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.............................. 4 7 Ma r c h 19, 1996
............................ 4 7 Ja nu a r y19, 1997
........................... 4 8 S u p e r v i s i o n ...................................... 4 8 T r a i n i n g ........................................ 4 9 E m e

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................................................................. A

- 1 A

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r en c e s .................................................. A

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p p en di x B H i s t o r yo f M a j o r P r o c e s s C h a n g e s ................................ B

- 1 A

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r P r o c e s s F l o wD i a g r a m s ....................... C

- 1 A

p p en di x D I nt e r b e d Q u en c h a n d D i s t r i b u t i o n S k et c h e s .......................... D

- 1 A

p p en di x E S t a g e 2 R e a c t o r T h e r m o c o u p l e P o i nt s p e r I n s t r u m entD i s p l a y ............ E

- 1 A

p p en di x F A v e r a g e B e d D i f f e

r ent i a lT em p e r a t u r e f

o r R e a c t o r 3 ( p r e - i n c i d ent )
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............. G

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.............. H

- 1 A

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byT o sc o a s o f Jun e 1997
................ I

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- 1 Li st o f Tab l e s

T a b l e 1 C r i t i c a lO p e r a t i n gL i m i t s f o r S t a g e 2 R e a c t o r s ........................ 1 4 T a b l e 2 S o m e

R e a c t o r 3 T em p e r a t u r e s - B e d 4 , B e d 5 , R e a c t o r I n l et / O u t l et ......... 1 9 T a b l e 3 T i m e

L i n e o f K eyE v ent s P r e c e di n gt h e D a yo f t h e A c c i d ent .............. 2 7 T a b l e 4 T i m e

L i n e o f K eyE v ent s t h e D a yo f t h e A c c i d ent ...................... 2 8 L i st of F i gu r e s

F i g u r e 1 S i t e L o c a t i o n M a p .............................................. 3 F i gu r e 2 F a c ilit y P l otP l a n ............................................... 4 F i g u r e 3 H y d r o c r a c k e

r Un i tF l o wB l o c k D i a g r a m ............................. 6 F i g u r e 4 S t a g e 2 S y s t em- S i m p l i f i e d F l o wD i a g r a m ............................ 7 F i g u r e 5 S t a g e 2 R e a c t o r s T h e r m o c o u p l e A r r a n g em ent
- I s o m et r i c D r a w i n g ......... 1 0 F i g u r e 6 H y d r o c r a c k e

r P l o tP l a n ......................................... 1 2 F i g u r e 7 R e a c t o r 3 T em p e r a t u r e s ( B e d 4 O u t l et , B e d 5 I n l et , R x I n l et / O u t l et )
....... 2 0 F i g u r e 8 R e a c t o r 3 T em p e r a t u r e s ( F o u r B e d 5 O u t l et)
......................... 2 0 F i gu r e 9 P hot ogr a p h- F i r s ta nd S e c ond S t a g e R e a c t o r s ......................... 2 4 F i g u r e 1 0 P h o t o g r a p h

- R e a c t o r 3 E f f l u entP i p i n g R u p t u r e ....................... 2 5

iiiF i g u r e 1 1 P h o t o g r a p h

- T em p e r a t u r e F i el d P a n elL o c a t i o n ........................ 2 5 F i g u r e 1 2 P h o t o g r a p h

- B a c k S i d e o f R e a c t o r 3 E f f l u entP i p i n gR u p t u r e ............. 2 6 F i g u r e 1 3 P h o t o g r a p h

- R u p t u r e d E f f l u entP i p i n ga f t e

r R em o v a l
................... 2 6 F i g u r e C

- 1 S t a g e 2 H y d r o c r a c k e

r H i g h P r e s s u r e S y s t em- P r o c e s s F l o wD i a g r a m ...... C

- 1 F i g u r e C

- 2 S t a g e 2 S i m p l i f i e d E m e

r g en c yD e p r e s s u r i n gS y s t em D i a g r a m ............ C

- 2 F i g u r e D

- 1 S t a g e 2 R e a c t o r I nt e r n a l s S k et c h
.................................. D

- 1 F i g u r e D

- 2 S t a g e 2 R e a c t o r I nt e r b e d Q u en c h a n d D i s t r i b u t i o n D et a i l s ............... D

- 2

ivT h e E P A AccidentI n ves t igat ion P r ogr am E P A h a s a r e s p o n s i b ilit y u n d e rs e c t io n 112(r) o f t h e C le a n A i r A c t A m e n dm e n t s o f 1990 (C A A ) f o rt h e pr ev ent i o n an d m it i g at i o n o f acci dent al ch em i cal r e leases. On e o f t h e f u n d am en t a l way s t o pr ev en t ch em i cal acci den t s i s t o un der s t a n d why acci dent s o ccuran d t o appl y

t h e le sso n s l ear n e d t o p r e v e n t fu t u r e in c i d e nt s . C o n s e q u e n t ly, E P A h a s a r e s p o n s i b ilit y t o in v e s t ig a t e a n d u n d e r s t a n d why cer t a in ch em i cal acci den t s h a v e o ccur r e d. A key o b j ect iv e o f t h e E P A ch em i cal acci dent in v e st i g at i o n pr o g r a m i s t o det e r m in e an d r e po r t t o t h e pub l i c t h e f act s, co n d it i o n s , ci r c um st an ces, an d causes o rl i k el y

causes o f ch em i cal acci den t s t h at r e sul t , o rco ul d h a v e r e sul t ed, in a f a t a l it y , s e r i o u s in ju r y , s u b s t a nt ia l p r o p e r t y d a ma g e , o rs e r i o u s o ff- s i t e imp a c t s , in c l u d in g a lar g e s c a le ev acuat i o n o f t h e gen e r a l pub l i c . T h e ul t ima t e go al o f an acci dent in v e st i g at i o n i s t o det e r m in e t h e r o o t causes in o r dert o r e duce t h e l i k el i h o o d o f r ecur r e n ce, m in im i ze t h e co n s equen ces asso ci at ed wit h acci den t al r e l eases, an d t o make ch em i cal pr o duct i o n , pr o cessin g , h a n d l in g, an d st o r age saf e r . T h i s r e po r t i s a r e sul t o f an E P A in v e st i g at i o n t o descr i b e an acci dent , det e r m in e it s r o o t causes an d co nt r i b u t in g f act o r s, an d i d en t if y

f

in d in gs an d r eco m m

e n d at i o n s . N o t e t h a t u n d e r s e c t i o n 1 1 2 (r)(1 ) o f t h e C A A , in d u s t r y h a s a g e n e ra l d u t y t o d e s i g n a n d ma int a in a

s a fe fa c ilit y t ak in g s u c h s t e p s a s ar e n ecessar y t o pr ev en t r e leases, an d t o m in im i ze t h e co n s equen ces o f acci dent al r e leas es wh i c h do o ccur . I n addi t i o n , un ders ect i o n 112 (r)(7 ), EPA h a s pr o m ul gat e d r e gul at i o n s f o rt h e pr epar at i o n o f r i s k ma n a gem e nt pr o g r a m s an d pl an s f o rt h e pr ev en t i o n o f acci dent al ch em i cal r e leases. Ho wev e r , co m p l

i a n ce an d en f o r cem en t wit h t h ese p r o v is io n s ar e n o t t h e fo c u s o f t h is r e p o r t b u t w ill b e a d d r e s s e d a t E P A ’ s d i s c r e t i o n in s e p ar a t e re p o rt s o ra c t i o n s . P r i o rt o r e leasin g an acci den t in v e st i g at i o n r e po r t , E P A m u st en sur e t h at t h e r e po r t co nt ain s n o co n f i d ent i al b u sin e ss in f o r mat i o n . T h e F r eedo m o f I n f o r mat i o n A c t ( F OI A ) , t h e T r ade S ecr et s A c t , an d E x ecut iv e Or der12600 r e qui r e f e der a l agen ci es t o pr o t ect co n f i d ent i al b u s in e s s in f o r mat i o n f

r o m pub l i c di scl o sur e . T o m eet t h ese pr o v i s i o n s , E P A h a s est ab l i s h e d a cl ear an ce pr o cess f o racci den t in v e st i g at i o n r e po r t s in wh i c h t h e co m p an i e s wh o h a v e sub m it t e d po t e nt i a ll y co n f i d ent i al in f o r mat i o n used in t h e r e po r t ar e pr o v i d ed a po r t i o n o f t h e dr af t r e po r t . T h e po r t i o n p r o v id e d c o n t a in s o n ly t h e fa c t u a l d e t a ils r e la t e d t o t h e in v e s t ig a t io n ( n o t t h e fin d in g s , t h e co n c l u si o n s n o rt h e r eco m m

e n d at i o n s )
. Co m p an i e s ar e asked t o r e v i ew t h i s f act ual po r t i o n t o co n f i r m t h at t h e dr af t r e po r t co nt ain s n o co n f i d en t i al b u sin e ss in f o r mat i o n . A s par t o f t h i s c le ar a n c e p r o c e s s , c o mp a n ie s o f t e n w ill p r o v id e t o E P A a d d it i o n a l fa c t u a l in fo r ma t io n . I n pr epar in g t h e f in a l r e po r t , E P A co n s i d er s an d ev al uat e s an y such addi t i o n al f

act ual in f o r mat i o n f

o r p o s s i b l e in c l u s io n in t h e fin a l r e p o r t . Ch em i cal acci dent in v e s t i g at i o n s b y E P A Headquar t er s ar e co n duct e d b y t h e Ch em i cal A cci dent I n v e st i g at i o n T eam ( C A I T ) l o cat ed in t h e Ch em i cal E m er gen c y P r epar edn e ss an d P r ev ent i o n Of f i ce ( C E PPO) at 401 M St r eet SW , W a s h in gt o n , D. C
. 20460, 202- 260- 8600. M o r e in f o r mat i o n ab o u t CE P P O an d t h e CA I T ma y b e f o un d at t h e CE P P O Ho m e page o n t h e I nt e r n et at ht t p ://www. epa. go v / ceppo . Co pi es o f t hi s r e po r t can b e o b t a in ed f r o m t h e CE P P O Ho m e page

vo rf r o m t h e Nat i o n al C e nt erf o rE n v i r o n m ent a l Pub l i cat i o n s an d I n f o r mat i o n ( N C E PI ) at 800

- 490- 9198. Chem icalSaf e t y and Haz a r d I n ves t igat ion B oar d ( C SB ) I n

t h e 1990 Clean A i rA c t A m en dm ent s , Co n g r e s s cr eat ed t h e Ch em i cal S a f e t y an d Hazar d I n v e st i g at i o n Bo ar d ( C S B )
. Mo del e d af t e rt h e Nat i o n al T r an spo r t a t i o n S a f e t y Bo ar d ( N T S B) , t h e CS B was di r ect ed b y Co n g r e ss t o co n duct in v e st i g at i o n s an d r e po r t t o t h e pub l i c t h e f in d in gs r e gar d in g t h e caus e s o f ch em i cal acci dent s . Co n g r e s s aut h o r i zed f u n d in g in No v e m b er1997 an d t h e C S B b e gan o p er at i o n s in J a nu ar y 1998. Sev e r a l in v e s t i g at i o n s b y t h e C S B ar e un der w ay . Mo r e in f o r mat i o n ab o u t CS B ma y b e f o un d at t h ei rHo m e page o n t h e I n t e r n et at ht t p ://www. ch em s a f e t y . g o vo rht t p ://www. cs b
. go v . E P A p l a n s t o c o mp le t e it s w o r k a n d is s u e p u b lic r e p o r t s o n in v e s t ig a t io n s in it ia t e d p r io rt o fu n d in g o f t h e C S B
. U n d e rit s e x is t in g au t h o r it ie s , E P A w ill c o nt inu e t o h a v e r o le s a n d r e s p o n s i b ilit ie s in r e s p o n d in g t o , a n d in v e s t ig a t in g , c h e mic a l acci dent s. T h e CS B, E P A an d o t h e r a g e n c i e s w ill b e c o o r d in a t in g t h e i re ffo r t s t o d e t e r min e t h e c au s e s o f acci dent s an d t o appl y le sso n s l ear n e d t o pr ev ent f u t u r e ev en t s . B a si s o f D eci si o n t o In v e st i g a t e t h e To sco A cci d e n t On J a nu ar y 21, 1997, an expl o s i o n an d f i r e o ccur r e d at t h e Hy dr o c r ackerUn i t o f t h e T o s c o Ref in e r y at Mar t in ez, Cali f o r n i a, r e sul t in g in o n e deat h , 46 wo r k erin j u r i es an d pr ecaut i o n ar y sh el t e r in g - in - pl ace f o rt h e sur r o un din g co m m

u n i t y . T h e acci den t in v o lv ed t h e r e lease an d aut o i g n i t i o n o f a m ix t u r e o f f

l am mab le hy dr o carb o n s an d hy dr o g en un derh i gh t e m p er at ur e an d pr essur e . E P A un der t o o k an in v e st i g at i o n int o t h e causes an d un der l yin g ci r c um st an ces asso ci at ed wit h t h i s acci den t b ecause o f it s ser i o u s co n s equen ces ( f at al it y , in j u r i es an d o f f s it e co n cer n ) , t h e po t e nt i a l f

o rgr eat erim p act s, an d t h e o ppo r t un i t y

t o lear n f

r o m t h i s acci dent h o w s imilar acci dent s co ul d b e pr ev ent e d. Ot her I n ves t igat ing Agencies I n vol ved in t h e T o s c o I n ves t igat ion T h i s in v e s t i g at i o n was co o r din a t e d am o n g in v e s t i g at o r s wo r k in g f o rUSE P A Headquar t er s , US E P A Regi o n 9, Calif o r n i a Div i s i o n o f Occupat i o n al S a f e t y an d Heal t h

( C ALOS HA ) , US Depar t m e n t o f L ab o r( DOL ) Occupat i o n al S a f e t y an d Heal t h

A d m in i s t r at i o n ( O S H A ) Regi o n 9, Co nt r a Co st a Co u nt y Heal t h

S e r v i ces Div i si o n ( CCCHS D ) an d t h e Cal if

o r n i a Bay A r ea A i r Q u al i t y

Man a g e m e nt D i st r i ct ( B A A Q MD )
. CAL O S H A , w i t h

assi st an ce o f Reg i o n 9 F e d e r a l OS HA , co n c ur r e nt l y

co n duct e d an in v e st i g at i o n f

o rv i o l at i o n s o f h eal t h

an d saf e t y o r der s as well as a pr o cess saf e t y ma n a gem e nt ( P S M ) audit . T h e Bur eau o f I n v e st i g at i o n o f CA Depar t m e nt o f O c c u p a t i o n a l S a fe t y a n d H e a l t h

c o n c u r r e nt ly c o n d u c t e d a c r imin a l in v e s t ig a t io n . CCCHS D co n c ur r e nt l y

co n duct e d an in v e st i g at i o n in t o t h e r o o t causes o f t h e acci dent . BA A Q MD c o nc u r r e nt l y

c o nd u c t e d a n inve s t i g a t i o n int o p o s s i ble vi o l a t i o ns o f a i rq u a l i t y

c o nt r o l r e g u l a t i o ns .
viE x ecut i ve Sum m a ry of t h e T o s c o AccidentI n ves t igat ion At appr o x ima t e l y

7:41 p. m . o n J a nu ar y 21, 1997 at t h e T o s c o A v o n R e f in e r y in M ar t in ez, C A , a sect i o n o f ef f l uen t pi pin g r upt ur ed o n t h e Hy dr o c r ackerS t age 2 React o r3. A m ix t u r e o f l

i g ht gases st ar t in g wit h m e t h an e t h r o ugh b u t a n e ; l i g ht gaso l in e; h eav y gaso l in e; gas o il an d hy dr o g en was r e leased f r o m t h e pi pe an d in st ant l y

i g n i t e d upo n co nt act wi t h

ai r , causin g an expl o s i o n an d f i r e . A T o sco Hy dr o c r ackero p er at o rch eckin g a f i el d t e m p er at ur e pan e l at t h e b a se o f t h e r eact o r w a s k ille d ; 4 6 T o s c o a n d c o nt r a c t o rp e r s o n n e l w e r e in ju r e d
. T h ir t e e n in ju r e d p e r s o n n e l w e r e t aken t o l o cal h o spi t al s, t r eat ed an d r e leased. T h er e wer e n o r e po r t ed in j u r i es t o t h e pub l i c . T h e imme d i a t e c au s e o f t h e hy d r o c arb o n a n d hy d r o g e n r e le a s e a n d s u b s e q u e nt fir e w a s a fa ilu r e an d r upt ur e o f a S t age 2 React o r3 ef f l uent pi pe due t o ex cessiv e l y

h i gh t e m p er at ur e, l i k el y

in ex ces s o f 1400 0 F
. T h i s h i gh o p er at in g t e m p er at ur e was in i t i a t e d b y a r eact o rt e m p er at ur e ex cur s i o n t h at b e gan in Bed 4 o f React o r3 an d spr ead t h r o ugh t h e n e x t cat al y s t b e d, Bed 5. T h e ex cessiv e h eat gen e r a t e d in Bed 5 r a i s ed t h e t e m p er at ur e in t h e r eact o ref f l uent pi pe. T h e ex cur s i o n was n o t b r o ught un derco nt r o l b ecause t h e S t age 2 r eact o r s wer e n o t depr essur e d an d shut do wn as r e qui r e d wh en t h e r eact o rt e m p er at ur es ex ceeded t h e 800 o F t e mp e r a t u r e limit specif i ed in t h e wr i t t e n o p er at in g pr o cedur es. T h e t e m p er at ur e ex cur s i o n b e gan wit h a h o t spo t in Bed 4 React o r3. T h e h o t spo t was m o st l i k el y

caused b y po o rf l o w an d h eat di st r i b u t i o n wi t h in t h e cat al y s t b e d. I n v e st i g at o r s co ul d n o t det e r m in e t h e specif i c cause o f t h e ma l d i s t r i b ut i o n . Oper at o r s di d n o t act iv at e an em er gen c y depr essur in g o f t h e r eact o r s wh en so m e int e r n al r eact o rt e m p er at ur e r eadin gs r each ed 800 o F b ecause t h ey wer e co n f used ab o u t wh et h e ra t e m p er at ur e ex cur s i o n was act uall y

o ccur r in g . T h ei r co n f usi o n was due t o a v ar i et y o f f

act o r s in cl udin g : f l uct u at in g t e m p er at ur e r eadin gs, a di sco nt inu at i o n o f makeup hy dr o g en f

l o w t o S t age 2, a m i s leadin g r ecy cle hy dr o g en pur i t y an al y s i s an d t h e ab sen ce o f addi t i o n al audi b le h i gh t e m p er at ur e al ar m s af t e rt h e f i r s t h i gh t e m p er at ur e o ccur r e n ce. T h ey wer e at t e m p t in g t o v e r if y

t e m p er at ur es in t h e r eact o rb y h a v in g an o p er at o ro b t a in t e m p er at ur e r eadin gs f r o m t h e f i el d pan e l s un dert h e r eact o r s. P o o rr a di o co m m

u n i cat i o n s h a m p er ed r e l a yin g t h ese r eadin gs t o t h e co n t r o l r o o m . E v en af t e ro p er at o r s in t h e co nt r o l r o o m n o t i ced t h at t h e React o r3 in le t t e m p er at ur e h a d in cr eased b e y o n d 800 o F, t h e y di d n o t depr essur e b u t b e gan t o t ake st eps t o co o l t h e r eact o rb y in cr easin g quen c h hy dr o g en f

l o w an d r e ducin g h eat in put f r o m t h e t r im f

u r n ace. I n v e st i g at o r s i d ent if i ed t h e f o ll o win g r o o t causes an d co nt r i b u t in g f act o r s o f t h e acci dent :

• C o n di t i o n s t o S uppo r t an d E n co ur age E m pl o y ees t o Oper at e React o r s in a S a f e M a n n e r W e re In a d e q u a t e . T h e em er gen c y depr essur in g sy st em was n o t used as r e qui r e d t o co nt r o l pr ev i o us t e m p er at ur e ex cur s i o n s . Man a gem e nt di d n o t t ake ef f ect iv e co r r ect iv e act i o n t o en sur e t h at t h ese em er gen c y pr o cedur es wer e f o ll o wed. A n o p er at in g en v i r o n m ent ex i s t e d t h at caused o p er at o r s t o t ake r i sks wh ile o p er at in g an d t o co nt inue pr o duct i o n despi t e ser i o u s h azar do us o p er at in g co n d i t i o n s . T e m p er at ur e limit s fo rt h e r eact o r s wer e in co n s i s t e nt l y

st at ed an d o p er at o r s di d n o t alway s ma int a in t e m p er at ur e viiw i t h in t h e s e limit s . M a n a g e me n t d i d n o t r e c o g n iz e o ra d d r e s s t h e c o n f lic t b e t w e e n accept ab le per f o r ma n ce go al s an d r i sks. Negat iv e co n s equen ces f r o m t h e past in st an ces o f use o f t h e depr essur in g sy st em ma y h a v e co n t r i b u t e d t o o p er at o r s’ r e l u ct an ce t o im p le m e nt depr es s u r in g wh en r e qui r e d.

• H uman F act o r s W e r e P o o r l y

Co n s i d er ed in t h e Desi gn an d Oper at i o n o f t h e React o r T e m p er at ur e Mo n it o r in g S y st em . Oper at o r s wer e usin g t h r ee dif f e r e nt in st r u m e nt at i o n s y s t e m s t o o b t a in t e mp e r a t u r e d a t a . N o t a ll t h e t e mp e r a t u r e d a t a w e r e imme d i a t e l y accessi b le, wh i c h di d n o t all o w o p er at o r s t o make cr it i cal deci si o n s qui ckl y . A l t h o ugh n o t pl an n e d b y desi gn , access t o t h e m o st cr it i cal m o n it o r in g po int s ( t h o se r eadin g t h e h i gh est t e m p er at ur es) h appen e d t o b e l o cat ed un der n eat h t h e r eact o r s an d co ul d n o t b e accessed fr o m t h e c o nt r o l r o o m . N o M a n a g e me nt o f C h a n g e ( M O C ) p r o c e s s w a s imp le me nt e d fo r t h e in st all a t i o n o f t h e o u t s i d e t e m p er at ur e pan e l s . T h e al ar m sy st em o n t h e dat a l o gger o n l y

all o wed o n e al ar m t o b e r eceiv e d at a t im e an d di d n o t di st in gui sh b e t w een em er gen c y al ar m s an d o t h e ro p er at in g al ar m s . T h e t e m p er at ur e co nt r o l sy st em caused t h e o p e r a t o r s t o mak e ma n y ma nu a l a d ju s t me n t s t o c o n t r o l t e mp e r a t u r e s , w h ic h ma d e t h e Hy dr o c r ackerr eact o rm o r e dif f i cul t t o o p er at e. Hy dr o g en pur i t y

an al y s i s dat a av ail ab le t o o p er at o r s l a gged sev e n m inut es b e h in d t h e act ual t im e o f t h e an al y s i s an d pr o v i d ed m

i s leadin g in f o r mat i o n t o t h e o p er at o r s.

• S uper v i s o r y M a n a gem e nt was I n adequat e . S e v e r a l appar e nt ser i o u s def i ci en ci es wer e ev i d en t . F o rex am ple, un it pr o cess o p er at o r s f a il e d t o f o ll o w po st ed em er gen c y pr o cedur es o n t h i s as well as pr ev i o us t e m p er at ur e ex cur s i o n in ci dent s. P r o b le m in ci dent s wer e n o t alway s pr o p er l y

co m m

u n i cat ed t o ma n a gem e nt an d in co n s i s t e nt appl i cat i o n o f em er gen c y pr o cedur es was t o le r a t e d b y ma n a gem e nt . No co m p r e h e n s iv e o p er at o r t r ain in g , in cl udin g r e f r esh e rt r ain in g , h a d b een im p le m e nt ed t o addr ess all h azar ds asso ci at ed wi t h

Hy dr o c r ackerUn i t o p er at i o n s . No ma n a gem e nt o f ch an ge pr o g r a m was im p le m e nt ed t o addr ess m ech an i cal ch an ges o ro p er at i o n a l ch an ges such as t h o s e n eeded f o rt h e ch an ge in cat al y s t . Ro o t cause in ci den t in v e st i g at i o n s wer e in adequat e in t h at t h ey di d n o t in v e st i g at e all t e m p er at ur e ex cur s i o n s . A l so t h ey di d n o t i d ent if y

t h e r o o t cause o f t h e ex cur s i o n n o rdi d t h ey det e r m in e why o p er at o r s wer e r e l u ct ant t o f o ll o w po st ed em er gen c y pr o cedur es.

• O per a t i o n al Readin ess an d Maint e n a n ce W e r e I n adequat e . T h e t e m p er at ur e m o n it o r( d at a l o gger ) in t h e co nt r o l r o o m t h at h a d m o st o f t h e r eact o rt e m p er at ur e r eadin gs was unr e l i ab le an d o u t o f ser v i ce so m e t im e s. I n t h e past , r eact o ro p er at i o n wo ul d co nt inue despi t e t h e dat a l o ggerb e in g o u t o f ser v i ce. Un dert h e co n d i t i o n s o f a t e m p er at ur e po int ri s in g m o re t h a n 5 0 o F ab o v e n o r mal , t h e dat a l o ggerco ul d n o t b e r e set in o r dert o r eceiv e addi t i o n al h i gh t e m p er at ur e al ar m s . Radi o co m m

u n i cat i o n s n eeded t o r e l a y t e m p er at ur e dat a f

r o m o u t s i d e pan e l s t o t h e co nt r o l r o o m wer e un r e l i a

b le an d di d n o t f u n c t i o n dur in g t h e in ci dent . Oper at o r s h a d t o r u n t h e un it wi t h

leakin g quen c h v a lv es an d st o p - g ap

v iiim easur es wer e used t o deal wi t h

leakin g h eat ex ch an gerf l an ges. T h e em er gen c y d e p r e s s u r in g s y s t e m w a s n o t t e s t e d t o e n s u r e it s r e liab ilit y w h e n n e e d e d
.

• O per a t o rT r ain in g an d Suppo r t W e r e I n adequat e . T r a in in g ma te r i a l s w e r e ou t of d a te a n d un i t specif i c t r ain in g was m o st l y

o n t h e j o b an d n o t well do cum e nt ed. Un i t specif i c r e f r esh e rt r ain in g h a d n o t b een dev e l o ped. Oper at o r s r eceiv e d in adequat e t r ain in g o n t e m p er at ur e in st r u m e nt at i o n . T h ey di d n o t un der s t a n d t h at zer o def aul t v a l u es o n t h e dat a l o ggerpo t e nt i a ll y

m eant ex t r em el

y

h i gh t e m p er at ur es. Oper at o r s di d n o t un der s t a n d t h at t h e decr ease in makeup hy dr o g en f

l o w was an in di cat i o n o f an ex t r em e t e m p er at ur e e x c u r s io n . T r a in in g fo rab n o r ma l o p e r a t in g s it u a t io n s a n d d r ills fo re m e r g e n c y p r o c e d u r e s w e r e n o t a d e q u a te .

• P r o cedur es W e r e Out d at ed an d I n co m p le t e . Pr o cedur es wer e s cat t e r e d t h r o ugh o u t v ar i o u s do cum e nt s an d h a d n o t b een updat e d as ch an ges wer e ma de t o o p er at in g equi pm ent an d t h e pr o cess. Reco m m

e n d at i o n s f r o m sev e r a l in ci den t s wer e n o t in co r p o r at ed int o pr o cedur es. P r o cedur es wer e n o t dev e l o ped f o rma n y o p er at i o n s , in cl udin g o b t a in in g t e m p er at ur e dat a f

r o m o u t s i d e f i el d pan e l s un der n eat h t h e r eact o r s. P r o c e d u r e s h a d c o n f lic t in g d iffe r e nt ia l t e mp e r a t u r e s limit s fo rc a t a l ys t b e d o p e r a t io n .

• P r o cess Hazar d A n al y s i s W a s F l awed. T h e pr o cess h azar d an al y s i s di d n o t addr ess all ex i s t in g kn o w n h azar ds an d o p er at in g ab n o r mal i t i e s. I t di d n o t r e f lect t h e act ual equi pm ent an d in s t r u m e nt at i o n us ed in t h e pr o ces s . I t di d n o t adequat e l y

addr es s pr ev i o us in ci den t s t h at h a d po t e nt i a l cat ast r o p h i c co n s equen ces, such as pr ev i o us r eact o r t e m p er at ur e ex cur s i o n s . No h azar d an al y s i s was per f o r m e d f o rt h e in st all a t i o n an d use o f t h e t e m p er at ur e f i el d pan e l s . I n v e s t ig a t o r s fr o m E P A , C ALO S H A a n d B A A Q M D d e v e lo p e d r e c o mme n d a t io n s ( s u mmar i z e d b e lo w ) t o a d d r e s s t h e r o o t c au s e s a n d c o nt r i b u t in g fa c t o r s t o p r e v e nt a r e c u r r e n c e o rs imilare v e nt a t T o s c o a n d o t h e rfa c ilit ie s . H y d r o p r o c e s s in g fa c ilit ie s s h o u ld c o n s id e r each r eco m m

e n d at i o n in t h e co nt ex t o f t h ei ro w n ci r c um st an ces, an d im p le m e nt t h em as appr o p r i at e.

• M an agem en t m u st en sur e t h at o p er at in g deci si o n s ar e n o t b a sed pr imar il y

o n co st an d pr o duct i o n . P e r f o r ma n ce go al s an d o p er at in g r i sks m u st b e ef f ect iv el y

co m m

u n i cat ed t o a ll e m p l o y e e s . F a c ilit y ma n a g e me nt mu s t s e t s a fe , a c h ie v ab le o p e r a t in g limit s a n d n o t t o le r a t e d e v i a t io n s fr o m t h e s e limit s . R i s k s o f d e v i a t io n fr o m o p e r a t in g limit s mu s t b e f u ll y

un der s t o o d b y o p er at o r s. A l so , ma n a gem e nt m u st pr o v i d e an o p er at in g en v i r o n m ent co n duciv e f o ro p er at o r s t o f o ll o w em er gen c y s hut do wn pr o cedur es wh en r e qui r e d.

• P r o cess in st r u m e nt at i o n an d co nt r o l s sh o u l d b e desi gn ed t o co n s i d erhu ma n f

act o r s co n s i s t e nt wi t h

go o d in dust r y pr act i ce. Hy dr o p r o cessin g r eact o rt e m p er at ur e co nt r o l s sh o u l d b e co n s o l i d at ed wit h all n ecessar y dat a av ail ab le in t h e co nt r o l r o o m . S o m e b ackup s y s t em o f t e m p er at ur e in di cat o r s s h o u l d b e us ed s o t h at t h e r eact o r s can b e

ixo p er at ed saf e l

y

in case o f in st r u m e nt ma lf un ct i o n . E ach al ar m sy st em sh o u l d b e desi gn ed t o all o w cr it i cal em er gen c y al ar m s t o b e di st in gui sh ed f r o m o t h e ro p er at in g al ar m s .

• A dequat e super v i s i o n i s n eeded f o ro p er at o r s, especi all y

t o addr ess cr it i cal o rab n o r mal si

t u at i o n s . S uper v i s o r s n eed t o en sur e t h at all r e qui r e d pr o cedur es ar e f o ll o wed. S uper v i s o r s sh o u l d i d ent if y

an d addr ess all o p er at in g h azar ds an d co n duct t h o r o ugh in v e st i g at i o n o f dev i at i o n s t o det e r m in e r o o t causes an d t o t ake co r r ect iv e act i o n . E qui pm ent an d j o b per f o r ma n ce i ssues r e l a t e d t o o p er at in g in ci dent s sh o u l d b e co r r ect ed by ma na g e m e nt .

• F a c ilit ie s s h o u ld ma in t a in e q u i p m e n t in t e g r it y a n d d i s c o n t inu e o p e r a t io n if in t e g r it y is co m p r o m i s ed. Hy dr o p r o cessin g o p er at i o n s especi all y

n eed t o h a v e r e l i ab le t e m p er at ur e m

o n it o r in g s y s t em s an d em er gen c y s hut do wn equi pm en t . E qui pm en t s h o u l d b e t e s t ed r e g u l ar ly a n d p r a c t ic e e m e r g e n c y d r ills s h o u ld b e h e ld o n a

r e g u l arb a s i s . M a in t e n a n c e an d in s t r u m e nt at i o n s uppo r t s h o u l d b e av ail ab le dur in g s t ar t up af t e requi pm ent in s t a lla t i o n o rma jo rma in t e n a n c e .

• M an agem en t m u st en sur e t h at o p er at o r s r eceiv e r e gul art r ain in g o n t h e un it pr o cess o p er at i o n s an d ch em i s t r y . F o rhy dr o c r acker s, t h i s sh o u l d in cl ude t r ain in g o n r eact i o n kin e t i cs an d t h e causes an d co n t r o l o f t e m p er at ur e ex cur s i o n s . Oper at o r s n eed t o b e t r a in e d o n t h e limit a t io n s o f p r o c e s s in s t r u me nt s a n d h o w t o h a n d le in s t r u me nt ma lfu n c t io n s . F a c ilit ie s n e e d t o e n s u r e t h a t o p e r a t o r s r eceiv e r e gul art r ain in g o n t h e use o f

t h e em er gen c y shut do wn sy st em s an d t h e n eed t o act iv at e t h ese sy st em s.

• T o s co ma n a gem e nt m u s t dev e l o p wr it t e n o p er at in g pr o cedur es f o rall ph as es o f H y d r o c r a c k e ro p e r a t io n s . T h e p r o c e d u r e s s h o u ld in c l u d e o p e r a t in g limit s a n d c o n s e q u e n c e s o f d e v i a t io n fr o m t h e limit s . T h e p r o c e d u r e s s h o u ld b e r e v i e w e d r e g u l ar ly an d updat e d t o r e f lect ch an ges in equi pm ent , pr o ces s ch em i s t r y , an d o p er at i o n . A s appr o p r i at e, t h e pr o cedur es s h o u l d b e updat e d t o in cl ude r eco m m

e n d at i o n s f r o m pr o ces s h azar d an al y s i s an d in ci den t in v e st i g at i o n s .

• P r o cess h azar d an al y s es n eed t o b e b a sed o n act ual equi pm ent an d o p er at in g co n d i t i o n s t h at ex i s t at t h e t im e o f t h e an al y s i s . T h e an al y s i s sh o u l d in cl ude t h e f a il u r e o f cr it i cal o p er at in g sy st em s, such as t e m p er at ur e m o n it o r s o rem er gen c y o p er at in g sy st em s. A M a n a gem e nt o f C h an ge r e v i ew s h o u l d b e co n duct e d f o rall ch an ges t o equi pm ent o rt h e pr o cess, as n ecessar y , an d sh o u l d in cl ude a saf e t y h azar d r e v i ew o f t h e ch an ge.

x

### 1. 0 Back gr ound 1. 1 F acil it y Des c ri pt ion T h e T o s c o A v o n R e f in e r y i s a 2, 300 acr e f ac ilit y lo c a t e d in E a s t e r n C o nt r a C o s t a C o u nt y n e ar M ar t in ez, C a l if

o r n i a in t h e San F

r an ci s c o B a y A r ea. T h e R e f in e r y was o r i g in all y

b u il t in 1913 as a S t a n d ar d O il o f C a lifo r n i a fa c ilit y; in 1976 T o s c o pur ch as ed t h e A v o n R e f in e r y f

r o m Ph illip s Pet r o leum . T h e R e f in e r y pr o ces s e s 140, 000 b ar r e l s perday o f cr ude o il , pr o ducin g gas o l in e, j e t f u el , an d di esel f

u el
. Ot h e rpr o duct s gen e r a t e d ar e co ke, sulf ur , am m

o n i a, an d sulf ur i c aci d. C r u d e o il is d e liv e r e d t o t h e R e fin e r y e it h e rt h r o u g h p i p e lin e o rt h r o u g h t w o mar in e t e r min a l s , pr imar il y

f

r o m pr o duct i o n f

i el ds in A l as ka an d C a l if

o r n i a. F i g u r e 1 is a s it e map s h o w in g t h e R e fin e r y a n d t h e imme d i a t e s u r r o u n d in g ar e a . L i g ht in d u s t r ia l ar e a s , r e s i d e nt ia l ar e a s a n d S u is u n B a y ar e lo c a t e d ap p r o x ima t e ly o n e mile fr o m t h e R e fin e r y . F i g u r e 2 is a fa c ilit y p l o t p l a n s h o w in g t h e lo c a t io n o f t h e H y d r o c r a c k e rU n it w it h in t h e R e fin e r y . T h i s in v e st i g at i o n r e po r t descr i b e s t h e co n d it i o n s an d ci r c um st an ces sur r o un din g t h e Janu ar y 21, 1997 acci den t , t h e ev en t s leadin g up t o t h e expl o s i o n , ex i s t in g pr o ces s s a f e t y ma n a gem e nt pr act i ces, t h e causes o f t h e acci den t an d co nt r i b u t in g f act o r s, an d r eco m m

e n d at i o n s . T h e acci dent o ccur r e d in t h e S t age 2 React o rar ea o f t h e Hy dr o c r ackerUn it an d t hus, descr i pt i o n o f pr o cesses a n d e v e n t s ar e fo c u s e d o n t h is ar e a o f t h e R e fin e r y . F o rr e a d e r s n o t fa miliarw it h t e c h n i c a l t e r m s asso ci at ed wi t h

r e f in e r i es o rch em i cal pr o cesses, so m e o f t h ese t e r m s ar e expl ain e d in a gl o ssar y in

A p p e n d ixJ
. 1 . 2 P r o cess D e scri p t i o n T h i s sect i o n descr i b e s t h e ch em i s t r y , pr o cess o p er at i o n s , co nt r o l sy st em , an d o p er at in g par a m e t e r s in t h e S t age 2 o f t h e Hy dr o c r ackerUn it . A h i st o r y o f ma j o rpr o cess ch an ges t o S t age 2 o f t h e Hy dr o c r ackerUn i t ar e sum mar i zed in A ppen d ixB. 1. 2. 1 H ydr o cr ack i ng Chem is t ry Hy dr o c r ackin g in v o lv es cat al y

t i c cr ackin g o f hy dr o carb o n o il in t h e pr esen ce o f ex cess hy dr o g en at h i gh t e m p er at ur e an d pr essur e . T h e pr o cess b r eaks l ar g erm o lecul e s int o smalle ro n es wh ile r eact in g t h em wit h hy dr o g en t o cr eat e m o r e o f t h e m o lecule s used in co m m

e r c i a l f

u el s, such as gaso l in e an d di esel
. S u lf uran d n it r o g en co m p o u n d s m u st f i r s t b e r e m o v e d f r o m t h e o il t o pr ev en t f o ul in g o f t h e hy dr o c r ackin g cat al y s t an d t o m eet f in a l pr o duct specif i cat i o n s . T h i s i s do n e b y r eact in g t h e sulf uran d n it r o g en co m p o u n d s wit h hy dr o g en t o f o r m hy dr o g en sulf i d e an d am m

o n i a, wh i c h ar e t h en ex t r act ed f r o m t h e pr o cess st r eam . T h e gen e r a l m ech an i s m in hy dr o c r ackin g in cl udes b r eakin g carb o n - carb o n sin g le b o n d s ( c r ackin g) f o ll o w e d by hy d r o g e n a t i o n ( a d d it i o n o f hy d r o g e n t o a c arbo n- c arbo n d o u b le bo nd )
.

1T y pi cal Cr ackin g React i o n C 11 H 24 + h e a t < C 5 H 10 + C 6 H 14 hydr oc a r b on oil p ent en e ( o le f i n) hex a ne Hy dr o g en at i o n React i o n C 5 H 10 + H 2 < C 5 H 12 + h e a t pent en e pent a n e
C r ackin g f o r m s o l ef in s ( c o m po un ds wit h do ub le - b o n ded car b o n s ) , wh i c h co ul d j o in t o get h ert o f o r m n o r mal par a f f in s ( c o m po un ds wit h s in g le - b o n ded carb o n s )
. Ho wev e r , hy dr o g en at i o n r api dl y fills o u t a ll t h e d o u b le b o n d s , o f t e n fo r min g is o p ar a ffin s , p r e v e nt in g r e v e r s io n t o le s s d e s i r ab le m

o le c u le s , s u c h a s s t r a i g ht c h a in p ar a f f ins w h i c h ha ve a l o w e ro c t a ne r a t ing . T h e cr ackin g r eact i o n i s en do t h er m i c ( r e qui r e s h eat ) an d t h e hy dr o g en at i o n r eact i o n i s ex o t h e r m i c ( p r o duces h eat )
. Heat l i b er at ed dur in g hy dr o g en at i o n i s gr eat ert h an h eat co n s um ed dur in g cr ackin g so t h e o v er all pr o cess i s ex o t h e r m i c . T h e pr imar y v ar i ab le s in v o lv ed in hy dr o c r ackin g ar e r eact o rt e m p er at ur e an d pr essur e , f eed r a t e , hy dr o g en co n s um pt i o n , cat al y s t co n d i t i o n , n it r o g en an d sulf urco nt ent o f t h e o il f

eed, an d hy dr o g en sulf i d e co nt en t o f t h e gases. Besi des ser v in g as a r eact an t , ex cess hy dr o g en i s added in o r dert o s uppr es s co ke f o r mat i o n o n t h e cat al y s t an d t o act as a co o l ant t o keep t h e t e m p er at ur e ri s e u n d e r c o nt ro l
. T h e h i gh ert h e t e m p er at ur e, t h e f a st ert h e hy dr o c r ackin g r eact i o n r a t e . At n o r mal r eact o r pr essur e an d f l o w r a t e co n d it i o n s , a 20 o F in cr ease in t e m p er at ur e al m

o st do ub le s t h e r eact i o n r a t e . T h e h eat gen e r a t e d f r o m t h e hy dr o c r ackin g r eact i o n causes t h e r eact o rt e m p er at ur e t o in cr ease an d accel er at es t h e r eact i o n r a t e . T o co nt r o l t h e r eact i o n r a t e , each r eact o rh a s sev e r a l cat al y s t b e ds b e t w een wh i c h co o l hy dr o g en i s in j ect ed as quen c h gas f o rt e m p er at ur e co nt r o l
. T h e act iv i t y

o f t h e cat al y s t gen e r a ll y

decl in es o v ert im e due t o an accum u l a t i o n o f co ke an d o t h e r depo si t s , unt il t h e cat al y s t r e qui r e s r e gen e r a t i o n . Regen e r a t i o n i s acco m p l

i s h e d b y shut t in g t h e un i t do wn an d b u r n in g o f f t h e carb o n depo si t s , o rb y r e m o v in g t h e cat al y s t an d r e pl acin g i t wi t h r e gen e r a t e d o rn e w cat al y s t .

