALTY Quantity Above Flash At or Above Hoiling 3 Point Penalty Point Penalty Gallons (m ) 0.15

0.25

5.000 lo 10.000 (18.9 10 37.9)

0.30

0.45

10.000 lo 25.000 (37.9 lo 94.6)

0.50

0.75

> 25 .000 (94.6)

0.75

1.15

1O.!XXl ft2 (929 m2) Are. > 2O.!XXl ft2 (1.858 m2) Are. > 30.!XXl ft2 (2.787 m2)

= = =

1.06 1.09 1.12

Note that as the possible tire area is increased (e.g., a warehouse), the credit factor is increased by a penalty factor (1-06 to 1-12), which mcreases the loss cootrol cremt factor and incrcases the MPPD, as it should. Large tire arcas offer greater exposure to tire loss than small tire areas.

r_ Water Curtains - 0.97 to 0.98 1be use of automatic water spray curtains between a source of ignition and a potential vapor release arca can be effective in reducing the vapor c10ud ignition potential.

To be effcctive, the curtain should be located at least 75 ft (23 m) from the vapor reJease poinl 10 allow time for deteaion of the release and automatic activation of the water curtain. A single tier of nozzles at a maximum elevation of 1S ft (5 m) will receive a cremt factor of 0.98. A secrod tierofnozzles, not exceeding 6 ft (2 m) alxwe lhe first tier, will receive a credit factor ofO.97.

g. Foam - 0.92 lo 0.97 If lite arca proteclion system includes me capability of injecti.ng foam liquid into a standard dcluge sprinkler system fmm a remOle manual control stalion. use a cre.dit factor of 0.94. 11lis credit is in addition 10 the credit taken for the deluge system itself. A totalIy automatic foom system re- ceives a credil of 0.92. Totally automatic means thc foom valve is automatically actuated when tire is detected. Manual foam application systcms for the protection of seal rings on open-top floating mof tanks receive a cremt of 0.97. Use a factor of 0.94 when tire detea.ion devices are uscd for actuating the foam system. Subsuñace foam systems and foam charntx:rs on cone roof tanks rcceive a credit factor of 0.95. Foam application amund the outer shell of a flarnmable liquid tank rcceivcs a credit factor of 0.97 if manually applied. 0.94 ir automatic. h.

Hand ExtinguishersIMonitors - 0.93 to 0.98 If tbere is an adequate supply available of hand and Plrtable fire extinguishers suitable for the fire risk. involved, use a cremt factor of 0.98. Where there is JX>tential for a large spill of Oarnmable material that, if ignited, could oot tx: controllcd effectively with hand extinguishers, do nol take a crcdit. Hand extinguisher credit is oot appropriate for process areas where large quantities of Oarnmable or combustible liquids can be spilled.

45

If monilOr guns have also been installed, use a credit factor of 0.97. Monitor guns that can be remOlCly operaled fmm a safe vantage point receive a credit factor of 0.95. Monitors equipped with foam injection capability receive a credit factor of 0.93.

i.

Cable Protection - 0.94 to 0.98 Instrument and electrical cable trays are very vulnerable lO damage froro tire exposurc when installed in pipeways and operating structures. 1be use of 14 10 16 gauge metal sheet below the tray with a water spray directed 0010 (he lOp side will provide reasonable protection which justifies a credit of 0.98. 1be use of fireproofing material 00 the metal sheet in lieu oC the water spray also receives a credit olO.98. If the cable raceway is buried below grade in a uench (either nooded ordry), use a credit olO.94.

el

el

TIte product of x el x constitutes the Loss Control Credit Factor for thc Proccss Unil and is 10 be cntcrcd inlO tine 7 ofthc Process Unit Analysis Summary, page 6.

46

PROCESS UNIT RISK ANALYSIS SUMMARY The Process Unit Risk Analysis Surnmary, page 6, gives a surnmary of all of the important Process Unit Risk Analysis infonnation. This starts with the F&EI and gives additional risk infonnation which is detennined from the F&EI, the Loss Control Credit Factor, the Area of Exposure, the Damage Factor and the Value of Production for the Month. The Process Unit Risk Analysis Surnmary, along with the F&EI, is a good risk analysis tool to be used in making decisions regarding the risk management program for the Manufacturing Unit of which the Process Unit is a parto The remainder of this guideline presents the process for detennination of the additional risk factors which are to be considered for the Process Unit which then leads to an overall view of the risk factors for the total Manufacturing Unil

1. The Fire and Explosion Index (F&El) The Fire and Explosion Index calculation is used for estimating the damage that would probably result from an incident in a process plant. A surnmary of a description of the F&EI is given on page 38 along with Table 6 which lists the degree of hazard for the various ranges of F&EI. All of the key infonnation and calculations which go to determine the F&EI are list in the fonn on page 4. The F&EI value is to be entered on line 1 of the Process Unit Risk Analysis Surnmary, page 6, and in the Manufacturing Unit Risk Analysis Surnmary, page 7.

