P. 1


# OAR Box 1107 Prepped by Ollie Stewart



# Document

Number: 

# 54 ) IV-B-4 Docket Number: 

# A-81-2 1

Printed 4/11/20083:03:4 7

PM Sheet 54 of 90P. 2

• 4 i



### MEMORANDU M 

# £-'8~ l - 2 IV-B- 4

DATE : Jun e 20 , 198 5 TO : Le s Evan s

Chemical s and Petroleu m Branc h FROM : Kare nFidle r

Radia nCorporatio n SUBJECT : Larg e Relie f Valv e Discharge s a t PV C an d EDC/VC Plant s Purpos e This memorandu

m present s informatio npertainin g t o larg e relie f valv e discharge s o f viny l chlorid e (VC ) fro m PV C an d EDC/VC plants . Informatio n wa s obtaine dfro

m 10-day complianc e report s submitte db y 2 3 PV C plant s an

d 1 3 EDC/VC plant s durin g th e 6-yea r perio dfro m 197 8 throug h198 3 (Refs . 1 , 2 , 3) . This informatio nha s bee nsummarize dfo r th e purpos e o f evaluatin g option s fo r regulatin g larg e relie f valv e discharge s unde r th e V C standard . Characterizatio no f Larg e Relie f Valv e Discharge s Fo r th e purpos e o f thi s memorandum , larg e relie f valv e discharge s ar e considere dt o b e thos e i nwhic hth e estimate damoun t o f V C discharge d exceed s 6,00 0 pounds . Fo r th e 60 9 relie f valv e discharge s incident s betwee n 197 8 and 198 3 fo r whic hcomplianc e informatio ni s available , Figur e 1 show s th e distributio no f discharge s b y size . A s show

ni nFigur e 1 , 6 1 discharge s (o r 1 0 percent ) wer e estimate db y plant s t o excee d6,00 0 pound s o f VC . A tota l o f 5 1 larg e discharge s wer e reporte db y PV C plant s an

d 1 0 larg e discharge s wer e reporte db y EDC/VC plants . I nPV C plants , 4 6 o f th e 5 1 larg e discharge s occurre dfro m polymeriza tio nreactors . Th e fiv e larg e nonreacto r discharge s a t PV C plant s occurre d fro m equipmen t associate dwit hth e polymerizatio nproces s suc ha s blowdow n vessels , stripper s an d see dtanks . Th e larg e relie f valv e discharge s reporte db

y EDC/VC plant s occurre dfro m equipmen t involve di nth e V C productio nan

d purificatio nprocesses , particularl y V C purificatio ncolumn s andVC storag e vessels . Th e analysi s fo r selectin g numerica l relie f valv e discharg e limit s fo r th e V C standar dwa s base dondischarg e performanc e dat a durin g th e 2-yea r perio dbetwee nAugus t 198 1 an d Jul y 1983 . Th e majorit y o f larg e relie f valv e discharg e incident s a t PV C plant s occurre dprio r t o thi s 2-yea r period . Specifically , 4 7 o f th e 5 1 larg e discharge s (o r 9 2 percent ) occurre dprio r t o Augus t 1981 . A t EDC/VC plants , 6 larg e discharge s wer e reporte ddurin g th e 2-yea r perio dfro m Augus t 198 1 t o Jul y 1983 , an

d 4 larg e discharge s wer e reporte dbefor e Augus t 1981 . Tabl e 1 summarize s th e annua l frequenc y

o f larg e discharg e incident s betwee n197 8 t o 1983 .
Progres s Center/320 0 E . Chape l Hil l Rd./Nelso n Hwy./P.O . Box 13000/Researc h Triangl e Park , N.C . 27709/(919)541-910 0P. 3



## Thi s memorandu

m provide s informatio no nal l larg e discharge s betwee n 197 8 and198 3 fo r whic hcomplianc e informatio ni s available . Thos e larg e discharge s occurin g durin g th e 2-yea r perio dcorrespondin g t o th e analysi s fo r selectin g th e numerica l limit s hav e bee nidentifie dseparately . Cause s o f Larg e Relie f Valv e Discharge s Reporte dcause s o f larg e relie f valv e discharge s vary . Table s 2 an d3 includ e a summar y

o f th e reporte dcause s o f th e larg e discharge s a t PV C an d EDC/VC plants , respectively , fo r whic hcomplianc e informatio ni s available . I ngeneral , th e larg e discharg e incident s investigate doccurre dfo r th e sam e type s o f reason s a s smalle r discharg e incidents . Example s o f th e type s o f reporte dcause s o f larg e discharge s include :