2F i gur e 1 S i te L o c a ti o n M a p T o s c o A v o n R e f i n e ry , M a rt i n e z , C a l i f o rn i a

3F i gur e 2 F acil it y P l otP l an T o s c o Avon Ref i nery , M a rt inez , Cal i f o rn ia

41. 2. 2 H ydr o cr ack e r Oper at ions T h e Hy dr o c r ackerUn i t in cl udes f o ursect i o n s , a Hy dr o g en P l ant , S t age 1 Un i t , S t age 2 Un i t , an d Gas P l ant . T h e Hy dr o g en P l ant pr o duces hy dr o g en f

o ruse in t h e Hy dr o c r ackerUn i t an d o t h e r pr o cess un i t s. S t age 1 hy dr o t r eat s t h e r e f in e r y gas o il s in React o r s A , B an d C t o r e m o v e sulf ur , n it r o g en co m p o u n d s, an d o t h e rim pur i t i e s, t o pr ev ent f o ul in g o f t h e S t age 2 cat al y s t . Cr ackin g an d hy dr o g en at i o n o ccurin t h e S t age 2 React o r s 1, 2 an d 3. T h e Gas P l ant f r act i o n a t e s t h e hy dr o c r acked pr o duct f r o m S t age 2 int o pr o p an e, b u t a n e , l i g ht an d h eav y hy dr o c r ackat es, an d di es el
. F i gur e 3 i s a s im p l

if

i e d f l o w b l o c k di agr a m o f t h e Hy dr o c r ackerUn i t s h o w in g h o w pr o cess st r eam s b e t w een t h e f o ursect i o n s ar e co n n ect ed. 1. 2. 3 S t age 2 Oper at ions S t age 2 i s descr i b e d in det a il h e r e b ecause i t was t h e pr o cess in wh i c h t h e acci dent o ccur r e d. T h e hy dr o c r ackin g t ech n o l o gy used in S t age 2 was l i cen sed as a Un i c r ackerb y Un i o n Oil o f Cal if

o r n i a in

1986. T h e o r i g in al Hy dr o c r ackerwas s t ar t e d up in 1963 un dera l i cen s e f r o m C h evr o n R e s e ar c h C o r p o r a t io n a n d w a s k n o w n a s a n I s o c r a c k e r , a t e r m w h ic h w a s s t ill u s e d in ma n y o f T o sco ’ s d o cu m e nt s. T h e hy dr o c r ackin g r eact i o n o ccur s in t h e h i gh pr essur e sy st em o f S t age 2 wh i c h o p er at es in t h e r a n g e o f 1350 t o 1735 po un ds pers quar e in ch gauge ( p s i g)
. F i gur e 4 i s a s im p l

if

i e d pr o ces s f l o w di agr a m o f t h e S t age 2 Hy dr o c r ackerHi gh P r essur e S y st em ; A ppen d ixC co nt ain s a m o r e det a ile d pr o cess f l o w di agr a m o f t h e S t age 2 Hi gh P r essur e S y st em . A

ch ar ge pum p pr o v i d es f r esh f

eed f r o m S t age 1 equall y

t o t h e t h r ee S t age 2 React o r s 1, 2, an d 3. P r eh eat ed hy dr o g en i s added t o t h e l i qui d f r esh f

eed af t e rt h e S t age 2 ch ar ge pum p. T h e t e m p er at ur e o f t h i s t w o - ph ase st r eam i s t h en r a i s ed f r o m ab o u t 350 0 F t o o v er550 o F by he a t ex ch an ge wi t h

t h e r eact o ref f l uent in t h e S t age 2 f eed/ e f f l uent ex ch an ger s . T h i s pr o v i d es m o st o f t h e h eat f o rS t age 2. A ddi t i o n al hy dr o g en i s pr eh eat ed in T r im Fu r n aces 1, 2 an d 3 an d co m b in ed wi t h

t h e f eed st r eam f r o m t h e f eed/ef f l uent ex ch an ger s , t o o b t a in a des i r e d in le t t e m p er at ur e, r a n g in g f r o m 600- 650 o F. T h e h eat ed m ix t u r e o f o il an d hy dr o g en ent e r s t h e t o p o f each r eact o rwh er e i t i s hy dr o c r acked t o pr o duce a m ix t u r e o f desi r ab le, l i g ht erhy dr o car b o n co m p o n ent s . T h ese r a n g e f r o m as l i g ht as m

e t h an e t o as h eav y as n apht h a ( up t o 10- 12 carb o n s )
. Wit h in each r eact o r , t h e o il /hy dr o g en f

eed passes sequen t i a ll y

t h r o ugh f

iv e b e ds o f cat al y s t . T h e cat al y s t used b y T o sco i s a zeo l it i c ( m o lecul arsi ev e) cat al y s t . E ach b e d i s desi gn ed t o ach i e v e ab o u t 60% r eact i o n co n v e r s i o n . Co o l r ecy cled hy dr o g en gas i s added as quen c h b e t w een t h e cat al y s t b e ds in t h e r eact o r s, limit in g t h e t e mp e r a t u r e r i s e c r e a t e d b y t h e e x o t h e r mic r eact i o n . T h e quen c h hy dr o g en i s in j ect ed ab o v e B e ds 2, 3, 4 an d 5 an d di s t r i b u t e d un if o r m l y

t h r o ugh a per f o r at ed pi pe di st r i b u t o rkn o w n as a quen c h r in g . T h e hy dr o carb o n s an d hy dr o g en ar e

567co llect ed o n quen c h t r ay s ab o v e Bed 2, 3, 4 an d 5 an d m ix ed in a quen c h b o xin t h e cent e ro f each t r ay . T h e m ix t u r e i s passed o v eran d t h r o ugh di st r i b u t i o n t r ay s in o r dert o m ixan d ev en l y di s t r i b u t e f l o w t o t h e n e x t cat al y s t b e d b e l o w. B e ds 2, 3 an d 5 h a v e t w o di s t r i b u t i o n t r ay s ab o v e t h em wh ile Bed 4 h a s o n l y

o n e. S ee A ppen d ixD f o rsket ch es o f t h e r eact o rint e r b ed di st r i b u t i o n sy st em . T h e r eact o ref f l uen t st r eam i s co o led in t h e f eed/ e f f l uent ex ch an ger s b y ex ch an gin g h eat wit h t h e in co m in g f eed st r eam . T h e co o l ed ef f l uen t st r eam f

r o m each r eact o ri s co m b in ed an d co o led f u rt h e r in h e a t e x c h a n g e rs b e f o re e nt e rin g t h e H i g h Pre s s u re Se p ara t o r (H PS). I n

t h e HP S , hy dr o g en an d o il ar e separ a t e d. Hy dr o g en an d l i g ht hy dr o carb o n gases ar e r ecy cled b ack t o t h e S t age 2 r ecy cle co m p r e sso r( calle d t h e I I Rco m p r e sso r )
. Makeup hy dr o g en i s added t o t h e r ecy cle gas do wn st r eam o f t h e co m p r e sso rt o ma int a in pr essur e in t h e r ecy cle gas sy st em . T h e r ecy cl e gas i s used as quen c h hy dr o g en o rh eat ed an d co m b in ed wit h o il f

eed t o t h e r eact o r s. T h e hy dr o g en par t i a l pr es s u r e o f t h e r ecy cle gas i s kept at a m in im u m o f 1100 po un ds pers quar e in ch ab s o l u t e ( p s i a) t o m in im i ze pet r o l eum co ke b u il dup o n t h e cat al y s t an d s u b s equen t cat al y s t deact iv at i o n . T h e pur it y o f t h e r ecy cl e gas can b e r a i s ed b y b l eedin g o f f a po r t i o n o f t h e r ecy cl e gas in o r dert o pur ge l i g ht hy dr o carb o n gas e s . T h e l i qui d ph as e ( o il ) f r o m t h e HPS i s pr es s u r e d do wn t o t h e L o w Pr es s u r e Separ a t o r( L PS) , t o f l ash t h e r e ma in in g l i g ht gases o v er h ead t o t h e S t age 1 st r i pper . T h e st r eam f

r o m t h e b o t t o m o f t h e L P S i s h eat ed in t h e st ab il i zerpr eh eat eran d f e d t o t h e Gas P l an t S y st em . T h e Gas P l an t f r act i o n a t e s t h e pr o duct f r o m S t age 2 int o pr o p an e, b u t a n e , l i g ht an d h eav y hy dr o c r ackat es, an d di esel
. 1. 2. 4 S t age 2 React o r M o nit o ri ng and Cont r o l S t age 2 React o r s wer e m o n it o r e d an d co nt r o lle d f r o m t h e co nt r o l r o o m usin g b o ar d m o unt e d in st r u m e nt s an d a per s o n al co m put er( P C)

- b ased dat a l o ggerdi spl a y . T e m p er at ur e di spl a y pan e l s l o cat ed un der n eat h t h e r eact o r s wer e al so used t o m o n it o rt e m p er at ur es; h o wev e rt h i s dat a co ul d n o t b e accessed f r o m t h e co nt r o l r o o m . T h e int e r n al r eact o rt e m p er at ur es wer e el ect r o n i call y m

o n i t o r e d b y 96 t h er m o co uples wh i c h wer e co n n ect ed t o t h e v ar i o u s t e m p er at ur e di spl a y in s t r u me n t s . 1. 2. 4. 1 T h erm o coupl es T h er m o co upl es used b y T o sco wer e t y pe “ J ”, i r o n - c o n st ant a n , sh eat h e d t h er m o co uples, desi gn ed t o b e f lex i b le t o all o w r o ut in g t o v ar i o u s l o cat i o n s in t h e r eact o rcat al y s t b e ds
. I n J a nu ar y 1996 an ar r a y o f 96 t h er m o co uples wer e in st alle d in si de each r eact o rt o in di cat e t h e in le t , m i ddle an d o u t let t e m p er at ur e o f each cat al y s t b e d ( e x cept Bed 1 in le t )
. T h ey wer e al so used t o det e r m in e t h e ax i a l t e m p er at ur e gr adi e nt ( t em per a t u r e dif f e r e n ce b e t w een po int s ab o v e an d b e l o w each o t h e rin cat al y s t b e d) an d t h e r a di al t e m p er at ur e gr adi e nt ( d if f e r e n ce in t e m p er at ur e am o n g po int s at t h e sam e le v e l in t h e cat al y s t b e d)
. T w elv e t h er m o co uples wer e l o cat ed in Bed 1, t w ent y - f o u r
8wer e l o cat ed in each Bed 2 t h r o ugh 4, an d t w elv e wer e l o cat ed in Bed 5. F i gur e 5 sh o w s t h e l o cat i o n o f t h e int e r n al S t age 2 r eact o rt h er m o co uples. A ddi t i o n al t h er m o co uples ( n o t sh o w n ) m

o n it o rt h e f eed, r eact o rin le t , r eact o ro u t let an d r eact o rskin t e m p er at ur es ( t h r ee skin t e m p er at ur es perr eact o r )
. F if t y - sixo f t h e t h er m o co upl e o u t put s wer e sen t t o a f i el d in st r u m e nt pan e l at t h e b a se o f t h e r eact o ran d t h e r e st ( 40) wer e r o ut ed t o t h e co nt r o l r o o m . T h e co nt r o l r o o m t h er m o co uple si gn al s wer e r o ut ed t o b o ar d m o unt e d in st r u m e n t s an d a P C

- b ased dat a l o gger( s ee n e x t sect i o n )
. A

ppen d ixE sh o w s, f o reach b e d, h o w ma n y in le t , m i ddle an d o u t let t e m p er at ur es wer e m o n it o r e d b y each t y pe o f in st r u m e nt . 1. 2. 4. 2 Cont r o lB oar d I n s t ru m e nt s T h e co nt r o l b o ar d in st r u m e nt s di spl a y e d t h e S t age 2 f l o w r a t e s an d t e m p er at ur es in di gi t a l , L E D l i g ht b ar , an d st r i p ch ar t f o r mat . F i gur e C- 1 in A ppen d ixC sh o w s t h e in st r u m e nt co nt r o lle r s used f o rpr o cess st r eam s in S t age 2 Hi gh P r essur e S y st em . T h e o il f

eed r a t e t o t h e r eact o r , an d hy dr o g en f

l o w t o t h e t r im f

u r n ace wer e r e gul at ed b y f

l o w co nt r o lle r s . T h e hy dr o g en f

l o w t o t h e f eed/ e f f l uen t h eat ex ch an ger s was f l o w co n t r o lle d so t h at a suf f i ci ent hy dr o g en t o o il r a t i o was ma in t a in ed. R ecy cle gas pr es s u r e was pr es s u r e co nt r o lle d b y hy dr o g en added f r o m t h e makeup co m p r e sso r s . React o rin le t t e m p er at ur e was input t o a co n t r o lle rt o r e gul at e t h e t r im f

u r n ace t e m p er at ur e wh i c h was t h en in put t o a co nt r o lle rt h at r e gul at ed t h e f u el gas pr essur e t o t h e t r im f u r n ace. A l t e r n at iv el y , t h e t r im f

u r n ace co ul d al so b e o p er at ed at a specif i ed f u el gas pr essur e . T h e cent e rin le t t e m p er at ur e f r o m each o f t h e f o url o werb e ds was in put t o a co nt r o lle rwh i c h ch an ged t h e f l o w o f quen c h hy dr o g en t o each b e d t o ma int a in a set t e m p er at ur e. Ot h e rt e m p er at ur es wer e di spl a y e d in t h e co nt r o l r o o m b u t wer e n o t aut o ma t i call y

r e gul at ed b y in st r u m e nt co nt r o lle r s . T h ese wer e Bed 1 t h r o ugh 4 o u t let t e m p er at ur es, t h e r eact o ro u t let t e m p er at ur e 1 , an d t h e dif f e r e nt i a l b e t w een r eact o rin le t an d o u t let t e m p er at ur e. S t r i p ch ar t s r eco r d ed t h e t e m p er at ur e o f t h e cent e rt h er m o co uple in t h e in le t o f Beds 2 t h r o ugh 5 an d t h e cent e rt h er m o co uple in t h e o u t let o f Beds 1 t h r o ugh 4. T h ese sam e t w o b e d po int s wer e al so m

o n i t o r e d b y t h e dat a l o gger .

1. 2. 4. 3 Dat a L ogger T h e dat a l o ggerm o n i t o rdi spl a y e d t e m p er at ur es an d l o cat i o n s o f 40 o f t h e 96 int e r n al r eact o r t h er m o co uples. S i gn al s f r o m t h e r e ma in in g 56 t h er m o co uples wer e di spl a y e d at a l o cal pan e l at t h e b a se o f t h e r eact o r( s ee n e x t sect i o n )
. Oper at o r s accessed t h e v ar i o u s di spl a y scr een s usin g a small , cust o m i zed key b o ar d an d o n - s cr een m e nu s. T h e dat a l o ggeral so di spl a y e d av er aged v a l u es o f cat al y s t b e d t e m p er at ur es. I f t h e o p er at o r s saw an er r o n e o u s r eadin g o n a t e m p er at ur e

1 Th is s amep o in t w a s d i s p laye d o n s t r i p c h ar t f o r B e d 5 , b u t w a s r e f e r r e d toas B e d 5 o u tle t e v e n th o u g h it w a s th er e ac to r o u tle t te mp e r atu r e . B e d 5 o u tle t te mp e r atu r e s w e r es h o w n o n th ed ata lo g g e r an d f i e l d p a n e l. 9F i gur e 5 S t age 2 React o r s T h erm o coupl e Ar r a ngem ent- I s o m e t ric Dr awing

10po int , t h at po int co ul d b e accessed an d desi gn at ed as “ b ad” f r o m t h e key b o ar d
. T h i s desi gn at i o n ex cl uded t h e “ b ad” po int f r o m b e d- av er age t e m p er at ur e calcul a t i o n . T h e dat a l o ggerdi spl a y e d t e m p er at ur es f r o m f

iv e po int s at t h e o u t let o f t h e f i r s t cat al y s t b e d, f iv e po int s at b o t h t h e in le t an d o u t let o f t h e n e x t t h r ee cat al y s t b e ds, an d o n e po int at t h e in le t an d f o urpo int s at t h e o u t let o f t h e f if

t h

b e d. I t al so di spl a y e d t h r ee skin ( e x t er n a l wall ) t e m p er at ur es perr eact o ran d t h e in le t an d o u t let t e m p er at ur es o f each r eact o r . T h e t h er m o co uples wer e co n n ect ed t o a f i el d m u l

t i

p le x e rt h at sen t a di git a l si gn al o v era sin g le pai ro f wi r e s t o t h e dat a lo g g e r . T h e s i g n a l c o min g int o t h e d a t a lo g g e rfr o m a

fie l d mu lt ip le x e rr a n g e d fr o m 0 o F t o 1400 o F
. I f a t h er m o co uple f a ile d o rin di cat ed a t e m p er at ur e t h at was ab o v e r a n g e, t h e m u l

t i

p le x e r wo ul d s e n da 0 s i gn al t o t h e dat a l o gger . T h e dat a l o ggerdi s p l a y e d updat e d t e m p er at ur es at 15 t o 40 seco n d in t e r v al s. T h e dat a l o ggerwas al so pr o g r a m m

e d t o r e t a in a r eco r d o f t e m p er at ur e in di cat i o n s , kn o w n as t h e dat a l o ggerh i st o r i a n . Dat a f

r o m t h e h i st o r i a n was av ail ab le t o t h e acci dent in v e st i g at o r s b u t di d n o t dupl i cat e ex act l y

wh at o p er at o r s saw o n t h e dat a l o ggert h e n i ght o f t h e acci dent b ecause t h e h i st o r i a n r eco r d s o n l y

so m e o f t h e in f o r mat i o n di spl a y e d. E v er y h o ur , t h e h i st o r i a n r eco r d ed t h e cur r e n t v a l u e o f all po int s . Bet w een t h ese per i o d i c r eadin gs, t h e h i st o r i a n r eco r d ed an d t im e st am ped t e m p er at ur e r eadin gs o n l y

if

t h ey ch an ged m o r e t h an a pr edet er m in ed am o u nt ( d eadb a n d )
. F o rall t h e po int s , t h e deadb a n d was 0. 5% , o r7 o F f

o rt h e 0 t o 1400 o F r a ng e . T h e h i st o r i a n cr eat ed a dat a f

ile ev er y ei ght h o ur s. I f t h e h i st o r i a n h a d n o t r eco r d ed a t e m p er at ur e f o r a t im e int e r v al ( b ecause it h a d n o t ch an ged si gn if i cant l y

f

r o m t h e pr ev i o us v a l u e) , t h e h i st o r i a n used t h e v a l u e f r o m t h e l a st pr ev i o us r eco r d ed v a l u e. T h e dat a f

ile s wer e st o r ed o n t h e co m put er h ar d dr iv e f o ro n e m o nt h
. T h e dat a l o ggerco ul d pr int f r o m t h e h i st o r i a n f

ile a v a l u e f o reach t e m p er at ur e at r e quest ed t im e int e r v al s. 1. 2. 4. 4 F i el d P a nel s f o r T e m p er at ur e M o nit o ri ng F i el d pan e l s wer e in s t alle d un dert h e r eact o r s dur in g t h e 1996 J a nu ar y - F e b r uar y t u r n ar o u n d in o r dert o pr o v i d e addit i o n al t e m p er at ur e r eadin gs in t h e cat al y s t b e ds. F i gur e 6 i s a pl o t pl an o f t h e Hy dr o c r ackero p er at i o n t h at sh o w s t h e l o cat i o n o f t h e pan e l un derReact o r3 r e l a t iv e t o t h e co nt r o l r o o m . S e v e n po int s f r o m each t h er m o co uple ar r a y wer e di spl a y e d o n t h e pan e l s . I n div i dual t e m p er at ur es co ul d b e di s p l a y e d b y t h e o p er at o r s at t h e pan e l us in g m u l

t i

p o int r o t ar y swit ch es; o n e swit ch t o sel ect t h e b e d desi r e d an d f iv e o t h e rswit ch es f o rsel ect in g t h e po int wi t h in each b e d. T h e f i el d pan e l co ul d di spl a y t e m p er at ur es b e t w een - 1 0 o F an d 1200 o F
. If t h e t e m p e r a t u r e w a s o u t s i d e t h i s ra n g e , t h e d i s p l a y w o u l d s h o w a ll d a s h e s (----). 1. 2. 4. 5 Al arm s E ach in put po int t o t h e dat a l o ggerh a d a h i gh an d l o w t e m p er at ur e al ar m . Hi gh t e m p er at ur e al ar m s f o rt h e cat al y s t b e d po in t s wer e set at 780 o F
. It i s n o t k n o w n w h a t a l ar m p o int s w e re s e t f o rt h e r eact o rin le t an d o u t let s. T h e r eact o rskin t e m p er at ur e l o w al ar m was 300 o F , w h ile t h e

11F i gur e 6 H ydr o cr ack e r P l otP l an T o s c o Avon Ref i nery

12h i gh al ar m was 1500 o F
. W h en a po int al ar m e d, t h e t e m p er at ur e r eadin g appear ed t o “ b l ink” an d t h e b ackgr o u n d co l o rb e h in d t h e r eadin g ch an ged f r o m b l ack t o r e d. T h e o p er at o rco ul d ackn o wledge t h e al ar m , af t e rwh i c h t h e r eadin g wo ul d b e st eady an d t h e b ackgr o u n d wo ul d st ay in

t h e al ar m co l o runt il t h e co n d i t i o n clear ed. T h e dat a l o ggerh a d o n e di gi t a l o u t put f o rh i gh t e m p er at ur e t h at was co n n ect ed t o t h e b o ar d an nu n c i a t o r . T h e t e m p er at ur e po int s si gn aled t h i s al ar m wh en ev ert h ey wer e in “ n ew” al ar m st at us. T h e b o ar d an nu n c i a t o ral ar m co n s i s t s o f a f l ash in g l i g ht an d audi b le h o r n o n t h e S t age 2 al ar m pan e l
. T h e o p er at o rwo ul d h a v e t o ackn o wledge t h e b o ar d an nu n c i a t o rt o sile n ce t h e h o r n an d st o p t h e an nu n c i a t o rf l ash
. I f t h e al ar m was ackn o wledged o n t h e dat a l o ggerkey b o ar d , i t was n o l o n g era “ n ew” al ar m an d so t h e di git a l o u t put t u r n ed o f f

. T h i s r e set t h e sy st em f

o rt h e n e x t “ n ew” al ar m t h at cam e in . T h e d a ta l o g g e ra l s o h a d a l ar m s , w ith ou tp u t s to th e a n nu n c i a tor , f o rp o ints m o r e th a n 5 0 o F ab o v e o rb e l o w t h e av er age t e m p er at ur e, an d l o w skin t e m p er at ur e al ar m s . On t h e co nt r o l b o ar d, a f l ash in g si gn al al ar m wo ul d o ccurf o rt h e quen c h co nt r o lle r s if quen c h v a lv e was m o r e t h an 50% o p en o n B e ds 2, 3, o r5 o rm o r e t h an 75% o p en o n B e d 4. 1 . 2 . 5 O p e ra t i n g P a ra m e t e rs T h e ma x im u m o il f

eed r a t e t o St age 2 was ab o u t 53, 000 b ar r e l s perday ( B PD)
. T h i s co r r e s p o n ded t o ab o u t 35, 000 B P D o f o il f

eed t o St age 1. Vo l u m e expan s i o n an d 40% o il r ecy cle r a t e ma de up t h e dif f e r e n ce b e t w een t h ese t w o f eed r a t e s. S t age 2 r eact o rn o r mall y o p er at ed at 650- 690 o F an d 1560 ps i g ( p o u n d s pers quar e in ch gauge)
. T y pi cal o p er at in g pr essur e s an d t e m p er at ur es f o rv ar i o u s pr o cess st r eam s in S t age 2 ar e sh o w n in F i gur e C- 1 in A

ppen d ixC
. T h e m in im u m hy dr o g en par t i a l pr es s u r e in St age 2 was ma int a in ed at 1100 ps i a . T h e r ecy cle gas hy dr o g en pur i t y

was ma int a in ed b e t w een 75- 84%
. T h e hy dr o g en t o o il r a t i o was ma int a in ed at 5500 ( 5000 m in im u m ) s t an dar dcub i c f eet ( S C F ) hy dr o g en t o b ar r e l ( b b l ) o f o il f eed. T h e n i t r o g en le v e l f

o rf eed t o S t age 2 was n o t t o ex ceed 14 par t s per millio n ( p p m )
. C r it ic a l o p e r a t in g limit s w e r e d e fin e d b y T o s c o t o e s t ab lis h t h e s a fe o p e r a t in g r a n g e fo rt h e u n it
. S o m e o f t h ese ar e l i s t e d b e l o w in T ab le 1 f o rS t age 2 wi t h

t h e r e po r t ed co n s equen ces o f d e vi a t i o n.

13Ta b l e 1 Crit icalOper at ing L i m i t s f o r St age 2 React o r s O p e r a t in g P ar a me t e r L imit C o n s e q u e n c e s o f D e v i a t io n Max im u m r eact o r t e m p er at ur e 800 o F P o ssi b le t e m p er at ur e r u n a way . P o ssi b le v e ssel f

a il u r e an d f i r e due t o t e m p er at ur e r u n a way . M a x imu m t e mp e r a t u r e f o rr eact o ro u t let 690 o F P o ssi b le do wn st r eam f

eed/ e f f l uent ex ch an gerf i r e . P o ssi b le f i r e , expl o s i o n if

i g n it i o n so ur ce pr esen t . Max im u m r eact o rb e d av er age dif f e r e nt i a l t e m p er at ur e 40 o F P o ssi b le t e m p er at ur e r u n a way . P o ssi b le v e ssel f

a il u r e an d f i r e due t o t e m p er at ur e r u n a way . Max im u m r eact o r d iffe r e nt ia l t e m p er at ur e 75 o F P o ssi b le t e m p er at ur e r u n a way . P o ssi b le v e ssel f

a il u r e an d f i r e due t o t e m p er at ur e r u n a way .

1. 2. 6 E m e r g en cy Dep r essu ri n g A

100 ps i perm inut e ( p s i /m in ) an d 300 ps i / m in

depr es s u r in g s y s t em s wer e in s t alle d in 1986. T h ese sy st em s wer e desi gn ed t o r api dl y

depr essur e t h e r eact o r s t o r e duce t h e r eact i o n r a t e an d h i gh t e m p er at ur es in em er gen c y sit u at i o n s . Bo t h em er gen c y depr essur in g v a lv es wer e l o cat ed at t h e gas o u t let l in e o f t h e HP S an d di sch ar g ed t o t h e f l ar e sy st em . T h e 100 ps i / m in

s y s t em was act iv at ed aut o ma t i call y

if

t h e r ecy cle co m p r e s s o rs hut do wn . T h e sy st em co ul d al so b e ma nu all y

act iv at ed b y an o p er at o rin t h e co nt r o l r o o m . On ce t h e 100 psi / m in

sy st em was act iv at ed, t h e f o ll o win g wo ul d aut o ma t i call y

o ccur : St age 2 ch ar ge pum p i s s hut do wn ; Fu el t o t h e t r im f

u r n ace i s shut o f f

; M akeup gas t o St age 2 i s s hut o f f

; Hy dr o g en t o r ecy cl e co m p r e sso rsuct i o n an d di sch ar g e st r eam s ar e st o pped; an d T h e Hy dr o c r ackerr eact o rs y s t em i s depr es s u r e d at t h e r a t e o f 100 ps i / m in

t o r e f in e r y f

l ar e sy st em . I n

addi t i o n , t h e o il f

eed f r o m S t age 1 wo ul d b e ma nu all y

div e r t ed t o st o r age t a nk s. I f t h e 100 psi / m in

sy st em was act iv at ed ma nu all y , t h e r ecy cle co m p r e sso rwo ul d co nt inue t o o p er at e. T h e 100 ps i / m in

s y s t em all o wed t h e un it t o b e r e s t ar t e d qui ckl y

if

t h e s it u at i o n co ul d b e co r r ect ed b e f o r e t h e un it was f u ll y

depr essur e d. I f r eact o rt e m p er at ur es co n t inued t o in cr ease wh il e t h e un it was b e in g depr es s u r e d, t h e o p er at o r s wer e in s t r u ct ed t o act iv at e t h e 300 ps i / m in

depr es s u r in g s y s t e m imme d i a t e l y. 14T h e 300 ps i / m in

s y s t em was act iv at ed o n l y

ma nu all y

us in g a s w i t ch in t h e co nt r o l r o o m . I t depr es s u r e d t h e St age 2 hi gh pr es s u r e s y s t em t o t h e r e f in e r y f

l ar e, div e r t ed make- up hy dr o g en , shut do wn t h e S t age 2 ch ar ge pum ps an d t h e r ecy cle co m p r e sso r , an d st o pped f u el t o t h e t r im f u r n ace. I f t h e 300 ps i /m in

s y s t em was act iv at ed, t h e un i t h a d t o b e depr es s u r e d t o le s s t h an 10 ps i g b e f o r e t h e un i t co ul d b e r e s t ar t e d. T h i s i s b ecause t h e r eact o r s ar e r e qui r e d t o b e un der pr essur e af t e rt h e v e ssel s wall s h a v e co o led b ecause o f t h e r i sk o f cat ast r o p h i c f a il u r e due t o t e m p erem b r it t lem ent . 1. 2. 7 O pe r a ting P e r s onne l T h e Hy dr o c r ackero p er at ed co nt inuo usl y

f

o r24 h o ur s a day st af f e d b y t h r ee ei ght
- h o uro p er at in g sh if t s . T h er e wer e n o r mall y

f

iv e o p er at o r s o n dut y at t h e Hy dr o c r ackerdur in g each sh if t . On e o p er at o rwas kn o w n as t h e No
. 1 Oper at o rwh o o v er saw t h e sh if t , assi st ed wit h b o ar d dut i e s if n ecessar y an d ma de o u t s i d e r o un ds at l east o n ce persh if t . T h e o t h e ro p er at o r s wer e kn o w n as No
. 2 Oper at o r s. On e was t h e Hy dr o g en Bo ar d Oper at o rwh o o p er at ed t h e co nt r o l sy st em f

o r t h e Hy dr o g en P l ant an d S t age 1. A n o t h e rwas t h e S t age 2 Bo ar d Oper at o rwh o o p er at ed t h e co nt r o l sy st em f

o rS t age 2, in cl udin g t h e h i gh an d l o w pr essur e sy st em s. T h e o t h e rt w o o p er at o r s wer e E a st P a d an d W e st P a d Oper at o r s wh o wer e r e spo n si b le f o rmakin g r o un ds t o ch eck equi pm ent , t akin g o u t s i d e r eadin gs an d o b t a in in g sam p l e s as n ecessar y f

o rt h e E a st P a d ( H y d r o gen Pl ant ) an d W e s t Pad ( S t a ge 1 an d St age 2) h i gh an d l o w pr es s u r e s y s t em s , r e spect iv el y . F i gur e 6 sh o w s t h e l o cat i o n o f t h e Hy dr o c r ackerco nt r o l r o o m an d S t age 2 React o r 3 on a

P l ot P l a n . 

### 2. 0 Descrip tio n o f th e Accid en t T h i s s ect i o n des c r i b e s t h e ev ent s t h at o ccur r e d o n J a nu ar y 21, 1997 leadin g up t o t h e expl o s i o n an d f i r e at t h e Hy dr o c r ackerUn it .

2. 1 E vent s of January 21, 1997 2. 1. 1 N ight Shif t ( 10 pmt o 6 am ) At ab o u t 4: 50 am o n Janu ar y 21, a cl am p o n t h e f l an ge o f t h e S t age 1 React o rA ef f l uent ex ch an gerb e gan t o l eak. T h e pr essur e an d f eed r a t e s t o React o rA wer e r e duced t o st o p t h e l eak, b u t t h i s act i o n was in ef f ect iv e. T h e f eed t o React o rA was div e r t ed t o React o r s B an d C at ab o u t 5: 20 am t o st o p t h e l eak. T h e ex t r a f eed t o t h ese r eact o r s l o wer e d t h ei rt e m p er at ur es an d limit e d t h e hy dr o t r eat in g r eact i o n . T h i s caused t h e n i t r o g en co nt ent in t h e S t age 1 ef f l uent t o r i se ab o v e t h e s p e c ifie d limit o f 1 4 p p m .

152. 1. 2 D ay Shif t ( 6 amt o 2 pm ) At 8:10 am , t h e n it r o g en co nt en t o f St age 1 ef f l uent was 196 ppm , ab o v e t h e s p ecif i ed limit o f 1 4 ppm . A cco r d in g t o t h e swin g sh if t S t age 2 Bo ar d Oper at o r , t h e h i gh n i t r o g en co nt ent ma t e r i al f r o m S t age 1 h a d t o co nt inue t o S t age 2 an d co ul d n o t b e sent t o t h e o f f

- t e st t a nk s b ecause t h ey wer e f u ll
. Because o f t h e h i gh n it r o g en le v e l s in t h e f eed t o t h e S t age 2 r eact o r s, t h e S t age 2 cat al y s t b ecam e “ p o i so n e d” causin g t h e S t age 2 cr ackin g r eact i o n t o decl in e. By 9: 30 am , t h e quen c h f

l o w s t o S t age 2 cat al y s t b e ds h a d b e gun t o dr o p o f f

, in di cat in g a r e duced r eact i o n . At 10 am , t h e n i t r o g en co nt ent f r o m St age 1 was 352 ppm
. At appr o x ima t e l y

11:30 am , t h e s t r i p ch ar t s sh o w ed n o t e m p er at ur e dif f e r e n t i a l acr o ss React o r3. Dur in g t h e day sh if t , t h e dif f e r e nt i a l t e m p er at ur es av er aged l e ss t h an 10 o F percat al y s t b e d f o rall S t age 2 r eact o r s an d t h e un i t was n o t pr o ducin g an y l

i g ht pr o duct
. F eed r a t e t o S t age 1, React o rB was r e duced in o r dert o en ab le b e d t e m p er at ur es t o b e in cr eased. A

co nt r act o rr e pai r ed t h e leak o n t h e React o rA ex ch an gerf l an ge cl am p b y in j ect in g seal ant int o i t . T h e l eak was st o pped b u t React o rA r e ma in ed do wn t o all o w t im e f o rt h e seal ant t o cur e . Mean wh ile , o p er at o r s co nt inued t o adj u st r a t e s an d t e m p er at ur es in React o r s B an d C in o r dert o in cr ease t h e r eact i o n an d r e duce t h e n i t r o g en co nt ent in t h e ef f l uent . At 12: 13 pm , t h e S t age 1 s t r i pperb o t t o m n i t r o g en an al y s i s was 66 ppm
. At 1:10 pm , i t was 40 ppm
. So m e t im e dur in g t h e day o f J a nu ar y 21, an o p er at in g pl an was wr it t e n in t h e s h if t l o gb o o k f

o rt h e ev en in g o f Janu ar y 21, t o pr epar e f o rt h e in t r o duct i o n o f o il t o React o rA t h e n e x t m o r n in g at 8 am . T h e pl an di r ect ed t h e o p er at o r s t o co nt inue t o r a i s e t e m p er at ur e in React o r s B an d C at a r e d u c e d r a te , in or d e rto g e t th e n itr og e n d o w n to 5 p p m orle s s , a n d th e n to in c r e a s e th e r a te to t h ese t w o r eact o r s as m u ch as t h e n it r o g en co n s t r aint all o wed. I n addit i o n , t h e o p er at o r s wer e di

r ect ed t o gr aduall y

in cr ease t e m p er at ur es in S t age 2 in o r dert o dr iv e t h e n i t r o g en o f f t h e cat al y s t . 2. 1. 3 S w i ng Shif t(2 pmto 10 pm ) On t h e swin g sh if t , t w o ex t r a o p er at o r s wer e added t o h e l p wi t h

S t age 1 pr o b le m s . On e was t h e No
. 1 Oper at o ro n t h e day sh if t wh o st ay ed o v ero n t h e swin g sh if t t o h e l p o u t an d m o n it o r r e pai r s o n t h e React o rA ex ch an gercl am p. T h e o t h e rwas a No
. 2 Oper at o r( w o r ked n i ght o f Janu ar y 20- 21) wh o was b r o ught in t o get S t age 1 React o rA up t o t e m p er at ur e b e f o r e pl an n e d intr od u c ti on of oil a t 8 a m th e n e x t m o r n in g ( J a nu ar y 2 2 )
. At th e s t ar t of th e s w in g s h if t, th e r e wer e n o l i g ht pr o duct s in t h e l o w pr essur e sect i o n o f S t age 2, in di cat in g l i t t le o rn o r eact i o n o ccur r in g . On l y

a f e w quen c h f

l o w s ( B eds 2 an d 3 in React o r1, Bed 2 in React o r2 an d Bed 3 in React o r3) wer e ab o v e 10% o f f

u ll

- scale f l o w wh i c h i s al so an in di cat i o n o f l o w r eact o ract iv i t y . St age 2 b e d in le t t e m p er at ur es v ar i ed f r o m ab o u t 612 t o 640 o F
. At 5: 38 pm , t h e n it r o g en an al y s i s f o rt h e St age 1 s t r i pperb o t t o m s was 47 ppm
.

16At 7:34:00 pm ( c o r r ect ed dat a l o ggert im e 2 ) , t h e React o r3 Bed 4, P o int 2 o u t let t e m p er at ur e in cr eased f r o m 628 o F t o 823 o F in 40 seco n d s. S ee T ab le 2 f o rt e m p er at ur e dat a . T h e dat a l o gger al ar m s o un ded di s p l a y in g a B e d 4 o u t let hi gh t e m p er at ur e an d al s o a hi gh B e d 5 in le t t e m p er at ur e. T h e S t age 2 Bo ar d Oper at o rh ear d t h e al ar m s an d saw t e m p er at ur es o f ab o u t 690 o F o n B e d 4 o u t l et an d 890 o F o n t h e Bed 5 in le t . A cco r d in g t o dat a l o ggerr eco r d s, React o r3, Bed 5 in le t t e m p er at ur e h a d r i s e n f

r o m 637 0 F t o 860 o F wit h in o n e m inut e. T h e st r i p r eco r d ero n t h e co n t r o l pan e l f

o rB e d 5 in le t t e m p er at ur e went f r o m ab o u t 640 o F t o f u ll scale ( 800 o F )
. T h e st r i p ch ar t r eco r d in g t h e Bed 4 P o int 3 ( cent e r ) o u t let t e m p er at ur e appear ed n o r mal
. A

b o u t 7:34:20 ( b as ed o n t h e dat a l o ggerr eadin g f o rB e d 5 in le t hi gh t e m p er at ur e) , t h e hy dr o g en quen c h f

l o w t o Bed 5 b e gan t o o p en f

u r t h e rt o r e duce t h e t e m p er at ur e, as was seen o n t h e st r i p ch ar t r eco r d er . I t co nt inued t o o p en t o 100% o n t h e s t r i p ch ar t r eco r d er . At ab o u t t h e s a m e t im e , t h e makeup hy dr o g en t o S t age 2 b e gan t o decr ease. T h e S t age 2 Bo ar d Oper at o rexpr essed co n cer n o v era po t e nt i a l ex cur s i o n an d wi t h in a m inut e t h e t w o No
. 1 Oper at o r s j o in ed h im in ev al uat in g t h e co nt r o l b o ar d an d dat a l o ggerr eadin gs. T h ey r e po r t ed seein g t h e dat a l o ggert e m p er at ur es st ar t t o b o un ce up an d do wn , f r o m n o r mal r a n g e t e m p er at ur es t o 0 an d b ack again . T h e S t age 2 Bo ar d Oper at o rst at ed t h at t h e Bed 4 an d 5 t e m p er at ur es wer e s w in gin g f r o m 0 t o 1200 o F , t h en b ack t o 650 o F
. T h e No
. 1 Oper at o rst at ed t h at t h ey co ul d n o t t r us t t h e f i gur es . At s o m e t im e pr i o rt o 7:37 pm , a No
. 2 Oper at o rwent t o ch eck t h e t e m p er at ur es at t h e f i el d pan e l un derReact o r3. T h e s udden in cr eas e in quen c h f

l o w t o Bed 5 caus e d t h e hy dr o g en f

l o w t o t h e t r im f

u r n ace( s ) t o f l uct u at e. T h i s in t u r n caused t h e hy dr o g en f

l o w co n t r o l v a lv e t o t h e t r im f

u r n ace t o o p en f

u r t h e r . S in ce t h e t r im f

u r n ace hy dr o g en i s t e m p er at ur e co nt r o lle d, t h i s caused an in cr ease in f

u el gas f l o w ( t o h eat up addit i o n al hy dr o g en in t h e t r im f

u r n ace) an d dr o pped t h e f u el gas pr essur e . At 7: 36: 20 pm ( a l ar m l o g h i st o r y t im e ) , a h i gh f

l o w al ar m o ccur r e d f o rt h e hy dr o g en f

l o w t o React o r1 t r im f u r n ace. B y 7:35 pm , t h e B e d 4 Po int 2 o u t let t e m p er at ur e h a d decr eas ed t o 637 o F an d t h e quen c h f

l o w t o B e d 5 w a s s t ill fu ll o p e n . T h e o t h e rfo u rB e d 4 o u t le t t e mp e r a t u r e s r e ma in e d n o r ma l d u r in g t h is t im e , wh i c h in cl uded P o int 3 ( cen t e ro u t let ) wh i c h was al so r eco r d ed o n t h e co n t r o l pan e l st r i p ch ar t s . A cco r d in g t o t h e dat a l o gger , b y 7:35 pm , t h e f o urB e d 5 o u t let t e m p er at ur es h a d decr eased b y 15- 30 o F each in r e spo n se t o t h e Bed 5 quen c h v a lv e o p en in g. B y 7:36 pm , t h e quen c h f

l o w t o B e d 5 h a d r i s e n t o f u ll s cale, an d t h e B e d 5 in le t t e m p er at ur e h a d decr eased t o 633 o F o n t h e dat a l o ggeran d h a d al so decr eased acco r d in gl y

o n t h e st r i p ch ar t r eco r d er . At 7: 36: 00, t h e React o r3 o u t let t e m p er at ur e h a d in cr eased 9 degr ees in 20 seco n d s,

2 Th ed ata lo g g e r r e c o r d e d timeth at w a s 5 2 min u t e s ah e a d o f ac tu al time ; th is r e p o r tu s e s th eac tu al time
. Th ed ata lo g g e r te mp e r atu r e s c ite d in th is r e p o r tar ef r o m th eh i s t o r ian f ilec r e ate d b y th ed ata lo g g e r c o mp u t e r . B e c a u s eth eh i s t o r ian f iles a v e s te mp e r atu r ed ata ac c o r d in g toa s p e c i f i e d p r o g r am ( s e eS e c tio n 1
. 2
. 4
. 3 ) , it may n o t d u p lic ateth ee x ac t s amete mp e r atu r eth at th eo p e r ato r s s a w o n th ed ata lo g g e r . 17f r o m 641 t o 650 o F , b u t t h i s was appar e n t l y

n o t n o t i ced b y t h e o p er at o r s. Oper at o r s sai d t h at t h ey di d n o t h earan y o t h e rh i gh t e m p er at ur e al ar m s . T h r o ugh o u t t h i s t im e , t h e o p er at o r s r e po r t ed t h at t h e t e m p er at ur es o n t h e dat a l o ggerco nt inued t o “ b o u n ce up an d do wn ”, f l uct u at in g b e t w een hi gh , n o r mal an d 0 t e m p er at ur e r eadin gs. Bet w een 7: 36 an d 7: 37 pm , t h e f u el gas pr essur e at t h e React o r1 t r im f

u r n ace h a d in cr eased t o 3 0 p s i w h ic h w a s o v e rt h e ma x imu m limit o f 2 8 p s i. T h e e x t r a N o . 1 O p e r a t o rr e d u c e d fir in g in t h e f u r n ace t o pr ev ent o v er f i r in g . He t o o k t h e t r im f

u r n ace o f f t e m p er at ur e co nt r o l an d put it o n f u el gas pr essur e co nt r o l
. He t h en swi t ch ed t h e Bed 5 quen c h f

l o w co nt r o lle rf r o m aut o ma t i c t o ma nu al co n t r o l an d cl o s ed t h e quen c h v a lv e t o Bed 5 b ecause h e was co n cer n e d ab o u t l o sin g t e m p er at ur e in t h e r eact o r . T h e S t age 2 Bo ar d Oper at o rst at ed t h at h e saw h i gh r ecy cle f l o w s t h

r o ugh t h e T r im Fu r n ace 1 an d 2. T h e ex t r a No
. 1 Oper at o rwas b l o c kin g h i s v i ew o f t h e T r im Fu r n ace 3 in st r u m e nt s. By 7: 37 pm , t h e Bed 5 o u t let t e m p er at ur es h a d all st ar t e d t o in cr ease in t e m p er at ur e, t h e h i gh est b e in g B e d 5 o u t let Po int 1 at 681 o F
. S ee F i gur es 7- 8 depi ct in g gr aph s o f t h e r e le v a n t React o r3 t e m p er at ur e ch an ges dur in g t h i s per i o d o f t im e . At 7:37 pm , t h e hy dr o g en makeup dr o pped t o zer o acco r d in g t o t h e P e r f o r ma n ce Mo n it o r in g S y st em ( P MS ) co m put er . T h e Hy dr o g en Bo ar d Oper at o ral er t e d t h e o t h e ro p er at o r s o f t h i s ch an ge. He sai d t h e hy dr o g en pl ant was b eco m in g o v erpr essur e d. E x cess hy dr o g en was di r ect ed t o t h e h eader / f

l ar e sy st em t o pr ev ent o v er pr essur e . At 7: 39: 02 pm ( acco r d in g t o al ar m l o g h i st o r y ) , a h i gh f

l o w al ar m f

o rt h e hy dr o g en b l o w do wn t o t h e f l ar e o ccur r e d. Bet w een 7: 37 an d 7: 39 pm , t h e ex t r a No
. 1 Oper at o rco nt r o lle d t h e o p er at i o n o f t h e t r im f

u r n ace wh il e t h e S t age 2 Bo ar d an d No
. 1 Oper at o r s co n t inued t o m o n it o rt e m p er at ur es an d t h e dat a l o ggerwh i c h co n t inued t o f l uct u at e. T h e S t age 2 Bo ar d Oper at o rn o t i ced o n t h e co n t r o l b o ar d t h at t h e quen c h f

l o w t o B e d 5 h a d b een ma nu all y

cl o s ed, an d at 7:38 pm , h e r e - o pen e d it . B e t w een 7:38 an d 7:39 pm , all f

o urB e d 5 o u t let t e m p er at ur es r o s e ab o v e 780 o F , w ith P o int 1 r eadin g a ma x im u m o f 1255 o F at 7:38:20 pm
. A ll f

o urB e d 5 o u t let t e m p er at ur es co nt inued t o r i s e unt il t h ey def aul t e d t o zer o at 7:39:20 ( s ee T ab le 2)
. F

r o m 7: 36: 20 t o 7: 39: 20 pm , t h e React o r3 o u t l et t e m p er at ur e r o se f r o m 650 o F t o a ma x imu m o f 1220 o F
. T h e r eact o rin le t t e m p er at ur e in cr eased f r o m 649 o F at 7:38:00 pm t o 693 o F at 7:39:00. T h e co nt r o l b o ar d s t r i p ch ar t s al s o r eco r d ed t h e s udden r i s e in r eact o rin le t an d o u t let t e m p er at ur es. At appr o x ima t e l y

7:39 pm , o p er at o r s h ear d a r a di o m e s s a ge f r o m t h e No
. 2 Oper at o rt h at was garb l e d an d un clear . T h e St age 2 B o ar d Oper at o rt h o ught h e h ear d “ 1250" o n t h e r a di o , b u t was n o t sur e . T w o un successf ul

at t e m p t s wer e ma de t o co nt act h im . T w o o p er at o r s ( E ast P a d an d ex t r a No
. 2 Oper at o r ) went o u t s i d e t o ch eck o n h im . T h e r eact o ro u t let t e m p er at ur e r eadin g o n t h e dat a l o ggerdef aul t e d t o 0 at 7:39:40 pm
.

18Ta b l e 2 Som e React o r 3 T e m p er at ur es - B e d 4, B e d 5, React o r I n l e t/Out l et
B e d 4 B ed 5 B ed 5 B ed 5 B ed 5 B ed 5 Rx 3 Rx 3 O u tle t I n le t Te mp O u tle t O u tle t O u tle t O u tle t O u tle t I n le t Te mp Te mp Te mp Te mp Te mp Te mp Te mp Time(pm) P t-133C2 P t -140C3 P t -134C1 P t -134C2 P t -134C4 P t -134C5 P t -141C P t -125C 7: 33: 00 628. 3 636. 9 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 33: 20 628. 3 636. 9 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 33: 40 636. 5 658. 0 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 34: 00 823. 2 720. 7 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 34: 20 732. 0 859. 5 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 34: 40 732. 0 859. 5 648. 6 646. 3 656. 8 645. 9 641. 3 632. 2 7: 35: 00 637. 3 792. 4 624. 2 627. 7 633. 4 645. 9 641. 3 632. 2 7: 35: 20 637. 3 715. 7 624. 2 627. 7 633. 4 615. 4 641. 3 632. 2 7: 35: 40 637. 3 664. 4 624. 2 640. 3 633. 4 615. 4 641. 3 632. 2 7: 36: 00 637. 3 633. 4 650. 3 647. 9 623. 6 615. 4 649. 9 632. 2 7: 36: 20 637. 3 633. 4 663. 9 667. 7 623. 6 615. 4 649. 9 632. 2 7: 36: 40 637. 3 660. 7 672. 9 667. 7 623. 6 625. 6 658. 9 632. 2 7: 37: 00 637. 3 660. 7 681. 1 676. 8 656. 0 645. 8 658. 9 632. 2 7: 37: 20 637. 3 660. 7 681. 1 676. 8 672. 0 673. 5 760. 7 632. 2 7: 37: 40 637. 3 660. 7 697. 3 707. 5 690. 7 673. 5 760. 7 640. 2 7: 38: 00 637. 3 660. 7 717. 2 876. 0 690. 7 673. 5 684. 6 640. 2 7: 38: 20 637. 3 660. 7 1255. 7 0. 0 783. 0 705. 8 701. 8 648. 8 7: 38: 40 637. 3 660. 7 0
. 0 0. 0 0
. 0 744. 0 788. 8 660. 0 7: 39: 00 637. 3 648. 0 0
. 0 0. 0 0
. 0 889. 0 983. 1 693. 0 7: 39: 20 637. 3 648. 0 0
. 0 0. 0 0
. 0 0. 0 1219. 6 754. 7 7: 39: 40 637. 3 655. 6 0
. 0 0. 0 0
. 0 0. 0 0
. 0 826. 5 7: 40: 00 637. 3 655. 6 0
. 0 0. 0 0
. 0 0. 0 0
. 0 889. 1 7: 40: 20 637. 3 655. 6 0
. 0 0. 0 0
. 0 0. 0 0
. 0 960. 7 7: 40: 40 637. 3 645. 7 0
. 0 0. 0 1397. 1 879. 9 0
. 0 1233. 5 7: 41: 00 637. 3 645. 7 0
. 0 0. 0 1398. 4 694. 9 0
. 0 0. 0 7 : 4 1 : 2 0 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 7 : 4 1 : 4 0 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? 0
. 0 ???? S o u r c e: D ata L o g g e r Hi s t o r ian Th etimelis te d in th etab lea bovei s t h ea c t u a l time ; th etimein th ed ata lo g g e r h i s t o r ian r e p o r tw a s 5 2 min u t e s ah e a d o f ac tu al time . Hi g h e s t te mp e r atu r e s r e c o r d e d p e r p o in t ar e b o ld ed
. Ar e ad in g o f 0
. 0 me an s te mp e r atu r e w a s a bove 1400 o F
. Ar e a d i n g o f 0
. 0 ???? m e a n s l o s s o f p o w e r t od ata lo g g e r c o mp u t e r . B e d 4 in le t te mp e r atu r e s d i d n o t v a r y d u r in g th ein c i d e n t . O n ly th eB e d 4 o u tle t te mp e r atu r eth at e x p e r i e n c e d an ab n o r mal r i s ein te mp e r atu r eis in c l u d e d in th etab le
. Un c h an g e d te mp e r atu r er e ad in g s me an th at te mp e r atu r ed i d n o t c h an g emo r e th an 7 o Ff r o m las t r e ad in g , th e r e f o r ed ata lo g g e r h i s t o r ian r e tain s las t p r e v io u s r e c o r d e d v alu e .