2. The Radius OC Exposure The F&EI, which was determined on page 5, is converted to a Radius of Exposure by multiplying the F&EI by a factor of 0.84 or by using Figure 7, page 48. This is detennined in either feet or meters. This radius of exposure is to be shown on plot plans for the Manufacturing Unit with the primary item ofyrocess equipment as the center of a circle using the Radius of Exposure. Cirdes should be drawn for each of the Process Units being analyzed in the Manufacturing Unit. The Radius of Exposure should be entered in the Process Unit Risk Analysis Summary on page 6, line 2.

When the Process Unit being evaluated is a small piece of equipment, the Radius of Exposure can be considered to start at the center of the item concemed. The Radius of Exposure for large pieces of equipment would extend outward fmm the equipment surface for a distance equal to what should be considered as the "radius." The additional area is added to the original area of the Process Unit being evaluated to detennine the Area of Exposure. For specific cases, the center of the Area of Exposure is very often a leak point. Examples of likely leak points include vents, expansion joints, loading/ unloading connections, etc. These would be the center of the Area of Exposure circle.

47

FIGURE 7 . RADIUS OF EXPOSURE 180

y =O.84*X

160 140

~

120

~

;;l

.... 100 -< CII:

Q ~

00

~

CII:

;;l

rn

~

80

V

O

c..

~ ~

60 40 20 O

/ O

......

20

/

V

40

/

V

60

/

V

V

100 120 80 FIRE & EXPLOSION INDEX

For Exposure Radius in meters multiply by 0.3048.

/

140

V

, 160

/

V

180

/

200

3.

The Area Of Exposure

1be Radius of Exposure defines an Area of Exposure. The Area of Exposure is calculated with the equation: ft2 or m2 or Area =1t(R1\2) Area= 1tR 2 1be Area of Exposure should be entered in the Process Unit Risk Analysis Surnmary on page 6, line

3. The area is that which contains equipment that could be exposed to a fue or to a fuel-air explosion generated in the Process Unit being evaluated. For evaluation of equipment that could be damaged in a fue or explosion, actually a volume is considered. This volume is a cylindrical volume of the plant surrounding the Process Unit with the area being the Area of Exposure and the height being equal to the Radius of Exposure. In sorne cases a spherical volume is appropriate. The volume is expected to be the amount of the Manufacturing Unit at risk in the event of a fue or explosion caused by an incident in the Process Unit under study. Below is a sketch of a vertical tank considered as a Process Unit; and the Radius of Exposure, Area of Exposure and volume are shown as an example .

!. . . . . ..

....., .......-.,...... ,P ..... .. m""• ."m .. .............

.,. . . ...-/' (

"

w . . ........... w ............................... , ...." ...••••

T

. . . .,.... .

~ Volume ~ .

....\

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······· ·· ········"··.....•..····..·····•·· .. . .........., . w",, . ..... ... ' Nm

.............."

......... ... . . . . ·· · · · · , , · ,· · · · , , · · · ·

..

····/:1 ..:·

..........., - • •

=

Height Radius ofExposure

F&EI = 100 Radius of Exposure = 84 ft (25.6 m) Area of Exposure = 22,170 ft 2 (2,060 m 2) Height of Cylindrical Volume = 84 ft (25.6 m) It is recognized that a tire and/or explosion incident does not spread out into a perfect circle producing equal damage in all directions. The actual damage can be affected by positioning of the equipment, wind di.rection and drainage layout, all of which are important factors influencing loss prevention designo However, the circle affords a good basis for later calculation of values. As a matter of interest, the Radius of Exposure was computed in early studies for the F&EI by considering the probable effects of spills of various flammable materials 3 in (8 cm) deep as well as the potential effects of vapor air mixtures and tire, considering several different sets of ambient conditions.

49

If the Area of Exposure is external to, but ineludes walls of buildings that are resistant to fue or explosion or both, the building may not be at risk and may be excluded from the Area of Exposure. If there is a blast wall or fire wall within the Area of Exposure, the area behind the wall would not be included When the material is stored in a warehouse or other building, the aboye reasoning leads naturally to the conclusion that only the volume of that building itself is at risk, provided the risk is fire only, not explosion, and the -construction is such that the walls and roof will not propagate fire. If the building