Operato r erro r - whe noperator s fai l t o follow establishe d standar doperatin g procedure s (SOP) ; Prematur e releas e - whe na pressur e relie f devic e relieve s a t a pressur e lowe r tha nth e minimu m rate dpressure ; Instrumen t malfunctio n- mos t commonl y involvin g pressur e an d temperatur e control s an dleve l indicators ; Equipmen t failur e - example s includ e failur e o f reacto r coolin g an dagitatio nequipment ; an d Powe r los s - resultin g fro m externa l andinterna l powe r o r electrica l failur e Preventabilit y

o f Larg e Relie f Valv e Discharge s No attemp t wa s mad e t o asses s th e preventabilit y o f eac ho f th e larg e relie f valv e discharg e incident s investigated . However , a revie w o f th e reporte dcause s o f th e larg e discharge s indicate s tha t man y o f th e discharge s ar e representativ e o f th e type s o f discharge s tha t hav e bee nconsidere din previou s analyse s t o b e preventabl e b y takin g reasonabl e measure s (Referenc e 4) . Inth e previou s analyses , discharge s cause db y operato r error , du e t o operato r negligance , o r failur e t o follow SO P wer e considere d clearl y preventable . Also , operato r error s resultin g fro m insufficien t trainin g o r lac k o f establishe dSO P wer e considere dpreventable . Othe r example s o f type s o f discharge s considere dclearl y preventabl e ar e prematur e release s an

drepetitiv e discharge s cause db y th e same se t o f preventabl e circumstance s a s previou s discharges . No t al l o f th e larg e discharge s fal l int o th e previousl y

identifie dcategorie s o f preventabl e discharg e types . Althoug hsome o f thes e discharge s ma y als o b e preventable , thi s judgmen t ca n no t be mad e i nal l case s base do nth e informatio ncontaine dinth e 10-day complianc e reports . Thus , i t canno t b e assume dtha t al l o f th e larg e relie f valv e discharge s ar e preventable .P. 4



## Factor s Affectin g Siz e o f Discharge s Availabl e complianc e informatio nonlarg e relie f valv e discharge s wa s reviewe dt o determin e how th e amoun t o f VC discharge ddurin g a relie f valv e discharg e inciden t i s affecte db y action s take nafte r th e discharg e begins . Fo r som e o f th e larg e discharge s investigated , Table s 2 and3 includ e a descriptio no f factor s reporte db y plant s tha t apparentl y contribute dt o th e siz e o f th e larg e discharge . Example s o f factor s reporte dt o influenc e discharg e siz e include :

Operato r erro r i nfailin g t o identif y an dimplemen t appropriat e action s t o sto pdischarge ; Polymerizatio nshortsto psystem inoperabl e du e t o operato r erro r o r lac k o f maintenance ; Plan t hadinsufficien t o r no backu ppowe r availabl e fo r agitatio n and/o r coolin g durin g powe r outages ; o r backu ppowe r generatio n capabilit y

wa s impaired ; Plan t ha dno D C powe r sourc e fo r instrumentatio ndurin g powe r outage ; Us e o f doubl e ruptur e dis c assemblie s instea do f ruptur e disc/relie f valv e assemblies , wher e th e latte r ar e feasible ; an d Failur e o f pressur e relie f valve s t o resea t properly .P. 5



## REFERENCE S 1 . Memorandu

m fro m Fidler , K . K. , Radia nCorporation , t o file . Augus t 21 , 1984 . Relie f valv e discharg e complianc e report s fro m Regio nVI . (Docke t Ite

m II-B-44) . 2 . Lette r an

dattachment s fro

m Varner , B. , EPA

Regio nV , t o Howie , R. , Radia nCorporation . Januar y 12 , 1984 . Respons e t o reques t fo r relie f valv e discharg e complianc e informatio nfo r PV C plants . (Docke t Ite m II-D-47) . 3 . Memorandu

m fro m Fidler , K . K. , Radian , t o file . Augus t 10 , 1984 . Relie f valv e discharg e complianc e report s fro m Regio nII . (Docke t Ite m II-B-30) . 4 . Memorandu