1920A f t e r7: 40 pm , t h e st r i p ch ar t r eadin gs f o rt h e r eact o rin le t an d o u t let t e m p er at ur es co nt inued t o r ead o f f s cale h i gh
. T h e r eact o rin le t t e m p er at ur e r each ed a ma x im u m o f 1234 o F on th e d a ta l o ggerat 7:40:40 pm b e f o r e def aul t in g t o 0. A b o u t t h e s a m e t im e , t h e ex t r a No
. 1 Oper at o r c a lle d t h e s h ift s u p e r v is o rb y p h o n e , w h o imme d i a t e l y r e t u r n e d t h e c a ll. T h e o p e r a t o rr e q u e s t e d t h e assi st an ce o f an in st r u m e n t t ech n i ci an t o wo r k o n t h e t e m p er at ur e l o ggero n S t age 2. A l so at t h i s t im e , t h e S t age 2 Bo ar d Oper at o rn o t i ced t h at t h e r eact o rin le t t e m p er at ur e h a d in cr eased t o o v er800 o F
. I n r e spo n se, h e r e duced f i r in g o n t h e t r im f

u r n ace an d l o wer e d t h e t e m p er at ur e set po int s t o t h e t o p t w o b e ds, as a m ean s o f in cr easin g quen c h f

l o w . At 7:41 pm , t h e h i gh es t r eco r d ed t e m p er at ur e o n t h e dat a l o ggerwas t h e B e d 5 Po int 2 o u t let t e m p er at ur e, wh i c h r e gi s t er ed 1398 o F
. At t h i s t im e , t h e t w o o u t s i d e o p er at o r s h a d r each ed t h e n o r t h w est co r n ero f t h e co n t r o l r o o m an d t h e S t age 2 Bo ar d Oper at o rwas l o wer in g t h e t e m p er at ur e s e t po int o n B e d 3. At appr o x ima t e l y

7:41:20, an expl o s i o n o ccur r e d, f o ll o wed b y a f i r e . S eco n d s b e f o r e t h e expl o s i o n , o n e o b ser v erdr iv in g b y t h e Hy dr o c r ackerUn i t r e po r t ed seein g a gl o w in g r e d- h o t pi pe el b o w in f

r o nt o f t h e S t age 2 r eact o r s. S e v e r a l T o sco an d co nt r act o rem pl o y ees r e po r t ed h ear in g a po p o rcr ack so un d, f o ll o wed b y t w o expl o s i o n s , o n e small an d o n e b i gger . A h o r i zo nt al st r a i g ht sect i o n o f 12" di am et erReact o r3 ef

f l uent pi pin g h a d r upt ur ed j u s t ups t r eam o f a 12" x10" di am et err e ducer
. B e y o n d t h e r e ducer , t h e 10" di am et erpi pe en t e r e d t h e t o p o f t h e 40- f o o t h i gh f

eed/ e f f l uen t ex ch an gerst r u ct ur e f o r React o r3. T h e hy dr o carb o n an d hy dr o g en m ix t u r e r e leased f r o m t h e pi pe r upt ur e appar e nt l y aut o i g n it e d v e r y s h o r t l y

af t e rt h e in it i a l r e l eas e, caus in g a f i r e b a ll o v er100 f eet h i gh
. I m m

e di at el y

f

o ll o win g t h e expl o s i o n , t h e 300 ps i / m in

depr es s u r in g s y s t em was act iv at ed an d o p er at o r s b e gan t o shut do wn t h e un it . A f t e rt h e expl o s i o n , t h er e was a po werf a il u r e an d t h e un it o p er at ed o n b ackup po weran d b a t t e r i es f o rs e v e r a l h o ur s . E m er gen c y r e s p o n s e pr o cedur es an d n o t if i cat i o n s wer e st ar t e d. 2. 2 E m e r g ency Res p ons e Act i ons T h e n e w s me d i a r e p o r t e d t h a t r e v e rb e r a t io n s fr o m t h e b l a s t w e r e fe lt 2 0 mile s a w a y , a n d s m o k e an d f l am es wer e v i si b le f r o m n earb y f

r eeway s. Wi th in m inu t e s of th e e xp l os i o n , T o s c o r e s p on d e d b y act iv at in g t h e E m er gen c y Co m ma n d Cent eran d em pl o y ee v o l u nt eerf i r e b r i g ade. T h e I n ci dent C o mma n d e rw a s o n s it e a t t h e t ime o f t h e e xp l o s io n a n d imme d i a t e l y s e t u p a n I n c i d e n t C o mma n d Po s t . T o sco n o t if i ed v ar i o u s agen ci es, in cl udin g Co n t r a Co st a Co unt y Heal t h

S e r v i ces Depar t m e nt ( CCCHS D ) , Cal if

o r n i a Of f i ce o f E m er g e n c y S e r v i ces, Bay A r ea A i rQu al it y Man a g e m e nt Di st r i ct (B A A Q M D ), C a l if

o r n i a D e p art m e nt o f F i s h a n d G a m e , N a t i o n a l R e s p o n s e C e nt e r , EP A R e g i o n I X , C ALO S H A a n d S a nt a F e R a ilr o a d
. S o me p r o b le ms o c c u r r e d w i t h

c o mmu n i c a t io n s a n d n o t if i cat i o n s b ecause t h e ph o n e l in es wer e o v er wh el m

e d wit h in co m in g call s . Co nt r a Co st a Co unt y f

i r e f i ght e r s wer e depl o y ed o u t s i d e t h e r e f in e r y an d wer e av ail ab le in case addi t i o n al as s i s t an ce was r e qui r e d. T o s c o h a d i t s o w n f

i r e b r i g ade an d di d n o t r e ques t o u t s i d e h e l p dur in g t h e in ci dent . 21T o sco r e q u e st ed at 8 : 2 6 p m t h at CCCHS D act iv at e t h e Co m m

u n it y A ler t Net w o r k an d si r e n s f o r a Lev e l 3 in ci d e nt . CCCHS D act iv at ed t h e Co m m

u n it y A c t i o n Net w o r k , an au t o ma t e d em er gen c y t e le ph o n e n o t if i cat i o n sy st em , wh i c h n o t if i ed r e si den t s ab o u t an h o uraf t e rt h e acci den t . T h e n o t if i cat i o n s y s t em r each ed 1, 440 o f 1, 851 h o us eh o l ds in t h e Cl y d e an d No r t h Co n c o r d ar eas t o war n t h em t o st ay in si de as a pr ecaut i o n . T h e co un t y t r i e d t o act iv at e a n e w s i

r e n w ar n in g s y s t e m fo rt h e fir s t t ime , b u t it fa ile d t o w o r k c o mp le t e ly. T h e un i t was i s o l at ed, depr es s u r e d, an d s hut do wn wh ile co o l in g wat e rwas appl i e d t o t h e f i r e an d s u r r o un din g s t r u ct ur es . A ppr o x ima t e l y

50 T o s c o f i r e f i ght e r s par t i c i p at ed in t h e r e s p o n s e us in g po r t ab le f i r e m o n i t o r s an d all o f t h e st at i o n ar y f

i r e m o n i t o r s in t h e ar ea. A ddi t i o n al f

i r e pum ps w e re s t ar t e d t h ro u g h o u t t h e re f in e ry a s re q u i re d t o ma int a in f

i re w a t e r p r e s s u re . Th e f i re f i g ht e rs spent m o st o f t h e n i ght b a t t l in g t h e f i r e . T h e f i r e was co nt ain e d t o t h e Hy dr o c r ackerS t age 2 React o r3 o u t let , co nt r o l v a lv es an d asso ci at ed pi pin g , an d ev ent u all y

b u r n ed o u t . Ni t r o g en was pur ged t h r o ugh t h e r eact o ran d dama ged pi pin g t o r e m o v e hy dr o carb o n v apo r s an d t o pr ev ent an y f

u r t h e rf l ar e- ups. S o m e sm o k e was em it t e d f r o m t h e b u r s t pi pe, af t e rt h e n it r o g en pur ge was in i t i a t e d. S e v e r a l f

l ar e- ups o f t h e f i r e o ccur r e d t h e n e x t day , due t o seepages o f hy d r o c arbo ns . 2. 3 C ons e que nc e s of E x pl os ion and F i r e 2. 3. 1 D eat h and I n j u ri es A

T o sco Hy dr o c r ackero p er at o r , wh o was in t h e pr o cess o f ch eckin g t h e t e m p er at ur e pan e l l o cat ed at t h e b a se o f React o r3, was k ille d
. H e w a s s e v e r e ly b u r n e d a s a r e s u lt o f b e in g in c l o s e p r o x imit y t o t h e fir e fr o m t h e r u p t u r e d p i p e . A c c o r d in g t o t h e c o r o n e r , h e di ed o f t h i r d- degr ee b u r n s o n 100 per cent o f h i s b o dy an d s m o k e inh a l a t i o n . A t o t a l o f 46 per s o n n e l wer e in j u r e d; ei ght wer e T o sco em pl o y ees an d 38 wer e co n t r act o rper s o n n e l
. I n j u r i es co n s i s t e d o f a f r act ur ed f o o t , em o t i o n a l t r auma , h eadach es, r in g in g ear s, cut s an d scr apes, an d t w i s t e d kn ees. T h i r t een in

j u r e d per s o n n e l wer e t aken b y am b u l a n ce t o l o cal h o spit al s, t r eat ed an d r e leased. T h er e wer e n o r e p o r t e d in ju r i e s t o t h e p u b lic o ro t h e ro ffs it e p e r s o n n e l. A s ma n y as 500 T o s c o em pl o y ees an d co nt r act wo r k er s wer e at t h e pl ant at t h e t im e o f t h e e xp l o s io n , w o r k in g t o c o mp le t e ma in t e n a n c e t u r n - ar o u n d p r o j e c t s . S o me o f t h e in ju r e d w e r e in si de o rn earco n t r act o rt r aile r s cl o s e t o t h e Hy dr o c r ackerUn it . T h e b l ast f r o m t h e expl o s i o n b l ew o u t t h e win d o w s o f o n e t r aile ran d t h e f l am es pr ev ent e d wo r k er s f r o m ex i t in g t h e t r aile r d o o r . T h e w o r k e r s c limb e d o u t o f t h e t r a ile rw in d o w fa c in g a w a y fr o m t h e fir e . M a n y p e r s o n n e l in

t h e sur r o un din g ar eas wer e kn o c ked do wn b y t h e f o r ce o f t h e expl o s i o n r e sul t in g in so m e o f t h e in j u r i es. S o m e wo r k er s wh o wer e kn o c ked do wn wer e in a t e nt r eceiv in g a saf e t y o r i e nt at i o n . Ot h e rper s o n n e l f

e ll o rt r i pped as t h ey t r i e d t o r u n away f

r o m t h e expl o s i o n an d f i r e b a ll
. A f

e w w e r e k n o c k e d d o w n by o t he rr u nning p e r s o nne l
.

222. 3. 2 E quipm ent Dam age T h e r upt ur e cr eat ed ab o u t an 18 in ch l o n g t earin t h e React o r3 ef f l uent pi pin g . T h e ph o t o g r aph s in

F i g u r e s 9

- 1 3 s h o w s o me o f t h e r e s u lt in g d a ma g e . T h e fir e me lt e d a lig ht p o le o n t h e r o a d n e x t t o t h e r eact o r s. T h e l o werpar t o f a m e t a l l a ddero n React o r3 was dama ged b y t h e h eat . S caf f o l d in g ar o u n d t h e S t age 1 an d 2 r eact o r s was m i ssh apen f

r o m t h e h eat o f t h e f i r e , b u t t h er e di d n o t appeart o b e m u ch b l ast dama ge. T h e f i r e f i ght in g equi pm ent n e x t t o React o rRo ad ( s ee F i gur e 6) was dama ged. W o o d en pl at f o r m s n eart h e un i t wer e ch ar r e d. T h e sixr eact o r s wer e co v e r e d wit h asb e st o s in sul a t i o n o v er l a i d wit h al um inum , wh i c h was b l acken ed b y t h e f i r e . A l ar g e v a lv e o n t h e f i r e wat e rpi pin g n eart h e r o ad was dama ged. 2. 3. 3 E nvir onm e nt alI m pact T h e win d dur in g in it i a l st ages o f t h e in ci dent was o u t o f t h e so ut h

- so ut h w est ; sm o k e, v apo r s an d p ar t i c u l a t e s r e le a s e d w e r e bl o w n by 5

- 7 m p h w ind t o w ar d s u n inhabi t e d ar e a s a n d S u i s u n B a y no r t h o f

t h e R e f in e r y . T o s c o es t ima t e d t h at 13 po un ds o f f

r i ab le as b e s t o s in s u l a t i o n f

r o m t h e dama ged pi

pin g an d equi pm ent was r e l eas ed. A i rs a m p l

in g f o ras b e s t o s was co n duct e d b y T o s c o in t h e imme d i a t e ar e a o f t h e acci den t . A ll r e sul t s wer e b e l o w t h e det ect i o n limit o f t h e t e s t a n d b e lo w t h e OS HA st an dar d o f 0. 1 f i b e r s percub i c cent im e t e rav er aged o v eran ei ght
- h o urper i o d
. T h e Bay A r ea A i rQual i t y

Man a gem e nt Di st r i ct ( B A A Q MD) r eceiv e d o n e pub l i c co m p l a int dur in g t h e in ci dent . A i rm o n i t o r in g was co n duct e d b y B AA Q M D whi c h s h o w ed l o w ( < 2. 4 par t s per b illio n ) b u t d e t e c t ab le a m o u n t s o f s ixo r g a n i c c h e mic a l s ( t o l u e n e , me t hyl t e r t
- b u t yl e t h e r , b e n z e n e , m

e t hyl ch l o r i de, carb o n t e t r ach l o r i de an d per c h l o r o e t hylen e)
. No n e o f t h e co n cent r at i o n s det ect ed wer e ab o v e l e v e l s o f co n cer n .

23F i gur e 9 F ir s t and Se c o nd Stage R e ac tor s

24F i gur e 10 R e ac tor 3 E f f l ue nt P i ping R uptur e

Fi g u r e 1 1 Fi e l d Pa n e lLo c a t i o n
25F i gur e 12 B a c k Side of R e ac tor 3 E f f l ue nt P i ping R uptur e

F i gur e 13 Rupt ur ed E f f l uent P i ping af t e r Rem oval
262 . 4 S u mma ry 2. 4. 1 K ey Even t s P r eced i n g t h e Day of t h e Acci d e n t T ab le 3 l i s t s so m e ev ent s t h at o ccur r e d in t h e 11 day s b e f o r e t h e acci dent . S o m e o f t h ese ev ent s ar e d i s c u s s e d in mo r e d e t a il in S e c t io n 3 o f t h is r e p o r t . Ta b l e 3 Ti m e Li n e o f K e y Ev en t s P r eced i n g t h e Day of t h e Acci d e n t January 10

Day s h if t S t age 1 an d 2 wer e in o p er at i o n . T e m p er at ur e m o n i t o r in g f o rS t age 2 was swit ch ed f r o m dat a l o ggert o n e w I /A co m put ersy st em . ( S ee S ect i o n 3. 3. 3. 1 o f t h i s r e po r t f o rf u r t h e rdi s c us s i o n ) January 11 A n int e r n al l eak was det ect ed in a S t age 1 h eat ex ch an ger , t h e st r i pperf eed pr eh eat er . January 12- 15 S t age 1 an d 2 o f t h e Hy dr o c r ackerwer e shut do wn an d int e r n al h eat ex ch an gerl eaks o n S t age 1 wer e r e pai r ed. Var i o u s co nt r o l v a lv es wer e r e pl aced o n S t age 2. January 16 S t age 1 was put int o o p er at i o n . React o rA f

eed/ e f f l uent ex ch an gerb e gan t o leak ex t e r n all y

f

r o m a f l an ge b u t t h en st o pped leakin g o n i

t s o w n . January 17 React o rA ex ch an gerb e gan t o leak again . L eak was r e pai r ed b y appl yin g seal ant t o cl am p o n ex ch an ger . January 18 F eed was int r o duced t o S t age 2. January 19

Day s h if t S t age 2 was o p er at in g. Co m p r e sso rB r e l i e f v a lv e was r e pl aced.
10: 20 pm A t e m p er at ur e ex cur s i o n o ccur r e d in Bed 4 o f React o r1. S o m e t e m p er at ur es ex ceeded 900 o F
. Oper at o r s di d n o t depr es s u r e St age 2 b u t co nt r o lle d t e m p er at ur e b y o t h e rm ean s. Oper at o r s r e po r t ed pr o b le m s wi t h I /A t e m p er at ur e m o n i t o r in g sy st em . January 20

Day s h if t T h e use o f I /A sy st em was di sco nt inu ed an d t h e dat a l o ggerwas put b ack in t o s e r v ic e . S w in g sh if t F eed r a t e t o S t age 1 was in cr eased.

272. 4. 2 K ey Even t s t h e Day of t h e Acci d e n t Ta b l e 4 Ti m e Li n e o f K e y Ev en t s t h e Day of t h e Acci d e n t January 21

4:50 am React o rA ef f l uent / f eed ex ch an gercl am p b e gan t o leak again an d t h e leak co ul d n o t b e co nt r o lle d. F eed t o React o rA was div e r t ed t o React o rB an d C, causin g r eact o rco o l in g an d h i gh n i t r o g en co nt ent in ef f l uent . 8:10 am Ni t r o g en co nt ent o f St age 1 ef f l uent was 196 ppm , ab o v e t h e s p ecif i cat i o n o f 14 ppm
. 10 am S t age 2 cat al y s t b e ds wer e po i s o n ed f r o m h i gh n i t r o g en le v e l s in t h e f eed an d cr ackin g was gr eat l y

r e duced. Ni t r o g en co nt ent f r o m St age 1 was 352 ppm
. S eal ant was in j ect ed int o cl am p o n React o rA h eat ex ch an ger . 2 pm T w o ex t r a o p er at o r s wer e added o n s w in g s h if t t o h e l p wi t h

St age 1 pr o b le m s . Dur in g swin g sh if t , o p er at o r s gr aduall y

in cr eased t e m p er at ur es in S t age 2 t o dr iv e n it r o g en o f f t h e cat al y s t . 7: 34 pm A t e m p er at ur e ex cur s i o n o ccur r e d in React o r3, Bed 4. I n le t t e m p er at ur e t o Bed 5 in cr eased r api dl y

as a r e sul t . 7:35 pm T h e quen c h v a lv e ab o v e B e d 5 o p en ed wi de. Dat a l o ggert e m p er at ur es b o un ced f r o m zer o t o n o r mal o rh i gh an d b ack. Makeup hy dr o g en t o S t age 2 b e gan t o decr ease. Bed 4 o u t l et t e m p er at ur e po in t decr eased t o 637o F. 7:36 pm B e d 5 in le t t e m p er at ur e decr eas ed t o 633 o F
. React o r3 o u t let t e m p er at ur e in cr eased t o 650 o F
. A No
. 2 Oper at o rwent o u t s i d e t o ch eck t e m p er at ur es o n t h e ex t e r n al pan e l s o m e t im e b e f o r e 7:37 pm
. . 7: 37 pm Bed 5 o u t let t e m p er at ur es wer e in cr easin g. Oper at o rma nu all y

cl o s ed quen c h v a lv e t o B e d 5. Hy dr o g en makeup t o St age 2 dr o pped t o zer o . 7: 38 pm Quen ch v a lv e t o Bed 5 was r e o p en ed. Bed 5 o u t let , r eact o rin le t an d o u t let t e m p er at ur es co nt inued t o r i s e ; s o m e o f t h es e ex ceeded 1200 o F. 7:39 pm Oper at o r s h ear d a garb le d r a di o m e s s a ge f r o m No
. 2 Oper at o r . T w o o p er at o r s wen t o u t s i d e t o ch eck o n No
. 2 Oper at o r . 7: 40 pm Bed 5 t e m p er at ur es an d t h e r eact o ro u t l et t e m p er at ur e r ead o f f scal e o n st r i p ch ar t s an d def aul t e d t o zer o o n dat a l o gger . Oper at o r s r e quest ed assi st an ce o f in st r u m e nt t ech n i ci an . 7:41 pm On e o f t h e B e d 5 o u t let po int s r ead 1398 o F o n t h e dat a l o gger . A s ect i o n o f t h e React o r3 ef f l uent pi pin g r upt ur ed causin g an expl o s i o n an d l ar g e f i r e . T h e N o . 2 O p e r a t o rw a s k ille d
.

28

### 3. 0 I n vestigatio n US E P A Regi o n 9 was n o t if i ed o f t h e acci dent at 9:03 pm o n J a nu ar y 21, 1997 an d an in v e s t i g at i o n t o det e r m in e t h e r o o t caus e o f t h e acci dent was b e gun J a nu ar y 23, 1997 b y Regi o n 9 an d Headquar t er s in v e s t i g at o r s . T h e in v e s t i g at i o n was co n duct e d un deraut h o r it i e s co nt ain e d in C E R C L A , Sect i o n 104, 42 U. S. C
. 9604 an d t h e C A A , Sect i o n 114, 42 U. S. C
. 7414, Sect i o n 112r
. T h e s c o p e o f t h e in v e s t i g at i o n was limit e d t o d e t e r min in g t h e c au s e s a n d c o n t r i b u t in g f act o r s asso ci at ed wi t h

t h e expl o s i o n an d f i r e in S t age 2, React o r3 o f t h e Hy dr o c r ackerUn i t . T h e pur po se o f i d ent if yin g t h ese causes an d f act o r s was t o un der s t a n d why t h e acci dent o ccur r e d s o t h a t t h e le s s o n s le ar n e d c o u l d b e ap p lie d b y T o s c o a n d o t h e rhy d r o p r o c e s s in g fa c ilit ie s in o r d e r t o p r e v e n t r e o c c u r r e n c e o f s imilar acci dent s. 3. 1 A ppr oach T h e in v e st i g at i o n t eam so ught t o det e r m in e why t h e r eact o ref f l uent pi pe f a ile d, t r i gger in g t h e expl o s i o n an d f i r e . T h e t eam co o r din a t e d it s ef f o r t s wit h o t h e ragen ci es t o det e r m in e t h e causes o f

t h i s ev en t . 3. 1. 1 C oor dinat i on wit h Ot her Agencies T h is in v e s t ig a t io n w a s c o o r d in a t e d a m o n g in v e s t ig a t o r s w o r k in g fo r :

• USE P A Headquar t er s , C h em i cal E m er gen c y Pr epar edn e s s an d Pr ev ent i o n Of f i ce ( C E PPO) , Wa s h in g t o n , D C
• USE P A R e gi o n 9, San F

r an ci s c o , C A
• Cal if

o r n i a Div i si o n o f Occupat i o n al S a f e t y an d Heal t h

( C ALOS HA ) , Co n c o r d, CA
• US Depar t m e nt o f L ab o r( DOL ) Occupat i o n al S a f e t y an d Heal t h

A d m in i s t r at i o n ( O S H A ) R e gi o n 9, San F

r an ci s c o , C A
• C o n t r a Co st a Co u n t y Heal t h

S e r v i ces Div i si o n ( CCCHS D ) , Mar t in ez, CA
• C al if

o r n i a Bay A r ea A i rQual i t y

Man a gem e nt Di st r i ct ( B A A Q MD) , Mar t in ez, CA T h e co o r din a t i o n co n s i s t e d o f co n s ul t a t i o n o n agen cy in f o r mat i o n r e quest s t o av o i d dupl i cat i o n o f ef

f o r t , sh ar in g do cum e nt s an d int e r v i e w r e sul t s, an d j o int l y

expl o r in g t h e po ssi b le causes o f t h e acci dent . CALOS HA , wi t h

assi st an ce o f Regi o n 9 F e der a l OS HA , co n c ur r e nt l y

co n duct e d an in v e st i g at i o n f

o rv i o l at i o n s o f h eal t h

an d saf e t y o r der s as well as a pr o cess saf e t y ma n a gem e nt ( P S M ) audi t . T h e Bur eau o f I n v e st i g at i o n o f CA Depar t m e nt o f Occupat i o n al S a f e t y an d Heal t h c o n c u r r e n t ly c o n d u c t e d a c r imin a l in v e s t ig a t io n . C o n t r a C o s t a C o u nt y H e a l t h

S e r v ic e s Depar t m e nt co n c ur r e nt l y

co n duct e d an in v e st i g at i o n int o t h e r o o t causes o f t h e acci dent . B AAQ M D c o nc u r r e nt l y

c o nd u c t e d a n inve s t i g a t i o n int o p o s s i ble vi o l a t i o ns o f a i rq u a l i t y

c o nt r o l r e gul at i o n s . T h e per s o n n e l f

r o m each agen cy in v o lv ed in t h e acci dent in v e st i g at i o n ar e l i s t e d in A

ppen d ix G.

29On M a y 29, 1997, CCCHS D an d T o s c o i s s u ed s e par a t e in v e s t i g at i o n r e po r t s di s c us s in g t h e ev en t s l eadin g up t o t h e acci den t , t h e causes an d co nt r i b u t in g f act o r s, an d r eco m m

e n d at i o n s . A p r esen t a t i o n d i scu ssin g t h e f in d in g s in b o t h r e p o r t s was ma d e b y T o sco an d CCCHS D in v e st i g at o r s t o t h e Co nt r a Co st a Co un t y Bo ar d o f S uper v i s o r s at a pub l i c m eet in g o n Jun e 3, 1997. 3. 1. 2 P h y si calEvi d en ce Col l ect i o n P i eces o f equi pm ent an d ev i d en ce wer e co llect ed, st o r ed an d i d ent if i ed b y usin g a pr o t o c o l appr o v ed b y T o sco an d t h e in v e st i g at in g agen ci es. T e st in g o f t h e r upt ur ed pi pe an d r eact o r t h er m o co uples was co n duct e d usin g a pr escr i b ed pr o t o c o l
. P hy s i cal ev i d en ce co llect ed in cl uded a b u ll pl ug f r o m a n i pple o n t h e 12" di am et eref f l uent l in e, t h e t h er m o well an d h ar d war e , b l in d f l an ge f r o m b o t t o m o f r eact o r#3 ef f l uent l in e, dama ged sect i o n o f ef f l uent pi pe, f iv e hy dr o g en quen c h v a lv es ( in let quen c h an d 4 b i g quen c h v a lv es) , t h er m o co uple b u n d le s f r o m React o r3, an d cat al y s t sam p l e s f r o m React o r3 ( t h r ee sam p le s perb e d)
. 3. 1. 3 I nf orm a t i on Sour ces Reviewed I nt e r v i e ws wit h T o s c o o p er at o r s an d ma n a gem e nt per s o n n e l wer e co n duct e d b y C ALOSHA in spect o r s wit h in t e r v i e w quest i o n s dev e l o ped wit h t h e assi st an ce o f all t h e agen ci es in v e st i g at in g. CAL O S H A t h en b r i e f e d t h e o t h e rin v e st i g at o r s o n d i scu ssi o n s f r o m t h e int e r v i e w s . I n v e st i g at o r s r e v i ewed do cum e nt s s uppl i e d b y T o s c o in cl udin g pr o cedur es , pr o ces s an d in s t r u m e nt at i o n di agr a m s ( P & I Ds) , r eact o rt e m p er at ur e dat a , st r i p ch ar t s , pr o cess f l o w dat a , al ar m l o gs, ma int e n a n c e r e c o r d s , ma n a g e me nt o f c h a n g e d o c u me nt s , s h ift lo g s , s h ift s u p e r int e n d e nt lo g s , wo r k per m it s, wr it t e n wit n ess st at em ent s , r eact o rint e r n al dr awin gs, cat al y s t dat a , in ci dent r e po r t s, pr o cess h azar d an al y s i s , en gin eer in g m e m o s an d r e po r t s, pi pe in spect i o n dat a , equi pm ent an d pi pin g desi gn specif i cat i o n s , t r ain in g ma t e r i al s, h eal t h

an d saf e t y pr act i ces, t e st dat a ( r upt ur ed pi

pe, t h er m o co uple, an d cat al y s t t e st s) , v i deo t apes o f r eact o rint e r n al s, an d CCCHS D an d T o sco Ref in in g Co m p an y acci dent in v e st i g at i o n r e po r t s. 3. 1. 4 M et hodol ogy A n E v en t s an d Causal F act o r s ( E & C F ) ch ar t was dev e l o ped t o est ab l i s h a sequen ce o f ev en t s f o r t h e acci den t . A wo r k s h o p was h e l d dur in g t h e week o f J u l y

21- 25, 1997 in Co n c o r d, Cal if

o r n i a wit h in v e st i g at o r s par t i c i p at in g in r e v i ewin g t h e E & CF ch ar t an d i d ent if yin g co nt r i b u t in g f act o r s t o t h e acci dent . S ee A ppen d ixH f o ra l i s t o f par t i c i p ant s in t h i s r o o t cause an al y s i s wo r k sh o p . T h e in v e st i g at o r s par t i c i p at in g in t h e r o o t cause wo r k sh o p used sev e r a l m e t h o d s t o i d ent if y

causes an d co nt r i b u t in g f act o r s t o t h e acci den t . A co n s ul t a n t in r o o t cause m e t h o d o l o g y assi st ed t h e in v e s t ig a t o r s in u s in g t h e me t h o d o l o g ie s , a n d fa c ilit a t e d d i s c u s s i o n o f t h e a n a l ys is
. I n v e s t ig a t o r s used t h e f o ll o win g m e t h o d s t o an al y ze t h e in f o r mat i o n co llect ed dur in g t h e in v e st i g at i o n :

30Hazar d- Bar r i er - T ar get A n al y s i s - used t o an al y ze t h e f i r e / e xp l o si o n h azar d t o t h e f a t a l it y ( N o . 2 O p e r a t o r) a n d in j u re d p art i e s . F aul t T r ee A n al y s i s - used t o i d ent if y

po ssi b le causes o f pi pe r upt ur e, co n t r o l sy st em f

a il u r e s, an d t e m p er at ur e ex cur s i o n . Man a gem e nt an d Ri sk Ov er si ght T r ee ( M ORT )

- used t o assess t h e adequacy o f v ar i o u s ma n a g e m e nt sy st em s su ch as: Pe rs o n n e l Erro rs C o nt ro l ro o m o p e r a t o re rro rs Desi gn T e m p er at ur e an d pr essur e in di cat in g sy st em , co n t r o l r o o m , f i el d t e m p er at ur e pan e l , ef f l uen t pi pin g sy st em , r eact o r Huma n F act o r s Desi gn o f t h e co n t r o l r o o m in f o r mat i o n dev i ces - ch ar t s , l o gger s M a n a g e me nt P o lic y a n d I m plem ent a t i o n I n cl udin g ser v i ces an d ma n a gem e nt expect at i o n s M a in t e n a n c e M a in t e n a n c e p l a n a n d imp le me n t a t io n Readin ess Mo n it o r in g sy st em r eady t o o p er at e Hazar d A n al y s i s P r o cess E v a l u at in g t h e in st all a t i o n an d desi gn o f t h e n e w t e m p er at ur e l o g g in g sy st em P r o cedur es Ro ut in e an d em er gen c y o p er at in g pr o cedur es appr o p r i at en ess an d c o mp le t e n e s s I n f o r mat i o n S y st em I n f o r mat i o n av ail ab le t o t h e o p er at o r s r e gar d in g pr o cess m o n it o r in g sy st em S uper v i s i o n D et ect in g an d co r r ect in g h azar ds, en f o r c in g saf e t y an d em er gen c y pr act i ces. T h e in v e st i g at o r s wo r k ed in t eam s usin g dif f e r e nt m e t h o d s o n v ar i o u s ar eas o f i d ent if i ed pr o b le m s . F act s co llect ed dur in g t h e in v e st i g at i o n wer e o r gan i zed an d do cum e nt ed t o expl ain t h e adequacy o rin adequacy o f saf e t y ma n a gem e n t . Ro o t causes wer e i d ent if i ed an d r eco m m

e n d at i o n s dev e l o ped t o addr es s t h e r o o t caus e s . A dr af t r e po r t wit h a des c r i pt i o n o f t h e acci den t , f act s an d an al y s i s , r o o t causes an d r eco m m

e n d at i o n s was dev e l o ped an d r e v i ewed b y t h e in v e st i g at o r s. P e t r o leum r e f in in g co n s ul t a nt s wer e calle d upo n wh er e n eeded t o pr o v i d e an assessm ent o f in f o r mat i o n used in t h e r e po r t .

313. 2 T es t i ng Res u l t s T h i s sect i o n descr i b e d t e st s co n duct e d o n t h e f a ile d pi pe, cat al y s t , r eact o rt h er m o co uples, an d t h e dat a l o gger . T h e pur po s e o f t hi s t e s t in g was t o f o cus o n t h e caus e o f t h e pi pe f a il u r e an d t h e t e m p er at ur e ex cur s i o n in React o r3 an d t h e co n d i t i o n s pr esent t h at le d t o t h ei ro ccur r e n ce. 3. 2. 1 R uptur e d P i pe T e s t ing & I n s p e c t ion T h e o n l y

in spect i o n h i st o r y av ail ab le f o rt h e par t i c ul arpo r t i o n o f t h e React o r3 ef f l uent pi pin g l in e was an ul t r as o n i c wall t h i c kn es s m eas ur em ent o f 0. 94 in ch es f r o m a 1991 in s p ect i o n . T h er e was n o r eco r do f o r i g in al gage t hi c kn es s f o rt h e ef f l uent pi pin g , whi c h was as s u m e d t o b e o r i g in al pi

pin g in s t alle d in 1963. T h er e wer e n o r eco r d s s h o w in g t h at i t h a d ev erb een r e pai r ed o r r e pl aced. T h e React o r3 o u t let pi pin g was o r i g in all y

specif i ed t o b e 12- in ch di am et erpi pin g o f 1- 1⁄4 % C h r o m i u m an d 1⁄2 % M o l y

b d enum all o y s t eel A S T M A 335 Gr ade P11 wi t h

a wall t hi c kn es s o f 0. 746" m in im u m o rs c h e dule 100. Sch e dule 100 12- in ch di am et erpi pe h a s a n o m in al wall t hi c kn es s o f 0. 843 in ch es . T h e cur r e nt A S T M s p ecif i cat i o n f

o rs t an dar dA 335 do es n o t s p ecif y m

in im u m pi pe t hi c kn es s b u t r e f e r e n ces s t an dar dA 530 f o rgen e r a l r e qui r e m e nt s whi c h in cl udes pi

pe wall t hi c kn es s . T h e cur r e nt A S T M s t an dar dA 530 s t at es t h at m in im u m wall t hi c kn es s at any p o in t s h a ll n o t b e mo r e t h a n 1 2
. 5 % u n d e rt h e n o min a l w a ll t h ic k n e s s s p e c ifie d
. F o ra n o min a l wall t h i c kn es s o f 0. 843 in ch es , t h e m in im u m wall t h i c kn es s wo ul d b e 0. 738 in ch es . Do wn s t r eam f

r o m t h e po int o f r upt ur e, t h e pi pin g was wel d ed t o a 12" x10" r e ducert o ma t c h t h e 10- in ch di am et erpi pe t h at en t e r e d t h e f eed/ e f f l uen t h eat ex ch an ger s . T h e pi pin g speci f i cat i o n s call e d f o rs c h e dul e 120 f o r10- in ch di am et erpi pe. No m in al t h i c kn es s o f t h i s pi pe i s 0. 843 in ch es . T h e po st
- acci den t t e st in g o f t h e sect i o n o f r upt ur ed ef f l uen t pi pe co n s i s t e d o f v i sual in spect i o n , t h i c kn ess m easur em en t s , ul t r aso n i c m easur em en t s , l i qui d pen e t r an t ex am in at i o n , ma gn et i c par t i c l e e x a min a t io n , me t a l c h e mic a l a n a l ys is , t e n s ile s t r e n g t h t e s t s , h ar d n e s s t e s t s , mic r o p h o t o g r ap h ic an al y s i s , an d m e t a ll o gr aph i c an al y s i s . T h e po int o f f

a il u r e o n t h e sect i o n o f pi pe was n o t a wel d , el

b o w o rr e ducer
. Near l y

all ( 21 o f 24) o f t h e m easur em ent s o f pi pe t h i c kn ess j u st upst r eam an d do wn st r eam o f t h e r upt ur ed sect i o n wer e gr eat ert h an t h e m in im u m pi pe t h i c kn ess specif i cat i o n o f 0. 746 in ch
. T e s t in g r e s u l t s in di cat ed t h at t h e pi pe f a ile d due t o ex ces s iv e l y

hi gh t e m p er at ur e. T h e t e m p er at ur e in t h e r upt ur ed pi pe r each ed 1700+ o F at t h e po int o f f

a il u r e , b a sed o n v i sual mic r o s c o p ic in s p e c t io n b y t h e lab
. T h e p i p e h a d b e e n s t r e t c h e d r e s u lt in g in a

t h ic k n e s s o f 0
. 3

- 0
. 4 in ch es at i t s t h in n e st po int . At t h e po int o f f

a il u r e , t h e pi pe h a d expan d ed in ci r c um f e r e n ce b y appr o x ima t e l y

5 in ch es, whi c h cr eat ed a l o cal i zed b u l g e in t h e pi pe pr i o rt o r upt ur e. Ot h e r sect i o n s o f t h e React o r3 ef f l uent pi pin g h a d al so expan d ed. C h e mic a l a n a l ys is fo rt h e b a s e me t a l s a mp le s w e r e fo u n d t o c o n f o r m t o t h e r e q u i r e me nt s fo r A S T M A 335- 94, Gr ade P11 an d t h e wel d m e t a l was f o un d t o b e o f t h e 1- 1⁄4 % C r , 1⁄2 % M o t y pe a n d w a s c o mp a t ib le w it h t h e b a s e me t a l. T h e min imu m t e n s ile s t r e n g t h o f t h e me t a l s h o u ld b e 6 0
32ks i acco r d in g t o A S T M A 335. T h i s co r r e s p o n ds t o a Ro ckwell Har d n e s s nu m b er( H R) o f 69 usin g t h e Ro ckwell B S cale. T e st in g sh o w ed t h at t h e h ar d n e ss o f b a se m e t a l sam p le s v ar i ed f r o m 7 6 t o 8 1 H R B ( R o c k w e ll H ar d n e s s nu mb e ru s in g R o c k w e ll B S c a le ) w h ile t h e h ar d n e s s o f t h e w e ld me t a l s a mp le s v ar i e d fr o m 7 0 t o 9 1 H R B
. 3. 2. 2 C at al ys t T e s t ing Cat a l y st sam p l e s f r o m all t h r ee S t age 2 r eact o r s wer e co llect ed an d an al y zed. I n spect i o n o f t h e cat al y s t b e d af t e rt h e acci dent r e v ealed a f u sed h ar d en ed p illaro f c a t a l ys t in B e d 4 o f each S t age 2 r eact o r . T h e cat al y s t sam p le s f r o m t h e p illar s h a d 2
. 5 t o 3 t ime s h i g h e rc ar b o n c o nt e n t t h a n s a m p le s o f l o o s e cat al y s t f r o m t h e s a m e b e ds
. T h i s h i gh carb o n co nt ent was due t o t h e b u il dup o f pet r o l eum co ke. Cat a l y st sam p le s f r o m t h e m i ddl e o f Bed 5 in React o r3 sh o w ed an 80% l o ss o f sur f ace ar ea, co n s i s t e nt wit h expo sur e t o ex t r em e t e m p er at ur es. T h e cat al y s t h a d b een in use f o r o n e y ear , s in ce i t was in s t alle d in t h e J a nu ar y 1996 t u r n ar o u n d
. 3. 2. 3 T herm ocoupl e T e s t ing A ll t h er m o co uples f r o m t h e React o r3 ar r a y s wer e t e st ed t o see if t h ey wo ul d giv e t e m p er at ur e r eadin gs. A ll b u t t h r ee di d; t h ese h a d l o o s e j u n c t i o n s in t h e silv erso l d er ed j o in t f r o m t h e t h er m o co uple t o t h e lead wi r e , wh er e an epo x y seal was l o cat ed. A cco r d in g t o t h e t h er m o co uple ve nd o r , t h e s ilv e rs o l d e rj o int w a s l i k e l y

t o ha ve be e n d a ma g e d by e xp o s u r e t o f i r e . M o ving t h e lead wi r e s ar o u n d t o make co nt act all o wed r eadin gs t o b e t aken
. Bed 4 o u t let an d Bed ar r a y s wer e t e st ed usin g a pr o p an e t o r c h t o det e r m in e if t h e lead wi r e s wer e sh o r t e d. T h e o n l y

pr o b le m s det ect ed wer e l o o s e j u n c t i o n s as descr i b e d ab o v e. T h e React o r3 t h er m o co uples wer e al so t e st ed f o rt e m p er at ur e accur acy , usin g a co nt r o lle d h eat so ur ce. T h e l ar g est dev i at i o n was 16 o F an d all dev i at i o n s wer e r eadin gs b e l o w t h e co nt r o lle d so ur ce t e m p er at ur e. T h e t h er m o co uple v e n d o rin di cat ed t h at m o i s t u r e in t h e in sul a t i o n o n t h ese t h er m o co uples was pr o b ab l y

leakin g v o l t age acr o ss t h e in sul a t i o n r e sul t in g in a l o w r eadin g. B a s e d o n t h e t e s t r e s u lt s , it is b e lie v e d t h a t t h e t h e r mo c o u p l e s w e r e w o r k in g p r o p e r ly p r io rt o t h e acci dent . 3. 2. 4 D at a L ogger T e s t ing Sin ce t h e o p er at o r s h a d r e po r t ed pr o b le m s wit h t h e dat a l o gger , t e s t s wer e co n duct e d o n t h e dat a l o ggeran d t h er m o co upl e ar r a y s usin g a sim u l a t o rco n n ect ed t o t h e dat a l o gger . Var i o u s o p e r a t in g c o n d it io n s a n d fa ilu r e s w e r e s imu la t e d t o d e t e r min e t h e r e s p o n s e o f t h e d a t a lo g g e ra n d t o d e t e r min e if it w a s ma lfu n c t io n in g . R e s u lt s o f t h e t h e r mo c o u p le a n d t h e d a t a lo g g e rt e s t in g sh o w ed t h at t h ey wer e l i k el y

t o h a v e f u n c t i o n ed pr o p er l y

o n t h e n i ght o f t h e in ci dent , wi t h

t h e ex cept i o n o f o n e o f t h e h i gh t e m p er at ur e al ar m s , wh i c h i s di scussed f u r t h e rin a l a t e rsect i o n .

33T h e o u t c o m e o f t h ese t e st s sh o w ed t h at f o ra 5 o F ch an ge ( s l o w o rf a s t ) , t h e h i s t o r i a n dat a di d n o t c h a n g e . F o r s l o w o rf a s t 5 0 o F an d 500 o F ch an ges , t h e s c r een updat in g t im e r a n g ed f r o m 13 t o 62 seco n d s, depen d in g o n t h e nu m b ero f input po in t s sh o w in g. F o rt e m p er at ur e in cr eases o f 0. 1 o F ev er y 20 s eco n d s f o r5 m inut es , t h e s c r een updat e t im e was ab o u t 20- 40 s eco n d s . A l o s s o f s i gn al to th e m u l

t i

p le x e rc au s e d th e te m p e r a t u r e d i s p l a y to d e f au l t to 0
. 0
. D a ta l o g g e rr e s p on s e to a sh o r t in a t h er m o co uple wi r e was t h at t h e t e m p er at ur e po int s def aul t e d t o t h e am b i ent t e m p er at ur e at t h e l o cat i o n o f t h e sh o r t . L o ss o f po wert o t h e m u l

t i

p le x e ro rt h e int e r f ace un it r e s u lt e d in s c r e e n a n d h i s t o r ia n h o ld in g t h e la s t g o o d v a lu e , e v e n a f t e r1 0 minu t e s . R e mo v a l o f a n input car d t o t e s t t h e dat a l o ggerr e s p o n s e o f f

a il u r e o f an input car d r e s u l t ed in r eadin gs o f 0. 0 f o rall t h er m o co upl es asso ci at ed wit h t h at input car d. I f po werwas shut do wn t o t h e dat a l o gger c o m p u t e r , t e m p e r a t u r e s w e r e d i s p l a y e d a s “0
. 0 ????” o n t h e d a t a l o g g e r . H i g h t h e r mo c o u p le r e a d in g s w e r e s imu la t e d fo llo w e d b y d i s c o n n e c t io n o f t h e s imu la t i o n . T h is t e s t ed h i gh in put t o t h e dat a l o ggerf o ll o wed b y t h er m o co uple f a il u r e . T h e dat a l o ggerpo int s t r i gger e d an al ar m at 780 o F
. Ho wev e r , t h e al ar m st at us cl ear ed wh en t h e t e m p er at ur e wen t ab o v e 1400 o F ; dat a l o ggerr eadin gs def aul t e d t o 0. 0. Usin g a co nt r o lle d h eat so ur ce, sev e r a l t h er m o co uples wer e h eat ed, t r i gger in g a h i gh t e m p er at ur e al ar m o n t h e dat a l o ggerat 780 o F
. T h e al ar m st at us cl ear ed wh en t h e t h er m o co upl es wer e co o led b e l o w 780 o F. R api d f u ll

- s cale ch an ges ( 0 t o 1400 o an d b ack) wer e sim u l a t e d o n sev e r a l t e m p er at ur e po int s . No unus ual r eadin gs wer e pr o duced an d t h e hi s t o r i a n dat a s h o w ed t h e r api d ch an ges . Heat in g t h e lead wi r e s in t h e t h er m o co uple sh eat h h a d n o ef f ect o n t h e r eadin gs. T e st in g sh o w ed t h at po int s ch an gin g b y +/

- 50 o F wo ul d al ar m b u t wo ul d n o t ch an ge s t at e ( r eadin g o n m o n it o rch an gin g f r o m b l inkin g t o st eady ) wh en ackn o wl edged o n t h e dat a l o gger key b o ar d
. T h e +/

- 50 o F al ar m wo ul d n o t b e t r i gger e d again if

an o t h e rpo int wer e t o ex ceed t h e limit
. ( S e e S e c t io n 1
. 2
. 4
. 5 d i s c u s s in g A l ar ms )
. T h is c o u l d e xp l a in w hy o p e r a t o r s in t h e c o n t r o l r o o m di d n o t r eceiv e addi t i o n al h i gh t e m p er at ur e al ar m s dur in g t h e Janu ar y 21 in ci den t . A po int t e st ed f o rl o w skin t e m p er at ur e ( < 300o F ) wo ul d ch an ge st at e wh en i

t was ackn o wledged o n t h e dat a l o gger . T o s c o ma n a gem e nt s t at ed t h ey di d n o t kn o w h o w o f t e n t h e t e m p er at ur es wer e b e in g updat e d o n t h e dat a l o ggerdi s p l a y dur in g t h e J a nu ar y 21, 1997 ex cur s i o n . T o s c o was n o t ab le t o r e pr o duce t h e o p er at o r s’ r e po r t s o f t e m p er at ur es dr o ppin g t o zer o b ecause t h e dat a l o ggerst o r ed dat a dif f e r e nt l y

t h an wh at was di s p l a y e d in t h e co nt r o l r o o m . Ho wev e r , pr int o ut s f r o m dat a l o gger sh o w ed zer o r eadin gs f o rso m e t h er m o co uples, so m e o f wh i c h l a t e rin di cat ed h i gh t e m p er at ur es.

343. 3 I nf orm a t i on Anal ys is 3. 3. 1 E f f l ue nt P i pe R uptur e T h e r e sul t s o f t h e pi pe t e st in g sh o w t h at t h e pi pe f a ile d b ecause o f ex t r em el

y

h i gh t e m p er at ur es. T e st s in di cat ed t h e dat a l o ggert e m p er at ur es wer e co r r ect ex cept wh en t h ey def aul t e d t o zer o b ecause t h ey ex ceeded t h e r a n g e o f t h e dat a l o gger . Resul t s o f t h e cat al y s t t e st in g sh o w ed t h at ex t r em el

y

h i gh t e m p er at ur es h a d o ccur r e d in Bed 5 o f React o r3. Based o n t h e dat a l o gger h i st o r i a n t e m p er at ur es ( T ab le 2) , t h e h i gh t e m p er at ur es wer e in it i a t e d b y a t e m p er at ur e ex cur s i o n wh i c h o r i g in at ed f r o m t h e o u t let o f Bed 4 o f React o r3. T h e h eat f r o m t h i s ex cur s i o n caused an elev at ed in le t t e m p er at ur e t o Bed 5, wh i c h sub s equent l y

in cr eased t h e r eact i o n r a t e an d t e m p er at ur e r i se acr o ss Bed 5. T h i s caused t h e ex t r em el

y

h i gh t e m p er at ur es in t h e Bed 5 o u t let an d t h e React o r3 ef f l uent pi pin g . 3. 3. 2 R eact or Tem p er at u r e Ex cu r s i o n T e m p er at ur e ex cur s i o n s ar e n o t unusual o ccur r e n ces in hy dr o c r ackin g, especi all y

dur in g st ar t up. T h e hy dr o c r ackin g r eact i o n gen e r a t e s h eat wh i c h in cr eases t e m p er at ur e an d causes t h e r eact i o n r a t e t o accel er at e. S in ce t h e hy dr o c r ackin g pr o cess i s ex o t h e r m i c ( g en er at in g h eat ) , o n ce a r eact i o n i s in i t i a t e d, r eact i o n r a t e an d t e m p er at ur e w ill c o nt inu e t o r i s e u n le s s p r o p e r ly c o n t r o lle d
. T h e co m m

o n causes o f t e m p er at ur e ex cur s i o n s in hy dr o p r o cessin g in cl ude:

& Un ev en f

l o w an d h eat di st r i b u t i o n in cat al y s t b e d, causin g h o t spo t s & I nt e r n al r eact o rf a il u r e s, leadin g t o cat al y s t m i g r a t i o n an d dead zo n e s & I n c o mp le t e s u lfid in g o f c a t a l ys t & Rai s in g r eact o rt e m p er at ur es t o o qui ckl y

wh en usin g f r esh h i gh l y

r eact iv e cat al y s t & F eed t e m p er at ur e t o o h i gh
& L o ss o f r ecy cle gas & L o w r ecy cl e gas o ro il f

l o w r a t e & I n adequat e r e ser v e quen c h gas capaci t y & I m pr o p erco nt r o l , o v er r eact i o n t o so m e pr o cess ch an ge o ro p er at o rin at t e n t i o n 3. 3. 2. 1 F l ow and Heat Dis t ri but ion P r o p erf l o w di st r i b u t i o n i s im p o r t a nt t o m in im i ze r i sk o f t e m p er at ur e ex cur s i o n s . T h er ef o r e, t h e co n d i t i o n s in t h e r eact o rt h at m i g ht h a v e int e r f er ed wi t h

un if o r m f

l o w o rh eat di st r i b u t i o n wer e r e v i ewed. S o m e o f t h e co n d i t i o n s di scussed b e l o w co ul d b e causes o f f

l o w o rh eat ma l d i s t r i b ut i o n an d so m e ar e ev i d en ce t h at un ev en f

l o w o rh eat di st r i b u t i o n h a d pr o b ab l y o ccur r e d. T ech n i cal Ser v i ces ( T o s co ’ s E n gin eer in g Suppo r t gr o up) n o t e d in A p r il 1996 t h at B e d 5 appear ed t o h a v e t h e wo r s t t e m p er at ur e dif f e r e nt i a l s in t h e r eact o r . T h i s was in di cat iv e o f f

l o w di st r i b u t i o n pr o b le m s an d ma y h a v e aggr av at ed t h e gen e r a t i o n o f ex t r em el

y

h i gh t e m p er at ur es in Bed 5, b u t it was n o t t h e so le cause sin ce t h e ex cur s i o n was in it i a t e d b y a h i gh Bed 4 o u t let
35t e m p er at ur e. A ppen d ixD sh o w s t h e l o cat i o n an d descr i pt i o n o f int e r - b ed di st r i b u t i o n sy st em used o n S t age 2. Di s t r i b u t i o n T r ay Pl uggage A

v i deo in s p ect i o n o f t h e in s i de o f t h e r eact o rint e r n al s s h o w ed s o m e cat al y s t pelle t s an d s uppo r t b a ll s o n t h e di st r i b u t i o n t r ay s, b u t n o t in an y si gn if i cant am o u nt s an d n o t f r o m ev er y cat al y s t b e d. M i gr at i o n o f cat al y s t f r o m t h e b e d do wn t o t h e di s t r i b u t i o n t r ay s can caus e pl uggage, wh i c h can caus e f l o w di s t r i b u t i o n pr o b l e m s . T h e cat al y s t can m i g r a t e if t h e cat al y s t s uppo r t s c r een s ar e dama ged o rh a v e h o le s in t h em . On e way t o det e r m in e if di s t r i b u t i o n t r ay s wer e pl ugged o r wh et h e rt h er e was so m e o t h e rim p edim e nt t o f l o w i s t o l o o k at t h e pr essur e dr o p acr o ss each cat al y s t b e d dur in g o p er at i o n . Ho wev e r , T o sco di d n o t m easur e t h e pr essur e dr o p acr o ss each b e d, o n l y

t h e t o t a l pr essur e dr o p acr o ss t h e r eact o r . T h e cat al y s t m i g r a t i o n o b ser v ed in si de t h e r eact o raf t e rt h e acci dent di d n o t appeart o b e si gn if i cant en o ugh t o int e r f er e wi t h

di st r i b u t i o n o f flo w . Cat a l y st Co k in g Co ke depo si t s in cat al y s t b e ds ar e in di cat iv e o f int e r n al r eact o rpr o b le m s , such as un ev en l

i qui d di st r i b u t i o n . T h e v i deo t ape o f in t e r n al in spect i o n o f all t h r ee r eact o r s af t e rt h e acci den t sh o w ed t h a t fu s e d c o k e d c a t a l ys t p illar s h a d fo r m e d in B e d 4 o f a ll t h r e e S t a g e 2 r eact o r s. T h e o t h e rb e ds in

all t h r ee r eact o r s di d n o t h a v e co ke p illar s . R eact o r1 h a d a cat al y s t p illaro n t h e b o t t o m o f B e d 4 at least sev e r a l f

eet h i gh wi t h

a ci r c um f e r e n ce o f 1' 10" at t h e b o t t o m an d 1' 7" at t h e t o p o f t h e p illar . R eact o r2 al so h a d a cat al y s t p illaro n t h e b o t t o m o f B e d 4 w h ic h w a s ap p r o x ima t e ly 5 fe e t h i g h , 2 ' 6 " in c i r c u m fe r e n c e a t t h e b o t t o m a n d 1 ' 6 " in c i r c u m fe r e n c e a t t h e t o p o f t h e p illar . I n React o r3, a p illaro f fu s e d c a t a l ys t w a s fo u n d in t h e c e nt e ro f B e d 4 , e x t e n d in g 8 fo o t u p w ar d f r o m t h e cat al y s t b o t t o m s uppo r t gr i d an d m eas ur in g in di am et erab o u t 2 f eet at t h e b a s e an d 8 in ch es at t h e t o p. Co ke depo si t s in Bed 4 o f S t age 2 r eact o r s h a v e b een f

o un d in pr ev i o us t u r n ar o u n d s. Co ke p illar s o rb a lls fo r min g in t h e c a t a l ys t ar e u s u a lly d u e t o lo w flo w o rp o o rmix in g . C o k e c a n fo r m at t e m p er at ur es as l o w as 800 t o 1000 o F
. L ar g e c o k e p illar s ar e u s u a lly fo r m e d o v e ra lo n g t ime an d ar e n o t l i k el y

t o b e t h e r e sul t o f o n e ex cur s i o n . L ar g e f o r mat i o n s o f co ke in a cat al y s t b e d i s n o t a f u ll y

un der s t o o d pr o cess. Hi gh t e m p er at ur es can cause co kin g , b u t co kin g o n t h e cat al y s t n ecessit a t e s h i gh ero p er at in g t e m p er at ur e t o ach i e v e desi r e d r eact i o n co n v e r s i o n . A l so , co kin g can in t e r f er e wit h f

l o w di st r i b u t i o n wh i c h in t u r n can cause l o cal i zed h o t spo t s in t h e b e d. T h e r e f o r e , t h e p r e s e n c e o f c o k e p illar s in B e d 4 o n ly o f S t a g e 2 in d i c a t e s s o me flo w d i s t r i b u t i o n an d ex cessiv e t e m p er at ur e pr o b le m s wer e o ccur r in g . B e d 4 Oper at in g Pr o b le m s T e mp e r a t u r e in s t ab ilit y in B e d 4 o f t h e S t a g e 2 r eact o r s h a v e b een n o t e d o n pr i o ro ccasi o n s , w h ic h ma y h a v e b e e n e v id e n c e o f flo w ma ld is t r ib u t io n . M o r e o p e r a t io n a l p r o b le ms h a d b e e n
36exper i en ced wi t h

B e d 4 in St age 2 t h an wi t h

o t h e rb e ds
. F o rex am ple, in J u n e /J ul y

o f 1995, T ech n i cal S e r v i ces n o t e d t h at o p t im i zat i o n was especi all y

dif f i cul t t o ach i e v e in t h e f o ur t h b e ds o f S t a g e 2
. I n p ar t ic u l ar , c o nt r o llin g t h e B e d 4 in le t t e mp e r a t u r e ap p e ar e d t o b e mo r e d iffic u lt co m p ar ed wi t h

o t h e rb e ds. I n ci dent s in v o lv in g S t age 2 Bed 4 t e m p er at ur e ex cur s i o n s h a d b een do cum e nt ed in React o r1, o n t h

r ee pr i o ro ccasi o n s . On e o f t h ese in ci dent s o ccur r e d t w o day s b e f o r e t h e Janu ar y 21 acci dent . T h ese ar e di scussed in m o r e det a il in S ect i o n 3. 3. 3. 2 o f t h i s r e po r t . I n spect i o n o f React o r1 af t e r J a nu ar y 21, 1997 s h o w ed t h at o n e t h er m o co uple l o cat ed in t h e cent e ro f B e d 4 was s l i g ht l y b o wed, po ssi b l

y

in di cat in g ex t r em el

y

h i gh o p er at in g t e m p er at ur es. A s a r e s u l t o f a t e m p er at ur e ex cur s i o n s ( s ) t h at o ccur r e d o n J u l y

23, 1992, s p eci al o p er at in g gui del in es wer e dr af t e d in Augus t , 1992 f o rReact o r3, Bed 4. T h e t e m p er at ur e dif f e r e nt i a l acr o s s B e d 4 w a s t o b e limit e d t o 2 5 o F an d t h e t e m p er at ur e in cr eases wer e t o b e ma de at h a lf t h e r e c o m m

e nd e d r a t e g ive n f o ro t he rbe d s . H o w e ve r , t h e s e d r a f t p r o c e d u r e s w e r e ne ve r in co r p o r at ed int o t h e S t an dar d Oper at in g P r o cedur es. Bed 4 P h ase Ch an ge On e f act o rt h at ma y h a v e co nt r i b u t e d t o t h e t e m p er at ur e ex cur s i o n was a ch an ge o f ph ases ( l i qui d t o gas an d v i ce v e r s a) in Bed 4. I t i s co m m

o n t o h a v e all gas ph ase in t h e l o werb e ds o f t h e r eact o r . E v en at t h e t o p o f t h e r eact o r , t h e pr o cess f l ui d i s gen e r a ll y

ab o u t 95% gas b y v o l u m e . B e ds 4 an d 5 t e n dt o h a v e all v apo rdur in g n o r mal o p er at i o n s . T o s c o per f o r m e d f l as h calcul a t i o n s t h at in di cat ed t h at t h e r eact ant s t r an si t i o n ed f r o m wet t o dr y cat al y s t wi t h in Bed 4 o f React o r3. Beds in wh i c h so m e o f t h e cat al y s t i s wet an d so m e o f t h e cat al y s t i s dr y ar e par t i c ul ar l y suscept i b l e t o h o t spo t s sin ce t h e r eact i o n r a t e an d m ech an i s m o f h eat gen e r a t i o n an d r e m o v a l ar e dif f e r e nt f o rwet , par t i a ll y

wet an d dr y cat al y s t . T e m p er at ur e gr adi e nt s ar e m o r e sen s it iv e t o l i qui d di st r i b u t i o n in t h e t r an sit i o n zo n e t h an in f

l o w r e gim e s wh er e t h e cat al y s t i s eit h er co m p le t e l y

wet o rdr y . T h er ef o r e, l i qui d di st r i b u t i o n t o t h e in le t o f t h e cat al y s t b e d i s cr i t i cal t o t e mp e r a t u r e s t ab ilit y, e s p e c i a lly in b e d s w h e r e a t r a n s it i o n b e t w e e n p h a s e s o c c u r s . T h e flo w r e gim e in B e d 4 po s s i b l

y

co nt r i b u t e d t o t h e f o r mat i o n o f a “ h o t s p o t . ” B e d 4 Di s t r i b u t i o n Des i gn T h e di st r i b u t i o n t r ay s ab o v e Bed 4 in each S t age 2 r eact o rwer e o f a dif f e r e nt desi gn f

r o m t h e di st r i b u t i o n t r ay s ab o v e o t h e rcat al y s t b e ds in S t age 2. T h i s co ul d h a v e b een a f act o rexpl ain in g why B e d 4 h a d m o r e f l o w di s t r i b u t i o n an d o p er at i o n a l pr o b le m s . B e d 4 h a d n o do wn co m e rt r ay an d t h e ch im n ey s o n t h e di st r i b u t i o n t r ay wer e o f a dif f e r e nt desi gn . ( S ee A ppen d ixD f o rdet a il s )
. T h e o r i g in al I s o c r ackerh a d f o urcat al y s t b e ds
. B e ds 1, 2, 3, an d 5 wer e t h e s a m e des i gn as t h ey wer e in t h e o r i g in al I s o c r acker
. W h en T o s c o upgr aded f r o m t h e C h evr o n I s o c r ackert o t h e Un o cal Un i c r ackerdes i gn in 1986, an o t h e rb e d o f dif f e r e nt des i gn was added an d calle d B e d 4. T h e m o dif i ed r eact o rin t e r n al s al o n g wit h t h e o t h e rch an ges ma de at t h e t im e was t h en l

i cen sed b y

37Un o cal as a Un i c r acker
. T o sco st at ed t h at t h ey wer e n o t ab le t o det e r m in e if t h e desi gn o f di s t r i b u t i o n t o B e d 4 was t h e caus e o f t h e co kin g pr o b le m s . Lev e l n ess o f D i st r i b u t i o n T r ay s T o a c h ie v e u n ifo r mit y o f flo w , d i s t r i b u t i o n t r a y s mu s t b e fa ir ly le v e l. S e v e r a l p r o b le ms w it h React o r3 di s t r i b u t i o n t r ay s wer e i d ent if i ed in an in s p ect i o n in F e b r uar y 1992. T h e Bed 5 quen c h pan h a d t h in n e d, B e d 4 an d B e d 5 quen c h pan s wer e b o wed do wn war d , an d s o m e o f t h e di s t r i b u t o rh a n g ers uppo r t b o l t s f o rB e d 4 wer e m i s s in g . T h es e it em s appear ed o n t h e ma in t e n a n ce wo r k l

i s t f o rt h e J a nu ar y 1996 t u r n ar o u n d
. Ho wev e r , n o do cum e nt at i o n was av ail ab l e t o in di cat e wh et h e rt h i s ma in t e n a n ce h a d b een co m p l e t e d. T h er ef o r e, it i s un cer t a in w h e t h e rt h e s e p r o b le ms s t ill e x is t e d a t t h e t ime o f t h e acci dent an d wh et h e rt h ey co ul d h a v e b een a f act o rin causin g t h e t e m p er at ur e ex cur s i o n . S o m e di st o r t i o n s o f t h e di st r i b u t i o n t r ay s wer e seen f

r o m t h e int e r n al in spect i o n o f all t h r ee S t age 2 r eact o r s co n duct e d af t e rJ a nu ar y 21, 1997. I n React o r3 ab o v e Bed 4, ab o u t 1⁄4 o f t h e quen c h t r ay was b e nt do wn war d
. T h e t r ay h a d s l i pped do wn ab o u t 12 in ch es b e l o w t h e t r ay s uppo r t r in g , an d t h e ma n w ay was l if

t e d 12 in ch es ab o v e t h e adj acen t t r ay sect i o n s . T h e quen c h pan ab o v e Bed 4 appear ed t o b e b o wed do wn war d
. T h e uppers u r f ace o f t h e Bed 4 cat al y s t h a d ab o u t a t w o f o o t deep depr essi o n in t h e cen t e r . T h e in spect i o n af t e rJanu ar y 21 in React o r3 sh o w ed t h at t h e quen c h t r ay ma n w ay ab o v e Bed 5 was war p ed ab o u t 3 in ch es ab o v e adj acent t r ay sect i o n s . T h e Bed 5 quen c h pan h a d dr o pped do wn in o n e pl ace an d was t o uch in g t h e t o p o f t h e sawt o o t h do wn co m e r s o n t h e n e x t t r ay . T h i s s e e m s s imilart o d a ma g e d e s c r i b e d fr o m t h e int e r n a l in s p e c t io n r e p o r t in 1992 o f “ 5 t h an d 4t h b e d quen c h pan s b o wed do wn in cen t e r . 5t h m o r e s e v e r e l y , act uall y

r e s t in g o n di s t r i b u t o rt r ay . ” T h e do wn co m e rt r ay in Bed 5 appear ed t o b e wav y in so m e sect i o n s as t h o ugh it h a d b een pr essed do wn b e t w een t h e t o ps o f t h e ch im n ey s o f t h e di st r i b u t o rt r ay b e l o w. T h e po st
- acci dent in spect i o n r e v ealed t h at t h e quen c h t r ay ab o v e Bed 4 in each o f t h e r eact o r s appear ed t o h a v e b een di s t urb e d. T h e pi pe r upt ur e wo ul d h a v e caus e d a v e r y l ar g e pr es s u r e dr o p in

t h e l o werpar t o f t h e r eact o rb ecaus e t h e pr es s u r e in t h e r eact o rwas appr o x ima t e l y

1560 ps i g as co m p ar ed t o t h e am b i ent pr essur e o f 0 psi g . T h er ef o r e, dama ge t o di st r i b u t i o n t r ay s ma y h a v e b een a r e sul t o f t h e dr amat i c pr essur e decr ease dur in g t h e pi pe r upt ur e. Because o f t h i s , i t was n o t po ssi b le t o det e r m in e wit h cer t a in t y wh et h e run le v e l di st r i b u t i o n t r ay s wer e a causat iv e f act o r in

t h e acci den t . I n v e st i g at o r s wer e ab le t o r u le o u t a nu m b ero f po ssi b le causes o f t h e t e m p er at ur e ex cur s i o n : 3. 3. 2. 2 Cat a l y s tCondit i on T h e cat al y s t h a d b een in use f o ra y earan d it h a d al r eady b een sulf i d ed. T h er ef o r e f r esh r eact iv e cat al y s t was n o t a l i k el y

cause.
38A s m e nt i o n e d ear l i e r , t h e S t age 2 r eact o r s wer e o p er at in g wi t h

par t i a ll y

deact iv at ed cat al y s t , wh i c h r e duced t h e cr ackin g/ sat u r a t i o n r eact i o n . I n v e st i g at o r s co n s i d er ed t h e po ssi b ilit y t h a t r eact iv at i o n o f t h e cat al y s t co m b in ed wi t h

r a i s in g f eed t e m p er at ur es m i g ht h a v e co nt r i b u t e d t o t h e t e m p er at ur e ex cur s i o n . At appr o x ima t e l y

7: 00 pm , so m e cr ackin g was o ccur r in g in S t age 2 b u t t h e t e m p er at ur e dif f e r e nt i a l s acr o ss each b e d wer e st ill le s s t h a n n o r ma l
. U n d e rt h e d i r e c t io n o f ma n a g e me n t , o p er at o r s wer e gr aduall y

in cr easin g t e m p er at ur es in S t age 2 t o r e st o r e cat al y s t act iv it y . T h e st r i p ch ar t in di cat ed t h at t h e r eact o rin le t t e m p er at ur e was in cr eas in g gr aduall y

as pl an n e d, n o s udden co nt r o l ch an ges o rt e m p er at ur e in cr eases wer e n o t e d. A sl o w , st eady r i se in in le t t e m p er at ur e f r o m 625 o F t o 640 o F o ccur r e d o v era t im e per i o d o f 4 h o ur s. At 7: 36 pm , t h e r eact o rin le t t e m p er at ur e was 640. 2 o F o n t h e dat a l o gger . Oper at o r s wer e al so wo r k in g o n r e ducin g t h e n it r o g en co n t en t in S t age 1 ef f l uen t in o r dert o r u n cl ean f

eed t h r o ugh t h e S t age 2 r eact o r s. T h e o p er at o r s expect ed t h at t h e S t age 2 cat al y s t wo ul d e v e n t u a lly c le a n it s e lf u p , if it w a s a t e mp o r ar y p o is o n in g . A cco r d in g t o co unt y in v e st i g at o r s, t h e cat al y s t ma nu f act ur erdeact iv at ed wit h n it r o g en co m p o u n d s so m e o f t h e sam e t y pe o f cat al y s t used wit h S t age 2 an d co n duct e d so m e t e st s t o see if

t h ey co ul d in duce a r api d t e m p er at ur e r i se. T h ey co ul d n o t pr o duce a t e m p er at ur e ex cur s i o n . Based o n co n s ul t a t i o n wit h en gin eer s wit h hy dr o p r o cessin g exper i en ce, E P A in v e st i g at o r s do n o t b e l i e v e t h at t h e pr o cess o f r eact iv at in g cat al y s t in S t age 2 co nt r i b u t e d t o t h e t e m p er at ur e ex cur s i o n . 3. 3. 2. 3 F eed T e m p er at ur e T h er e wer e n o s udden in cr eas es in r eact o rin le t t e m p er at ur e t h at wo ul d h a v e caus e d t h e f eed t o b eco m e t o o h o t . T h e st r i p ch ar t sh o w s a sl o w st eady r i se in r eact o rin le t t e m p er at ur e, wh i c h ne ve rr o s e ab o v e 6 4 0 o F
. A l s o , t h e r api d t e m p er at ur e r i s e f i r s t o ccur r e d in B e d 4 an d n o t in t h e t h

r ee b e ds ab o v e it . 3. 3. 2. 4 Oiland Recycl e Gas F l owr a t e T h e r ecy cle hy dr o g en co m p r e sso rdi d n o t f a il an d f l o w dat a f

r o m st r i p ch ar t an d co m put er pr int o ut s sh o w ed n o in t e r r upt i o n in r ecy cl e gas f l o w . T hus l ack o f r ecy cle gas f l o w was r u le d o u t as a cause o f t h e ex cur s i o n . T h e r a t e o f r ecy cle gas an d o il f

eed di d n o t appeart o b e a pr o b le m . T h e o il f

eed f l o w r a t e was appr o x ima t e l y

6, 000 BP D in each o f t h e S t age 2 r eact o r s an d was ab o v e t h e m in im u m r e qui r e d f l o w r a t e as specif i ed in t h e o p er at in g pr o cedur es. T h e in le t r ecy cle gas r a t e appear ed t o b e suf f i ci ent f o rt h e am o u nt o f o il b e in g f eed t o t h e r eact o r . T h e r a t i o o f in le t ( e x c l udin g quen c h ) gas t o o il f

l o w was ab o u t 11, 000 S C F / b b l an d ex ceeded t h e des i gn m in im u m o f 6, 000 S C F / b b l
. I f t h e g a s r a t e is t o o lo w , t h e t e n d e n c y fo rc h a n n e lin g a n d ma ld is t r ib u t io n o f g a s a n d o il flo w w i t h in t h e 39cat al y s t b e d, an d t hus l o cal h o t spo t s, in cr eases . A l t h o u g h a

c a t a l ys t p illarw a s fo u n d in B e d 4 , in v e st i g at o r s b e l i e v e it s cr o ss- sect i o n a l ar ea i s t o o small t o h a v e m u ch adv e r s e ef f ect o n f

l o w di s t r i b u t i o n . 3. 3. 2. 5 Quench F l ow t o B e d 5 Because Bed 5 t e m p er at ur es wen t o u t o f co nt r o l , in v e st i g at o r s f o cused o n t h e r o le o f quen c h f

l o w t o B e d 5
. T h e q u e n c h flo w is c o nt r o lle d b y t h e s in g le B e d 5 in le t t e mp e r a t u r e , w h ic h is r e c o r d e d b o t h o n t h e dat a l o ggeran d t h e st r i p ch ar t . T h e quen c h v a lv e ab o v e Bed 5 f u ll y

o p en ed o n aut o ma t i c co nt r o l in r e spo n se t o Bed 5 in le t t e m p er at ur e ex ceedin g i t s co nt r o lle rset po int . On t h e s t r i p ch ar t , t h e s e t po int t e m p er at ur e appear ed t o b e b e t w een 640 an d 650 o F
. B y 7:36 pm o n J a nu ar y 21, t h e B e d 5 in le t t e m p er at ur e h a d dr o pped b ack t o ab o u t 625 o F o n t h e st r i p ch ar t ( b el o w t h e set po int ) , so t h e quen c h v a lv e aut o ma t i call y

cl o s ed. At appr o x ima t e l y

7:37 pm , t h e ex t r a No
. 1 Oper at o rs w i t ch ed t h e B e d 5 quen c h f

l o w co nt r o lle r f r o m aut o ma t i c t o ma nu al co n t r o l an d cl o s ed t h e quen c h v a lv e. He di d t h i s b ecause h e was co n cer n e d ab o u t po ssi b l

y

l o sin g t e m p er at ur e in t h e r eact o rsy st em as a r e sul t o f t h e decr eased Bed 5 in le t t e m p er at ur e. E P A in v e st i g at o r s est ima t e d t h at t h e quen c h v a lv e t o Bed 5 was cl o s ed at l east o n e m inut e, per h aps t w o m inut es, b e f o r e it was l a t e ro p en ed b y t h e S t age 2 Bo ar d Oper at o r . T h i s was est ima t e d b y co r r e l a t in g t e m p er at ur es an d t im e s f r o m t h e dat a l o ggert o t e m p er at ur e peaks o n t h e st r i p ch ar t ( a l s o acco unt in g f o rt im e o f f s et in st r i p ch ar t pen s ) f o rBed 5. T h i s st r i p ch ar t al so r eco r d ed quen c h f

l o w t o Bed 5. Because quen c h was cl o s ed ma nu all y , t h e B e d 5 in le t t e mp e r a t u r e r o s e ab o v e it s s e t p o in t t o ab o u t a ma x imu m o f 6 7 0 O F o n t h e st r i p ch ar t . T h e dat a l o ggerh i st o r i a n r eco r d ed t h e Bed 5 in le t t e m p er at ur e as 660 o F b e t w een 7:36:40 an d 7:38:40, f o rab o u t 2 m inut es . A l s o b y 7:37 pm , all f

o urB e d 5 o u t let t e m p er at ur es ( a s r eco r d ed b y t h e dat a l o gger ) wer e r i s in g . By 7: 38 pm , o n e o f t h e Bed 5 o u t let t e m p er at ur es h a d r each ed 717 o F an d an o t h e rh a d r each ed 876 o F
. At appr o x ima t e l y

7: 39, t h e quen c h v a lv e was o p en ed ma nu all y

b y t h e S t age 2 Bo ar d Oper at o r , wh o was n o t awar e t h at it h a d b een cl o s ed. Quen ch f

l o w r o se an d r each ed al m

o st f u ll s cal e o n t h e s t r i p ch ar t at appr o x ima t e l y

7:41 pm
. T e m p er at ur es co nt inued t o r i s e in B e d 5 unt il t h e expl o s i o n . I f

quen c h h a d b een le f t o n aut o ma t i c co nt r o l , it wo ul d h a v e l o wer e d t h e B e d 5 in le t t e m p er at ur e b u t it wo ul d n o t h a v e r e s p o n ded t o r i s in g B e d 5 o u t let t e m p er at ur es . I n o r dert o det e r m in e if t h e t e m p o r ar y l ack o f quen c h was an aggr av at in g f act o rin t h e acci den t , E P A per f o r m e d a sim p l

i f

i e d h eat b a l a n ce b a sed o n a Bed 5 in l e t t e m p er at ur e o f 860 o F , t h e ma x im u m t e m p er at ur e r each ed at 7:34:20 pm . T h e pur po s e o f t h es e calcul a t i o n s was t o s ee if t h e h eat gen e r a t e d wi t hin B e d 5 c o u l d ha ve be e n c o o le d by ma xim u m f

l o w o f q u e nc h g a s , if t h e q u e nc h va lv e ha d be e n le f t f u ll y o p en ed b y t h e o p er at o r s wh en t h e Bed 5 in le t f i r s t ab r upt l y

in cr eased. T h e r e sul t s in di cat e t h at ma x im u m quen c h f

l o w t o B e d 5 wo ul d h a v e b een in s u f f i ci ent t o co o l B e d 5 b ack t o a n o r mal o p er at in g t e m p er at ur e o f 650 o F
. At le a s t t h r e e t ime s t h e ma x imu m d e s i g n q u e n c h flo w w o u l d h a v e b een r e qui r e d t o co o l Bed 5 b ack t o n o r mal o p er at in g t e m p er at ur e. 40T h e calcul a t i o n s t ake int o acco unt o n l y

t h e am o u nt o f co o l in g capaci t y

av ail ab le an d do n o t f act o rin act ual h eat t r an sf err a t e s, wh i c h m ean s t h at act ual h eat t r an sf err a t e wo ul d h a v e b een sl o w ert h an assum e d in t h e calcul a t i o n s. T h er ef o r e, wi t h

t h e b e st h eat t r an sf err a t e , t h e ma x im u m quen c h in g wo ul d n o t h a v e b een suf f i ci ent . Ho wev e r , t h e calcul a t i o n s assum e t h at t h e ent i r e b e d co nt ent s wo ul d h a v e un der g o n e an acceler at ed r eact i o n . On l y

o n e Bed 5 in le t t e m p er at ur e r e a d in g w a s a v a ilab le , s o it is a s s u me d t h a t t h is t e mp e r a t u r e w a s fa ir ly u n ifo r m a c r o s s t h e in le t o f B e d 5
. T h e c a lc u la t i o n s u s e d t h e ma x imu m d e s i g n q u e n c h c ap a c it y o f 3 2 millio n s t a n d ar d c u b i c f eet perday ( MMS CF D) , as r e f e r e n ced in t h e Un i c r ackerma nu al pr o v i d ed b y t h e l i cen so r . T h e r e sul t s o f t h e h eat b a l a n ce cal cul a t i o n s ar e n o t un expect ed. Quen ch capacit y i s t y pi call y desi gn ed t o h a n d le m in o rt e m p er at ur e ex cur s i o n s . T h e si gn if i can t in cr ease in Bed 5 in le t t e m p er at ur e acceler at ed t h e r eact i o n r a t e , wh i c h in t u r n , acceler at ed t h e gen e r a t i o n o f h eat f r o m t h e r eact i o n . T h e hy dr o c r ackin g r eact i o n r a t e do ub le s f o rappr o x ima t e l y

ev er y 20 o F in cr ease in t e m p er at ur e. T h er ef o r e, an in cr ease o f 223 o F wo ul d h a v e in cr eased t h e r eact i o n r a t e b y appr o x ima t e l y

4000 t im e s . T h e elev at ed t e m p er at ur es in B e d 5 went b e y o n dt h e po int wh er e t h ey co ul d b e ef f ect iv el y

co nt r o lle d b y quen c h
. T h e r eact i o n r a t e co ul d o n l y

b e sl o w ed do wn b y l o wer in g t h e hy dr o g en par t i a l pr es s u r e , whi c h r e qui r e s depr es s u r in g . 3. 3. 3 C ont r olof T e m p er at ur e E x cur s ion I f

addi t i o n al quen c h gas i s un ab le t o co nt r o l a t e m p er at ur e ex cur s i o n in a hy dr o c r ackin g r eact o r , t h e n lo w e r in g t h e p ar t ia l p r e s s u r e o f t h e hy d r o g e n w ill s l o w t h e r eact i o n ; t h i s i s n o r mall y acco m p l

i s h e d b y depr essur in g . Depr essur in g n o t o n l y

r e duces t h e hy dr o g en par t i a l pr essur e , b u t r e duces t h e st r e ss o n t h e r eact o rsh ell an d co n n ect ed pi pin g . I n so m e sit u at i o n s , st o ppin g t h e o il f eed i s en o ugh t o sl o w do wn t h e r eact i o n . I n o t h e rcases, f eed ma y b e co nt inued t o ser v e as a h eat sink
. Oper at o r s at t h e Hy dr o c r ackerUn it h a d av ail ab le wr i t t e n em er gen c y o p er at in g pr o cedur es wh i c h wer e dat e d Oct o b e r1991. T h e pr o cedur es co v e r e d 23 dif f e r e nt em er gen c i e s , an d h o w o p er at o r s sh o u l d h a n d le each par t o f t h e Hy dr o c r ackerUn i t ( H y d r o gen P l ant , S t age 1 an d S t age 2) dur in g an em er gen c y . On e o f t h e em er gen c y pr o cedur es co v e r e d h o w t o h a n d le t e m p er at ur e ex cur s i o n s . T h i s pr o cedur e was al so po st ed o n t h e co nt r o l b o ar d. F o ra t e m p er at ur e ex cur s i o n o n S t age 2, t h e pr o cedur e r e qui r e d t h e S t age 2 Bo ar d Oper at o rt o t ake t h e f o ll o win g act i o n s : ( 1 ) F o ran y r eact o rt e m p er at ur e po int 5 o F ab o v e n o r mal , ch an ge r eact o rco nt r o l s t o r e t u r n t h e t e m p er at ur e po int t o n o r mal
. T h i s ma y in cl ude r e ducin g t r im f

u r n ace o u t let t e m p er at ur e, in cr easin g quen c h t o h o t b e ds, speed up I I Rco m p r e sso ro radd quen c h t o r eact o rin le t v i a F I C

729. ( 2 ) F o ran y r eact o rt e m p er at ur e po int 25 o F ab o v e n o r mal , do t h e f o ll o win g : Hi t t h e “ s ix sh o r t s ” un i t al ar m , cl o s e appr o p r i at e o il f

eed co nt r o l v a lv e, r e duce t r im f

u r n ace f i r in g , ci r c ul at e ma x im u m hy dr o g en t h r o ugh h o t r eact o r , an d ma int a in n o r mal un it pr essur e . Reduce t e m p er at ur e in

h o t r eact o rt o 50 o F b e l o w n o r mal o p er at in g le v e l as qui ckl y

as po ssi b le. A dd quen c h t o r eact o r
41in le t as n eeded v i a F I C- 729. Co nt inue t o co o l r eact o rat a r a t e o f 100 o perh o urt o 500 o F o r 100 o F b e lo w o p e r a t in g t e mp e r a t u r e p r io rt o s hu t d o w n , w h ic h e v e ris lo w e r . ( 3 ) F o ran y r eact o rt e m p er at ur e 50 o F ab o v e n o r mal o rif an y r eact o rt e m p er at ur e ex ceeds 800 o F , imme d i a t e l y a c t iv a t e t h e 300 ps i / m inut e depr es s u r in g s y s t em wh i c h caus e s t h e f o ll o win g : (a ) IIRc o m p re s s o r s hu t s d o w n . ( b ) S t a ge 2 ch ar ge pum p s hut s do wn . ( c ) M akeup hy dr o g en t o S t age 2 st o p s. ( d ) T r im f

u r n aces t r i p . ( e ) R ecy cle gas f r o m HP S S e par a t o rOv er h ead st o p s. ( f

) R ecy cle gas t o HDS No
. 1& 2 Un it st o p s. T h e wr it t e n em er gen c y pr o cedur es al so co nt ain e d specif i c in st r u ct i o n s f o reach o f t h e o t h e r Hy dr o c r ackerUn it o p er at o r s f o rassi st in g t h e S t age 2 Bo ar d Oper at o rdur in g an y o f t h e ab o v e t h

r ee cases o f t e m p er at ur e ex cur s i o n s . A l t h o ugh so m e o f t h e t e m p er at ur es o b ser v ed b y o p er at o r s o n t h e dat a l o ggerm o n it o rex ceeded 800 0 F dur in g t h e J a nu ar y 21 in ci dent , t h e o p er at o r s di d n o t depr es s u r e t h e un it as r e qui r e d b y t h e em er gen c y pr o cedur es. 3. 3. 3. 1 Awar e nes s of E m er gency Sit u at ion T h e o p er at o r s in it i a ll y

di d n o t t ake t h e specif i ed st eps t o co n t r o l t h e t e m p er at ur e ex cur s i o n b ecause t h ey di d n o t co m p r e h e n d t h at t h e t e m p er at ur e ex cur s i o n was r eal
. T h er e wer e sev e r a l r easo n s why t h ey wer e un sur e o f t h e sit u at i o n t h at was o ccur r in g t h e ev en in g o f Janu ar y 21: Co n f usin g T e m p er at ur e Readin gs T h e dat a l o ggert e m p er at ur es o n t h e co nt r o l r o o m m o n i t o rwer e f l uct u at in g b e t w een h i gh , l o w, an d zer o r eadin gs, an d t h en b ack t o n o r mal , causin g t h e o p er at o r s t o b e l i e v e t h e r eadin gs wer e in er r o r . Just pr i o rt o t h e expl o s i o n , o n e o p er at o rr e po r t ed t h at at l east h a lf o f t h e t h er m o co upl es o n t h e dat a l o ggerf o rS t age 2 wer e n o t wo r k in g pr o p er l y . Based o n po st
- acci dent t e st in g, i t was det e r m in ed t h at t h e dat a l o ggerdi s p l a y s " 0 " wh en t h e t e m p er at ur e r eadin g i s o v er1400 o F. Oper at o r s di d n o t un der s t a n d t h e si gn if i can ce o f t h ese “ 0 " r eadin gs. P r o b le ms w it h T e mp e r a t u r e M o n it o r in g Oper at o r s t h o ught t e m p er at ur e dat a m i g ht b e er r o n e o u s b ecause t h e dat a l o ggerh a d exper i en ced ma lfu n c t io n s a t t ime s . T h e d a t a lo g g e rh a d b e e n ma lfu n c t io n in g o n ly o n e d a y e ar lie ro n J a nu ar y 20. On J a nu ar y 10, 1997, t h e dat a l o ggerwas t aken o u t o f s e r v i ce an d a n e w t e m p er at ur e mo n it o r in g s y s t e m , k n o w n a s a F o xb o r o I n t e llig e nt Au t o ma t i o n ( I /A ) d i s t r i b u t e d d i g it a l c o n t r o l sy st em , was in st all e d t o di spl a y r eact o rt e m p er at ur es in t h e co nt r o l r o o m . Dur in g t h e t im e t h at t h e S t age 2 I /A sy st em was o p er at i o n a l , o p er at o r s r e po r t ed t h at o v erh a lf o f t h e t e m p er at ur e
42po int s wer e per i o d i call y

dr o ppin g t o 0. T h e S t age 2 t e m p er at ur e m o n i t o r in g sy st em was swi t ch ed f r o m t h e I / A sy st em b ack t o dat a l o ggero n Janu ar y 20 b ecause t h e I /A was in co r r ect l y

cal cul a t in g t h e wei g ht ed cat al y s t av er ages. I t was av er agin g in zer o s f o rsev e n o f t h e t w elv e po int s per t h er m o co upl e b u n d le b ecause t h e addit i o n al sev e n po int s wer e n o t wi r e d int o t h e I / A sy st em y e t . I n

addi t i o n , o p er at o r s h a d exper i en ced co m put erpr o b le m s wi t h

S t age 1 I /A sy st em in t h e past a n d s t a t e d t h a t t h e p r o b le ms t h e y s a w o n t h e S t a g e 2 d a t a lo g g e rlo o k e d s imilart o t h o s e p r o b le ms . Dur in g S e pt em b e r1996, t h e S t age 2 dat a l o ggerf a ile d t o per f o r m pr o p er l y

o n t w o o ccas i o n s . On ce, t h e dat a l o ggers t o pped updat in g t w i ce an d h a d t o b e r e s e t b y in s t r u m e nt t ech n i ci an s t o r e st o r e ser v i ce. On an o t h e ro ccasi o n , it was r e po r t ed t h at t h e dat a l o ggerh a d st o pped wo r k in g a n d r e p a ir s w e r e ma d e t o r e s t o r e it t o s e r v ic e . O p e r a t o r s r e lie d o n b o ar d mo u nt e d in s t r u me nt s t o co nt inue o p er at in g t h e un it . I n J u l y

1996, t h e S t age 2 React o r3 o u t let t e m p er at ur e s i gn al t o t h e co nt r o l b o ar d as well as t h e dat a l o ggerdi s p l a y was l o s t , appar e nt l y

due t o a f a ile d t h er m o co upl e. I n

t h e pas t , o p er at o r s h a d s een t h e St age 1 dat a l o ggerdi s p l a y “ l o c k up”, m ean in g t h e t e m p er at ur e r eadin gs di d n o t ch an ge. A cco r d in g t o t h e o p er at o r s, it was di f f i cul t t o det e r m in e t h at t h er e was a pr o b l e m wit h t h e di spl a y un t il it was n o t i ced t h at t h e t e m p er at ur es h a d n o t ch an ged in r e spo n se t o a co nt r o l ch an ge. S t r i p C h ar t v s . D a ta L o g g e rD a ta T h e S t age 2 Bo ar d Oper at o rh ear d t h e dat a l o ggeral ar m f

o rt h e h i gh Bed 4 o u t let an d Bed 5 in le t t e m p er at ur e an d st at ed t h at h e ackn o wledged t h e al ar m o n t h e dat a l o gger . Ho wev e r , t h e co nt r o l b o ar d st r i p ch ar t f o rBed 4 l o o k ed n o r mal b ecause t h e Bed 4 o u t let po int t h at caused t h e al ar m i s n o t t h e s a me p o in t t h a t is link e d t o t h e c o n t r o l b o ar d d i s p la y. T h e B e d 5 in le t t e mp e r a t u r e in cr ease was di spl a y e d o n t h e co nt r o l r o o m st r i p ch ar t , b u t dr o pped b ack t o n o r mal af t e rt h e quen c h v a lv e t o B e d 5 f u ll y

o p en ed. Audi b le T e m p er at ur e A l ar m s A

Bed 4 o u t let ( p o int 2) t e m p er at ur e an d t h e Bed 5 in le t t e m p er at ur e ex ceeded b o t h t h e h i gh t e m p er at ur e al ar m set t in g o f 780 o F an d t h e +50 o F o v ern o r mal al ar m set t in g o n t h e dat a l o gger . T h e o p er at o r s st at ed t h at t h ey h ear d o n e h i gh t e m p er at ur e al ar m o n t h e dat a l o ggerf o rBed 4 o u t let an d Bed 5 in le t h i gh t e m p er at ur es. F r o m o p er at o rst at em ent s , it appear s t h at t h er e was n o del a y b e t w een t h e o ccur r e n ce o f t h e Bed 4 o u t let an d Bed 5 in le t h i gh t e m p er at ur es an d t h e al ar m s r eceiv e d b ecause o f t h em . Oper at o r s di d n o t r eceiv e addi t i o n al audi b le h i gh t e m p er at ur e al ar m s f r o m t h e dat a l o gger , despi t e Bed 5 o u t let an d r eact o rin le t an d o u t let t e m p er at ur es l a t e r ex ceedin g h i gh t e m p er at ur e al ar m set po int s . Oper at o r s di d n o t imme d i a t e l y n o t i c e t h e B e d 5 o u t let , r eact o rin le t an d o u t l et t e m p er at ur es r i sin g ab o v e cr it i cal limit s . T h er e was a dif f e r e nt al ar m sy st em f

o rt h e t e m p er at ur e po in t s o n t h e st r i p ch ar t s t h an f

o rt h o s e po int s o n t h e dat a l o gger . T h e al ar m f

o rt e m p er at ur e po int s ( cent e rin le t an d o u t let o f b e d) o n t h e
43co nt r o l b o ar d was a f l ash in g l i g ht o n t h e co nt r o l b o ar d. A l ar m s f o rdat a l o ggert e m p er at ur es pr o duced an audi b le al ar m an d f l ash in g l i g ht o n t h e co nt r o l b o ar d. T h e nu m b er s o n t h e dat a l o ggerscr een wo ul d t u r n f

r o m b l ack t o r e d an d b l ink o n t h e scr een . W h en t h e ackn o wledge b u t t o n was pus h e d o n t h e dat a l o ggerkey b o ar d , t h e r eadin g s t o pped b l inkin g b u t t h e b ackgr o u n d co l o rr e ma in ed r e d. W h en t h e t e m p er at ur e cam e b ack int o n o r mal r a n g e, t h e r e d b ackgr o u n d r e v e r t ed t o b l ack. T h e dat a l o ggerm u st b e r e set t o r eceiv e n e w audi b le h i gh t e m p er at ur e al ar m s . I n po st
- acci dent t e st s f o r+5 0 o F ab o v e n o r mal t e m p er at ur es, t h e dat a l o ggerwo ul d n o t r e - a l ar m wh ile i t was in t h e ab n o r mal co n d it i o n wh en t h e ackn o wl edge b u t t o n was pr essed o n t h e key b o ar d
. I t al so t o o k 2. 5 m

inut es f o rt h e al ar m t o clearwh en t h e t e m p er at ur e dr o pped t o n o n - al ar m le v e l s . Dur in g t h e J a nu ar y 21 in ci dent , t h e B e d 4 o u t let ( p o int 2) an d B e d 5 in le t t e m p er at ur es r o s e an d r e t u r n ed t o n o r mal , acco r d in g t o t h e dat a l o ggerh i st o r i a n f

ile ( s ee S ect i o n 1. 2. 4. 3 an d T ab le 2) , wh i c h sh o u l d h a v e cl ear ed t h e al ar m st at us o n t h e dat a l o gger . T h e S t age 2 Bo ar d Oper at o rst at ed t h at h e ackn o wledged t h e al ar m o n t h e dat a l o gger . I t seem s clearf r o m t h e dat a l o ggert e st s t h at f o rt h e +50 o F ab o v e n o r mal co n d it i o n , t h e dat a l o ggeral ar m can n o t b e r e set in a r easo n ab l y

sh o r t t im e . T h i s sit u at i o n wo ul d pr ev ent o p er at o r s f r o m r eceiv in g h i gh t e m p er at ur e al ar m s f r o m o t h e rpo int s in t h e r eact o r . Makeup Hy dr o g en F l o w an d Recy cle Hy dr o g en P u r i t y Oper at o r s wer e co n f used b y makeup hy dr o g en f

l o w dr o ppin g t o zer o . T y pi call y , an in cr ease in r eact iv it y co n s um es m o r e hy dr o g en an d causes an in cr ease in dema n d f o rhy dr o g en . T h i s was wh at o p er at o r s n o r mall y

expect ed t o see dur in g a t e m p er at ur e ex cur s i o n . I n cr eased pr essur e in t h e r ecy cl e gas caused t h e makeup hy dr o g en f

l o w t o decr ease b ecause t h e makeup hy dr o g en t o S t age 2 was pr essur e co nt r o lle d. T h e in cr ease in pr essur e was due t o f o r mat i o n an d b u il dup o f m e t h an e in t h e r ecy cle gas , wh i c h in cr eas ed i t s den s it y an d pr es s u r e . W h en t h e t e m p er at ur e ex cur s i o n b e gan , t h e m e t h an e was gen e r a t e d f r o m a h i gh t e m p er at ur e r eact i o n calle d hy dr o g en o l y s i s . Hy dr o g en o l y s i s cr eat ed gr eat am o u nt s o f m e t h an e an d h eat . T h i s r eact i o n n o r mall y

o ccur s at t e m p er at ur es o v er800 o F. T h e in cr ease in m e t h an e co n t ent caused a dr o p in t h e hy dr o g en pur i t y

o f t h e r ecy cle gas. Oper at o r s di d n o t kn o w t h at t h e r ecy cle gas ( hy d r o gen ) pur i t y

h a d dr o pped b ecause o f a t im e l a g in

r eceiv in g an al y s i s f r o m t h e hy dr o g en pur it y an al y zer . T h e hy dr o g en pur i t y

r eadin gs appear ed n o r mal t o t h e o p er at o r s pr i o rt o t h e expl o s i o n ( 92. 7% at 7:36:18 pm )
. A po s t
- in c i d ent s t udy b y T o sco o f t h e an al y zeran d sam p l

in g sy st em det e r m in ed t h at t h e t im e r e qui r e d f o rt h e an al y zert o in di cat e a ch an ge in t h e pr o cess was appr o x ima t e l y

7 m inut es. T h i s m eant t h at t h e n o r mal r eadin g at 7:36:18 pm was act uall y

t h e hy dr o g en pur it y o f t h e r ecy cle gas 7 m inut es b e f o r e , due t o t h e an al y s i s l a g t im e . A l o w hy dr o g en pur it y al ar m o ccur r e d at 7: 41: 26 pm , v e r y cl o s e t o t h e t im e o f t h e expl o s i o n , co n f i r m in g t h at pur it y h a d dr o pped b ecause o f an in cr ease in t h e m e t h an e co n t en t .