m fro m Howie , R . H . an

dFidler , K . K. , Radia nCorporation , t o file . Apri l 16 , 1984 . Numerica l limit s fo r relie f valv e discharges . (Docke t Ite

m II-B-26) .> a



### o e

at 0 

## c 

## u 

## 400- | 

## 39 0 10 0 

## 9 0 8 0 7 0 8 0 6 0 4 0 3 0 20 - 1 0 39 3 Frequenc y of discharge s Cumulativ

e frequency b

y percen t 10 0
8 8 8 8 9 0 9 1 

## 9 3 

## *± 9 8
8 1 7 5 8 6 8 6

3 7 3 0

1 0 1 0 9 1 1 2 6

0-1.00 0 1,000 - 2.000 - 3.000 - 4,000 - 6,000 - 8,000 - 7,000 - 8,000 - 9,000 - k4An 

### m

2,00 0 3.00 0 4,00 0 6,00 0 6.00 0 7,00 0 8,00 0 9.00 0 10,00 0 >1 

### ° ' o w 

### Pound s V C Emitte d pe r Discharg e Figur e 1 Distributio n o f relie f valv e discharge s b ysiz eP. 7



## TABL E 1 . FREQUENCYOF LARG E RELIE F VALV E DISCHARG E INCIDENT S BETWEEN

197 8 an

d198 3

Yea r No. o f Larg e Discharges 3 

## PV C EDC/V C 197 8 2 0 2 197 9 1 2 2 198 0 1 2 0 198 1 5 1 198 2 2 5 198 3 0 0
a 

## Relie f valve discharge s during whic hth e estimate damoun t o f V C discharge d exceede d6,00 0 pounds .TABL E 2 . SUMMAR Y O F LARG E RELIE F VALV E DISCHARG E INCIDENT S A T PVC PLANT S BETWEE N197 8 AN D 198 3

Plan t Discharg e Cod e Amoun t (Pounds ) Dat e Sourc e Caus e o f Discharg e Factor s Affectin g Siz e o f Discharg e 

### R- l

R- 2
R- 3 50.00 0

30,00 0

33,00 0
38,00 0

10,00 0

10,24 9 6,50 0 17,92 6 8/13/7 8

11/26/7 8

3/23/8 0

6/21/7 8 5/5/8 0 9/9/8 0 Suspensio n reacto r

Suspensio n reacto r

7/27/7 9 Suspensio n reacto r
10/20/7 9 Suspensio n reacto r

12,090 * 5/22/8 2 Suspensio n reacto r

Suspensio n reacto r Suspensio n reacto r Suspensio n reacto r Suspensio n reacto r Prematur e failur e o f 2 ruptur e disc s o n doubl e R D assembl y Powe r failur e

Operato r erro r i n settin g reacto r temperatur e controlle r Prematur e failur e o f 2 ruptur e disc s o n doubl e R D assembl ydurin g powe r failur e
Operato r erro r durin g reacto r chargin g operation s cause d hydrofu l

Prematur e ruptur e dis c failur e durin g charging ; SR

V lifte d durin g hea t u p Electrica l shor t o n reacto r temperatur e controlle r Reacto r coolin g contro l loo p instrumen

tatio n faile d Imprope r contro l o f reactio n whe n analo g temperatur e an d pressur e contro l instrumentatio n drifte d ou t o f calibratio n Becaus e doubl e R D assembl ywa s use d instea d o f SRV/RD , n o metho d wa s availabl e fo r stoppin g discharge . Shortsto p coul d no t b e successfull yadde d becaus e operato r faile d t o clos e Iner t ven t valve . Reaso n fo r unsuccessfu l shortsto p wa s no t immediatel yidentified . Operato r lef t contro l room ; unqualifie d operato r di d no t reac t properl yt o hig h temperatur e an d pressur e alarm . Decisio n t o kil l reactio n wa s no t mad e unti l afte r severa l powe r dips . Becaus e doubl e R D assembl yburst , n o metho d wa s availabl e fo r stoppin g discharge . Caus e o f overpressur e no t Immediatel y Identified . Operato r erro r causin g hydrofu l Interfere d wit hregula r metho d o f addin g shortstop . SO P wa s t o continu e batc heve n afte r R D failure . Operator s attempte d t o equaliz e pressur e wit h anothe r reacto r bu t valv e di d no t operate . Stea mvalv e wa s leaking ; shortsto p injectio n tubin g wa s blocked . Plan t nitroge n pressur e wa s to o lo wt o injec t shortstop . •Discharg e occurre d durin g 2-yea r perio d betwee n Augus t 198 1 an d Jul y1983 . Performanc e durin g thi s 2-yea r perio d wa s th e basi s fo r propose d numerica l relie f valv e discharg e limit s i n th e V C standar d (se e 4 0 FR 1182) .TABL E 2 . (Continued )