44T h i s 7: 41 pm al ar m was caused b y t h e m e t h an e pr o duced sev e n m inut es ear l i e rwh en t h e t e m p er at ur e ex cur s i o n b e gan at 7: 34 pm
.

A c c e s s i b ilit y o f T e mp e r a t u r e D a t a Oper at o r s di d n o t h a v e access t o all t h e S t age 2 r eact o rt e m p er at ur e dat a in t h e co nt r o l r o o m b ecause so m e o f t h e r eadin gs co ul d o n l y

b e o b t a in ed at t h e f i el d pan e l s o u t s i d e un der n eat h t h e r eact o r s. T h e o p er at o r s t y pi call y

used t h e f i el d pan e l s t o v e r if y

quest i o n ab l e co nt r o l r o o m r eadin gs o rt e m p er at ur e ex cur s i o n s . F o rex am ple, dur in g a t e m p er at ur e ex cur s i o n t h at o ccur r e d o n Janu ar y 19 ( s ee S ect i o n 3. 3. 3. 2) , o p er at o r s o b t a in ed v e r if i cat i o n o f t e m p er at ur es f r o m t h e f i el d pan e l b e f o r e t akin g an y act i o n . On Janu ar y 21, an o p er at o rwent o u t s i d e t o t h e f i el d pan e l t o o b t a in t e m p er at ur e dat a as h a d b een do n e in past pr act i ce. Oper at o r s in si de t h e co nt r o l r o o m di d n o t t ake an y act i o n t o depr essur e t h e un i t b ecause t h ey di d n o t b e l i e v e t h e dat a l o gger . T h e co nt r o l r o o m o p er at o r s wer e n o t ab le t o un der s t a n d t h e gar b le d r a di o t r an sm i ssi o n s f r o m t h e No
. 2 Oper at o ro u t s i d e. I f t h e co nt r o l r o o m o p er at o r s h a d r eceiv e d a r e po r t o f h i gh t e m p er at ur es, t h i s m

i g ht h a v e caused t h em t o act iv at e t h e depr essur in g sy st em . T w o m o r e o p er at o r s wen t t o ch eck o n t h e No
. 2 Oper at o ro u t s i d e. T h e expl o s i o n o ccur r e d j u st af t e rt h e t w o o p er at o r s l e f t t h e c o nt ro l ro o m . W h en t h e f i el d pan e l s wer e in s t all e d in J a nu ar y 1996, o p er at o r s as ked ma n a gem e nt t o b r in g t h i s t e m p er at ur e dat a in t o t h e co n t r o l r o o m . T h ey expr essed co n cer n s t o ma n a gem e n t ab o u t h a v in g t o o b t a in t e m p er at ur e dat a f

r o m t h e pan e l s o u t s i d e. Oper at o r s wer e t o l d b y ma n a gem e n t t h at t h e r eadin gs f r o m t h e addit i o n al t h er m o co upl es av ail ab l e f r o m t h e f i el d pan e l s co ul d n o t b e ma de av ail ab le in t h e co nt r o l r o o m due t o co st an d t h at t h ey sh o u l d "j ust l iv e wit h it ". T h e S t age 2 Bo ar d Oper at o rst at ed t h at i t was v e r y t im e - c o n sum in g t o r ead an d r eco r d t e m p er at ur es f r o m t h e f i el d pan e l s . T o t ake r eadin gs f r o m a f i el d pan e l r e qui r e d ab o u t 45 m inut es . Oper at o r s st at ed t h at t h ey t o o k r eadin gs f r o m t h e f i el d pan e l s o n ce perday , calle d t h em in b y r a di o an d l o gged t h em o nt o an ent r y l o g. T o s c o ma n a g e me nt p e r s o n n e l p r o v id e d c o n f lic t in g in fo r ma t io n ab o u t t h e p u r p o s e o f t h e p a n e ls , an d why t h ey wer e in st alle d un dert h e r eact o r . T h e P r o duct i o n A r ea S uper v i s o rsai d t h at h e di d n o t kn o w why t h e pan e l s wer e in st alle d un dert h e r eact o ras o ppo sed t o in t h e co nt r o l r o o m , a l

th ou g h h e d i d s a y th e i rf u n c ti on w a s to g iv e a d d i ti on a l d a ta p o ints w ith w h i c h to m o n itorth e r eact o rt e m p er at ur es. T h e P r o duct i o n T ech n i cal S e r v i ces Man a gerst at ed t h at t h e t h er m o co upl es wer e added as an en gin eer in g pr o j ect t o b e t t e rdet ect h o t spo t s in t h e b e ds an d t o det e r m in e wei g ht ed cat al y s t av er ages. A co nt r act en gin eerh a d r eco r d ed t h e r eadin gs f o rt h i s pur po se. T h e P r o d u c t i o n T e c hni c a l S e r v i c e s M a na g e r ’ s u n d e r s t a nd in g w a s t h a t t h e p a ne l s w e r e ne ve rint e nd e d t o b e used b y t h e o p er at o r s t o o p er at e t h e un it , b u t t o co llect dat a t o det e r m in e if in st all a t i o n o f a n e w I / A t e m p er at ur e m o n it o r in g sy st em was j u st if i e d. T h e Co nt r o l E n gin eerdi d n o t kn o w why t h e pan e l s wer e in st alle d un dert h e r eact o r , b u t t h o ught t h at t h e pan e l s h a d b een used t o h e l p T ech n i cal S e r v i ces m o n it o rcat al y s t act iv it y r a t h ert h an used as an o p er at in g t o o l
.

45No M a n a gem e nt o f C h an ge ( M OC ) was dev e l o ped an d /o rim p le m e nt ed f o rt h e f i el d pan e l in st all a t i o n an d use. No wr it t e n o p er at in g pr o cedur es wer e in co r p o r at ed in t o S O P s f o ro b t a in in g dat a f

r o m t h e f i el d pan e l s dur in g n o r mal o rab n o r mal co n d it i o n s . Based o n t h e dat a co ll ect ed f r o m t h e pan e l s , T ech n i cal S e r v i ces co n c l uded in J u n e o f 1996 t h at t h e po in t s in t h e S t age 2 r eact o r s wit h t h e h i gh est t e m p er at ur es wer e t h o s e wh i c h co ul d o n l y

b e r ead at t h e f i el d pan e l s . On J a nu ar y 20, 1997 t h e us e o f t h e I / A s y s t em was di s c o nt inu ed b ecaus e t h e I /A was in co r r ect l y cal cul a t in g t h e wei g ht ed cat al y s t av er age t e m p er at ur e ( W CA T )
. I f t h e I /A sy st em h a d b een pr o p er l y

co n n ect ed t o all 96 t h er m o co uples an d accur a t e l y

calcul a t in g W C A T s, t h e o p er at o r s w o u l d h a v e h a d imme d i a t e access t o all S t age 2 r eact o rt e m p er at ur e dat a in o n e pl ace in t h e c o n t r o l r o o m . T h is mig ht h a v e g iv e n t h e m mo r e t ime t o r e s p o n d t o in c r e a s in g t e mp e r a t u r e s , especi all y

t h o s e t e m p er at ur es f r o m t h er m o co uples wh i c h t e n d ed t o r ead h i gh ert h an o t h e r m

o ni t o r ing p o int s . T e s t in g o f t h e I /A equi pm ent an d s o f t war e s h o u l d h a v e o ccur r e d b e f o r e t h ey wer e put int o act ual us e. M O C #150108 dat e d F e b r uar y 5, 1996 co v e r e d “ P l a n n e d C h an ges t o E x i s t in g Hy dr o c r acker Co nt r o l S y st em . ” T h i s do cum e nt in cl uded wo r k o n t h e t r an sf ero f t e m p er at ur e in f o r mat i o n f

r o m t h e ex i s t in g P C

- b ased m o n it o r in g sy st em t o P l ant I n f o r mat i o n ( P I ) co m put ersy st em an d I /A sy st em s af t e run it st ar t up. A l t h o ugh it i s n o t clear l y

st at ed t o wh i c h par t o f t h e Hy dr o c r acker Un it t h i s t r an sf erappl i e d, in v e st i g at o r s assum e d t h at it appl i e d t o S t age 2 sin ce t h e I /A sy st em was al r eady in use f o rS t age 1. T h e MOC st at ed t h at t h e n e w equi pm ent an d so f t war e wo ul d b e t e st ed b e f o r e t h e sy st em w a s co m m

i ssi o n ed
. I n

addi t i o n t o o p er at i o n a l pr o b le m s , o p er at o r s h a d n o adv a n ced n o t if i cat i o n t h at t h e I /A t e m p er at ur e m o n i t o r in g s y s t em was t o b e im p le m e nt ed o n J a nu ar y 10, 1997. T h ey wer e n o t in st r u ct ed h o w t o use o raccess in f o r mat i o n f

r o m t h e n e w I /A sy st em . T h e S t age 2 Bo ar d Oper at o rsai d h e was n o t in v o lv ed wi t h

an y MOC f o rt h e ch an ge t o t h e I /A sy st em . T h e P r o duct i o n A r ea S uper v i s o rst at ed t h at t h er e was n o MOC f o rt h e swit ch t o I /A f

o rS t age 2 b ecause i t was a di spl a y ch an ge o n l y

wi t h

m o r e dat a po int s . He ackn o wledged t h at t h er e wer e n o f o r mal t r ain in g sessi o n s o n t h e S t age 2 ch an ge t o I /A , j u st o n - t h e - j o b ( O T J ) t r ain in g , an d t h at S t age 2 o p er at o r s wer e al r eady qual if

i e d o n t h e I /A in gen e r a l f

r o m b e in g qual if

i e d o n S t age 1. R a d i o C o mmu n i c a t io n s A cco r d in g t o o p er at o r s, t h e r a di o t r an sm i ssi o n f

r o m t h e No
. 2 Oper at o rwh o was sen t o u t s i d e o n Janu ar y 21, was f u zzy wit h ex cessiv e st at i c so un ds. Oper at o r s h a d in di cat ed in t h e past t h at r a di o s di d n o t alway s pr o v i d e r e l i ab le co m m

u n i cat i o n b ecause o f b a d b a t t e r i es, b u sy ch an n e l s , an d n o desi gn at ed em er gen c y ch an n e l
.

463. 3. 3. 2 No E m er gency Depr es s u ri ng Us ed E v en af t e ro p er at o r s r eal i zed, m o m e nt s b e f o r e t h e expl o s i o n , t h at t h e React o r3 o u t let an d in l e t t e mp e r a t u r e s h a d c limb e d ab o v e 8 0 0 o F , t h ey di d n o t depr essur e t h e r eact o ras t h e em er gen c y o p er at in g pr o cedur es r e qui r e d. T h e 100 ps i /m in

an d 300 ps i /m in

em er gen c y depr es s u r in g s y s t em s , in s t alle d in 1986, wer e int e n d ed t o b e us ed t o r api dl y

r e duce pr es s u r e an d r eact i o n r a t e an d b r in g a t e m p er at ur e ex cur s i o n un derco nt r o l
. I n st ead o f depr essur in g , t h e o p er at o r s b e gan t o adj u st quen c h gas f l o w s in o r dert o co o l t h e r eact o r . P r i o rT e m p er at ur e E x cur s i o n s Oper at o r s di d n o t depr essur e t h e r eact o rb ecause t h ei rpast pr act i ce t o co nt r o l l ar g e t e m p er at ur e ex cur s i o n s h a d b een t o in cr ease quen c h , r e duce r eact o rin le t t e m p er at ur es, an d/ o rst o p f eed f l o w t o t h e r eact o r . Man y o f t h e o p er at o r s r e po r t ed t h at t h ey h a v e exper i en ced nu m e r o us t e m p er at ur e ex cur s i o n s , b u t m o st co ul d r ecall o n l y

o n e in st an ce wh en t h e un it was depr essur e d usin g eit h ert h e 100 o r300 ps i / m in

s y s t em . On e o p er at o rin di cat ed t h at t h e depr es s u r in g s y s t em h a d b een us ed o n l y

o n ce in t h e l a st f iv e y ear s, per h aps o n l y

t w i ce in t h e l a st t e n y ear s. Do cum e nt at i o n was av ail ab le f o rt h r ee pr ev i o us t e m p er at ur e ex cur s i o n s t h at o ccur r e d o n J u l y

23, 1992; M ar c h 19, 1996; an d J a nu ar y 19, 1997, s u m mar i zed b e l o w: J u l y

23, 1992 A s o p er at o r s wer e r a i s in g t e m p er at ur es in S t age 2 t o st ar t cr ackin g, t e m p er at ur e ex cur s i o n s o ccur r e d at ab o u t 1 pm in Bed 4 o u t let o f React o r3 an d Bed 1 o u t let o f React o r1. A ddin g a d d i t i o n a l q u e n c h hy d r o g e n w a s n o t e ffe c t iv e in c o nt r o llin g t h e e x c u r s io n . F e e d w a s s t o p p e d a n d t h e 100 ps i / m inut e depr es s u r in g s y s t em was act iv at ed, r e s u l t in g in a gr as s f i r e at t h e f l ar e. So m e o f

t h e do cum e n t at i o n f

o rt h i s ev en t r e f e r e n ces t e m p er at ur e ex cur s i o n s in React o r2, so it i s n o t clearwh et h e rt h e ex cur s i o n o ccur r e d in t w o o rall t h r ee S t age 2 r eact o r s. M ar c h 19, 1996 On M ar c h 19, 1996, t h er e was a t e m p er at ur e ex cur s i o n in S t age 2, React o r1, wh i c h b e gan in B e d 3 an d pr o g r e s s e d t o B e ds 4 an d 5. Dur in g t h i s ex cur s i o n , t h e B e d 4 t e m p er at ur e was o v er 800 o F f

o r13 m inut es an d r each ed a ma x im u m o f 1000 o F
. T h e ma x im u m est ima t e d r eact o ro u t let t e m p er at ur e dur in g t h e ex cur s i o n was 920 o F
. T h e o p er at o r s di d n o t act iv at e t h e em er gen c y depr essur in g sy st em . T h e o p er at o r s st o pped o il f

eed t o React o r1 ab o u t 17 m inut es af t e rBed 3 o u t let t e m p er at ur e ex ceeded 800 o F an d ab o u t 3 m inut es af t e rt h e Bed 4 o u t let t e m p er at ur e ex ceeded 800 o F
. A b o u t 7 m inut es af t e rf eed was di sco nt inu ed, t e m p er at ur es at t h e o u t let o f Bed 4 b e gan t o f a ll
. Wi t h in an o t h e r6 m inut es, t h e r eact o ro u t let t e m p er at ur e b e gan t o f a ll
. A s a r e sul t o f

t h e in ci dent , t h e t e m p er at ur e co nt r o l gui del in es f o rS t age 2 r eact o r s wer e r e i ssued o n A p r il 4, 1996 t o t h e o p er at o r s , po s t ed o n t h e co nt r o l b o ar d an d r e v i ewed in s a f e t y m eet in gs . T h es e gui del in es wer e :

47( 1 ) M a x imu m a x ia l o rr a d i a l t e mp e r a t u r e d iffe r e nt ia ls in a

c a t a l ys t b e d mu s t b e h e ld t o le ss t h an 4 5 o F. ( 2 ) B ed in l e t t e m p er at ur e m u st b e r e duced if an y t e m p er at ur e r i ses 5 o F ab o v e n o r mal
. ( 3 ) O il f

eed t o a r eact o rm u st b e st o pped if an y po int i s 25 o F ab o v e n o r mal
. ( 4 ) T h e un i t m u s t b e depr es s u r e d at 300 ps i perm inut e if an y po int i s 50 o F ab o v e n o r ma l orov e r8 0 0 o F. J a nu ar y 19, 1997 At ab o u t 10: 20 pm o n Janu ar y 19t h , a t e m p er at ur e ex cur s i o n o ccur r e d in Bed 4 o f React o r1. T h e cen t e ro u t l et t e m p er at ur e in Bed 4 in cr eased f r o m 653 o F t o o v er800 o F dur in g a 20- m inut e per i o d
. Oper at o r s di d n o t act iv at e t h e em er gen c y depr essur in g sy st em . Dur in g t h i s ex cur s i o n , t h e aut o ma t i c quen c h co nt r o l was o v er r i dden an d m o r e quen c h f

l o w was added ma nu all y

t o B e ds 2 an d 4. Bed in l e t t e m p er at ur es cam e do wn , b u t t h e Bed 4 cen t e ro u t l et t e m p er at ur e co n t inued t o in cr ease t o m o r e t h an 800 o F as in di cat ed o n t h e co nt r o l b o ar d di spl a y . T h e No
. 2 Oper at o rwent o u t s i d e t o ch eck t h e f i el d pan e l an d r e po r t ed t e m p er at ur es in ex cess o f 900 o F
. F eed t o t h e r eact o r was st o pped an d f u el gas f l o w t o t h e t r im f

u r n ace was r e duced. A b o u t 5 m inut es af t e rpu llin g t h e o il f

eed, t h e Bed 4 cent e ro u t let t e m p er at ur e r each ed a ma x im u m o f 998 o F
. T h e t e m p er at ur e t h en d e c r e a s e d , fa llin g b e lo w 8 0 0 o F in ab o u t 1 m inut e. T h e o p er at o r s t h en co nt inued l o wer in g React o r 1 t e m p er at ur es t o 550 o F , an d r e int r o duced f eed appr o x ima t e l y

o n e h o url a t e r . S u p e r v is io n E m er gen c y depr essur in g was n o t em pl o y ed b e f o r e t h e expl o s i o n o n Janu ar y 21, ev en t h o ugh t h e o p er at o r s r eal i zed in t h e l a st f e w m inut es b e f o r e t h e expl o s i o n t h at t e m p er at ur es di d ex ceed 800 o F
. T h e o p er at o r s di d n o t h a v e aut h o r it y t o del a y t h i s deci si o n . Because o p er at o r s di d n o t act iv at e t h e r e qui r e d depr es s u r in g f o rt h i s an d pr i o rt e m p er at ur e ex cur s i o n s , s uper v i s o r y r o le s an d r e s p o n s i b ilit y fo re n fo r c in g p r a c t ic e s w e r e r e v i e w e d a s p o s s i b le r o o t c au s e s fo rt h is acci dent . T o sco ’ s Hy dr o c r ackerT r ain in g Manu al st at ed t h at No
. 1 Oper at o r s sh o u l d pr o v i d e leader sh i p f o r t h e r e st o f t h e o p er at o r s f o rwo r k an d per s o n al saf e t y , en v i r o n m ent a l pr o t ect i o n , en er gy co n s er v a t i o n an d ma int e n a n ce- co st co n t ain m ent . T h ey m u st t h o r o ugh l y

kn o w t h e o p er at i o n s o f t h e e n t i r e u n it t o p r o v id e p r o p e rg u i d a n c e a n d r e s o lv e p r o b le ms in a

t ime ly ma n n e r . T h e y mu s t b e ab l e t o r e spo n d t o em er gen c i e s in a cal m , co m p o s ed an d ef f ect iv e ma n n e r . T h e ma nu al al so s t a t e d t h a t “ H o w e v e r , s in c e t h e N o . 2 O p e r a t o r s h a v e a p r imar y r e s p o n s i b ilit y t o t e n d t o t h e equi pm ent , t h e No
. 1 Oper at o r s sh o u l d alway s giv e t h em f

i r s t ch an ce t o co r r ect an y pr o b le m s . T h e No
. 1 Oper at o rsh o u l d o n l y

int e r v en e wh en t h e sit u at i o n clear l y

call s f o rsuch act i o n s . T h e No
. 1 Oper at o r s wal k

a f in e l in e. T h ey sh o u l d b e o n t o p o f t h in gs an d pr o v i d e leader sh i p f o rt h e o p er at i o n o f t h e Co m p l e x , b u t t h ey sh o u l d alway s av o i d do in g t h e j o b s o f t h e No
. 2 Oper at o r s. ” T h e T r ain in g Manu al al so st at ed t h at t h e S t age 2 Bo ar d Oper at o ri s aut h o r i zed t o in i t i a t e e m e r g e n c y s t e p s fo rc o n t r o llin g a r u n a w a y r eact i o n wi t h o u t f i r s t co n s ul t in g wi t h

t h e No
. 1

48Oper at o r . T h e S t age 2 Bo ar d Oper at o ri s r e spo n si b le f o rt akin g deci siv e st eps t o m in im i ze t h e dan g ero f a r u n a way r eact i o n . I n

t h e ev ent o f a S t age 2 t e m p er at ur e ex cur s i o n , t h e E m er gen c y Oper at in g P r o cedur es st at ed t h at t h e No
. 1 Oper at o r s sh o u l d : 1) A d v i se S t age 2 Bo ar d Oper at o ras n eeded. 2) No t if y

t h e T r act - A F o r e ma n b y r a di o an d ask h im t o co o r din a t e t h e act iv i t i e s o f o t h e run i t s. T h e pr o cedur es f o r r e s p o n din g t o a t e m p er at ur e ex cur s i o n ( a s di s c us s e d in Sect i o n 3. 3. 3 o f t hi s r e po r t ) , wer e l i s t e d un dert h e sect i o n f

o rt h e S t age 2 Bo ar d Oper at o rin t h e E m er gen c y P r o cedur es. A l t h o ugh i

t i s t h e S t age 2 Bo ar d Oper at o rwh o wo ul d n o r mall y

act iv at e t h e depr essur in g sy st em , t h e No
. 1 Oper at o r s di d n o t en sur e t h at st an dar d o p er at in g o rem er gen c y pr o cedur es wer e f o ll o wed wh en t e m p er at ur es ex ceeded 800 o F o n Janu ar y 21 o ro n pr ev i o us o ccasi o n s . T h e S t age 2 Bo ar d Oper at o rst at ed t h at all qual if

i e d o p er at o r s h a v e aut h o r i t y

t o shut do wn t h e un i t an d ev er y o n e in t h e co nt r o l r o o m h a d t h i s aut h o r i t y . T o sco ma n a gem e nt st at ed in a m eet in g wit h in v e st i g at o r s t h at al t h o ugh t h ey kn ew o f t h e Janu ar y 19, 1997 t e m p er at ur e ex cur s i o n r i ght af t e ri t o ccur r e d, t h ey wer e n o t imme d i a t e l y a w ar e t h a t t h e t e m p er at ur e h a d go n e as h i gh as 900 o F
. T h e act ual t e m p er at ur e r eadin g was n o t wr it t e n o n an y o f

t h e o p er at o ro rsuper v i s o rl o gs. T h e P r o duct i o n A r ea S uper v i s o rst at ed in an in t e r v i e w t h at t o h i s kn o w le dge t h e 800 o F limit h a d n o t b e e n e x ceeded wh ile h e h a s b een super v i s o r . T h e P r o duct i o n A r ea S uper v i s o rst at ed t h at f a il u r e t o use t h e em er gen c y depr essur in g sy st em f

o ra t e m p er at ur e ex ceedin g 800 o F wo ul d b e co n s i d er ed a ser i o u s ma t t e ran d co ul d b e sub j ect t o di sci p l

in ar y act i o n al t h o ugh t o h i s kn o w le dge n o o p er at o rh a s ev erb een di sci p l

in ed f o rn o t in it ia t in g t h is a c t io n a s r e q u i r e d
. T h er e was n o f o r mal dele gat i o n o f aut h o r i t y

f

o rNo
. 1 Oper at o r s t o h a v e ma n a gem e nt r e s p o n s i b ilit ie s . T w o N o . 1 O p e r a t o r s w e r e o n s h ift t h e n i g ht o f t h e e xp l o s io n . T h e r e w a s n o wr i t t e n po l i c y f

o rdesi gn at in g wh o i s in ch ar ge o f o p er at i o n s wh en t w o No
. 1 Oper at o r s ar e o n t h e sam e sh if t . T h e s h ift s u p e r v is o rfo rt h e H y d r o c r a c k e rh a d r e s p o n s i b ilit y fo ro t h e ru n it s in h i s z o n e ( T o s c o ’ s r e f in e r y o p er at i o n s ar e div i ded in t o t h r ee zo n e s f o rma n a gem e n t pur po ses) an d was n o t alway s o n - s i t e at t h e Hy dr o c r acker
. T h e Hy dr o c r ackerUn it i s par t o f o n e zo n e , wh i c h al so in cl uded t h e f o ll o win g un i t s : No
. 3 HDS , No
. 3 Ref o r m er s , No
. 1 HDS , No
. 2 HDS , But a di en e, Ben zen e S a t u r a t i o n S y st em , Ref o r mat e F r act i o n a t i o n , A l kyl a t i o n P l ant , #2 Hy dr o g en , A P I S e par a t o r , W a st ewat erT r eat m e nt P l ant , No
. 1 I s o m er i zat i o n , MT BE pl an t , No
. 2 Ref o r m er . T r a ining T r ain in g f o rt h e Hy dr o c r ackero p er at o r s was r e v i ewed t o det e r m in e if o p er at o r s h a d t h e n ecessar y pr epar at i o n an d kn o w le dge t o o p er at e t h e Hy dr o c r ackerr eact o r s saf e l

y . T o sco ’ s Hy dr o c r acker T r ain in g P r o g r a m do cum e nt , dat e d M a y 1989, di s c us s e d r u n a way r eact i o n s an d h o w t o r e s p o n d t o t h em b y usin g t h e em er gen c y depr essur in g sy st em . 49T h e f o ll o win g gui del in es f o rdeal in g wi t h

an un co nt r o ll ab le t e m p er at ur e r i se ar e st at ed in t h e S t age 2 Co nt r o l Bo ar d sect i o n o f t h e t r ain in g ma nu al :

“ 1
. W h e n an y r eact o rt e m p er at ur e as in di cat ed b y t h e Mo o r e co nt r o ll e r s i s 5 o F ab o v e n o r mal , y o u m u st ch an ge t h e co nt r o l set po int s t o b r in g i t b ack t o n o r mal
. Co n s ul t t h e E m er gen c y P r o cedur es Manu al f

o rm e t h o d s t o acco m p l

i s h t h i s . 2. W h en an y r eact o rt e m p er at ur e as in di cat ed b y t h e Mo o r e co nt r o ll e r s i s r i sin g an d is 2 5 o F ab o v e t h e n o r mal t e m p er at ur e, y o u m u st pull t h e o il f

eed o u t o f t h e h o t r eact o r . Yo u can l eav e t h e o il in t h e o t h e rr eact o r s. 3. W h en t h e t e m p er at ur e co nt inues t o r i se an d i s 50 o F ab o v e n o r mal ( o rh a s ex ceeded 800 o F , wh i c h e v e ri s r each ed f i r s t ) , y o u m u s t act iv at e t h e 300 ps i / m in

depr es s u r in g sy st em an d dum p t h e co n t ent s o f t h e S eco n d S t age t o t h e f l ar e. A s t h e b o ar d per s o n , y o u ar e aut h o r i zed t o t ake t h ese st eps wi t h o u t f i r s t co n s ul t in g wi t h t h e No
. 1 Oper at o r . Yo u ar e r e spo n si b l e f o rt akin g deci siv e st eps t o m in im i ze t h e dama ge o f

a r u n a way r eact i o n . ” On e o f t h e Hy dr o c r ackero p er at o r s ( t h e n o n l o an t o t h e T r ain in g Depar t m e nt ) st at ed t h at m o st o f t h e t r ain in g f o rt h e Hy dr o c r ackero p er at i o n s i s o n - t h e - j o b t r ain in g in st ead o f cl assr o o m t r ain in g . E ach o p er at o rper f o r m e d a t a sk un derr e v i ew o f o t h e ro p er at o r s. Oper at o r s t o o k an an o r al ex am giv e n b y a super v i s o ran d sen i o rNo
. 1 Oper at o r s. Oper at o r s h a d n o f o r mal t r ain in g sessi o n s o n t h e S t age 2 ch an ge t o I /A sy st em , j u st o n - t h e - j o b t r ain in g , acco r d in g t o t h e P r o duct i o n A r ea S uper v i s o r . I n in t e r v i e ws, m o st o f t h e o p er at o r s st at ed t h at t h ey kn ew t h e co n d i t i o n s t h at r e qui r e d em er gen c y depr es s u r in g , b u t ackn o wledged t h at depr es s u r in g was r ar e l y used as r e qui r e d f o rex t r em e t e m p er at ur e ex cur s i o n s . T h i s o n - t h e - j o b pr act i ce un f o r t un at el y

ma y h a v e l ead o p er at o r s t o b e li e v e t h at t e m p er at ur e ex cur s i o n s co ul d usuall y

b e co n t r o ll e d wit h o u t usin g depr essur in g . Oper at o r s ma y n o t h a v e un der s t o o d t h e el ev at ed r i sk o f l o sin g co nt r o l o f t h e r eact i o n at t e m p er at ur es n ear800 o F , wh i c h i s why depr es s u r in g i s r e qui r e d. T r ain in g r eco r d s f o rt h e Hy dr o c r ackersh o w ed n o do cum e nt at i o n f

o run i t
- s pecif i c in i t i a l , s upplem ent a l o rr e f r es h e rt r ain in g . T h e Pr o duct i o n T r ain in g Super v i s o rs t at ed t h at Hy dr o c r acker un i t
- s pecif i c r e f r esh e rt r ain in g h a d n o t y e t b een dev e l o ped b ecause t h e T r ain in g Depar t m e nt was n o t s u r e wh at was r e qui r e d f o rr e f r es h e rt r ain in g . So m e t r ain in g t h at was co n duct e d dur in g t h e u t ilit y s h ift a n d w e e k ly s a fe t y me e t in g mig ht h a v e c o n s t i t u t e d r e fr e s h e rt r a in in g ( s u c h a s e m e r g e n c y p r o c e d u r e s a n d d r ills ) b u t t h is t r a in in g h a d n o t b e e n d o c u me nt e d a s r e fr e s h e rt r a in in g . S o m e o p er at o r s h a d r eceiv e d so m e r eact o rsaf e t y t r ain in g , wh i c h was giv e n b y a co n s ul t a nt . T h e t r ain in g in cl uded t h e causes an d pr ev ent i o n o f t e m p er at ur e ex cur s i o n s in hy dr o p r o cessin g r eact o r s. S ixo f T o sco ’ s 25 Hy dr o c r ackero p er at o r s, in cl udin g t w o wh o wer e o n t h e ev en in g sh if t o n Janu ar y 21, at t e n d ed t h i s t r ain in g . Oper at o r s wer e t o l d dur in g t h e t r ain in g t h at un ch ecked h o t spo t s co ul d r e sul t in cat ast r o p h i c f a il u r e s o f r eact o r s o rpi pin g .

50I t i s unkn o w n wh et h e rall Hy dr o c r ackero p er at o r s at T o sco r eceiv e d t r ain in g o n t h e f o ll o win g : o p er at in g wi t h

deact iv at ed cat al y s t , h o w t h e hy dr o g en pur i t y

an al y zero p er at ed, o rt h e im p act o f m

e t h an e f o r mat i o n in pr essur e co nt r o l o f r ecy cle gas. T h e o p er at o r s di d n o t kn o w t h at wh en t h e t e m p er at ur e o f t h e t h er m o co upl e went b e y o n d 1400 o F , t h e dat a l o ggerwo ul d s h o w zer o r eadin gs. E m e r g e n c y D e p r e s s u r in g S y s t e m R e liab ilit y On e o p er at o rst at ed t h at t h e depr essur in g sy st em do es n o t alway s wo r k r i ght an d i s n o t r e l i ab le. T h e Pr o duct i o n A r ea Super v i s o rs t at ed t h at t o h i s kn o w le dge, h e do es n ’ t b e l i e v e t h e depr es s u r in g sy st em can b e t e st ed, cer t a in l y

n o t o n - l in e. T h e Co nt r o l E n gin eerst at ed t h at t h e depr essur in g s y s t em can b e t e s t ed an d t h at i t was t e s t ed in 1986 wh en t h e un it was f i r s t b r o ught o n l

in e as a Un i c r acker
. He was n o t awar e o f an y t e s t s s in ce 1986, b u t h e s a i d h e wo ul d n o t b e expect ed t o b e in v o lv ed in s u b s equent t e s t s . T e s t in g pr o cedur es f o rt h e 100 an d 300 ps i / m in

depr es s u r in g s y s t em wer e des c r i b e d in t h e 1986 Un i c r ackerPr o ces s M a nu al , al t h o ugh T o s c o di d n o t in co r p o r at e t h em in t o t h ei ro p er at in g pr o cedur es. Oper at o r s h a d en co unt e r e d dif f i cul t i e s wh en t h e depr essur in g sy st em was act iv at ed f o r t e m p er at ur e ex cur s i o n s in t h e past . T h ese dif f i cul t i e s in cl uded gr ass f i r e s at t h e f l ar e ( J ul y

22 an d 23, 1992) an d a gen e r a t i o n o f a cl o ud o f f

l am mab le v apo r( J ul y

22, 1992)
. T h e 100 ps i / m in depr essur in g sy st em was aut o ma t i call y

act iv at ed o n Jul y

22 wh en t h e r ecy cle gas co m p r e sso r t r i pped. T h ese exper i en ces co ul d h a v e co nt r i b u t e d t o t h e o p er at o r s’ r e l u ct an ce t o em pl o y em er gen c y depr essur in g an d r e in f o r ced o p er at o r s’ deci si o n s t o h a n d le sev e r e t e m p er at ur e ex cur s i o n s b y o t h e rm ean s. P r o cedur es I n v e st i g at o r s r e v i ewed t h e Hy dr o c r ackerS t ar t up an d S hut do wn pr o cedur es, E m er gen c y pr o cedur es an d t h e S t an dar d Oper at in g P r o cedur es ( S OP )
. E m er gen c y pr o cedur es h a d n o t b een updat e d s in ce Oct o b e r1991. M o s t o f t h e SOPs h a v e n o t b een updat e d s in ce 1991. So m e o f t h e pr o cedur es di d n o t ma t c h equi pm ent an d in s t r u m e n t at i o n in t h e pr o ces s f l o w di agr a m ( P F D ) , pr o ces s an d in s t r u m e nt at i o n di agr a m s ( P & I Ds ) o rdi s c us s i o n o f equi pm ent in t h e HAZ O P s t udy
. Oper at o r s ma y n o t h a v e f o ll o wed wr i t t e n pr o cedur es if t h e pr o cedur es wer e o u t d at ed, n o l o n g er ma t c h e d pr o cess co n d it i o n s o requi pm en t , o rwer e n o l o n g err e le v a n t . Oper at o r s al so per f o r m e d s e ve r a l t a s k s f o rw h i c h t h e r e w e r e no w r i t t e n p r o c e d u r e s . On e ex am ple o f a m i s ma t c h e d pr o cedur e was in t h e E m er gen c y Oper at in g P r o cedur es f o rt h e sit u at i o n o f r eact o rt e m p er at ur es 5 o F o r2 5 o F ab o v e n o r mal
. I n t h i s case, t h e E m er gen c y Oper at in g P r o cedur es in st r u ct o p er at o r s t o add quen c h t o t h e r eact o rin le t b y act iv at in g F I C- 729 an d n o t t o add em er gen c y quen c h t o t h e r eact o ro u t let ( c h a in v a lv e)
. T h e pr o cess f l o w di agr a m an d P& I D o n l y

s h o w a h a n d

- o per a t e d quen c h f

l o w v a lv e af t e rB e d 5, ( H C

- 729A o n t h e PF D an d HV- 729A o n t h e P& I D )
. T h e HAZ O P s t udy ( s ee Sect i o n 3. 3. 4) s t at ed t h at an o p en o rleakin g em er gen c y in le t quen c h v a lv e HV- 729 co ul d caus e a dev i at i o n o f “ m o r e f l o w ” o f hy dr o g en t o 51r eact o r . Ho wev e r , t h e HAZ O P di d n o t i d ent if y

t h es e quen c h v a lv e( s ) HC- 729 o rHV- 729 specif i call y

as a m ean s t o co nt r o l eit h erh i gh t e m p er at ur e o r“ m o r e r eact i o n ” dev i at i o n s in t h e r eact o r . S o i t was n o t clearif quen c h co ul d b e added t o r eact o rin le t o ro u t let o rper h aps b o t h
. A n ex am ple o f a SOP t h at ma y h a v e n o l o n g erb een r e le v a nt was SOP#20 whi c h r e qui r e d t h at wh en o p er at o r s depr essur e d S t age 2 t h ey m u st f i r s t ma nu all y

cl o s e t h e makeup hy dr o g en co nt r o l v a lv e f r o m S t age 1 t o S t age 2 t o pr ev ent a depr essur in g o f S t age 1. T hi s v a lv e r e po r t edl y

wo ul d n o t cl o s e b ecaus e t h e co nt r o l v a lv e wi r in g was appar e nt l y

dama ged in M ar c h 1989 an d was n e v e r r e pai r ed. A cco r d in g t o desi gn , act iv at i o n o f t h e em er gen c y depr essur in g sy st em wo ul d au t o ma t i c a lly c l o s e t h is v a lv e . T o s c o ma n a g e me nt d i d n o t k n o w w h e t h e rt h is p r o c e d u r e w a s s t ill v a l i d as o f J a nu ar y 21. SOP #20 was un dat e d. T e mp e r a t u r e o p e r a t in g limit s v ar i e d a m o n g t h e d iffe r e nt d o c u me nt s p r o v id in g o p e r a t in g in s t r u c t io n s . F o re x a m p le , t h e H y d r o c r a c k e rO p e r a t in g L imit s d o c u me nt s t a t e d t h a t t h e S t a g e 2 r eact o ro u t let t e m p er at ur e ma x im u m i s 690 o F , wh ile S O P #9- React o rOper at i o n s - S um mar y o f L imit s a n d G u id e lin e s s t a t e d t h a t t h e S t a g e 2 r eact o rma x im u m o u t let i s 800 o F. T h e H y d r o c r a c k e rO p e r a t in g L imit s s t a t e d t h a t t h e t r im fu r n ace t u b e wall t e m p er at ur e ma x im u m i s 1000 o F , wh ile S O P #9 st at ed t h at t h e t r im f

u r n ace skin t e m p er at ur e i s 950 o F ma x imu m. T h e S t a g e 2 st ar t up pr o cedur es st at ed t h at n o b e d t e m p er at ur e r i se sh o u l d ex ceed 30 o F , wh ile SOP#5 & #9 st at ed t h at t h er e sh o u l d b e n o m o r e t h an 40 o F r i s e perb e d. I t i s as s u m e d t h at t h i s appl i e d f o rt h e ma x imu m a v e r a g e t e m p er at ur e dif f e r e n ce, s in ce SOP#25 s a i d t o us e av er age t e m p er at ur e o f t h e b e d in st ead o f t h e in div i dual po in t s wh en ev al uat in g t h e ma x im u m r eact o rb e d o u t l et t e mp e r a t u r e s . T h e in c o n s is t e nt t e mp e r a t u r e o p e r a t in g limit s c o u l d h a v e le d o p e r a t o r s t o n o t t ak e limit s s e r i o u s l y. SOP#5 dat e d M ar c h 8, 1990 s t at ed t h at Un o cal ’ s r eco m m

e n d at i o n calle d f o rn o m o r e t h an 30 o F t e m p er at ur e dif f e r e nt i a l perb e d, h o wev e r , i t n o t e d t h at T o sco ’ s exper i en ce h a d sh o w n t h at 40 o F p e rb e d w a s w e ll w it h in s a fe t y limit s . S O P # 5 n o t e d t h a t “ I n fa c t o f t e n t ime s w e mu s t o p e r a t e w it h such a h i gh del t a t e m p er at ur e t o b a l a n ce o u t cr ackin g in t h e en t i r e r eact o rsy st em . ” But t h i s S O P al so st at ed t h at “ A r eact o rb e d w ill b e c o me in c r e a s in g l y u n s t ab le a s t h e b e d d iffe r e nt ia l t e m p er at ur es get h i gh eran d h i gh er . A b e d can dev e l o p r u n a way r eact i o n s an d o n e w ill h a v e a d a ng e r o u s s it u a t i o n o n ha nd
. ” I n

a T ech n i cal Ser v i ces m e m o r a n dum dat e d A p r il 4, 1996, n e w o p er at in g gui del in es f o rSt age 2 r eact o r s wer e pr o p o s ed b a sed o n t e m p er at ur e dat a f

r o m addit i o n al t h er m o co upl es in st all e d in J a nu ar y 1996 an d t h e M ar c h 19, 1996 t e m p er at ur e ex cur s i o n . On e o f t h e gui del in es was t o ma in t a in a

ma x imu m 4 5 o F r a di al an d 45 o F a x ia l t e mp e r a t u r e d iffe r e nt ia l. T h e 4 5 o F ma x imu m t e m p er at ur e dif f e r e nt i a l appl i e d t o b o t h co nt r o l r o o m an d f i el d r eadin gs. I n

M ar c h o f 1996, T ech n i cal S e r v i ces n o t e d t h at React o r1 Bed 1 o u t let r a di al dif f e r e nt i a l t e m p er at ur es r e ma in ed as h i gh as 54 o F
. I n J u n e o f 1996, T ech n i cal Ser v i ces en gin eer s f o un d t h at f iv e o u t o f f

if

t een S t age 2 r eact o rb e ds h a d ax i a l an d r a di al dif f e r e n t i a l t e m p er at ur es gr eat ert h an

5245 o F
. I n J u l y

1996, T ech n i cal Ser v i ces r e po r t ed t h at f iv e b e ds h a d ma x im u m t e m p er at ur e dif f e r e nt i a l s b e t w een 45- 55 o F a n d t w o b e d s h a d ma x imu m t e mp e r a t u r e d iffe r e nt ia ls ab o v e 5 5 o F. T h e r e w e r e o t h e rin d i c a t io n s t h a t o p e r a t o r s p e r h ap s c o u l d n o t a lw a ys s t a y w it h in o p e r a t in g limit s o rf o ll o w wr it t e n pr o cedur es. S O P #2 st at ed t h at t h e quen c h v a lv es in t h e S t age 2 sh o u l d n o t b e o p en ed up m o r e t h an 50% ( o rm o r e t h an 75% f o rB e d 4, whi c h h a s a b i ggerquen c h v a lv e)
. B u t t h e S O P al so sai d t h at t h e quen c h v a lv es ma y h a v e t o b e o p en ed up t o o m u ch in o r dert o ma int a in a f l at t e m p er at ur e pr o f ile f o rt h e cat al y s t b e ds ( t h a t i s , keepin g t h e o u t let t e m p er at ur es f r o m all b e ds as cl o s e t o each o t h e ras po ssi b le)
. S o m e o p er at o r s expl ain e d a dif f e r e nt pr o b le m wit h t h e quen c h v a lv es; al t h o ugh t h e co nt r o l b o ar d set t in g in di cat ed t h ey ar e cl o s ed, so m e hy dr o g en f

l o w wo ul d co nt inue. T o co m p en sat e f o rt h e quen c h v a lv e leakin g, o p er at o r s wo ul d o p er at e t h e b e d ab o v e each quen c h v a lv e at h i gh erb e d o u t let t e m p er at ur es. W r i

t t e n pr o cedur es ( S OP #2) di r ect ed o p er at o r s t o ma int a in sam e o u t let t e m p er at ur es f o reach b e d, b u t st at ed t h at t h i s i s r ar e l y

po ssi b l e b ecause t h e t r im f

u r n ace was usuall y

a limit a t io n ( f ir in g t o o h ar d )
. So m e o p er at in g pr act i ces wer e le f t up t o o p er at o rj udgm ent an d di s c r e t i o n , s in ce t h er e wer e n o wr it t e n pr o cedur es f o r :

& Oper at in g wi t h

deact iv at ed cat al y s t & S hut do wn o f o n e r eact o ran d t r an sf er en ce o f it s f eed int o t w o par a lle l r eact o r s & Deal in g wi t h

leakin g h eat ex ch an ger s dur in g st ar t u p & Oper at in g r eact o rwi t h o u t t h e dat a l o ggerf u n c t i o n in g & Readin g t e m p er at ur es at o u t s i d e f i el d pan e l
& S a f e l

y

o p e r a t in g d u r in g p o s s i b le in s t ru m e nt ma lf u n c t i o n o rw h e n t e m p e r a t u r e in di cat i o n s wer e j udged unr e l i ab le. & Rai s in g b e d t e m p er at ur es t o co m p en sat e f o rleakin g quen c h v a lv es. T h e P r o duct i o n T r ain in g S uper v i s o rin t h e P r o duct i o n Depar t m e nt st at ed t h at t h e Hy dr o c r acker do es n o t h a v e all o f i

t pr o cedur es f o r mal i zed o rin cl uded in T o s c o ’ s pr o cedur e ma n a gem e nt sy st em . I n int e r v i e ws, T o sco ma n a gem e nt ackn o wledged t h at t h e o p er at in g pr o cedur es ar e in co m p le t e . Updat e d pr o cedur es f o rt h e Hy dr o c r ackerh a d n o t y e t b een dev e l o ped. P r o cedur es f o rt h e Hy dr o c r ackerUn i t S t age 2 wer e n o t kept cur r e nt wi t h

ch an ges in pr o cess, equi pm ent o ro p er at in g pr act i ces an d di d n o t appeart o h a v e b een t e st ed f o rint e gr at i o n in t h e o p er at in g en v i r o n m ent . F o rex am ple, t h e wr i t t e n pr o cedur es wer e n o t updat e d t o r e f lect in st all a t i o n o f t h e I /A sy st em , in cl udin g t h er m o co uples added in t h e r eact o r s, t h e t e m p er at ur e f i el d pan e l s in st alle d un der n eat h t h e S t age 2 r eact o r s, an d t e m p er at ur e di spl a y h ar d war e in t h e Hy dr o c r ackerco nt r o l r o o m . I n an o t h e rex am ple, M O C #15004 in di cat ed t h at a ch an ge in o p er at in g pr o cedur es was r e qui r e d b u t t h e wr i t t e n pr o cedur es wer e n o t updat e d. T hi s M O C in v o lv ed makin g a pi pin g ch an ge s o t h at hy dr o g en can b e s uppl i e d t o HDS/HDA Un i t ( s ee F i gur e 2) f r o m #2 Hy dr o g en Pl ant wh en t h e #1 Hy dr o g en Pl ant i s do wn . I n F e b r uar y o f 1996, t h e cat al y s t in all t o p b e ds o f S t age 2 wer e r e pl aced wi t h

a m o r e r eact iv e cat al y s t . No ch an ges wer e

53ma de t o t h e wr i t t e n o p er at in g pr o cedur es t o r e f lect t h e cat al y s t ch an ge an d t h e in cr eased r i sk o f t e m p er at ur e ex cur s i o n s due t o in cr eased r eact iv it y . T h e wr i t t e n pr o cedur es di d n o t addr ess t h e po t e nt i a l h azar d f o rr eadin g t e m p er at ur es at t h e o u t s i d e pan e l s wh en r eact o rt e m p er at ur es ex ceeded o p er at in g limit s . T h e p r o c e d u r e s d i d n o t co n s i d erhu ma n f

act o r s such as in co r r ect act s, act s o u t o f sequen ce, f a il u r e t o t ake act i o n , an d act s t aken wh i c h wer e n o t appr o p r i at e o rn ecessar y . Reco m m

e n d at i o n s f r o m in ci den t in v e st i g at i o n s wer e n o t in co r p o r at ed in t o wr it t e n pr o cedur es. F o rex am ple, t h e r eco m m

e n d at i o n s sh o w n b e l o w em er ged f r o m t h e A d v e r s e Happen in g Repo r t o f J u l y

23, 1992 an d wer e dr af t e d int o SOP#49 b u t t h e dr af t was n o t f o r mall y

appr o v ed an d in co r p o r at ed int o pr o cedur es.

• L imit p r e - c r a c k in g b e d in le t t e mp e r a t u r e in c r e a s e s t o 2 0 o F perh o ur . • O n c e c r a c k in g h a s b e e n in it ia t e d , limit b e d in le t t e mp e r a t u r e in c r e a s e s t o 1 0 o F per h o ur . • L imit a n y s in g le b e d in le t t e mp e r a t u r e in c r e a s e t o 2 o F ma x imu m p e rmo v e . • L imit t h e R eact o r3, Bed 4 t e m p er at ur e dif f e r e nt i a l t o a ma x im u m o f 25 o F.
• A ft e rc r a c k in g h a s b e e n in it ia t e d , limit R eact o r3, Bed 4 in le t t e m p er at ur e in cr eases t o h a lf t h e ab o v e r eco m m

e n d ed v a l u es f o rt h e o t h e rb e ds. I t appear s t h at ex cess h eat t r an sf er r e d f r o m t h e b e ds ab o v e t e n d t o b o o s t t h e in le t t e m p er at ur e o f t h e n e x t l o wer b e d m o r e t h an des i r e d, e. g. a 2 o F ch an ge can easil y

b e b o o s t e d t o a 3- 5 o f o rev en h i gh erin cr ease. • D o n o t r a i s e React o r3, Beds 2 an d 4 in le t t e m p er at ur es at t h e sam e t im e . • L o o k int o t h e adequacy o f t h e b e d in le t t e m p er at ur e co nt r o lle r s . I n

J a nu ar y 1992, a m o r e r eact iv e cat al y s t was in s t alle d in t h e S t age 2 r eact o r s . . A t e m p er at ur e ex cur s i o n o n J u l y

23, 1992 r e s u l t ed in s ugges t i o n s o n t h e A d v e r s e Happen in g R e po r t t o r a i s e t e mp e r a t u r e s in S t a g e 2 a b it s l o w e rn e x t t ime a s t h e n e w c a t a l ys t is s t ill “ h o t . ” S a f e t y an d P e r f o r ma n ce Go al s On e n e gat iv e co n s equen ce o f us in g t h e 300 ps i /m in

depr es s u r in g s y s t em i s t h at i t co m p le t e l y

s hut s do wn s t h e S t age 2 r eact o r s, h a l t in g pr o duct i o n . On e o p er at o rst at ed t h at t h er e i s a l o t o f expect at i o n f

r o m t h e E n gin eer in g Depar t m e nt t o pr o duce b ar r e l s an d keep up t e m p er at ur es. T o sco ma n a gem e nt st at ed t h at t h ey di d n o t kn o w why o p er at o r s di d n o t depr essur e S t age 2 dur in g past t e m p er at ur e ex cur s i o n s . T h ey st at ed t h at per h aps t h e o p er at o r s t o o k pr i d e in keepin g t h e un i t o p er at i o n a l
. T o s c o ma y h a v e h a d p r o b le ms b a la n c in g p r o d u c t i o n g o a l s w it h ma in t a in in g s a fe t e mp e r a t u r e limit s . B ecause o f t h e f i r in g limit a t io n s o f t h e t r im fu r n aces; so m e t im e s b e d t e m p er at ur es wo ul d h a v e t o b e in cr eas ed t o co m p en s a t e f o rt h e h eat n eeded. I n M ar c h o f 1996, T ech n i cal Ser v i ces st at ed t h at t o r e duce h i gh b e d t e m p er at ur e dif f e r e nt i a l s , t r im f

u r n ace f i r in g wo ul d h a v e t o b e 54in cr eased t o ma int a in t h e desi r e d r eact i o n co n v e r s i o n l e v e l
. Ho wev e r , t h ey al so n o t e d t h at wit h ch ar ge r a t e s ab o v e 32 MBP D , t h er e was l i t t le capacit y l e f t in t h e t r im f

u r n aces wit h o u t r e ducin g r a t e o rin cr eas in g di es el pr o duct i o n . On A p r il 11, 1996, T ech n i cal S e r v i ces ackn o wledged t h at po o rS t age 2 r eact o rs t ab ilit y w o u l d pr o b ab l y

n o t all o w t h em t o ach i e v e le ss t h an 0. 5% b u t a n e co nt ent in t h e l i g ht hy dr o c r ackat e pr o duct
. I n

J u l y

1996, T ech n i cal Ser v i ces r e po r t ed t h at o p er at o r s wer e n o t ab le t o r e duce di es el pr o duct i o n t o t ar g et le v e l s due t o S t age 2 React o rb e d t e m p er at ur e dif f e r e nt i a l s . F iv e b e ds h a d ma x imu m t e mp e r a t u r e d iffe r e nt ia ls b e t w e e n 4 5

- 5 5 o F a n d t w o b e d s h a d ma x imu m t e mp e r a t u r e d iffe r e nt ia ls ab o v e 5 5 o F
. T h e ma x imu m t e mp e r a t u r e d iffe r e nt ia l limit is 4 5 o F. S uper v i s o r s an d o p er at o r s di d n o t appeart o h a v e b een giv e n gui dan ce t o r e so lv e co n f l i c t s b e t w een saf e t y an d per f o r ma n ce go al s. F o rex am ple, n o gui dan ce was giv e n o n h o w t o ach i e v e desi r e d pr o duct i o n r a t e s wi t h in specif i cat i o n wi t h o u t ex ceedin g o p er at in g limit s s u c h a s ma x imu m b e d t e m p er at ur e dif f e r e n t i a l s an d ma x im u m t r im f

u r n ace f i r in g . Oper at o r s f e l

t t h at t h ey wer e expect ed t o keep t h e Hy dr o c r ackero p er at i o n a l un dera nu m b ero f adv e r s e o p er at in g co n d it i o n s . F o rex am pl e, o p er at o r s wo ul d get dat a o n l y

f

r o m co n t r o l b o ar d st r i p ch ar t s ( d at a f r o m Mo o r e co nt r o ll e r s ) , wh en t h e dat a l o ggerwas n o t f u n c t i o n in g. On e o p er at o rf e l

t t h at t h ey wer e “ r un n in g b l in d” wh en t h ey r e l i e d o n l y

o n cent e rpo int r eadin g f r o m t h e Mo o r e co nt r o ll e r . S e v e r a l o ccur r e n ces o f S t age 2 r eact o ro p er at i o n s co nt inuin g despit e in s t r u m e nt ma lf un ct i o n wer e pr ev i o us l y

di s c us s e d in Sect i o n 3. 3. 3. 1. T h e P r o duct i o n A r ea S uper v i s o rsai d t h at r e l yin g o n l y

o n t e m p er at ur e dat a f

r o m t h e co nt r o l b o ar d wo ul d n o t b e an accept ab le si t u at i o n ; t h i s wo ul d b e in suf f i ci ent in f o r mat i o n t o o p er at e t h e r eact o r an d t h e r eact o rwo ul d h a v e t o b e shut do wn . T h i s super v i s o rsai d h e was n o t awar e o f an y per i o d in

J a nu ar y 1997 wh en b o t h t h e t e m p er at ur e l o ggeran d t h e I /A wer e n o t f u n c t i o n al at t h e s a m e t ime
. T h e r eact o rf eed/ e f f l uent h eat ex ch an gerf l an ges t e n d ed t o leak dur in g ev er y st ar t up b ecause o f t h er ma l st r e ss o n t h e pi pin g . T h ese l eaks so m e t im e s r e sul t ed in sm o k in g an d v apo rcl o uds. Oper at o r s wo ul d use st eam r in g s ( s h r o uds) an d st eam l a n ces t o di sper se v apo r s at t h e leakin g f l an ges. T h e st agin g in f

r o nt o f t h e S t age 2 ex ch an ger s was used b y o p er at o r s t o at t ach st eam l a n ces. 3. 3. 4 P r o ces s Haz a r d Anal ys is ( P HA) A

pr o cess h azar ds an al y s i s ( P HA ) t ech n i que kn o w n as a h azar d an d o p er ab ilit y s t u d y ( H AZ O P ) was per f o r m e d f o rSt age 2 dur in g t h e per i o d J u n e 1 t h r o ugh J u l y

31, 1994 ( b as el in e)
. T h e pur po se o f a P H A i s t o i d ent if y

saf e t y h azar ds an d o p er ab ilit y p r o b le ms , a s s o c i a t e d c au s e s a n d

55co n s equen ces, saf e guar d s, an d r i sks. T h e an al y s i s h e l p s det e r m in e wh er e im p r o v e m e nt s t o t h e pr o cess desi gn an d o p er at i o n ar e n eeded. T h e 1994 S t age 2 HAZ O P was r e v i ewed b y in v e s t i g at o r s t o s ee if t h e s a f e t y h azar ds in v o lv ed in t h e Janu ar y 21 acci den t h a s b een i d ent if i ed, an d if so , h o w t h ey wer e addr essed. T h i s was do n e t o det e r m in e if so m e def i ci en cy in t h e HAZ O P co nt r i b u t e d t o t h e acci dent . T h e HAZ O P st udy in cl uded St age 2 equi pm ent an d as s o ci at ed pi pin g , whi c h wer e div i ded int o di s c r e t e n o des f o r sy st emat i c an al y s i s . F o reach h azar d scen ar i o i d en t if i ed in t h e HAZ O P , saf e guar d s wer e i d ent if i ed, wh i c h in cl uded b o t h ma nu al an d aut o ma t i c m ean s f o rdet ect in g, pr ev ent in g , o r m

i t i g at in g t h e i d ent if i ed h azar d. Reco m m

e n d at i o n s wer e ma de b y t h e HAZ O P t eam wh en ex i s t in g saf e guar d s wer e n o t co n s i d er ed adequat e . On e o f t h e st at ed assum p t i o n s f o rt h e HAZ O P was t h at t h e b a sel in e HAZ O P t o o k cr edit f o r pr o cedur es b e in g in pl ace. T h e 1994 HAZ O P al s o s t at ed t h at “ H o w ev er , n o t all o f t h e un it pr o cedur es h a v e b een co m p l e t e d. T h e o p er at i o n s r e pr esen t a t iv e i s assi st in g in t h e dev e l o pm ent o f un i t pr o cedur es . ” On e o f t h e st at ed assum p t i o n s t h at was appl i e d t h r o ugh o u t t h e HAZ O P st udy was t h at “ t h e I /A s y s t e m p r o v id e s a g r e a t d e a l o f fle x ib ilit y w it h a l ar ms a n d in d i c a t io n s fo rt h e o p e r a t o r s . T h is st udy co n s i d er ed o n l y

t h o s e al ar m s an d co n t r o l in di cat i o n s n o t e d o n t h e P & I D s. ” I t i s n o t cl ear wh et h e rt h e HAZ O P t eam assum e d use o f t h e S t age 2 I /A t e m p er at ur e m o n it o r in g sy st em , wh i c h was n o t y e t in pl ace. Ho wev e r , t h e P & I D s o n l y

in cl uded t h o s e t e m p er at ur e in di cat i o n s , al ar m s , an d co nt r o l s asso ci at ed wit h t h e dat a l o ggeran d Mo o r e co nt r o lle r s / in d i cat o r s. T h e P r o cess Hazar d A n al y s i s M a n a ger( w h o was n o t P H A M a n a gerwh en t h e 1994 P H A was do n e ) co ul d n o t cl ar if y

wh et h e ruse o f t h e I /A sy st em h a d b een assum e d b y t h e S t age 2 HAZ O P t eam . I n

an y case, t h e I / A sy st em was n o t r e l i ab l y

f

u n c t i o n al in S t age 2 an d was n o t used t o pr o v i d e t e m p er at ur e in di cat i o n s at t h e t im e o f t h e pr epar at i o n o f t h e PHA in 1994. T e m p er at ur e al ar m s t h at wo ul d h a v e b een av ail ab le wit h t h e I /A sy st em wer e n o t in f

act av ail ab le t o t h e o p er at in g em pl o y ees at t h e t im e t h e P H A was pr epar ed. T h e I / A sy st em pr o v i d ed t e m p er at ur e r eadin gs b u t was n o t a co nt r o lle ro f t h e b e d t e m p er at ur es f o rS t age 2. T h e l e v e l o f det a il in t h e HAZ O P saf e guar d s f o rS t age 2 r eact o r s wer e n o t specif i c as t o wh i c h t y

pe o f in st r u m e nt co nt r o l sy st em s wer e in pl ace. I t o n l y

specif i ed wh et h e rt h er e was, f o r ex am ple, an al ar m , f l o w in di cat o ro raut o ma t i c o rma nu al co nt r o lle rt o co nt r o l t h e pr o cess par a m e t e r . F o rex am ple, f o rh i gh err eact o rt e m p er at ur es, o n e o f t h e saf e guar d s l i s t e d was t h at t e m p er at ur e al ar m s wer e av ail ab le f o rall b e ds. I t was n o t specif i ed wh et h e rt h ese al ar m s wer e co n n ect ed t o t h e dat a l o ggero rt h e I /A sy st em . A l ar m s wer e n o t in st alle d f o rt h o s e t e m p er at ur e po in t s t h at wer e r ead at t h e f i el d pan e l ; h o wev e rt h e f i el d pan e l s wer e n o t in pl ace in 1994 wh en t h e HAZ O P was do n e . A n o t h e rassum p t i o n st at ed f o rt h e HAZ O P was t h at t h e r e sul t s o f a cat ast r o p h i c f i r e at t h e Hy dr o c r ackerUn it wer e n o t addr essed in t h e HAZ O P
. T h e l o ss o f in div i dual co m p o n ent s o rt h e 56ef f ect o n in div i dual pi eces o f equi pm en t wer e di scussed, as wer e t h e ef f ect s o f l o ss o f a r eact o r , e t c . T h e H AZ O P t e a m a s s u me d t h a t fir e d e t e c t io n w a s limit e d t o o p e r a t o ro b s e r v a t io n a n d t h a t t h er e wer e n o f ix e d hy dr o g en sulf i d e o rco m b ust i b le gas det ect o r s in t h e un i t . T h e HAZ O P t eam assum e d t h at m o st o f t h e ar eas o f t h e pl ant wer e pr o t ect ed an d co ul d b e accessed wi t h

f

i r e m

o n i t o r s an d wi t h

o t h e rf i r e f i ght in g equi pm ent . T h e HAZ O P l i s t e d h i gh ert e m p er at ur e as a po ssi b le dev i at i o n in t h e o p er at i o n o f a r eact o r . T h e causes f o rh i gh ert e m p er at ur e i d ent if i ed wer e l o ss o f quen c h co nt r o l , h i gh in le t f eed t e m p er at ur e, c h a n n e l in g d u e to c o k in g orp oorinte r - b e d d i s t r i b u ti on , r e d u c ti on in hy d r og e n f

l ow oroil f

l ow f o r an y r easo n . T h e po ssi b le co n s equen ces l i s t e d f o rh i gh err eact o rt e m p er at ur es wer e o p er at i o n a l upset ; po ssi b l e r eact o rt e m p er at ur e ex cur s i o n , po ssi b le un it shut do wn , cat al y s t co kin g an d po ssi b le r eact o rdama ge r e sul t in g in f

i r e . S a f e guar d s l i s t e d f o rt h ese co n s equen ces wer e ma nu al ma n i p u l a t io n o f q u e n c h flo w c o n t r o l v a lv e s , b e d t e mp e r a t u r e a l ar m a v a ilab ilit y, au t o ma t i c q u e n c h f l o w in cr ease, aut o ma t i c t r im f

u r n ace o u t l et t e m p er at ur e co nt r o l , av ail ab ilit y o f o il flo w a n d v a lv e po si t i o n in t h e co nt r o l r o o m , an d o p er at o rem er gen c y pr o cedur es in pl ace. Depr essur in g o ruse o f t h e em er gen c y quen c h was n o t specif i call y

m e nt i o n e d as a saf e guar d
. T h e HAZ O P assum e d pr o p er l y

f

u n c t i o n in g equi pm ent an d per s o n n e l an d di d n o t t ake int o acco unt hu ma n an d o t h e rf act o r s such as t h o s e i d ent if i ed in t h e Janu ar y 21 acci dent , wh i c h in cl uded in s t r u me nt p r o b le ms , d a t a mis int e r p r e t a t i o n , fa ilu r e t o fo llo w p r o c e d u r e s , a n d a l ar ms n o t act iv at in g. T h e Janu ar y 21 acci dent n o t o n l y

in v o lv ed h i gh ero p er at in g t e m p er at ur es, b u t a r api dl y accel er at in g hy dr o c r ackin g r eact i o n . F o r“ m o r e r eact i o n ” dev i at i o n in t h e r eact o r s, saf e guar d s in t h e HAZ O P wer e l i s t e d as 1) nu m e r o us co m p r e sso ral ar m s av ail ab le in co nt r o l r o o m , 2) r eact o r b e d t e m p er at ur e dev i at i o n al ar m s in co nt r o l r o o m , 3) quen c h f

l o w co nt r o lle r s can b e ma nu all y ma n i pul at ed an d 4) t e m p er at ur e in di cat o ran d al ar m was av ail ab le f o rt e m p er at ur e dev i at i o n o f t r im f

u r n ace o u t let hy dr o g en . Man i pul at in g quen c h ma y co nt r o l t h e r eact i o n if

t e m p er at ur es h a v e n o t go n e t o o h i gh , b u t o n l y

if

t h e o p er at o r s h a v e t h e dat a r eadil y

accessi b le t o t h em t o t ake t im e l

y act i o n . E m er gen c y pr o cedur es , depr es s u r in g o rus e o f t h e em er gen c y quen c h wer e n o t m e nt i o n e d as a saf e guar d again s t ser i o u s co n s equen ces. F o rh i gh ert e m p er at ur es in f

l o w f r o m t h e S t age 2 r eact o r s t h r o ugh t h e f eed/ e f f l uent ex ch an ger s , t h e causes l i s t e d in t h e HAZ O P wer e h i gh ert e m p er at ur e upst r eam , o p en b y pass v a lv e f o r ex ch an gerf eed, an d f o ul ed o rpl ugged ex ch an ger s . T h e co n s equen ces l i s t e d wer e h i gh er ex ch an geref f l uent t e m p er at ur es, po ssi b le in cr eased t r im f

u r n ace f i r in g an d po ssi b le r a t e r e duct i o n . C o n s equen ces o f pi pe r upt ur e, expl o s i o n an d f i r e ( s uch as t h o s e t h at o ccur r e d o n J a nu ar y 21) wer e n o t i d en t if i ed. S a f e guar d s li s t e d wer e o p er at o rm o n it o r in g o f r eact o ro u t l et t e m p er at ur es an d l o cal ex ch an gero u t let t e m p er at ur e gauge. T h e t e m p er at ur e al ar m sy st em ( s uch as t h e r eact o r o u t let h i gh t e m p er at ur e al ar m ) o rdepr essur in g wer e n o t l i s t e d as po ssi b le saf e guar d s. T h e HAZ O P addr essed l o ss o f o il f

l o w upst r eam as po t e nt i a ll y

causin g a h i gh t e m p er at ur e wav e in

t h e S t age 2 r eact o r s an d i d ent if i ed as a s a f e guar d t h e “ aut o mat i c act iv at i o n o f t h e 100 ps i / m in 57d e p r e s s u r in g s t a t io n . ” T h is s a fe g u ar d is in fa c t n o t au t o ma t i c a lly a c t iv a t e d fo rlo s s o f o il flo w t h

r o ugh t h e r eact o r s , b u t r e qui r e s o p er at o rint e r v ent i o n t o ma nu all y

act iv at e t h e 100 ps i / m in depr es s u r in g s t at i o n . T h e 100 ps i /m in

depr es s u r in g s y s t em i s o n l y

aut o ma t i call y

act iv at ed if t h e IIRc o m p re s s o r f a il s . T h e HAZ O P was n o t updat e d t o co n s i d erHy dr o c r ackerdes i gn ch an ges in cl udin g t h e ch an ge o f c o n t r o l r o o m e q u i p m e n t , a d d it i o n o f fie l d t e mp e r a t u r e in d i c a t o r s a n d me t h o d s o f c o nt r o llin g t e m p er at ur e. I n gen e r a l , hu ma n f

act o r s wer e n o t addr essed as par t o f P r o cess Hazar d A n al y s i s . T h e h azar d an al y s i s di d n o t co n s i d ert h e co n s equen ces o f t h e f a il u r e o f t h e dat a l o gger , t h e co nt r o l r o o m t e m p er at ur e m o n i t o r in g s y s t em o rt h e100 an d 300 ps i /m in

em er gen c y depr es s u r in g sy st em s. 3. 3. 5 I n- P l antE m er gency Not i f i cat i on Man y co nt r act o r s wo r k in g n earb y wer e in j u r e d o n Janu ar y 21 as t h e r e sul t o f b e in g in t r aile r s l o cat ed le s s t h an 100 f eet f r o m t h e Hy dr o c r ackerUn i t r eact o r s . T h es e co nt r act o rt r aile r s wer e n o t desi gn ed t o wi t h st an d expl o s i o n an d f i r e . Oper at o r s in si de t h e co nt r o l r o o m di d n o t n o t if y co nt r act o rper s o n n e l o f t h e po t e nt i a l expl o s i o n h azar d o rso un d an em er gen c y al ar m . T h e E m er gen c y Oper at in g pr o cedur es st at e t h at if a S t age 2 r eact o rt e m p er at ur e i s 50 o F ab o v e n o r mal , o rex ceeds 800 o F , t h e S t age 2 Bo ar d Oper at o rsh o u l d h it t h e “ s ixsh o r t s ” al ar m . S ixsh o r t b l ast s o f

t h e un it call h o r n in di cat e t h at t h e pr o cess un it i s exper i en cin g so m e t y pe o f o p er at i o n a l pr o b le m t h at co ul d pr esent dan g ert o t h e peo p le wo r k in g in t h e un i t . Co nt r act o r s ar e t r ain e d t h at w h e n t h e p r o c e s s u n it e m e r g e n c y a l ar m is s o u n d e d , t h e y s h o u ld imme d i a t e l y s t o p w o r k , s hu t d o w n all i g n i t i o n so ur ces an d pr o ceed v i a a saf e r o ut e t o a desi gn at ed ev acuat i o n ar ea. 

### 4. 0 Cau ses o f th e Jan u ary 21 Accid en t Based o n all t h e in f o r mat i o n co llect ed an d an al y s i s o f dat a , in v e st i g at o r s det e r m in ed t h e causes o f t h e pi pe r upt ur e an d t h e t e m p er at ur e ex cur s i o n . Fu r t h e ran al y s i s o f pr o cess saf e t y ma n a gem e nt pr act i ces an d o t h e rin f o r mat i o n gat h er ed dur in g t h e in v e st i g at i o n was used b y in v e st i g at o r s t o det e r m in e t h e r o o t causes an d f act o r s wh i c h co nt r i b u t e d t o t h e f a il u r e t o co n t r o l t h e t e m p er at ur e ex cur s i o n an d co nt r i b u t e d t o t h e o ccur r e n ce o f t h e f a t a l i t y

an d in j u r i es o n Janu ar y 21, 1997. 4. 1 C aus e of the P i pe R uptur e T h e imme d i a t e c au s e o f t h e hy d r o c arb o n r e le a s e a n d s u b s e q u e nt fir e w a s a fa ilu r e a n d r u p t u r e o f a S t age 2 React o r3 ef f l uent pi pe due t o ex ces s iv e l y

h i gh t e m p er at ur e, l i k el y

in ex ces s o f 1400 0 F. T h i s h i gh t e m p er at ur e was in i t i a t e d b y a r eact o rt e m p er at ur e ex cur s i o n t h at b e gan in Bed 4 o f React o r3 an d spr ead t h r o ugh t h e n e x t cat al y s t b e d, Bed 5. T h e ex cessiv e h eat gen e r a t e d in Bed 5 r a i s ed t h e t e m p er at ur e in t h e r eact o ref f l uent pi pe. T h e ex cur s i o n was n o t b r o ught un der

58co nt r o l b ecause t h e S t age 2 r eact o r s wer e n o t depr essur e d an d shut do wn as r e qui r e d wh en t h e r eact o rt e m p er at ur es ex ceeded all o wab le limit s ( 8 0 0 o F)
. 4. 2 C aus e of t h e T e m p er at ur e E x cur s ion W h en h eat gen e r a t e d f r o m a hy dr o c r ackin g r eact i o n i s n o t un if o r m l y

di ssi pat e d acr o ss t h e cat al y s t b e d, an ar ea o f h i gh ert e m p er at ur e i s cr eat ed ( a h o t spo t ) , wh i c h can acceler at e t h e r eact i o n r a t e in t h at ar ea an d in t u r n , cr eat e m o r e h eat . On Janu ar y 21, a h o t spo t appar e nt l y

o ccur r e d in Bed 4 o f React o r3 wh i c h t e m p o r ar il y

elev at ed o n e o f t h e Bed 4 o u t let t e m p er at ur e po int s . T h e imme d i a t e c au s e o f t h e t e mp e r a t u r e e x c u r s io n in B e d 4 w a s p r o b ab ly p o o rflo w a n d h e a t di st r i b u t i o n wi t h in t h e cat al y s t b e d. P a st pr o b le m s wi t h

t e m p er at ur e co nt r o l in t h i s b e d an d t h e ex ces s iv e co ke depo s i t b u il dup ar e ev i d en ce o f t h i s po o rdi s t r i b u t i o n . T h e co ke p illar s fo u n d in Bed 4 af t e rt h e acci dent wer e l i k el y

f

o r m ed o v era l o n g per i o d o f t im e an d wer e n o t t h e r e sul t o f o n ly t h e J a nu ar y 2 1 e x c u r s io n . T h e p r e s e n c e o f t h e c o k e p illar s in d i c a t e u n e v e n liq u i d di st r i b u t i o n , wh i c h in t u r n , caused t e m p er at ur e h o t spo t s t h at pr o b ab l y

o ccur r e d in t h e b e ds d u r in g t h e i ro p e r a t in g h i s t o r y. O c c u r r e n c e o f c o k e p illar s in o n ly B e d 4 o f a ll S t a g e 2 r eact o r s r e v eal t h at t h e f l o w di st r i b u t i o n in t h e f o ur t h cat al y s t b e ds was so m e wh at dif f e r e nt f r o m t h e o t h e r cat al y s t b e ds. T o sco st at ed in t h ei rr e po r t t h at t h e f l o w r e gim e in Bed 4 was a po ssi b l e f act o rt h at co nt r i b u t e d t o f o r mat i o n o f t h e h o t spo t . T h ei rexpl an at i o n was b a sed o n f

l ash cal cul a t i o n s t h ey per f o r m e d, wh i c h in di cat ed t h at t h e r eact ant s t r an si t i o n ed f r o m wet t o dr y cat al y s t wi t h in Bed 4 o f React o r3. T o sco expl ain e d t h at b e ds in wh i c h so m e o f t h e cat al y s t i s wet an d so m e o f t h e cat al y s t i s dr y ar e par t i c ul ar l y

s u s cept i b le t o h o t s p o t s . T h ei ran al y s i s al s o s uppo r t ed po o rf l o w di s t r i b u t i o n as a cause o f t h e t e m p er at ur e ex cur s i o n . H i s t o r ic a lly, T o s c o h a d p r o b le ms w it h t e mp e r a t u r e in s t ab ilit y in B e d 4 , w h ic h le d T o s c o t o d e v e lo p s p e c i a l o p e r a t in g limit s a n d g u i d e lin e s fo rt h is b e d
. H o w e v e r , t h e s e g u i d e lin e s w e r e n o t in co r p o r at ed int o t h e wr it t e n o p er at in g pr o cedur es . A l t h o ugh B e d 4 h a d a dif f e r e nt l y

des i gn ed f l o w d i s t r i bu t i o n s y s t e m t h a n t h e o t he rc a t a l y s t be d s , inve s t i g a t o r s d o no t ha ve e n o u g h in f o r mat i o n t o co n c l ude wh et h e rt h e dif f e r e nt des i gn co nt r i b u t e d t o o p er at in g pr o b le m s wi t h

t h i s b e d. Ot h e rpo ssi b le r easo n s wer e co n s i d er ed an d r u le d o u t as t h e l i k el y

causes o f t h e t e m p er at ur e ex cur s i o n , b a sed o n in f o r mat i o n an d ev i d en ce av ail ab le. T h ese f act o r s wer e di scussed pr ev i o usl y in

S ect i o n 3 an d in cl uded: cl o s in g o f t h e Bed 5 quen c h v a lv e, deact iv at ed cat al y s t , f eed t e m p er at ur e t o o hi gh , l o s s o f r ecy cle hy dr o g en , pl ugged di s t r i b u t i o n t r ay s , an d in s u f f i ci ent o il o r gas f l o w r a t e . I n v e st i g at o r s co ul d n o t det e r m in e wh et h e rt h e int e r n al dama ge t o t h e di st r i b u t i o n t r ay s an d quen c h zo n e was a cause o f t h e ex cur s i o n sin ce t h e dama ge m i g ht h a v e b een an ef f ect o f t h e

59in ci dent . F o rex am ple, t h e di st o r t e d di st r i b u t i o n t r ay s co ul d h a v e b een a r e sul t o f t h e r api d depr es s u r in g af t e rt h e f a il u r e o f t h e ef f l uent pi pe. 4. 3 F ail u r e t o Cont r o lT e m p er at ur e E x cur s ion I n i t i a ll y , t h e o p er at o r s di d n o t t ake appr o p r i at e st eps t o co nt r o l t h e t e m p er at ur e ex cur s i o n b ecause t h ey di d n o t co m p r e h e n d t h at a t e m p er at ur e ex cur s i o n was h appen in g . T h er e wer e sev e r a l r easo n s why o p er at o r s wer e un sur e o f t h e sit u at i o n in cl udin g :

& T h e dat a l o ggert e m p er at ur es wer e f l uct u at in g b e t w een h i gh , l o w, an d zer o r eadin gs, causin g t h e o p er at o r s t o b e l i e v e t h e dat a was in er r o r .

& Oper at o r s di d n o t kn o w t h at t h e r eadin gs o n t h e dat a l o ggerdef aul t e d t o zer o wh en t h e t e m p er at ur e ex ceeded t h e r a n g e o f t h e dat a l o gger .

& Oper at o r s t h o ught t e m p er at ur e dat a m i g ht b e in er r o rb ecause t h e dat a l o ggerh a d exper i en ced ma lf un ct i o n s at t im e s. I t h a d ma lf un ct i o n e d o n e day pr i o rt o t h e acci dent . & Oper at o r s b e l i e v e d t h at o p en in g t h e quen c h v a lv e t o Bed 5 co nt r o lle d t h e t e m p er at ur e ex cur s i o n b ecause t h e Bed 5 in le t t e m p er at ur e r eadin g t h at h a d r i sen ab n o r mall y r e t u r n ed t o n o r mal
. T h e Bed 4 o u t let t e m p er at ur e r eadin g al so r e t u r n ed t o wi t h in n o rma l ra n g e .

& T h e t e m p er at ur e dat a o n t h e Bed 4 st r i p ch ar t appear ed n o r mal an d di d n o t v e r if y

t h e h i gh Bed 4 o u t let t e m p er at ur e o n t h e dat a l o gger . W h ile t h i s i s co n s i s t e nt b ecause a dif f e r e nt Bed 4 po int was di spl a y e d o n t h e st r i p ch ar t , o p er at o r s ma y h a v e expect ed t o see m o r e t h an o n e Bed 4 o u t let po int r i se dur in g an ex cur s i o n .

& Hy dr o g en makeup decr eased, n o t in cr eased, as o p er at o r s expect ed dur in g an ex cur s i o n .

& Oper at o r s wer e co n f used b y makeup hy dr o g en f

l o w dr o ppin g t o zer o . Oper at o r s wer e un awar e t h at t h e m e t h an e b u il dup in t h e r ecy cle gas caus e d t h e makeup hy dr o g en f

l o w t o dr o p .

& Oper at o r s di d n o t kn o w t h at t h e r ecy cle gas ( hy d r o gen ) pur i t y

h a d dr o pped b ecause o f t h e t im e l a g f o rr eceiv in g an al y s i s f r o m t h e hy dr o g en pur i t y

an al y zer .

& O p e r a t o r s d i d n o t imme d i a t e l y n o t i c e t h a t t h e B e d 5 o u t le t , r eact o rin le t an d o u t let t e mp e r a t u r e s h a d r i s e n ab o v e c r it ic a l limit s . O p e r a t o r s d i d n o t r eceiv e addi t i o n al audi b le h i gh t e m p er at ur e al ar m s f r o m t h e dat a l o gger .

& Oper at o r s wer e di st r act ed f r o m n o t i cin g t h at Bed 5 o u t let t e m p er at ur es wer e in cr easin g b ecause t h ey wer e b u sy t r yin g t o co nt r o l t h e t r im f

u r n ace f i r in g .

60T h e o p er at o r s h ear d an d r e spo n ded t o a h i gh t e m p er at ur e al ar m f

o rt h e Bed 4 o u t let an d Bed 5 in le t h i gh t e m p er at ur es, b u t di d n o t r eceiv e an y o t h e raudi b le h i gh t e m p er at ur e al ar m s despi t e Bed 5 o u t let an d r eact o rin le t an d o u t let t e m p er at ur es al so ex ceedin g h i gh t e m p er at ur e al ar m set po int s . On e Bed 4 o u t let an d t h e Bed 5 in le t t e m p er at ur e ex ceeded t h e +50 o F o v ern o r mal al ar m set po int , b u t po st
- acci den t t e st s sh o w ed t h at t h e dat a l o ggerwo ul d n o t r e - a l ar m in t h i s sit u at i o n wh en t h e ackn o wl edge b u t t o n was pus h e d o n t h e dat a l o ggerkey b o ar d
. T e s t in g al s o s h o w ed t h at i t t o o k 2. 5 m inut es f o rt h e +50 o F al ar m t o clearwh en t h e t e m p er at ur e dr o pped t o n o n - al ar m le v e l s . T h er ef o r e, f o rt h e +50 o F ab o v e n o r mal co n d i t i o n , t h e dat a l o ggeral ar m can n o t b e r e set in a r easo n ab l y

sh o r t t im e . T h i s sit u at i o n wo ul d pr ev ent o p er at o r s f r o m r eceiv in g h i gh t e m p er at ur e al ar m s f r o m o t h e rpo int s in t h e r eact o r . E v en wh en o p er at o r s r eal i zed, m o m e nt s b e f o r e t h e expl o s i o n , t h at t h e r eact o ro u t let an d in le t t e mp e r a t u r e s h a d c limb e d ab o v e 8 0 0 o F , t h ey di d n o t depr essur e t h e r eact o ras t h e em er gen c y o p er at in g pr o cedur es r e qui r e d. I n s t ead t h ey b e gan t o adj u s t quen c h gas f l o w s in o r dert o co o l t h e r eact o r . Oper at o r s di d n o t depr essur e t h e r eact o rb ecause t h ei rpast pr act i ce t o co nt r o l t e m p er at ur e ex cur s i o n s h a d b een t o in cr ease quen c h , r e duce r eact o rin le t t e m p er at ur es, an d/ o r st o p f eed f l o w t o t h e r eact o r . 4. 4 R oot Caus es and Cont ri but ing F a ct or s Ro o t causes ar e t h e un der l yin g pr im e r easo n s, such as f a il u r e o f par t i c ul arma n a gem e nt sy st em s, t h at all o w f aul t y

desi gn , in adequat e t r ain in g o rdef i ci en ci es in ma int e n a n ce t o ex i s t . T h ese, in t u r n , l ead t o un saf e act s o rco n d it i o n s wh i c h can r e sul t in an acci dent . T h e co nt r i b u t in g f act o r s ar e r easo n s t h at , b y t h em selv es, do n o t lead t o t h e co n d it i o n s t h at ul t ima t e l y

caused t h e ev ent ; h o w e v e r , t h e s e fa c t o r s fa c ilit a t e t h e o c c u r r e n c e o f t h e e v e nt o rin c r e a s e it s s e v e r it y . B ecause o f t h e co m p le x it y o f causes f o rt h i s acci dent , n o di st in ct i o n h a s b een ma de b e t w een t h e r o o t causes an d co nt r i b u t in g f act o r s. Ho wev e r , t h ey ar e pr esent e d t o get h erin r e l a t iv e o r dero f im p o r t a n ce. T h e r o o t causes an d co n t r i b u t in g f act o r s i d ent if i ed b e l o w f o rt h e Janu ar y 21 acci den t h a v e b r o a d appl i cat i o n s t o a v ar i et y o f si t u at i o n s an d sh o u l d b e co n s i d er ed le sso n s f o rin dust r i e s t h at o p er at e s imilarp r o c e s s e s , e s p e c i a lly fo rc h e mic a l a n d p e t r o le u m r e fin in g in d u s t r ie s .