Plan t Discharg e Cod e Amoun t (Pounds ) Dat e Sourc e Caus e o f Discharg e Factor s Affectin g Siz e o f Discharg e 

### R- 6 6,00 0

6,75 0

7,720 * 12,825 * 3/24/7 8

10,00 0 1/5/7 9 12,00 0 11/17/7 9
8,560 * 8/15/8 2

4/18/7 8
12,60 0 7/3/7 8 7,50 0 9/30/7 8

8/21/8 1 10/10/8 1 Suspensio nreacto r

Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r


### R- 8

R-1 0 R-l l 8,71 0

41,86 6
7,35 6 8,00 0 9/28/7 8

6/NA/8 1
2/10/8 0 3/29/7 8 Dispersio nreacto r

Dispersio nreacto r Suspensio nreacto r Blowdow ntank
Blowdow ntank Suspensio nreacto r Blowdow ntan k Suspensio nreacto r Powe r failur e require dplan t t o shutdown ; manua l ventin g wa s necessar y t o avoi d relie f valv e discharge s fro m 4 reactor s Malfunctio ni

nreacto r charg e pum

pcause d reacto r t o be overfille dwit hwate r Powe r failur e whe nmai nhighvoltag e feede r t o plan t wa s knocke dout ; manua l venting o f 2 reactor s wa s require d Wate r continue dt o ente r reacto r afte r charg e becaus e o f failur e o f automati c contro l valv e Prematur e ruptur e dis c failur e Powe r failur e cause dsi xreactor s t o overpressur e an

ddischarg e Circui t breake r failur e cause dpowe r los s t o coolin g towe r pump s Wate r contaminatio nI ncontainmen t system rela y cause dwron g reacto r t o be droppe d Lo w instrumen t ai r prevente dcontainmen t system fro m operatin g an

dwron g reacto r wa s droppe d Wron g ruptur e dis c installe d Manua l valv e oncontainmen t syste m controlle r line wa s close d Operato r erro r whe nreacto r temperatur e controlle r wa s i nmanua l mod e Suspensio nreacto r Plant-wid e powe r failur e Emergenc y powe r use dfo r reacto r agitatio n an dcooling , bu t 4 reactor s require d controlle dmanua l ventin g t o preven t overpressure . Relie f valv e faile dt o resea t an d eventuall y

hadt o b e reseate dmanually . Emergenc y

powe r wa s als o los t becaus e voltag e surg e blew

fuses . Flo w mete r tha t woul dIndicat e wate r flo w int o reacto r malfunctioned . No informatio nprovided . Backu pgenerato r malfunctioned ; plan t wa s evacuate dbefor e shortsto pcoul db e adde d t o al l reactors . N o 10-day

report . No 10-day

report . N o 10-da y report .
No 10-day

report . N o 10-da y report . No 10-day

report . Emergenc y

breake r fo r agitatio n malfunctioned . •Discharg e occurre ddurin g 2-yea r perio dbetwee nAugus t 198 1 an dJul y 1983 . Performanc e durin g thi s 2-yea r perio dwa s th e basi s fo r propose d numerica l relie f valv e discharg e limit s i nth e V C standar d(se e 4 0 F

R1182) .Plan t Discharg e

Cod e Amoun t (Pounds ) R-1 3 11,30 0

10,30 0 9,54 0 13,20 0 9,90 0 8,38 3 9,45 0 9,81 7 9,50 0 8,60 0 8,20 0 10,09 2 41,86 6

R-1 9 8,39 0

9,55 1 11,13 0 6,24 0 9,85 0 Dat e

1/1/7 8 3/11/7 8 3/24/7 8 4/15/7 8 6/9/7 8 7/22/7 8 8/21/7 8 6/5/7 9 11/19/7 9 2/9/8 0 2/24/8 0 6/15/8 0 3/6/8 0

3/10/7 8 5/2/7 8 11/7/7 8 11/13/7 8 1/2/7 9 TABL E

Sourc e Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r Blowdow ntankand strippe r colum

n Suspensio nreacto r Dispersio nreacto r Suspensio nreacto r Dispersio nreacto r Dispersio nreacto r See dtan k
Reacto r
Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r Suspensio nreacto r Dispersio nreacto r 2 . (Continued )

Caus e o f Discharg e Reacto r overcharg e Temperatur e controlle r incorrectl y place di nmanua l mod e Reacto r overcharg e Reacto r overcharg e Operato r error-wron g reacto r wa s washe d Failur e t o clos e botto m valv e o nreacto r befor e charg e Pressur e transmitte r failur e Reacto r overcharg e an dfailur e o f relie f valv e t o containmen t syste m Prematur e ruptur e dis c failur e Hydroful . Relie f valv e t o containmen t system plugge d Hydroful . Relie f valv e t o containmen t syste m plugge d Us e o f wate r an

dnitroge nt o dislodg e a plu g i nseedtankcause doverpressur e ( Powe r failur e an

dsubsequen t coolin g wate r los s cause d6 reacto r an d 6 blowdow

ntank s t o discharg e Coolin g wate r los t t o al l reactors ; emergenc y

ven t valv e opene do n2 reactor s Overcharg e o f VC

M Abnormall y

fas t reaction ; prematur e ruptur e dis c failur e durin g shortsto p Reacto r temperatur e transmitte r damage d b y maintenanc e personne l Pressur e transmitte r froze ; reacto r wa s manuall y vente dt o reliev e apparen t overpressur e Factor s Affectin g Siz e o f Discharg e No 10-day

report . No 10-da y report . N o 10-day

report . i ' .S?. , ; • ' N o 10-da y report . No 10-da y report . No 10-day

report . No 10-da y report . No 10-day

report . N o 10-day

report . N o 10-da y report . No 10-da y report . Du e t o storm , discharg e wen t unnotice dfo r 7 5 minutes . Backupfeede r dow

nfo r maintenance . Newl y Installe dautomati c shortsto psyste m wa s no t operabl e becaus e o f leaks ; manua l shortsto pwa s use dinstead . Non e given . Non e given . Non e given . Caus e fo r oyerheate dreactio nno t immediatel y

Identified . Non e given . » • .TABL E 2 . (Continued )

Plan t " Discharg e Cod e Amoun t (Pounds ) Dat e Sourc e Caus e o f Discharg e Factor s Affectin g Siz e o f Discharg e R-1 9 (cont. )

R-2 0
R-2 2 9,54 0

10,87 0 8,30 0 13,20 0 6,30 0 6,00 0 8,00 0 6,00 0 4/12/7 9

4/12/8 0 4/20/8 0 9/17/8 0 5/20/8 1 6/11/7 8 6/14/8 1 5/4/7 8 Suspensio n reacto r

Reacto r Reacto r Reacto r Dispersio n reacto r Bul k reacto r (po-po ) Bul k reacto r (po-po ) Bul k reacto r (po-po )

R-23 Prematur e ruptur e dis c failur e Prematur e ruptur e dis c failur e Operato r erro r Powe r failur e Malfunctio n i n coolin g wate r contro l Overpressur e Pressur e transmitte r ou t o f calibratio n and fle x lin e t o pressur e transmitte r plugge d 13,00 0 2/14/7 9 Bul k reacto r (po-po ) Exces s initiato r i n experimenta l batc h
7,00 0 3/14/7 9 Bul k reacto r (po-po ) Overpressur e durin g experimenta l batc h 8,00 0 6/24/7 9 Bul k reacto r (po-po ) Overpressure ; caus e unknow n t o alternat e RD . 7,83 8 8/6/7 9 Solutio n reacto r Prematur e ruptur e dis c failur e Shortsto p additio n wa s delaye d becaus e o f Insufficien t Injectio n pressur e an d plugge d Injectio n line . N o 10-dayreport . N o 10-dayreport . N o 10-dayreport . Non e given . N o 10-dayreport . N o 10-dayreport . Ruptur e dis c only ; ventin g wa s stoppe d b y switchin g t o alternat e RD . Afte r switchin g t o backup ruptur e disc , I t burst , an d ventin g ha d t o b e stoppe d b y manuall yclosin g bloc k valv e belo wRD . Ruptur e dis c only ; discharg e wa s stoppe d b yswitchin g t o alternat e RD . Ruptur e dis c only ; discharg e wa s stoppe d
Non e given .TABL E 3 . SUMMAR YO F LARG E RELIE F VALVE DISCHARG E INCIDENT S A T EDC/VC PLANT S BETWEE N 197 8 AN D198 3
Plan t Discharg e Cod e Amoun t (Pounds ) Dat e Sourc e Cause o f Discharg e Factor s Affectin g Siz e o f Discharg e 