& Co n d i t i o n s t o S uppo r t an d E n co ur age E m pl o y ees t o Oper at e React o r s in a Sa f e M a n n e r W e re In a d e q u a t e . A l t h o u g h T o s c o ma n a g e me nt in d i c a t e d in it s s a fe t y p o lic y t h a t s a fe t y w a s a p r io r it y , it fa ile d t o imp le me nt it s s a fe t y p o lic y c o n s is t e nt ly fo ra ll le v e ls o f t h e c o mp a n y. T h is la c k o f e m p h a s is fo r saf e o p er at i o n o f t h e Hy dr o c r ackerUn i t le d t o r i sky pr act i ces. On past o ccasi o n s , t h e em er gen c y depr essur in g sy st em was n o t used t o co nt r o l ex cessiv e o p er at in g t e m p er at ur es in S t age 2 r eact o r s as r e qui r e d b y T o sco ’ s wr i t t e n em er gen c y o p er at in g pr o cedur es. T o sco ma n a gem e nt di d n o t t ake suf f i ci ent co r r ect iv e act i o n t h at wo ul d en sur e use o f t h e em er gen c y depr essur in g sy st em . A co n f l i c t ex i s t e d b e t w een pr escr i b ed pr o cedur e an d past pr act i ce; past pr act i ce was t o v e r if y

dat a an d get co nt r o l o f r eact o rt e m p er at ur es wi t h o u t
61d e p r e s s u r ing . I n a c t i o n o n t h e p ar t o f ma na g e m e nt ma y ha ve be e n int e r p r e t e d by o p e r a t o r s a s un s p o k en ma n a gem e nt s uppo r t o f o p er at o r s ’ act i o n s t o co nt r o l s e v e r e ex cur s i o n s wi t h o u t shut t in g do wn t h e Hy dr o c r acker
. W h en o p er at o r s h a d n o t f o ll o wed pr escr i b ed em er gen c y depr essur in g pr o cedur es in t h e past , t h ey h a d n o t en co unt e r e d an y o p er at in g pr o b le m s as a r e sul t . Oper at o r s wer e ab le t o b r in g t e m p er at ur e ex cur s i o n s un derco nt r o l b y o t h e rm ean s wi t h o u t equi pm ent dama ge. Ho wev e r , t h ey h a d en co unt e r e d dif f i cul t i e s wh en t h e 100 ps i /m in

depr es s u r in g s y s t em was act iv at ed. T h es e dif f i cul t i e s in cl uded gr ass f i r e s at t h e f l ar e an d a r e lease o f f

l am mab le v apo r . Gr ass f i r e s at a f l ar e u s u a lly ar e c au s e d b y s p illo v e ro f liq u i d fr o m t h e flar e t o t h e g r o u n d
. N o r ma lly, a k n o c k

- o u t dr um s e par a t e s l i qui d f r o m gas b e f o r e t h e gas co nt inues t o t h e f l ar e, b u t un derex t r em el

y

h eav y f l o w r e l ease co n d it i o n s , t h e dr um ’ s separ a t i o n capacit y ma y b e ex ceeded. T h i s pr o b l e m wo ul d b e m

o r e s e v e r e if t h e 300 ps i / m in

depr es s u r in g i s act iv at ed s in ce m o r e f l o w r a t e i s in v o lv ed. Depr essur in g cr eat es an upset co n d it i o n in t h e un it f o rwh i c h o p er at o r s m u st b e pr epar ed an d t r ain e d. F o rex am ple, o n o n e o ccas i o n wh en t h e 100 ps i / m in

depr es s u r in g was aut o ma t i call y act iv at ed, t h e split t e rl o st li qui d l e v e l , wh i c h in t u r n , caused a pum p seal f

a il u r e . T h e pum p seal f a il u r e r e sul t ed in a v apo rr e l ease. T h ese n e gat iv e exper i en ces ma y h a v e co nt r i b u t e d t o o p er at o r r e l u ct an ce t o em pl o y em er gen c y depr essur in g an d r e in f o r ced o p er at o r s’ deci si o n s t o h a n d le sev e r e t e m p er at ur e ex cur s i o n s b y o t h e rm ean s. Oper at o r s kept t h e Hy dr o c r ackerUn i t r u n n in g despi t e adv e r s e o p er at in g co n d i t i o n s , such as so m e r eact o rt e m p er at ur e dat a n o t qui ckl y

accessi b le ( a v a il ab le o n l y

at f i el d pan e l s ) , ma lf un ct i o n in g t e m p er at ur e in st r u m e nt at i o n , leakin g ex ch an gerf l an ges, leakin g quen c h v a lv es, po o rr a di o per f o r ma n ce et c. Run n in g t h e Hy dr o c r ackerUn i t t o f u ll capaci t y

caused co nt r o l pr o b le m s f o r o p er at o r s an d ma de i t dif f i cul t t o ma int a in saf e t e m p er at ur es. Do cum e nt at i o n in di cat ed t h at s o me t ime s p r o d u c t i o n w a s limit e d b y t h e t r im fu r n ace f i r in g capacit y . F l uct u at i o n s in t r im f

u r n ace f i r in g caused o p er at o r s t o make ma n y ma nu al adj u st m e nt s t o r eact o rt e m p er at ur es. On e o p er at o rs t at ed t h at t h er e i s “ a l o t o f expect at i o n t o pr o duce b ar r e l s . ” Us e o f t h e 300 ps i / m in depr es s u r in g s y s t em i s v e r y di s r upt iv e an d h a l t s pr o duct i o n s in ce t h e un i t m u s t b e s hut do wn an d t h en l a t e rb e r e st ar t e d. Oper at o r s wer e n a t u r a ll y

r e l u ct ant t o shut t h e un i t do wn an d b e acco unt ab le f o rt h e n e gat iv e co n s equen ces o f int e r r upt in g pr o duct i o n . Ho wev e r , t h e r i sk o f r u n a way r eact i o n s in t h e hy dr o c r ackin g pr o cess di ct at es t h at o p er at o r s m u st qui ckl y

st o p f l o w o f f eed o rdepr essur e ev en at t h e r i sk o f so m e t im e s shut t in g t h e un it do wn un n ecessar il y . I n

r e b u il d in g S t age 2 r eact o r s an d co nt r o l s af t e rt h e Janu ar y 21 acci dent , T o sco desi gn ed t h e depr essur in g sy st em t o aut o ma t i call y

act iv at e wh en t e m p er at ur es r i se ab n o r mall y

h i gh
. T h er ef o r e, depr essur in g i s n o l o n g eran o p er at o rdeci si o n un derspecif i ed co n d it i o n s . Ho wev e r , t h e r o o t causes asso ci at ed wit h o p er at o ract i o n s an d at t it udes r e gar d in g pr o duct i o n v e r s us saf e t y n eed t o b e addr essed in o r dert o pr ev ent o t h e racci dent s. M a x imu m b e d t e mp e r a t u r e d iffe r e n t ia l limit s w e r e s t a t e d in c o n s is t e nt ly in v ar i o u s d o c u me n t s . T o s c o w a s n o t o p e r a t in g w it h in t h e o r ig in a l c a t a l ys t b e d t e mp e r a t u r e limit a t io n s ( ma x imu m o f
6230 o F dif f e r e nt i a l perb e d) as r eco m m

e n d ed b y Un o cal in 1986 ( H y d r o cr ackerl i cen s o r ) , ev en t h o ugh t h ey h a d ch an ged t o a m o r e r eact iv e cat al y s t . T h e b a si s f o rall o win g h i gh erb e d d iffe r e nt ia ls ( ma x imu m o f 4 0 o F av er age an d 45 o F ax i a l an d r a di al ) i s n o t clear . Oper at o r s wer e n o t a lw a ys ab le t o ma in t a in b e d t e mp e r a t u r e d iffe r e n t ia ls e v e n w i t h in t h e h i g h e s t limit c it e d , 4 5 o F. T h e o p er at in g t e m p er at ur e gui del in es r e i s s u ed o n A p r il 4, 1996 as a r e s u l t o f an ex cur s i o n di d n o t def in e t h e n o r mal t e m p er at ur es t h at m u st b e ma in t a in ed. I n cr easin g b e d t e m p er at ur e dif f e r e n t i a l limit s in c r e a s e s t h e r i s k o f t e mp e r a t u r e e x c u r s io n s . W r it t e n do cum e nt s in di cat ed t h at o p er at o r s f o un d it n ecessar y t o in cr ease b e d t e m p er at ur es t o s t a y w it h in o t h e ro p e r a t in g c o n s t r a in t s s u c h a s ma in t a in in g min imu m c o n v e r s io n p e rb e d , ma int a in in g pr o duct i o n r a t e an d sh if t in g h i gh ert e m p er at ur es t o b e ds t o r e duce t r im f

u r n ace f i r in g , an d co m p en sat in g f o rl eakin g quen c h v a lv es. Do cum e nt at i o n sh o w s t h at T o sco ma n a gem e nt was a w ar e o f t h e c o n f lic t s b e t w e e n s a fe o p e r a t in g limit s a n d p e r f o r ma n c e g o a l s b u t t o o k n o a c t io n t o a d d r e s s t h e s e c o n f lic t s . M a n a g e me nt ’ s la c k o f r e g ar d fo rfir m o p e r a t in g limit s c o nt r i b u t e d t o a c u lt u r e w h e r e o p e r a t o r s ma y n o t h a v e t ak e n t h e limit s s e r i o u s l y. O p e r a t o r s w e r e a w ar e t h a t t h e y h a d t aken ch an ces in t h e past b y o p er at in g wit h ma lf un ct i o n in g in st r u m e nt s an d wit h o u t t h e dat a l o gger . W h en per f o r ma n ce go al s an d r i s k s wer e n o t def in e d b y ma n a gem e nt , deci s i o n s ab o u t h azar ds an d r i sk wer e l e f t up t o o p er at o rdi scr e t i o n .

& Huma n F act o r s W e r e P o o r l y

Co n s i d er ed in t h e Desi gn an d Oper at i o n o f t h e T e m p er at ur e Mo n it o r in g S y st em . T h e co nt r o l r o o m was n o t des i gn ed an d pl an n e d wi t h

a pr o p erf it o f peo p le , equi pm ent an d e n v i r o n m e n t , w h ic h limit e d o p e r a t o r s ' ab ilit y t o q u i c k ly r e c o g n iz e a n d r e s p o n d t o a t e mp e r a t u r e ex cur s i o n . T h e t e m p er at ur e m o n it o r in g sy st em f

o rS t age 2 Hy dr o c r ackerr eact o r s was in adequat e f o ro p er at in g a co m p le xr eact i o n un derh i gh t e m p er at ur e an d pr essur e . Oper at o r s wer e r e qui r e d t o a d ju s t t e mp e r a t u r e s ( ma n y t ime s ma nu a lly) a n d r e ma in w it h in c e r t a in c o n s t r a int s w h ile ach i e v in g t ar g et pr o duct i o n go al s. Oper at in g co n s t r aint s an d pr o duct i o n t ar g et s o f t e n ch an ged depen d in g o n f

eed ch ar act er i s t i cs, o u t put n eeds, cat al y s t age an d o t h e ro p er at in g co n d i t i o n s . T h ese co n s t r aint s in cl uded ma int a in in g a specif i ed b e d t e m p er at ur e pr o f ile , n o t ex ceedin g t r im f u r n ace f i r in g capaci t y , ach i e v in g specif i ed pr o duct co n v e r s i o n , n o t ex ceedin g r eact o ran d cat al y s t b e d t e mp e r a t u r e limit s , a v o i d in g h o t s p o t s in b e d s , a n d min imiz in g c o k in g o f c a t a l ys t . I n

o r dert o o p er at e t h e Hy dr o c r ackeref f i ci ent l y

an d saf e l

y , suf f i ci ent r eact o rt e m p er at ur e dat a i s cr i t i cal an d n eeds t o b e r eadil y

accessi b le. T h e o p er at o r s wer e usin g t h r ee dif f e r e nt in st r u m e nt at i o n sy st em s t o o b t a in r eact o rt e m p er at ur e dat a . T h ese sy st em s wer e n o t int e gr at ed an d t hus r e qui r e d m o r e ef f o r t t o ef f ect iv el y

m o n it o rt h e r eact o rco n d it i o n s . T h e M a y 1989 Hy dr o c r ackerT r ain in g P r o g r a m do cum e n t descr i b e d t h e co n t r o l r o o m as a “ h o dgepo dge” o f in st r u m e n t s an d ackn o wl edged t h at r e pl acem en t o f in st r u m e n t s h a d n o t f o ll o wed an y o v er all pl an . Wit h o u t t h e n ecessar y t e m p er at ur e dat a , o p er at o r s co ul d n o t r eadil y

det ect o rr e spo n d t o h o t spo t s in a cat al y s t b e d, an d r u n a way r eact i o n s co ul d o ccur . Dur in g t h e Janu ar y 21 in ci den t , o p er at o r s r e l i e d o n t h e st r i p ch ar t dat a t o make deci si o n s, sin ce dat a f

r o m t h e f i el d pan e l was n o t r eadil y

accessi b le an d t h ey di d n o t b e l i e v e t h e dat a l o ggerr eadin gs. T h e st r i p ch ar t s gav e an 63in co m p le t e pi ct ur e o f t h e r eact o rco n d i t i o n sin ce t h e ch ar t s o n l y

di spl a y e d a f e w o f t h e t o t a l t h er m o co uple r eadin gs. T h e f i el d pan e l t e m p er at ur e dat a was n eeded b y o p er at i o n s f o rsaf e an d ef f i ci ent o p er at i o n o f t h e S t age 2 r eact o r s. Oper at o r s wer e in st r u ct ed b y ma n a gem e nt t o co llect an d r eco r d f i el d pan e l dat a dail y . Mo st o f t h e h i gh est ( m o s t cr it i cal ) t e m p er at ur es wer e t h o s e t h at co ul d o n l y

b e r ead o u t s i d e at t h e f i el d pan e l s . Ob t a in in g f i el d pan e l t e m p er at ur es r e qui r e d t o o m u ch t im e , wh i c h di d n o t all o w qui ck deci si o n s t o b e ma de. W h en a t e m p er at ur e ex cur s i o n do es o ccur , get t in g t e m p er at ur e d a t a imme d i a t e l y is v it a l fo ro p e r a t o r s t o b e a w ar e o f t h e s it u a t io n a n d r e s p o n d ap p r o p r i a t e l y in t im e . On t h e n i ght o f t h e acci den t , m inut es wer e l o st wh il e t h e o u t s i d e o p er at o rwas t r yin g t o r e l a y f

i el d pan e l r eadin gs . T h e in s t all a t i o n an d us e o f f

i el d pan e l s t o acqui r e addit i o n al t e m p er at ur e dat a was n o t ma n a ged appr o p r i at el y . No ma n a gem e nt o f ch an ge pr o cess was co n duct e d t o co n s i d ert h e im p act s o f usin g t h e f i el d pan e l s . T h e pur po se o f t h e in st all a t i o n o f t h e f i el d pan e l was n o t cleart o all per s o n n e l asso ci at ed wi t h

t h e Hy dr o c r acker
. S o m e t h o ught t h e t e m p er at ur e pan e l was an exper im e nt t o d e t e r min e if a c ap it a l e xp e n d it u r e w a s w o r t h w h ile , w h ile o p e r a t o r s r e lie d o n it fo ra d d i t i o n a l t e m p er at ur e m o n it o r in g . A l so , t h er e was n o def in e d t im e l in e f o rwh en dat a f

r o m t h e addi t i o n al t h er m o co uples wo ul d b e av ail ab le in t h e co nt r o l r o o m . P o o rco m m

u n i cat i o n s ex i s t e d b e t w een ma n a gem e nt an d o p er at o r s o n t h i s i ssue. Oper at o rco n cer n s ab o u t t h e pan e l s wer e n o t addr essed. Oper at o r s h a d t o ma n a ge wit h co n f l i c t in g t e m p er at ur e in f o r mat i o n f

r o m t h e dif f e r e nt sy st em s. Man a gem e nt r eco gn i zed t h i s co n f l i c t in t h e st an dar d o p er at in g pr o cedur es, b u t n o pr o cedur es wer e in pl ace t o specif y

h o w t o o p er at e wh en o n e o f t h e in st r u m e nt sy st em s was ma lf un ct i o n in g . T h e r e w a s limit e d r e d u n d a n c y o f t e mp e r a t u r e r e a d in g s , w h ic h d i d n o t a llo w a n accur a t e a s s e s s m e n t o f p o s s i b le in s t r u me n t ma lfu n c t io n . T h e o n ly r e d u n d a nt t e mp e r a t u r e p o in t s w e r e t h o s e o n t h e co nt r o l b o ar d st r i p ch ar t s wh i c h di spl a y e d o n l y

t h e cent e rin le t an d o u t let o f each b e d. Oper at o r s di d n o t h a v e hy dr o g en pur it y in f o r mat i o n n eeded t o assess t h e sit u at i o n o n Janu ar y 21 b ecause o f a sev e n m inut e l a g t im e in get t in g in f o r mat i o n f

r o m t h e hy dr o g en pur i t y

an al y zer . T h i s del a y co nt r i b u t e d t o o p er at o r s n o t b e in g awar e o f ex cessiv e m e t h an e gen e r a t i o n as t h e t e m p er at ur e ex cur s i o n b e gan . T h e r e w a s limit e d au t o ma t i c c o n t r o l o f q u e n c h flo w s in c e t h e c o nt r o lle r s u s e d o n ly o n e t e m p er at ur e po int perb e d. Respo n din g qui ckl y

t o t e m p er at ur e ex cur s i o n s in so m e cases r e qui r e d t h e o p er at o r s t o o v er r i de t h e aut o ma t i c quen c h co nt r o lle rin o r dert o co nt r o l h o t spo t s in t h e cat al y s t b e d n eart e m p er at ur e po int s t h at wer e n o t l inked t o t h e quen c h v a lv e co nt r o lle r . Oper at o r s wo ul d o p en t h e quen c h f

l o w v a lv e usin g ma nu al co nt r o l v e r s us t h e aut o ma t i c co nt r o l
. W h en m u l

t i

p le t e m p er at ur e po int s ex ceeded t h e h i gh t e m p er at ur e al ar m set t in g , n o addi t i o n al al ar m s co ul d b e r eceiv e d unt il t h e f i r s t h i gh t e m p er at ur e al ar m was ackn o wledged an d r e set . T h e h i gh t e m p er at ur e al ar m was set at 780 o F , wh i c h m ean t o p er at o r s m i g ht n o t b e awar e o f a pr o b le m
64unt il t e m p er at ur e h a d al m

o st ex ceeded t h e ma x im u m saf e o p er at in g t e m p er at ur e o f t h e r eact o r . Yet t h e o p er at o r s wer e r e qui r e d t o t ake st eps t o co nt r o l t e m p er at ur es 25 o F ab o v e n o r mal ( w i t h o ut depr essur in g ) as st at ed in t h e em er gen c y o p er at in g pr o cedur es. On Janu ar y 21, so m e o f t h e Bed 5 o u t let t e m p er at ur es in cr eased b y m o r e t h an 25 o F , b u t b o ar d o p er at o r s wer e di st r act ed b y t r im f

u r n ace f i r in g an d di d n o t n o t i ce t h e Bed 5 an d r eact o ro u t let t e m p er at ur es r i sin g . T h e desi gn o f in st r u m e nt at i o n was n o t well int e gr at ed an d was n o t adequat e t o addr ess t h e sit u at i o n s o f

t e m p er at ur e r i sin g v e r y r api dl y , an d ma n y t e m p er at ur e po int s ex ceedin g limit s .

& Super v i s o r y M a n a gem e nt W a s I n adequat e . I t appear s t h at super v i s o r y co nt r o l o f o p er at i o n s f o rt h e Hy dr o c r ackerwas def i ci en t an d co nt r i b u t e d t o t h e l ack o f adh e r e n ce t o r e qui r e d em er gen c y pr o cedur es. I n co n s i s t e nt appl i cat i o n o f

t h e use o f em er gen c y o p er at in g pr o cedur es was t o le r a t e d. S uper v i s i o n was n o t pr esent at t h e un i t ev en t h o ugh t h er e h a d b een a successi o n o f o p er at in g pr o b le m s j u st pr i o rt o t h e f in a l t e m p er at ur e ex cur s i o n t h at lead t o t h e expl o s i o n an d f i r e . T h e No
. 1 Oper at o rwas pr esent t o pr o v i d e leader sh i p f o rt h e o t h e ro p er at o r s, b u t h i s aut h o r i t y

t o make sur e r e qui r e d pr o cedur es ar e f o ll o wed was n o t cl ear . S uper v i s o r s wer e n o t alway s awar e o f t e m p er at ur e ex cur s i o n s o rma x im u m r eact o rt e m p er at ur es t h at h a d b een exper i en ced in t h e past . Man a gem e nt was n o t awar e t h at S t age 2 h a d b een o p er at ed wit h o u t t h e dat a l o ggerf u n c t i o n in g. I n s o m e cas es , s uper v i s o r s di d n o t kn o w wh i c h pr o cedur es wer e o rwer e n o t in ef f ect . A n ex am ple o f t h i s i s SOP#20 wh i c h in s t r u ct ed t o ma nu all y

cl o s e t h e makeup hy dr o g en co n t r o l v a lv e b e f o r e act iv at in g em er gen c y depr essur in g . S uper v i s o r s f a ile d t o r eco gn i ze all t h e h azar ds asso ci at ed wit h t h e Hy dr o c r ackerUn i t st ar t up an d o p er at i o n . T h ese h azar ds in cl uded all o win g o p er at o r s t o access f i el d pan e l s dur in g po t e nt i a ll y sev e r e t e m p er at ur e ex cur s i o n s , all o win g o p er at i o n s o f h eat ex ch an ger s t h at leaked ch r o n i call y , an d h a v in g co nt inued o p er at i o n o f S t age 2 r eact o r s wh en t h e dat a l o ggerwas o u t o f ser v i ce. S uper v i s o r s al so di d n o t h a v e a pl an f

o rim p le m e nt in g t h e use o f t h e I /A t e m p er at ur e m o n i t o r in g sy st em an d wer e n o t f o ll o win g ma n a gem e nt o f ch an ge pr o cedur es t h at wo ul d h a v e i d ent if i ed t h e co n s equen ces o f ch an ge t o t h e sy st em an d pr epar ed o p er at o r s f o rit s use. Ro o t cause in v e st i g at i o n s co n duct e d f o rpr ev i o us ex cessiv e t e m p er at ur e ex cur s i o n s wer e in adequat e . I t appear s t h at n o t all t e m p er at ur e ex cur s i o n s wer e do cum e nt ed, an d ma n a gem e nt ma y h a v e b een un awar e o f t h e ser i o u s n a t u r e o f so m e o f t h e ex cur s i o n s . Man a gem e nt di d n o t in v e st i g at e why o p er at o r s wer e r e l u ct ant t o f o ll o w em er gen c y o p er at in g pr o cedur es, an d f a ile d t o d e v e l o p so l u t i o n s t o ad d r ess t h e cau ses. T h e f a il u r e t o f u ll y

in v e st i g at e sev e r a l “ n earm i ss” t e m p er at ur e ex cur s i o n s an d addr ess causes o f t h ese in ci den t s dem o n s t r at es t h e l ack o f pr o p er ma n a gem e nt o v er si ght an d co n cer n . T h e l ack o f at t e nt i o n sen d s t h e wr o n g m e ssage t o o p er at o r s ab o u t t h e r eal dan g erpo sed b y t h e t e m p er at ur e ex cur s i o n s . I n addi t i o n , n o ab at em ent ef f o r t s wer e ma de in r e gar d t o ex cessiv e r eact o rb e d t e m p er at ur es, o t h e rt h an r e i ssuin g gui del in es.

65& Oper at i o n a l Readin ess an d Maint e n a n ce W e r e I n adequat e . P o o rfa c ilit y fu n c t i o n a l o p e r ab ilit y a n d p o o rma int e n a n c e w e r e c o nt r i b u t in g fa c t o r s in t h e acci dent . T w i ce in J a nu ar y o f 1997, o p er at o r s h a d t o r e l y

o n s in g le b e d in le t an d o u t let t e m p er at ur e po int s f r o m t h e Mo o r e ( s t r i p ch ar t ) co nt r o lle r s wh ile swit ch in g f r o m t h e I /A sy st em t o t h e dat a l o gger an d v i ce v e r s a. No int e r im sy st em was av ail ab le t o en sur e t h at t h e o p er at in g em pl o y ees h a d suf f i ci ent o p er at in g dat a t o saf e l

y

o p er at e t h e r eact o r s. F o rt e n day s in J a nu ar y o f 1997, St age 2 was o p er at in g wit h a n e w t e m p er at ur e m o n it o r in g sy st em t h at w a s n o t f u ll y

f

u n c t i o n in g ( t h e I /A sy st em )
. N o p r e- st ar t u p saf e t y r e v i ew w a s co n duct e d f o rt h e im p l e m e n t at i o n o f t h e S t age 2 I /A sy st em . T h e I / A sy st em was n o t r eadin g all t h e t h er m o co uple t e m p er at ur es an d was in co r r ect l y

calcul a t in g wei g ht ed cat al y s t t e m p er at ur e av er ages. Oper at o r s h a d al so exper i en ced r ecent o p er at in g pr o b le m s wi t h

t h e dat a l o gger , wh i c h was o n e f act o rleadin g o p er at o r s t o do ub t dat a l o ggerr eadin gs o n t h e ev en in g o f Janu ar y 21. On e t y pe o f al ar m f

o rt h e dat a l o ggerwas n o t f u n c t i o n in g pr o p er l y . T h e t e m p er at ur e r i se in Bed 4 o u t let an d Bed 5 in le t o n Janu ar y 21 ex ceeded t h e al ar m set t in g o f m o r e t h an 50 o F ab o v e n o r mal
. Po s t
- in c i d ent dat a l o ggert e s t in g dem o n s t r at ed t h at t h e dat a l o ggeral ar m wo ul d n o t r e al ar m f

o ran o t h e rh i gh t e m p er at ur e wh en t h e ackn o wl edge b u t t o n was push e d o n t h e dat a l o gger key b o ar d
. T h e dat a l o ggeral ar m f

o rgr eat ert h an 50 o F

ab o v e n o r mal wo ul d al so n o t r e set it self in a r easo n ab l y

sh o r t t im e ( less t h an 2. 5 m inut es) af t e rt h e t e m p er at ur e dr o pped b ack t o n o r mal
. T h i s si t u at i o n wo ul d pr ev ent o p er at o r s f r o m r eceiv in g h i gh t e m p er at ur e al ar m s f r o m o t h e rpo int s in

t h e r eact o r . Un r e l i ab le r a di o co m m

u n i cat i o n s equi pm ent wer e used b y o p er at o r s. T h e r a di o s wer e r e qui r e d t o r e l a y b o t h r o ut in e an d em er gen c y in f o r mat i o n b e t w een t h e o u t s i d e o p er at o ran d t h e co nt r o l r o o m p e r s o n n e l. B a s e d o n o p e r a t o rs t a t e m e n t s , p r o b le ms e x is t e d w it h ma in t a in in g p r o p e rb a t t e r y po weran d h a v in g en o ugh ch an n e l s av ail ab le t o acco m m

o dat e co m m

u n i cat i o n s n eeds. P r o b le m s ma int a in in g b a t t e r y po werwer e ackn o wledged in SOP# 30 dat e d M a y 1990 an d appar e nt l y

t h es e p r o b le ms h a d s t ill n o t b e e n a d d r e s s e d b y t h e t ime o f t h e J a nu ar y 2 1 acci dent . T h e S t age 2 quen c h v a lv es wo ul d n o t f u ll y

cl o s e all t h e t im e an d o p er at o r s h a d t o make a d ju s t me n t s t o b e d t e mp e r a t u r e s t o c o mp e n s a t e , w h ic h s o me t ime s r e s u lt e d in h i g h e rb e d t e mp e r a t u r e s . T h e h i g h e rt h e o p e r a t in g t e mp e r a t u r e o f t h e b e d , t h e mo r e lik e l y t h e p o s s i b ilit y o f t e m p er at ur e r u n a way sin ce r eact i o n r a t e in cr eases wit h t e m p er at ur e. A d j u st in g t e m p er at ur es t o c o mp e n s a t e fo rle ak in g q u e n c h v a lv e s ma y h a v e ma d e it mo r e d iffic u lt fo ro p e r a t o r s t o s t a y w it h in p r e s c r ib e d b e d t e mp e r a t u r e d iffe r e nt ia l limit s . Oper at o r s wer e expect ed t o deal wi t h

adv e r s e si t u at i o n s wi t h o u t adequat e o p er at in g pr o cedur es o rt ech n i cal s uppo r t f r o m ma n a gem e nt . T h e deact iv at ed cat al y s t ma y n o t h a v e co nt r i b u t e d t o t h e acci dent , b u t t h e co n d it i o n s causin g t h e deact iv at i o n an d t h e l ack o f pr epar at i o n t o h a n d le t h i s
66sit u at i o n sh o w def i ci en ci es in o p er at i o n a l r eadin ess an d o p er at in g pr o cedur es. F o rex am ple, t h e cat al y s t deact iv at i o n st ar t e d wh en f

eed f r o m t h r ee r eact o r s was f o r ced int o t w o r eact o r s b ecause o f

l ack o f r o o m in t a nk age n eeded t o div e r t so m e o f t h e f eed. A

wi r in g pr o b le m i d ent if i ed in SOP#20 wo ul d n o t h a v e all o wed o p er at o r s t o depr es s u r e St age 2 wi t h o u t f i r s t ma nu all y

cl o s in g a hy dr o g en co nt r o l v a lv e. T h i s si t u at i o n ex i s t e d b ecause o f wi r in g o n t h e co nt r o l v a lv e t h at h a d b een dama ged in M ar c h 1989 an d, acco r d in g t o S O P #20, was n e v e r r e pai r ed. T h e em er gen c y depr essur in g sy st em was n o t t e st ed r e gul ar l y

t o en sur e it wo ul d f u n c t i o n wh en n eeded. Oper at o r s o p er at ed wi t h

h eat ex ch an ger s t h at ch r o n i call y

leaked dur in g st ar t up. T h ese leaks r e qui r e d ma int e n a n ce int e r v ent i o n dur in g st ar t up t o st o p t h e leaks an d cr eat ed o p er at in g h azar ds f r o m f

l am mab le v apo rcl o uds. T h ese leakage pr o b le m s del a y e d st ar t up o f t h e un i t in Janu ar y 1997. T o s c o i d en t if i ed t h e n eed t o r e pl ace m i s s in g s uppo r t b o l t s f o rdi s t r i b u t i o n t r ay s in S t age 2 r eact o r s f o rt h e J a nu ar y 1996 ma in t e n a n ce t u r n ar o u n d
. T h e do cum e n t at i o n f

o rt h i s n eeded wo r k was in co m p le t e an d in v e st i g at o r s ar e n o t cer t a in if

t h e wo r k was do n e . T h e sect i o n o f ef f l uent pi pe t h at r upt ur ed h a d b een ul t r aso n i call y

t e st ed f o rm e t a l t h i c kn ess o n l y o n ce ( in 1991) dur in g i t s 33 y ear s o f l

if

e. A s in g le pi pe m e t a l t hi c kn es s m eas ur em ent i s n o t a r e l i ab le way t o pr edi c t an accur a t e co r r o si o n r a t e f o rpi pin g in hy dr o g en ser v i ce.

& Oper at o rT r ain in g an d Suppo r t W e r e I n adequat e . T h e Hy dr o c r ackerT r ain in g Manu al was o u t o f dat e an d di d n o t r e f lect ch an ges ma de t o t h e pr o cess o v ert im e . T h e un it
- s pecif i c t r ain in g at t h e Hy dr o c r ackerwas m o st l y

o n - t h e - j o b t r ain in g w i t h

lit t le o rn o c l a s s r o o m t r a in in g . A l s o , d o c u me nt a t io n o f u n it

- s p e c ific t r a in in g w a s limit e d
. A n e x a m p l e o f t o o mu c h r e lia n c e u p o n o n - t h e - j o b t r a in in g in c l u d e d t h e p a s t p r a c t ic e o f c o nt r o llin g s e v e r e t e m p er at ur e ex cur s i o n s wi t h o u t depr es s u r in g . M a n a gem e nt h a d n o t dev e l o ped r e qui r e d un it
- s pecif i c r e f r esh e rt r ain in g . T h e t ech n i cal in f o r mat i o n sy st em in pl ace was le ss t h an adequat e f o rsaf e o p er at i o n o f t h e Hy dr o c r acker
. Oper at o r s l acked adequat e t r ain in g o n in st r u m e nt at i o n ; t h ey appar e nt l y

di d n o t k n o w t h e limit a t io n s o f s o me o f t h e mo n it o r in g a n d c o n t r o l in s t r u me nt s u s e d in S t a g e 2
. F o r ex am ple, t h ey di d n o t un der s t a n d t h e si gn if i can ce o f zer o r eadin gs o n t h e dat a l o gger . Oper at o r s h a d n o t r eceiv e d t r ain in g o n t h e n e w I / A t e m p er at ur e m o n i t o r in g sy st em in st alle d f o rS t age 2 w h e n it w a s o p e r a t io n a l fo r1 0 d a ys in J a nu ar y. T h e o p er at o r s di d n o t un der s t a n d t h e s i gn if i can ce o f a s udden decr eas e in makeup hy dr o g en f

l o w . T h i s decr ease co n f l i c t e d wit h t h e o p er at o r s’ past exper i en ce in v o lv in g t e m p er at ur e ex cur s i o n s , wh i c h h a d gen e r a ll y

caused makeup hy dr o g en f

l o w t o in cr ease. No t all t h e o p er at o r s h a d

67suf f i ci ent t r ain in g o n t h e r eact i o n kin e t i cs o f hy dr o c r ackin g an d t h e im p o r t a n ce o f t akin g pr escr i b ed act i o n s o n ce t e m p er at ur es h a v e ex ceeded cer t a in limit s .

& P r o cedur es W e r e Out d at ed an d I n co m p le t e . T h e l ack o f co m p le t e , specif i c, an d int e gr at ed o p er at in g in st r u ct i o n s f o rt h e Hy dr o c r ackerS t age 2 co nt r i b u t e d t o t h e f a il u r e t o co nt r o l t h e t e m p er at ur e ex cur s i o n . Because o p er at o r s wer e used t o o p er at in g wi t h

o u t d at ed pr o cedur es, t h ey ma y n o t h a v e t aken wr i t t e n pr o cedur es as ser i o u sl y

as t h ey sh o u l d h a v e wh en t h ey ch o s e t o co nt r o l ex t r em el

y

h i gh r eact o rt e m p er at ur es b y m ean s o t h e r t h an depr es s u r in g . W r it t e n o p er at in g pr o cedur es wer e o u t
- o f

- d at e, an d wer e n o t updat e d as m u l

t i

p le ch an ges wer e ma de t o t h e Hy dr o c r ackerUn it . A ch an ge was ma de t o use a m o r e r eact iv e S t age 2 cat al y s t in M ar c h o f 1996, b u t t h e wr it t e n o p er at in g pr o cedur es wer e n o t updat e d t o r e f lect t h i s ch an ge in pr o ces s ch em i s t r y . T h e pr o cedur es wer e n o t updat e d as ch an ges wer e ma de t o t h e t e m p er at ur e m

o n it o r in g s y s t em . T h e o p er at in g pr o cedur es di d n o t ma t c h equi pm en t in t h e un it o rin t h e co nt r o l r o o m . T h e o p er at in g pr o cedur es di d n o t ma t c h des c r i pt i o n s o f o p er at i o n s an d equi pm ent descr i b e d in t h e pr o cess h azar d an al y s i s . C o n f lic t in g g u i d a n c e r e g ar d in g b e d t e mp e r a t u r e d iffe r e nt ia l limit s w a s p r o v id e d in d iffe r e nt d o c u me nt s a s d i s c u s s e d in S e c t io n 3 o f t h is r e p o r t . H a v in g d iffe r e nt o p e r a t in g limit s fo rt h e s a me o p e r a t in g v ar i ab le ma y h a v e c o nt r i b u t e d t o o p e r a t o r s n o t u n d e r s t a n d in g o rn o t t ak in g s t a t e d limit s s e r i o u s l y . A f t e rt h e J u l y 1992 t e m p er at ur e ex cur s i o n , t h e cat al y s t ma nu f act ur eran d T ech n i cal S e r v i ces r eco m m

e n d ed t h at t h e t e m p er at ur e dif f e r e nt i a l o f Bed 4 o f React o r3 b e limit e d t o a ma x imu m o f 2 5 o F
. T h is r e c o mme n d a t io n w a s c o nt a in e d in a

d r a f t S O P w i t h

g u i d e lin e s fo rr a is in g r a t e o f cr ackin g, b u t i t was n o t in co r p o r at ed int o t h e appr o v ed wr it t e n pr o cedur es. B e d t e mp e r a t u r e d iffe r e nt ia l limit s w e r e n o t c le ar ly s t a t e d in t h e p r o c e d u r e s . I n v e s t ig a t o r s assum e d t h at av er age dif f e r e nt i a l i s t h e dif f e r e n ce b e t w een t h e av er age o u t let an d av er age in le t t e m p er at ur es. T o sco ’ s wr it t e n st an dar d o p er at in g pr o cedur es an d st ar t up o p er at in g pr o cedur es do n o t expl ain t h e dif f e r e n ce b e t w een ma x im u m av er age an d ma x im u m b e d t e m p er at ur e d iffe r e nt ia l limit s . Reco m m

e n d at i o n s f r o m sev e r a l in ci den t s an d acci den t s at t h e Hy dr o c r ackerUn it wer e n o t in co r p o r at ed int o t h e wr it t e n pr o cedur es. W r it t e n o p er at in g pr o cedur es di d n o t ex i s t f o rdeal in g w i t h

ma n y o f t h e c o n d it io n s o rs it u a t io n s t h a t o p e r a t o r s w e r e h a n d lin g in t h e t ime le a d in g u p t o t h e acci den t o n Janu ar y 21, such as o p er at in g wit h deact iv at ed cat al y s t , t r an sf er r in g f eed f r o m t h

r ee r eact o r s t o t w o , an d suspect ed in st r u m e n t ma lf un ct i o n . T h er e was n o wr it t e n o p er at in g pr o cedur e dev e l o ped o rim p le m e nt ed t h at pr o v i d ed clearin st r u ct i o n s f o rsaf e l

y

ch eckin g t h e f i el d p a n e l s . D e c i s i on s ab ou t r i s k s in v o lv e d w i th

f

i e l d p a n e l s w e r e le f t to th e d i s c r e ti on of th e o p er at o r s.

68No wr it t e n pr o cedur e was av ail ab le t o ma n a ge t h e ch an ge f r o m t h e t e m p er at ur e in di cat i o n dat a l o ggert o t h e I /A t e m p er at ur e di s p l a y o n J a nu ar y 10, 1997 o rt h e s w i t ch b ack t o t h e dat a l o gger o n Janu ar y 20. P r o cess saf e t y in f o r mat i o n an d o p er at in g pr o cedur es r e gar d in g t h e ch an ge wer e n o t updat e d as r e qui r e d b y M O C pr o cedur es . T h e S O P s di d n o t r e f e r e n ce co n d i t i o n s wh en em er gen c y o p er at in g pr o cedur es sh o u l d b e imp le me nt e d
. C o n s e q u e n c e s o f d e v i a t io n fr o m o p e r a t in g limit s ( s u c h a s fir e a n d e xp l o s io n ) w e r e gen e r a ll y

n o t addr es s e d o rm e nt i o n e d in t h e wr it t e n o p er at in g pr o cedur es , al t h o ugh t h ey wer e lis t e d in a

s e p ar a t e d o c u me nt .

& P r o cess Hazar d A n al y s i s W a s F l awed
. Hazar ds wer e n o t pr o p er l y

i d ent if i ed t h r o ugh a cur r e nt pr o cess h azar d an al y s i s , causin g a m

i s un der s t a n d in g o f r i sks asso ci at ed wi t h

t e m p er at ur e ex cur s i o n s , desi gn ch an ges, equi pm ent m

o dif i cat i o n s , an d o p er at in g an o mal i e s. P o ssi b le h azar ds f r o m ch an ges ma de in t h e co nt r o l r o o m o rin st r u m e nt at i o n wer e n o t adequat e l y

co n s i d er ed t h r o ugh ma n a gem e nt o f ch an ge pr o cedur es. T h e 1994 HAZ O P s t udy as s u m e d t h at in di cat o r s an d al ar m s f o rall b e d t e m p er at ur e r eadin gs wer e av ail ab le in t h e co nt r o l r o o m . W hile t hi s as s u m p t i o n was v a l i df o rt h e 1994 HAZ O P, i t wo ul d n o l o n g erb e v a l i daf t e rt h e f i el d t e m p er at ur e r eado u t pan e l s wer e in s t alle d in J a nu ar y 1996. Ch eckin g t e m p er at ur es at t h e f i el d pan e l s b ecam e t h e accept e d pr act i ce t o v e r if y

elev at ed o r quest i o n ab le r eact o rt e m p er at ur es. Oper at o r s wer e put at ser i o u s r i sk wh en t h ey wen t t o ch eck f i el d pan e l s wh ile t h e r eact o rma y h a v e b een ex ceedin g i t s saf e , ma x im u m all o wab le t e m p er at ur e o f

800 o F
. T h e f a il u r e t o r eco gn i ze h azar ds asso ci at ed wit h o p er at o r s usin g t h e f i el d t e m p er at ur e pan e l s was a f act o rco n t r i b u t in g t o t h e o p er at o rf a t a l it y . P o t e nt ia l r i s k in v o lv e d w it h r e a d in g fie l d t e mp e r a t u r e p a n e ls d u r in g ab n o r ma l c o n d it io n s w a s n e v e rev al uat e d b ecause n o saf e t y an al y s i s o f t h i s act iv it y was co n duct e d. Man a gem e nt di d n o t r e spo n d in a t im e l

y

ma n n e rt o o p er at o r s’ co n cer n s ab o u t h a v in g t h e l o cat in g t h e t e m p er at ur e pan e l s un dert h e S t age 2 r eact o r s. S a f e wo r k pr act i ces wer e n o t dev e l o ped o rim p le m e nt ed f o r r eadin g t e m p er at ur es f r o m t h e f i el d pan e l s . L i kewi se, n o est ab l i s h e d wr i t t e n pr o cedur es o r t r ain in g was dev e l o ped t o t e ll o p er at o r s wh en it was saf e o run saf e t o ch eck f i el d t e m p er at ur e pan e l s . T h e HAZ O P assum e d t h at n ecessar y pr o cedur es wer e in pl ace f o rall o p er at i o n s . T h e HAZ O P f o rS t age 2 o f t h e Hy dr o c r ackerUn i t di d n o t addr ess all ex i s t in g kn o w n h azar ds an d o p er at in g ab n o r mal it i e s an d was n o t appr o p r i at e f o rt h e pr o cess as it act uall y

ex i s t e d. I n sev e r a l in st an ces, t h e HAZ O P was f l awed in t h at it was n o t b a sed upo n t h e way t h e pr o cess act uall y o p er at ed at t h e t im e t h e an al y s i s was co n duct e d. I t i s n o t clearif t h e HAZ O P assum e d t h at t h e I /A t e m p er at ur e sy st em was f u n c t i o n al o rn o t . C o nt r o l o f t e mp e r a t u r e w i t h in c r it ic a l o p e r a t in g limit s is e s s e nt ia l fo rs a fe o p e r a t io n o f t h e Hy dr o c r acker
. T h e us e o f t h e 100 an d 300 ps i / m in

em er gen c y depr es s u r in g s y s t em s was n o t m

e n t i o n e d in t h e HAZ O P as a saf e guar d f o rr eact o rt e m p er at ur e ex cur s i o n s . T h e HAZ O P di d
69n o t addr ess l o ss o rdy sf un ct i o n o f t e m p er at ur e m o n i t o r in g sy st em s o rem er gen c y depr essur in g s y s t em s . T h e HAZ O P m i s t aken l y

s t at ed t h at aut o ma t i c act iv at i o n o f t h e 100 ps i / m in

em er gen c y depr essur in g wo ul d o ccurf o rt h e em er gen c y co n d it i o n o f l o ss o f o il f

l o w t h r o ugh t h e r eact o r . T h e 100 ps i / m in

depr es s u r in g i s aut o ma t i call y

act iv at ed o n l y

if

t h e r ecy cl e gas co m p r e s s o rt r i p s . T h e HAZ O P di d n o t addr ess t h e use o f em er gen c y quen c h t o t h e in l e t o f t h e r eact o ras was di scussed in t h e E m er gen c y P r o cedur es f o ra t e m p er at ur e ex cur s i o n . T h e pr o cess h azar d an al y s i s di d n o t adequat e l y

addr ess pr ev i o us in ci den t s t h at h a d a li k el y po t e n t i a l f

o rcat ast r o p h i c co n s equen ces in t h e wo r kpl ace, such as pr ev i o us r eact o rt e m p er at ur e e x c u r s io n s a n d fa ilu r e t o ma int a in t e mp e r a t u r e s b e lo w 8 0 0 o F
. T h e HAZ O P di d n o t i d ent if y

f

i r e an d expl o s i o n as co n s equen ces f r o m ex t r em e t e m p er at ur es in r eact o ref f l uent pi pin g an d f eed/ e f f l uent ex ch an ger s . T h e HAZ O P di d n o t co r r ect l y

i d ent if y

t h e f r equen c y an d t hus t h e r i sk o f

hy dr o car b o n an d hy dr o g en sulf i d e r e leases f r o m ex ch an gerf l an ge l eaks, b ecause it r a nk ed t h ese o ccur r e n ces as n o t l i k el y

o v erpl ant l if

et im e , wh en act uall y

t h ese l eaks o ccur r e d f r equent l y . T h e HAZ O P di d n o t i d en t if y

ex cessiv e m e t h an e gen e r a t i o n f

r o m a t e m p er at ur e ex cur s i o n as a c au s e o f l o w hy d r o g e n p u r i t y .

& Bar r i er s A g ain s t Hazar do us W o r k Co n d it i o n s W e r e I n adequat e . T h e T o sco em pl o y ees an d co nt r act o r s wh o wer e in j u r e d dur in g t h e expl o s i o n an d f i r e wer e n o t pr o p er l y

aler t e d t o o rpr o t ect ed f r o m h azar do us wo r k co n d i t i o n s . Co nt r act o r s wer e n o t n o t if i ed t h at t h e un i t was exper i en cin g o p er at i o n a l pr o b le m s . Oper at o r s di d n o t f o ll o w em er gen c y o p er at in g pr o cedur es t h at r e qui r e d t h em t o so un d t h e pr o cess un i t em er gen c y al ar m so t h at co nt r act o r s co ul d ev acuat e. 

### 5. 0 Reco m me n d atio n s A s descr i b e d in t h e Ro o t Causes an d Co nt r i b u t in g F act o r s sect i o n ab o v e, t h e r o o t causes o f t h i s acci den t ar e co m p le xan d int e r c o n n ect ed. I n v e st i g at o r s dev e l o ped r eco m m

e n d at i o n s addr essin g t h e r o o t causes o f t h e acci den t t o pr ev ent a r e o ccur r e n ce o rs imilare v e n t a t t h is a n d o t h e r fa c ilit ie s . T ak e n in d iv i d u a lly, t h e r e c o mme n d a t io n s d e s c r i b e d b e lo w ma y n o t c o n v e y t h e s i g n ific a n c e t o p r e v e nt i o n o f a

r e c u r r e n c e o ro f a

fu t u r e s imilar acci dent ; t o get h er , h o wev e r , t h ey illu s t r a t e h o w mu lt ip le la ye r s o f p r o t e c t io n w o r k t o p r e v e nt c a t a s t r o p h i c in c i d e n t s . T o s c o h a s imp le me nt e d ma n y o f t h e r e c o mme n d a t io n s fr o m t h e i ro w n in v e s t ig a t io n r e p o r t a n d f r o m t h e CCCHS D in v e s t i g at i o n r e po r t , wh i c h wer e b o t h f

in a l i zed in M a y 1997. A l

i s t o f act i o n s u n d e r t ak e n b y T o s c o is in A p p e n d ixI
. T h e r e c o mme n d a t io n s in t h is r e p o r t ap p l y n o t o n ly t o T o sco b u t ar e go o d pr act i ces t h at sh o u l d b e car ef ull y

co n s i d er ed f o rpo ssi b le im p le m e nt at i o n b y hy d r o p r o c e s s in g o p e r a t io n s a t o t h e rfa c ilit ie s a s w e ll a s o t h e rp r o c e s s in d u s t r ie s .