### V- 2
V- 6 8.500 *

11,000 * 11/2/8 2

2/9/8 2 V C furnac e

V C colum n Powe r failur e cause doverpressur e i n

viny l furnac e Viny l colum

noverpressure ddurin g startu pbecaus e coolin g wate r valve s wer e lef t I nincorrec t positio nafte r maintenanc e Pressur e contro l valve s faile dclose du e t o electrica l andai r failure ; no D C back-u p powe r source . . :-,,'-'.•:'. > Relie f valve di dno t resea t becaus e o f erro r i nvalve assembly . Reaso nfo r overpressur e no t readil y detected . 

### V- 7 9,600 * 10/30/8 2 Ligh t end s colum n



### V- 9
V-1 0

V-l l 13,878 *

7.50 0 3/25/8 2

4/30/7 8 V

C storag e tank

VC colum n

7,50 0 7,00 0

12,00 0 6,00 0 6/1/7 9

9/8/7 9

5/23/7 8 8/31/7 8 V C rundow nspher e Quenc hcolumn , HC I colum n
Storag e tank Compressor s Ligh t end s colum noverpressure dbecaus e o f faile dpressur e transmitte r

6,00 0 7/28/7 9 

### N A Produc t storag e vesse l overpressure d whe na valve I nth e tank' s Incinerato r ven t heade r wa s close dfo r maintenanc e Powe r failur e cause doverpressur e inVC colum n

VC rundow

nspher e wa s overfille d HC I colum

nand2 quenc hcolum s overpressure dwhe nVC uni t wa s shutdow n t o repai r faile dthrus t bearin g I n refrigeratio nsystem Operato r erro r fillin g storag e tank Proces s compresso r emergenc y valv e discharge dwhe na relay protectin g th e compresso r moto r operated . Misconmunlcatio noccurre dwhe ntryin g t o dea l wit ha faile dvalv e Overpressur e conditio nno t detecte dbecaus e backu ppressur e transmitte r indicate dcolum n pressur e wa s normal . Operato r close dsafet y valv e becaus e h e believe di t wa s leaking ; thi s cause d safet y ruptur e dis c t o burst . Approximatel y

2 0 minute s wer e require dt o sto pdischarg e b

y equalizin g pressur e wit hanothe r tank . N o backu ppowe r availabl e fo r refluxpumps . Higher-tha nnorma l HC I i nV C colum nbecaus e o f prio r HC I colum

nupset . Sphere' s leve l Indicatio nequipmen t wa s readin g 2 0 percen t lo w andhighpressur e alarm failed .

N o 10-day

report . No 10-day

report .
N o 10-day

report . •Discharg e occurre ddurin g 2-yea r perio dbetwee nAugus t 198 1 an dJul y 1983 . Performanc e durin g thi s 2-yea r perio dwa s th e basi s fo r propose d numerica l relie f valve discharg e limit s i nth e V C standar d(se e 4 0 F

R1182) .TABL E 3 . (Continued )

Plan t Discharg e Cod e Amoun t (Pounds ) Dat e Sourc e Caus e o f Discharg e Factor s Affectin g Siz e o f Discharg e V-1 3 46,556 * 12/22/8 1 V C column , VC ven t heade r 43,209 * 6/2/8 2 V C column , VC reboiler , VC refluxdru

m Powe r failur e cause d2 VC column s and

dry VC ven t collectio nheade r t o overpressur e Powe r failur e cause d3 VC columns , 1 reboile r an

d1 reflu

xdru m t o overpressur e No backu ppowe r o r cooling .
No backu ppowe r o r cooling . •Discharg e occurre ddurin g 2-yea r perio dbetwee nAugus t 198 1 an dJul y 1983 . Performanc e durin g thi s 2-yea r perio dwa s th e basi s fo r propose d numerica l relie f valve discharg e limit s i nth e V C standar d(se e 4 0 F R1182) .