70• M an agem en t S y st em P o l i c y an d I m plem en t a t i o n T o s c o , a n d a ll in d u s t r y ma n a g e me nt , mu s t imp le me n t a n d ma in t a in a n e n v i r o n m e nt t h a t fo s t e r s s a fe o p e r a t io n s d a y a f t e rd a y. M a n a g e me nt mu s t a c t iv e l y d e mo n s t r a t e a c o mmit me nt t o s a fe t y b y en sur in g t h at o p er at in g deci si o n s ar e n o t b a sed pr imar il y

o n co st an d pr o duct i o n an d t h at em pl o y ees at all l e v e l s o f t h e o r gan i zat i o n can ar t i cul a t e t h e co m p an y saf e t y po l i c y . T h i s c o mmit me n t in c l u d e s d e fin in g r e a lis t i c p e r f o r ma n c e g o a l s a n d o p e r a t in g r i s k s , a n d c o mmu n i c a t in g t h e s e e ffe c t iv e l y t o a ll e m p l o y e e s . F a c ilit y ma n a g e me nt mu s t s e t s a fe , a c h ie v ab le o p e r a t in g limit s a n d e n fo r c e p r a c t ic e s t o ma int a in o p e r a t io n s w it h in t h o s e limit s . T o s c o n e e d s t o e s t ab lis h a

fir m p o lic y t h a t limit s ar e n o t fle x ib le a n d mu s t n o t b e e x ceeded, an d t h at if n ecessar y , pr o duct i o n r a t e s s h o u ld b e r e d u c e d t o s t a y w it h in o p e r a t in g limit s . F a c ilit y ma n a g e me nt mu s t e n s u r e t h a t e m p l o y e e s fu lly u n d e r s t a n d t h e n e e d t o u s e a n d fo llo w em er gen c y s y s t em s an d pr o cedur es . M a n a gem e nt m u s t des i gn , t h o r o ugh l y

ex am in e an d t e s t em er gen c y sy st em s an d pr o cedur es t o en sur e t h ei ref f ect iv en ess an d t o m in im i ze n e gat iv e co n s equen ces t o t h e pr o cess an d t o saf e t y if

such pr o cedur es o rsy st em s ar e used. Man a gem e nt m u st en sur e t h at all pr o cedur es, especi all y

em er gen c y pr o cedur es, ar e up- t o - d at e an d r e f lect all cur r e n t pr act i ces. Man g er s m u st in si st t h at all pr o cedur es b e f o ll o wed an d t h at o p e r a t in g limit s b e o b s e r v e d ; w h e n p r o c e d u r e s o rlimit s ar e n o t fo llo w e d o ro b s e r v e d , ma n a g e me nt mu s t d e t e r min e t h e u n d e r l yin g r e a s o n s , s u c h a s a n e v a l u a t i o n o f w h e t h e rt h e limit s o r p r o c e d u r e s ar e fau l t y , a n d t ak e imme d i a t e c o r r e c t iv e a c t io n . • H uman F act o r s Co n s i d er at i o n s T h e Hy dr o c r ackert e m p er at ur e in st r u m e n t at i o n an d co nt r o l s at T o sco sh o u l d b e desi gn ed co n s i d er in g hu ma n f

act o r s so t h at t h er e i s a go o d f i t o f peo p le , equi pm ent an d en v i r o n m ent co n s i s t e nt wit h go o d in dust r y pr act i ce. T h e sy st em sh o u l d b e r eex am in ed an d r e v i sed as n e c e s s ar y t o e n ab le ap p r o p r i a t e o p e r a t o rmo n it o r in g a n d in t e r v e n t i o n . H y d r o p r o c e s s in g fa c ilit ie s sh o u l d co n s i d er , as T o sco h a s addr essed co n s o l i d at i o n an d int e gr at i o n o f all t e m p er at ur e in di cat o r s f o rhy dr o c r ackerr eact o r s in o n e co nt r o l sy st em wit h all t e m p er at ur es di spl a y e d in t h e c o nt ro l ro o m . F a c ilit ie s w it h c o mp le xr eact i o n s an d pr o cess f l o w sy st em s, such as hy dr o c r ackin g, sh o u l d co n s i d eruse o f a sy st em t h at r e qui r e s le ss o p er at o rma nu al ma n i pul at i o n t o st ay wi t h in cr it i cal o p e r a t in g limit s . F o re x a m p l e , c o mp u t e rmo n i t o r in g a n d c o n t r o l o f c r it ic a l p r o c e s s p ar a me t e r s ma y a llo w o p e r a t o r s g r e a t e rfle x ib ilit y a n d ma n a g e me n t o f t h e p r o c e s s . F o rhy d r o c r a c k in g , u s e o f a co m put ersy st em wo ul d all o w quen c h co nt r o l t o b e l inked t o m o r e t h an o n e t e m p er at ur e po int o rb e pr o g r a m m

e d t o r e s p o n d quen c h co nt r o l can b e l inked t o m o r e t h an o n e t e m p er at ur e po int in

t h e sy st em o rb e pr o g r a m m

e d t o r e spo n d b a sed o n a wi derv ar i et y o f t e m p er at ur e sit u at i o n s . T h e co m put ercan al so b e pr o g r a m m

e d t o make in cr em ent a l t e m p er at ur e ch an ges b a sed o n a in

put r a t e , all o win g eas i e rs t ar t up an d s hut do wn o f t h e un i t .

71H y d r o p r o c e s s in g fa c ilit ie s s h o u ld c o n s id e rh a v in g a b a c kup s y s t em o f cr i t i cal t e m p er at ur e in d i c a t o r s , t o a llo w r e d u n d a n c y o f t e mp e r a t u r e d a t a . S u c h r e d u n d a n c y w ill h e lp t o id e n t ify in st r u m e nt pr o b le m s wi t h

co n f i d en ce an d all o w co nt inued saf e o p er at i o n wh en o n e t e m p er at ur e s y s t e m is ma lfu n c t io n in g . I n d u s t r y in g e n e r a l, s h o u ld e x a min e t h e p r o c e s s p ar a me t e r s t h a t ar e cr i t i cal t o s a f e o p er at i o n an d co n s i d err e dun dant in s t r u m e nt at i o n as a b ackup in cas e o f in s t r u m e nt ma lfu n c t io n . T h e t e m p er at ur e in di cat i o n an d co n t r o l sy st em used at t h e T o sco Hy dr o c r ackersh o u l d h a v e an al ar m sy st em t h at h a s suf f i ci ent h i gh pr i o r i t y

al ar m s t h at can b e r eceiv e d in depen d ent l y

o f o n e a n o t h e r . O t h e rin d u s t r ie s s h o u ld e x a min e t h e i rp r o c e s s mo n it o r in g a n d c o n t r o l in s t r u me n t a t io n t o en sur e t h at in em er gen c y o rupset sit u at i o n s , co nt r o l r o o m o p er at o r s ar e appr o p r i at el y

n o t if i ed o f t h e st at us o f cr it i cal par a m e t e r s so t h e o p er at o rcan t ake n ecessar y st eps t o co r r ect t h e si t u at i o n . S a f e t y cr it i cal al ar m s sh o u l d b e di st in gui sh ed f r o m o t h e ro p er at i o n a l al ar m s . A l ar m s sh o u l d b e limit e d t o t h e nu mb e rt h a t a n o p e r a t o rc a n e ffe c t iv e l y mo n it o r . H o w e v e r , u l t ima t e p l a nt s a fe t y sh o u l d n o t so le l y

r e l y

o n o p er at o rr e spo n se t o a co nt r o l sy st em al ar m . T o s c o s h o u ld imp r o v e o re limin a t e la g t ime in r e c y c le g a s a n a l yz e ra n d p r o v id e a d d it i o n a l c ap ab ilit y fo rt h e d e t e c t io n o f r e c y c l e g a s ab n o r ma lit ie s . T o s c o ma y w a n t t o c o n s id e rt h e u s e o f a co nt inuo us r eal

- t im e an al y zerdedi cat ed t o S t age 2 r ecy cle gas an al y s i s . Huma n f

act o r s an d r i sks f r o m t e m p er at ur e co nt r o l ma lf un ct i o n s sh o u l d b e in co r p o r at ed int o t h e un i t ’ s pr o cess h azar d an al y s i s . • S u p e r v is io n T o s c o ma n a g e me n t s h o u ld c o n s id e rfo r ma l d e le g a t i o n o f t a s k a s s i g n me n t au t h o r it y t o N o . 1 Oper at o r s. A sh if t super v i s o rsh o u l d b e pr esen t at t h e un it dur in g em er gen c y o rab n o r mal sit u at i o n s o rwh en a gr eat erpo t e nt i a l f

o rpr o b le m s ex i s t , such as st ar t up af t e rma int e n a n ce o r int r o duct i o n o f n e w equi pm ent . A s an int e r im s t ep, addit i o n al s uper v i s o r y co v e r a ge s h o u l d b e pr o v i d ed unt il pr o cedur es ar e updat e d an d t r ain in g i s im p r o v e d. T o s c o ma n a gem e nt s h o u l d co n s i s t e n t l y

en f o r ce pr o p eract i o n s an d pr o m pt l y

addr ess an y im p r o peract i o n s wit h r e spect t o em er gen c y pr o cedur es. S uper v i s o r s sh o u l d en sur e t h at pr o cedur es f o rh azar d an al y s i s an d ma n a gem e n t o f ch an ge ar e f o ll o wed. S uper v i s o r s m u st en sur e t h at o p er at o r s ar e t r ain e d an d t e st ed t o im p le m e nt em er gen c y pr o cedur es. S uper v i s o r s sh o u l d b e educat ed o n t h e h azar ds asso ci at ed wit h all aspect s o f o p er at i o n , s t ar t up an d s hut do wn o f Hy dr o c r ackerUn it an d s h o u l d co n duct t h o r o ugh pr e- s t ar t u p a n d p r e - s hu t d o w n s a fe t y r e v i e w s . S u p e r v is o r s s h o u ld id e nt ify c r it ic a l o p e r a t in g limit s a n d e n s u r e t h a t o p e r a t in g c o n d it io n s s t a y w it h in s a fe limit s . E v e n t s in w h ic h o p e r a t in g limit s h a v e b e e n ex ceeded sh o u l d b e t h o r o ugh l y

in v e st i g at ed b y super v i s o r s t o det e r m in e t h e r o o t causes o f t h ese ev ent s . E qui pm ent , an d pr o cedur al an d j o b per f o r ma n ce i ssues t h at r e l a t e t o such ev ent s sh o u l d b e co r r ect ed.

72T o sco ma n a gem e nt , an d in dust r y , m u st in v e st i g at e all dev i at i o n s f r o m expect ed pr o cess co n d i t i o n s an d pr o cedur es t o un der s t a n d t h e un der l yin g r easo n s f o rt h ese dev i at i o n s ; especi all y f o rsaf e t y cr it i cal par a m e t e r s . I f t h e un der l yin g r easo n s ar e n o t suf f i ci en t l y

i d en t if i ed an d addr essed, t h en t h e dev i at i o n s can r e o ccur . T h e in v e st i g at i o n pr o cess sh o u l d in cl ude so l i c it in g an d r e s p o n din g t o o p er at o rin put r e gar d in g o p er at in g pr act i ces an d pr o cedur es . T o s c o ma n a gem e nt m

u st in v e st i g at e Hy dr o c r ackert e m p er at ur e ex cur s i o n s an d det e r m in e t h e cause an d co r r ect iv e act i o n n ecessar y t o pr ev en t such ex cur s i o n s such as en gin eer in g an d desi gn ch an ges n ecessar y t o e n s u r e u n ifo r m flo w d i s t r i b u t i o n w it h in t h e H y d r o c r a c k e rc a t a l ys t b e d s . F a c ilit ie s s h o u ld fr e e l y ex ch an ge saf e t y r e l a t e d l e sso n s l ear n e d am o n g o t h e r s wit h in t h ei rin dust r y . • F a c ilit y R e a d in e s s a n d M a in t e n a n c e A ll fa c ilit ie s s h o u ld e s t ab lis h r e q u i r e me nt s fo re q u i p m e nt in t e g r it y a n d n o t o p e r a t e u n le s s in t e g r it y i s ma int a in ed. T o sco sh o u l d pr o p er l y

ma int a in r eact o rint e r n al s t o en sur e t h at t h e hy d r o p r o c e s s in g e q u i p m e nt c a n b e o p e r a t e d w it h in e s t ab lis h e d s a fe o p e r a t in g limit s . A ll t e m p er at ur e in st r u m e nt sy st em s t h at ar e cr it i cal t o saf e o p er at i o n an d em er gen c y shut do wn equi pm ent m u st b e ma int a in ed in r e l i ab le o p er at in g o r der
. E qui pm ent f u n c t i o n s, in cl udin g al ar m s a n d r a d i o s , s h o u ld b e t e s t e d r e g u l ar ly. F a c ilit ie s mu s t a d d r e s s a n y p r o b le ms w it h e m e r g e n c y s y s t e m s imme d i a t e l y a n d n o t o p e r a t e u n t il t h e s e s y s t e m s ar e fu lly o p e r a t io n a l. P r a c t ic e e m e r g e n c y d r ills s h o u ld b e h e ld o n a

r e g u l arb a s i s . Sin ce i t i s n o t unus ual f

o rpr o b le m s t o dev e l o p wh en equi pm ent i s f i r s t b e in g us ed o rs t ar t e d up, ma n a gem e nt s h o u l d h a v e t ech n i cal an d ma int e n a n ce s uppo r t per s o n n e l av ail ab le at t h e un it dur in g st ar t up o f n e w equi pm en t o raf t e rma j o rma in t e n a n ce h a s b een per f o r m e d. T o sco sh o u l d dev e l o p a per man ent so l u t i o n f

o rt h e pr o b le m o f leakin g h eat ex ch an gerf l an ges an d make t h e n ecessar y ch an ges t o pr ev ent h azar do us hy dr o car b o n leaks. A l so , quen c h v a lv es sh o u l d b e ma in t a in e d s o t h a t t h e y d o n o t le ak
. T h e fa c ilit y’ s ma int e n a n c e p r o g r a m s h o u ld in c l u d e imp le me nt a t io n o f a

me c h a n ic a l in t e g r it y t e s t in g a n d in s p e c t io n p r o g r a m fo rv e s s e ls a n d p i p in g t h at i s co n s i s t e nt wit h cur r e n t pr o cess in dust r y r eco m m

e n d ed pr act i ces.
• T r a in in g an d Suppo r t T o sco an d all in dust r y m u st pr o v i d e t r ain in g f o ro p er at o r s wh en an y ch an ges t o t e m p er at ur e in di cat i o n an d co nt r o l sy st em s ar e ma de. Man a gem e nt sh o u l d pr o v i d e t r ain in g f o ro p er at o r s o n t h e r eact i o n kin e t i cs o f hy dr o c r ackin g, an d causes an d co nt r o l o f t e m p er at ur e ex cur s i o n s . T h e t r ain in g sh o u l d in cl ude t h e b e h a v i o ro f t h e hy dr o g en sy st em in t h e Hy dr o c r acker , especi all y d u r in g s e v e r e t e mp e r a t u r e e x c u r s io n s . O p e r a t o r s s h o u ld b e t r a in e d t o u n d e r s t a n d t h e limit a t io n s o f

t h e p r o c e s s in s t r u me n t s , t h e in s t r u me n t d e fau l t v a lu e s , a n d h o w t o h a n d le p o t e nt ia l in s t r u me n t ma lf un ct i o n s . A ll o p er at o r s sh o u l d b e r e t r ain e d o n t h e use o f t h e em er gen c y depr essur in g sy st em , an d t h e r a t i o n ale f o rim p le m e nt in g em er gen c y pr o cedur es.

73• P r o cedur es E v er y hy dr o p r o cessin g o p er at i o n sh o u l d dev e l o p wr it t e n o p er at in g pr o cedur es t o co v e rall an t i ci pat e d ph ases o f o p er at i o n s . Man a gem e n t sh o u l d dev e l o p a f o r mat f o ro p er at in g pr o cedur es wh i c h pr o v i d es specif i c st eps f o reach o p er at i o n a l ph ase in cl udin g r e f e r e n ce t o equi pm ent an d c o nt r o ls in t h e c o nt r o l r o o m . T h is fo r ma t s h o u ld a l s o a d d r e s s o p e r a t in g limit s fo r each ph ase an d t h e c o n s e q u e n c e s o f d e v i a t io n fr o m t h o s e o p e r a t in g limit s . F a c ilit ie s n e e d t o imp le me nt a me t h o d o f

r e v i ewin g an d updat in g pr o cedur es s o t h at appr o v ed an d t e s t ed ch an ges ar e in co r p o r at ed int o t h e pr o cedur es do cum e nt . T o sco m u st r e v i se pr o cedur es t o r e f l ect cur r e n t o p er at in g m e t h o d s an d equi pm en t an d co n s o li d at e all pr ev i o us S O P s , m e m o s, an d pr o cedur es int o o n e ma nu al f

o rease o f o p er at o ruse. T h e p r o c e d u r e s s h o u ld in c l u d e in s t r u c t io n s fo ro p e r a t o r s t o fo llo w w h e n in s t r u me nt p r o b le ms ar e suspect ed o ro t h e rpr o cess upset s o ran o mal i e s o ccur . T h e o p er at in g pr o cedur es n eed t o b e updat e d wi t h

a des c r i pt i o n o f t h e in s t r u m e nt at i o n def aul t v a l u es an d limit a t io n s . T o s c o s h o u ld specif i call y

r e v i ew an d r e - i ssue o p er at in g pr o cedur es r e l a t e d t o t e m p er at ur e ex cur s i o n s at t h e Hy dr o c r acker
. A l t h o ugh t h ese r eco m m

e n d at i o n s r e gar d in g pr o cedur es ar e di r ect ed at T o sco , all in dust r y sh o u l d e x a min e t h e i rp r o c e d u r e s t o e n s u r e t h a t s imilarc o n d it io n s ar e a d d r e s s e d
. • P r o cess Hazar d A n al y s i s F a c ilit ie s s h o u ld e v a l u a t e p r o c e s s h azar ds b a sed o n act ual equi pm ent an d o p er at in g co n d i t i o n s pr esen t an d used in t h ei ro w n o p er at i o n s . T h e P H A sh o u l d r e f lect t h e act ual in st r u m e n t at i o n an d equi pm ent in use at t h e t im e t h e P H A i s do n e . T o sco sh o u l d r e v i se t h ei rP H A b a sed o n t h e act ual t e m p er at ur e in st r u m e nt at i o n in use an d t h e pr o cedur es av ail ab le. T h e use o f em er gen c y sy st em s sh o u l d b e appr o p r i at el y

specif i ed in t h e P H A an d t h e descr i pt i o n s o f em er gen c y equi pm ent o r sy st em s descr i b e d in t h e P H A sh o u l d ma t c h t h e equi pm en t in t h e f i el d. T o sco sh o u l d en sur e t h at us e o f 100 ps i / m in

an d 300 ps i / m in

depr es s u r in g s y s t em s an d em er gen c y quen c h ar e co r r ect l y des c r i b e d in t h e PHA
. Ri sks o ro p er at in g pr o b le m s i d ent if i ed f r o m act ual o p er at in g pr act i ce, n earm i sses o racci dent s sh o u l d b e addr essed an d ev al uat e d in t h e pr o cess h azar d an al y s i s . F o rex am ple, t h e P H A n eeds t o i d ent if y

ex cessiv e m e t h an e gen e r a t i o n as a po ssi b le cause o f l o w hy dr o g en pur i t y . T h e pr o cess h azar d an al y s i s pr o cess sh o u l d h a v e input an d r e v i ew b y o p er at in g per s o n n e l
. T h e pr o cess h azar d an al y s i s sh o u l d co n s i d ert h e f a il u r e o f cr i t i cal o p er at in g sy st em s, such as t e m p er at ur e m o n i t o r s o r em er gen c y o p er at in g sy st em s. T o s c o n eeds t o r e v i ew an d updat e t h e St age 2 Hy dr o c r ackerpr o ces s f l o w di agr a m s , an d pr o ces s an d in st r u m e n t at i o n di agr a m s t o r e f l ect cur r e n t equi pm en t co n f i gur at i o n . Man a gem e n t o f C h an ge ( M OC ) r e v i ews s h o u l d b e co n duct e d f o rall ch an ges t o pr o ces s , equi pm en t o rpr o cedur es

74t o en sur e t h at all n ecessar y h azar d o rsaf e t y r e v i ews ar e ex ecut e d, t r ain in g i s co n duct e d an d do cum e nt co nt r o l i s ex ecut e d.

75

### APPENDICES Ap p e n d i x A R ef er en ces 1. R e port on the Januar y 21, 1997 Hydr ocr a cker I

n cident at the A v on R e f

i ner y . M a y 29, 1997. T o s c o R e f in in g C o m p an y , M ar t in ez, C a l if

o r n i a. 2. 30- Day W r itten Fi nal R e port, Hydr ocr a cker E x

plos ion and Fi r e , Tos c o A v on R e f

i ner y , Januar y 21, 1997. F e b r uar y 19, 1997. T o s c o R e f in in g C o m p an y , M ar t in ez, C a l if

o r n i a. 3. 72- hour W r itten F o llow

- up N o tif ication, Hydr ocr a cker E x

plos ion and Fi r e , Tos c o A v on R e f

i ner y , Januar y 21, 1997
. T o s c o R e fin in g C o mp a n y, M ar t in e z , C a lifo r n i a . 4. Summar y R e port to the B oar d of Super v is or s on the I n ves tigation of the C aus es of the Tos c o A v on R e f

i ner y I n cident of 1- 21- 97. M a y 29, 1997. Willia m H
. A l t o n a n d L au r a L
. Br o w n . Co nt r a Co st a Co unt y Heal t h

S e r v i ces Depar t m e nt , Mar t in ez, Cal if

o r n i a. 5. Labor ator y analys is of 5 air s a mples in C ontr a C o s ta C ounty . J a nu ar y 21, 1997. B a y A

r ea A i rQual it y Man a gem e n t Di st r i ct . S a n F

r an ci sco , Cal if

o r n i a. 6. C itations and N o tif ications of P e nalty I s s u ed to Tos c o A v on R e f

i ner y f o r V i olations of C

a lif or nia Labor C ode. J u l y

10, 1997. Depar t m e nt o f I n dus t r i a l R e l a t i o n s , Div i s i o n o f Occupat i o n al S a f e t y an d Heal t h , S t at e o f Cal if

o r n i a. CALOS HA Co n c o r d Di st r i ct Of f i ce, Co n c o r d, Cal if

o r n i a. 7. Documentation W o r k

s h eets f o r C itations and N o tif ications of P e nalty I s s u ed to Tos c o A v on R e f

i ner y f o r V i olations of C a lif or nia Labor C ode. J u l y

10, 1997. Depar t m e nt o f I n dust r i a l Rel a t i o n s, Div i si o n o f Occupat i o n al S a f e t y an d Heal t h , S t at e o f Cal if

o r n i a. CAL OS HA Co n c o r d Di st r i ct Of f i ce, Co n c o r d , Cal if

o r n i a. 8. N o tes f r

om M eeting between E P

A inves tigator s and Tos c o management. J u l y

28, 1997. 9. Not e s f r

om M eet i ng between E P

A i n ves t i gat or s and CCCHSD i n ves t i gat or s . J u l y

1 7 , 1997. 10. M anagement Over s i ght and R i s k Tr ee ( M OR T)
. Oct o b e r1996. C o n g er& E l s ea, I n c. , W ood s t oc k , G e or g i a . 11. M anagement Over s i ght and R i s k Tr ee M anual. 1996. Do r i an C o n g eran d Ke n E l s ea, W ood s t oc k , G A
. 12. V i deotape of C ontr a C o s ta C ounty B oar d of Super v is or ’ s meeting, A g enda I t em D. 7 A

p r il 22, 1997. C o nt r a C o s t a C o un t y T e le v i s i o n , M ar t in ez, C a l if

o r n i a.

A- 113. V i deotape of C ontr a C o s ta C ounty B oar d of Super v is or ’ s meeting, A g enda I t em D. 7 Ju n e 3, 1997. C o nt r a C o s t a C o unt y T e le v i s i o n , M ar t in ez, C a l if

o r n i a. 14. R e actor Saf ety I n Hydr opr oces s i ng. M ar c h 1987. C h ar le s S. M c C o y , Or in da, C a l if

o r n i a. PaperNo
. AM

- 87- 56 pr es ent e d at t h e 1987 Nat i o n al Pet r o leum R e f in e r s A s s o ci at i o n A n nu al M eet in g, San A nt o n i o , T e x a s , M ar c h 29- 31, 1987. 15. Hydr ocr a cking, Section 4. 4 of P e tr oleum R e f

i ner y E n

f

o r cement M anual
. J u n e , 1980. P r epar ed f o rUS E n v i r o n m en t a l P r o t ect i o n A g en cy , W a sh in gt o n , DC b y P E DCo

E n v i r o n m ent a l , I n c. , A r l

in gt o n , T X
. Nat i o n al T ech n i cal I n f o r mat i o n S e r v i ce Do cum e nt No
. PB 84- 188861, 16. OSHA I n s t r u ction TE D 1. 15, C H

- 1 , Section X Y : C hapter Z, P e tr oleum R e f

i ning Pro cesses . Dr af t . No v e m b er7, 1995. OSHA Of f i ce o f Sci e n ce an d T ech n o l o gy A ssessm ent . 17. P e tr oleum R e f

i ning f o r the N ontechnical P e r s on. 2n d edi t i o n . 1985. Willia m L
. L e ffle r . P e n nW e ll B o o k s , T u ls a , O k lah o ma . 18. P e tr oleum R e f

i ning, Technology and E c onomics
. 1994. J a m e s H. Gar y an d Glen n E
. Han d wer k
. M ar cel Dekker , I n c. , New Yo r k , New Yo r k
. 19. Chemical and P r oces s T echnology E n cyclopedia. Hydr ocr a cking. 1974. Do ugl as M
. C o n s id in e , e d
. M c G r a w - H ill B o o k C o mp a n y, N e w Y o r k , N e w Y o r k
. 20. Guidelines f o r I

n ves tigating C h emical P r oces s I n cidents
. 1992. C e nt erf o rC h em i cal P r o cess S a f e t y , A m er i can I n st it ut e o f Ch em i cal E n gin eer s, New Yo r k , New Yo r k
. 21. N o tes f r

om meeting between E P

A inves tigator s and R i char d P a lmer of P a lmer and A s s o c i ate s in Mill V a lley , C A
. J u l y

18, 1997 22. C h emical E ngineer s ’ Handbook. 1973. F if t h

edi t i o n . Per r y , R o b e r t H. A n d C h il t o n , C e c il H
. , e d it o r s . M c G r a w - H ill B o o k C o mp a n y, N e w Y o r k , N e w Y o r k
. 23. C A L OSHA I n ves tigation Summar y and N a r r a tive of Tos c o R e f

i ning C o mpany Event of 1/21/97. J u n e 5, 1997. I n v e s t i g at i o n I n v e s t i g at i o n Sum mar y Num b er201480126, R e po r t in g I D 0950622, OSHA

- 36 Num b er361162992, I n s p ect i o n # 125766932. 24. M a r k

s ’ Standar d Handbook f o r M echanical E ngineer s , “ T ab le 8. 7. 3- Pr o p er t i es o f C o m m

e r c i a l St eel Pi pe”. 1987. Nint h E d it i o n . E ugen e A
. A v al o n e an d T h eo do r e B au m e i s t e rIII, e d it o r s . M c G r a w -H ill B o o k C o . N e w Y o r k
.

A- 225. A nnual B ook of A S TM Standar ds , V o lume 01. 01- Steel- P i ping, Tubing, Fittings
. “ A ST M Des i gn at i o n A 335/A 335M

- 94. St an dar d Specif i cat i o n f

o rSeam le s s F e r r i t i c A ll o y - St eel Pi pe f o rHi gh

- T em per a t u r e Ser v i ce. ” 1995. A m er i can So ci et y f

o rT e s t in g an d Mat e r i al s, P h il a del p h i a, P A
. 26. A nnual B ook of A S TM Standar ds , V o lume 01. 01- Steel- P i ping, Tubing, Fittings
. “ A ST M Des i gn at i o n A 530/A 530M

- 92a. St an dar d Specif i cat i o n f

o rGen e r a l R e qui r e m e nt s f o rSpeci al i zed C arb o n an d A ll o y St eel Pi pe. ” 1995. A m er i can So ci et y f

o r T e s t in g a n d M a t e r i a l s , P h ila d e lp h i a , P A
. 27. A nnual B ook of A S TM Standar ds , V o lume 01. 01- Steel- P i ping, Tubing, Fittings
. “ A ST M Des i gn at i o n A 370- 94. St an dar d T e s t M e t h o d s an d Def in i t i o n s f o rM ech an i cal T e s t in g o f St eel Pr o duct s . ” 1995. A m er i can So ci et y f

o rT e s t in g an d M a t e r i al s , P h ila d e lp h i a , P A
. 28. I ndependent R eview of the C ontr a C o s ta C ounty Health Ser v ices Department of the Tos c o A v on R e f

i ner y I n cident of Januar y 21, 1997. J a nu ar y 1998. T h e Nat i o n al I n s t i t ut e f o rCh em i cal S t udi es, Ch ar le st o n , W e st Vi r g in i a .

A- 3Appendix B His t o ry of M a j o r P r oces s Changes 1963 Hy dr o c r ackerwas co n s t r uct e d un dera l i cen s e f r o m C h evr o n R e s ear ch Co r p o r at i o n an d put int o ser v i ce. Un it was kn o w n as t h e I s o c r acker
. 1976 T o s c o pur ch as ed A v o n R e f in e r y f

r o m Ph illip s P e t r o le u m. 1978 Or i g in al Ho n e yw ell an al o g elect r o n i c co nt r o lle r s an d r eco r d er s f o rSt age 2 wer e ch an ged t o F o xb o r o Spec200 an al o g elect r o n i c co nt r o lle r s . 1986 M o dif i cat i o n s wer e in co r p o r at ed in acco r d an ce wi t h

a t ech n o l o gy l

i cen s e fr o m U n io n O il o f C a lifo r n i a mak in g t h e u n it a U n ic r a c k e r . M o d ific a t io n s in cl uded a depr essur in g sy st em , n e w r eact o rt h er m o co uples, n e w hy dr o g en quen c h r in g s in S t age 2, n e w int e r n al s in S t age 2, an d n e w sin g le l o o p di gi t a l co nt r o l s ( M o o r e 352 co nt r o lle r s ) f o rt h e hy dr o g en quen c h s y s t em . A n addi t i o n al b e d ( B ed 4) was added whi c h h a d a l ar g erquen c h v a lv e t h an t h e o t he re x i s t ing f o u rbe d s . 1986 A F o xb o r o Vi deo s pec Di s t r i b u t e d C o nt r o l Sy s t em ( D C S ) was in s t alle d o n S t age 1 an d t h e Hy dr o g en P l ant . 1989 T h e l o w pr es s u r e s ect i o n o f St age 2 was co n v e r t ed t o M o o r e 352 s in g le l o o p di gi t a l co nt r o lle r s an d PC b a s e d dat a l o gger s f o rSt age 1 an d St age 2 w e r e in s t a lle d
. 1990 T h e Vi deo s pec DC S s y s t em f

o rSt age 1 an d t h e Hy dr o g en Pl an t was r e pl aced wit h F o xb o r o I nt e llig e n t Au t o ma t i o n ( I / A ) D C S s y s t e m . J a n 1992 Cat a l y s t was ch an ged t o Z

- 753 t y pe ( 106) in S t age 2 r eact o r s . 1994 T h e St age 1 I /A s y s t em was upgr aded b y pr o v i d in g addit i o n al co n s o les an d al ar m di spl a y s . J a n 1996 M a j o rma int e n a n ce t u r n ar o u n d o ccur r e d. T h e St age 2 cat al y s t ( C r it e r i o n Z

- 753) was r e m o v e d an d s e nt o f f f

o rr e gen e r a t i o n an d t h en r ech ar ged t o t h e l o werf o urSt age 2 b e ds
. T h e t o p b e ds in St age 2 wer e ch ar ged wi t h

a n e w t y pe ( m o r e act iv e) o f cat al y s t ( C r i t e r i o n Z

- 763)
. T h e St age 2 t h er m o well s an d t h er m o co upl es wer e r e pl aced wit h 12- po in t ar r a y st yl e t h er m o co upl es. A ddit i o n al t h er m o co upl es added wer e in st all e d wit h f

i el d pan e l di s p l a y o n l y . T h e t o p quen c h di s t r i b u t o r s wer e m o dif i ed. Dec 24, 1996 T h e St age 1 m o n it o r in g po int s wer e b r o ught int o t h e I /A s y s t em . F e b 16, 1996 Hy dr o c r ackerwas s t ar t e d up. J a n 10, 1997 T h e 40 t e m p er at ur e m o n i t o r in g po int s di s p l a y e d o n t h e St age 2 dat a l o gger w e r e tr a n s f e r r e d f r om th e d a ta l o g g e rto th e I /A s y s t e m . J a n 12- 15, 1997 A n un s c h e duled ma int e n a n ce t u r n ar o u n d o ccur r e d t o r e pai rt u b e leak in a S t age 1 h eat ex ch an ger . J a n 20, 1997 St age 2 po int s wer e r e m o v e d f r o m I /A s y s t em an d r e t u r n ed t o dat a l o gger .

B- 1Appendix C S t age 2 Hydr ocr a ck er P r oces s F l ow Diagr am s

C- 1C- 2A ppe ndix D I nte rbe d Que n c h and D i s t ri bution Sk e t c h e s

D- 1F i gur e D- 2 S t age 2 React o r I n t e rb ed Quench and Dis t ri but ion Det a il s

D- 2A ppe ndix E S tage 2 R e ac tor T h e rm o c o upl e P o ints pe r I n s t ru m e nt D i s p l ay B e d 1 L o cat i o n o f T h er m o co upl e St ri p Ch ar t s Dat a L o gger Fi e l d Pa n e l To t a l
B e d in le t B e d m i ddle 2 2 B e d o u t let 1* 5 5 10 To t a l 1 * 5 7 1 2

B e d 2, 3, an d 4 ( p erb e d) L o cat i o n o f T h er m o co upl e St ri p Ch ar t s Dat a L o gger Fi e l d Pa n e l To t a l
B e d in le t 1 * 5 5 1 0 B e d m i ddle 4 4 B e d o u t let 1* 5 5 10 To t a l 2 * 1 0 1 4 2 4

B e d 5 L o cat i o n o f T h er m o co upl e St ri p Ch ar t s Dat a L o gger Fi e l d Pa n e l To t a l
B e d in le t 1 * 1 4 5 B e d m i ddle 2 2 B e d o u t let 4 1 5 To t a l 1 * 5 7 1 2 *T h i s po int i s al s o t h e s a m e po int di s p l a y e d o n dat a l o gger .

E-1A ppe ndix F A ve r age B e d D i f f e r e ntialT e m p e r atur e f o r R e ac tor 3 (pr e -inc ide n t) React o r3 cat al y s t b e d t e m p er at ur es at 20: 00: 00 ( d at a l o ggert im e ) o r7: 08 pm act ual t im e Pt
. 1 O F Pt
. 2 O F Pt
. 3 O F Pt
. 4 O F Pt
. 5 O F Avg
. O F ° T acr o s s Bed , o f React o rin l e t 632. 2 632. 2 B e d 1 o u t let 659. 1 640. 6 645. 6 645. 5 653. 5 648. 9 16. 7 B e d 2 in le t 625. 8 623. 5 625. 7 630. 2 629. 3 626. 9 B e d 2 o u t let 639. 4 629. 1 634. 4 635. 1 640. 4 635. 7 8
. 8 B e d 3 in le t 619. 2 616. 3 622. 0 621. 2 623. 1 620. 4 B e d 3 o u t let 628. 1 623. 8 627. 7 630. 2 626. 2 627. 2 6
. 8 B e d 4 in le t 620. 3 618. 5 622. 1 624. 3 620. 9 621. 2 B e d 4 o u t let 632. 6 628. 3 630. 0 630. 5 632. 3 630. 7 9
. 5 B e d 5 in le t 629. 3 629. 3 B e d 5 o u t let 657. 0 646. 3 648. 9 645. 9 649. 5 20. 2 React o ro u t let 641. 3 641. 3

A cco r d in g t o t h e st r i p ch ar t , ab o u t 10 h o ur s b e f o r e t h e acci den t , t h e quen c h t o Bed 5 b e gan t o decr ease. T h i s m ean s t h at t h e po i s o n in g h a d st ar t e d t o af f ect Bed 5 at appr o x ima t e l y

9: 30 am J a nu ar y 2 1
. T h e s t r i p c h ar t s fo rB e d s 3 o r4 a l s o s h o w t h e q u e n c h fa llin g o ff a t ap p r o x ima t e ly t h e s a me t ime
.

F- 1Appendix G A gency P e r s onnelI n vol ved in T o s c o Accident I n ves t igat ion Dav i d C hun g, Sen i o rC h em i cal E n gin eer U. S
. E P A Ch em i cal E m er gen c y P r epar edn e ss an d P r ev en t i o n Of f i ce ( C E P P O ) Wa s h in g t o n , D C K a t h leen F

r ankl in , Ch em i cal E n gin eer U. S
. E P A Ch em i cal E m er gen c y P r epar edn e ss an d P r ev en t i o n Of f i ce Wa s h in g t o n , D C G o r d o n Wo o d r o w , E nvi r o nm e n t a l S c i e nt i s t U. S. E P A R e gi o n 9 S uper f un d Div i si o n , S t at e P l an n in g an d A ssessm ent S ect i o n S a n F

r an ci sco , CA N. Åk e Jaco b s o n , Ch em i cal E n gin eer U. S. E P A R e gi o n 9 S a n F

r an ci sco , CA Ro n A n der s o n , Ch em i cal E n gin eer US E P A co nt r act o r , E c o l o g y an d E n v i r o n m ent , I n c. S u p e r f u n d T ech n i cal A ssessm en t & Resp o n se T eam ( S T A RT ) S a n F

r an ci sco , CA Car l a M. F r it z, S a f e t y E n gin eer C a lifo r n i a D e p t . o f I n d u s t r ia l R e la t i o n s Div i si o n o f Occupat i o n al S a f e t y an d Heal t h Co n c o r d , CA Ri ch ar d Ro b e r t s, S a f e t y E n gin eer C a lifo r n i a D e p t . o f I n d u s t r ia l R e la t i o n s Div i si o n o f Occupat i o n al S a f e t y an d Heal t h S a n Jo se, CA Jean P a t t e r s o n , I n v e st i g at o r C a lifo r n i a D e p t . O F I n d u s t r ia l R e la t i o n s Div i si o n o f Occupat i o n al S a f e t y an d Heal t h Bur eau o f I n v e st i g at i o n s S a n F

r an ci sco , CA

G- 1A n dy S a lcedo , Regi o n al S a f e t y E n gin eer U. S
. Dept
. o f L ab o r O c c u p a ti on S a f e ty & H e a l th

A d m in i s tr a t i o n , R e g i on 9 Of f i ce o f T ech n i cal Suppo r t S a n F

r an ci sco , CA Willia m H
. A l t o n , P
. E
. , H azar do us Mat e r i al s Co n s ul t a nt Co nt r a Co st a Co unt y Heal t h

S e r v i ces Depar t m e nt E nvi r o nm e nt a l D ivi s i o n Mar t in ez, CA L aur a L
. Br o w n , Hazar do us Mat e r i al s Co n s ul t a nt Co nt r a Co st a Co unt y Heal t h

S e r v i ces Depar t m e nt E nvi r o nm e nt a l D ivi s i o n Mar t in ez, CA Jef f r ey Go v e , A i rQual it y I n spect o rI I C a lifo r n i a B a y A r e a A i rQ u a lit y M a n a g e me n t D i s t r i c t E n f o r cem ent Div i si o n S a n F

r an ci sco , CA

G- 2Appendix H P art i cipant s on T o s c o Avon Ref i nery Root Caus e Anal ys is U. S
. E n v i r o n m en t a l P r o t ect i o n A g en cy Cr ai g Mat t h i e ssen , S r . Ch em i cal E n gin eer Dav i d C hun g, Sen i o rC h em i cal E n gin eer K a t h leen F

r ankl in , Ch em i cal E n gin eer N. Åk e Jaco b s o n , Ch em i cal E n gin eer Willia m W e is , C E R C L A E n fo r c e m e nt C a s e M a n a g e r G o r d o n Wo o d r o w , E nvi r o nm e n t a l S c i e nt i s t R o n A n d e r s on , E n g in e e r- E c ol og y & E n v i r o n m e nt ( c ontr a c t or ) U. S
. Occupat i o n al S a f e t y an d Heal t h

A d m in i s t r at i o n A n dy S a lcedo , Regi o n al S a f e t y E n gin eer Cal if

o r n i a OS HA Di ck Ro b e r t s, A sso ci at e S a f e t y E n gin eer Car l a F r it z, Co m p l

i a n ce S a f e t y E n gin eer B a y Ar e a Ai rQ u a l i t y Jef f r ey Go v e , A i rQual it y I n spect o r Mo h a ma d Mo azed, A i rQual it y E n gin eer Di ck W o casek, A i rQual it y E n gin eer F a c ilit a t o r Do r i an Co n g er , Gen e r a l Man a ger- Co n g er& E l sea, I n c.

H- 1Appendix I F ol l o w- up Act i ons Undert ak en by T o s c o as of June 1997 A f t e rt h e J a nu ar y 21, 1997 Hy dr o c r ackeracci dent , T o s c o in s t alle d a nu m b ero f f

eat ur es :

• C o m pl et e co n t r o l o f t h e S t age 2 o n t h e I / A sy st em ( a co m put er i zed di st r i b u t e d co n t r o l sy st em . • M a int a ine d har d

- w i r e d s hu t d o w n bu t t o ns . • B ed t e m p er at ur e dif f e r e nt i a l gr eat ert h an 60 degr ees aut o ma t i call y

act iv at es quen c h f

l o w . • C o m put erco nt r o lle d t e m p er at ur e r a m p in g f o rr eact o rst ar t
- up. • I n c r eased r e spo n se t im e ( f r o m 7 t o 3. 5 m inut es) f o rt h e hy dr o g en pur i t y

an al y zer . • R epl acem en t o f r eact o rin t e r n al s ( d i s t r i b ut o rt r ay s, quen c h r in g s, et c)
. & A dded t w o m o r e r eact o ref f l uen t t e m p er at ur e po in t s . • T h e P l a nt I n fo r ma t io n ( P I ) s y s t e m w ill s t o r e a v e r a g e t e mp e r a t u r e d a t a fo ra ye ar . T h e c o n t r o l r o o m w ill s t o r e t e mp e r a t u r e r e a d in g s e v e r y 2 s e c o n d s fo ra s ixmo n t h p e r i o d
. T o s c o h a s in s t a lle d t e mp e r a t u r e d e v i a t io n s a fe g u ar d s fo rt h e fo llo w in g c o n d it io n s :

• A n y t e m p er at ur e po int in t h e r eact o rm o r e t h an 5 o F an d 15 o F ab o v e n o r mal act iv at es an audi b le al ar m . • A n y t e m p er at ur e po int in t h e r eact o rm o r e t h an 25 o F ab o v e n o r mal act iv at es t h e em er gen c y hy dr o g en quen c h s y s t em , adds hy dr o g en , s t o p s f eed, an d s hut s do wn t h e t r im f u r n ace f o ra sin g le r eact o r . • A n y t e m p er at ur e po int in t h e r eact o rm o r e t h an 50 o F ab o v e n o r mal o ran y 2 po int s o v er 800 o F aut o ma t i call y

act iv at es t h e 300 ps i / m in

depr es s u r in g s y s t em . I f o n e po int go es o v er 800 degr ees , t h e s y s t em “ r em em b e r s ” it f o r10 m inut es . I f an o t h e rt e m p er at ur e po int go es o v er800 degr ees wi t h in t h at s a m e 10 m inut e per i o d , t h en t h e aut o ma t i c s hut do wn w ill b e imp le me nt e d
. • A n y t w o o f t h e t h r ee t h er m o co uples in t h e r eact o ref f l uent pi pe o v er800 o F act iv at es t h e 300 ps i / m in

depr es s u r in g s y s t em , wh i c h s hut s do wn all t h r ee r eact o r s . I n s t r u m e nt at i o n ( t h e r m o c o uple) def aul t v a l u es ar e n o w di s p l a y e d as **** in s t ead o f def aul t in g t o zer o ( a n y po int o v er999. 99 o F w ill d e fau l t t o  )
. T h e o p er at o r s can cl i c k o n t h e ** ** t o s e e wh at t h e t e m p er at ur e was , i f it was l e s s t h an 1400 o F
. A r e a d in g fr o m b a d t h e r mo c o u p le w ill b e di s p l a y e d as 999. Oper at o r s r eceiv e d t r ain in g o n 62 dif f e r e nt o p er at in g pr o cedur es, t h r ee day s o f t r ain in g o n t h e I /A sy st em , f o urh o ur s o f t r ain in g o n r eact i o n kin e t i cs. T h ey w ill r eceiv e an 8- h o urt r ain in g sessi o n o n r u n a w a y sim u l a t i o n s o n t h e I / A sy st em . Man a g e m e n t d i scu ssed w it h t h e o p er at o r s t h e n eed t o s hu t d o w n t h e p l a nt w it h o u t fe aro f d i s c ip lin ar y a c t io n if s a fe t y is in q u e s t io n . T o s c o is w o r k in g o n o v er100 dif f e r e nt pr o cedur es .

I-1A ppe ndix J G l o s s a ry
A P I A m e r ic an P e tr o l e u m I n s titu te A S T M A me r i c a n S o c i e t y f

o r Te s tin g an d M ate r ials
au to ig n itio n I n s tan t s e lf

- s u s tain e d c o mb u s tio n o f f

lammab lemate r ials in c o n tac t w ith air wh e n th e mate r ials ar eat a te mp e r atu r eh i g h e n o u g h tos e lf

- i g n ite
. B AAQMD B a y Ar e a Ai r Qu ality M a n a g e me n tD i s t r i c t( S tateo f C alif o r n ia) b lin d f lan g e A l s ok n o w n as a s o lid b lan k
. A s o lid me tal d i s c w ith b o lt h o le s toallo w it tob ef itte d toa p i p eo r v e s s e l f o r p o s itiv ec l o s u r e . B P D B a rre l s p e r d a y B T U B r itis h Th e r mal Un it- a u n it o f e n e r g y b u l l p l u g cy l i n d r i c a l s o l i d p i ece o f p i p es t o c k wh i c h i s t h r e a d ed i n t oa p i p eco u p l i n g o r f l a n g e d t oa pi peo p e n i n g. C A A C le an A i r A c t C A I T EP A ’ s C h e mic al A c c i d e n tI n v e s tig atio n Te am C A L O S HA C alif o r n ia D i v i s i o n o f O c c u p atio n al S a f e ty an d H e alth CCCH S D Co n t r a Co s ta Co un ty H e alth S e r v ic e s D e par tme n t C E P P O EP A ’ s C h e mic al Eme r g e n c y P r e p ar e d n e s s an d P r e v e n tio n O f f i c e C E R C L A C o mp r e h e n s iv eEn v i r o n m e n tal R e s p o n s e , C o mp e n s atio n , an d L iab ility A c t Cr Ch r o m i u m C S B U .S . C h e mic al S a f e ty an d H azar d I n v e s tig atio n B o a r d D C S D is tr ib u t e d C o n t r o l S y s t e m - c o mp u t e r ize d in s t r u me n tc o n t r o ls
. D e ad b a n d A p r e d e t e r min e d amo u n t o f c h an g eb e tw e e n tw ome as u r e d v alu e s , s u c h as te mp e r atu r e r e ad in g s . D e ad zo n e A n ar e a in s i d eth ec ataly s tb e d wh e r elittleo r n of l o w is o c c u r r i n g , r e s u ltin g in in c r e a s e d r e s i d e n c etimein th is ar e a . E& C F Ev e n t an d C a u s al F a c t o r s F C C F lu id C ataly tic C r ac k e r f las h c alc u latio n C alc u latio n o f r ateo f p h as ec h an g ef r o m liq u i d tov a p o r f o r h yd r o c ar b o n s u n d e r s p e c i f i c o p e r atin g c o n d itio n s ( t e m p e r atu r e , p r e s s u r e , c o n c e n tr atio n )
. F l o w c o n t r o lle d ( A s o p p o s e d toman u ally c o n t r o lle d )
. A u to matic c o n t r o l o f a p r o c e s s s t r e am th at u s e s its me as u r e d f l o wr ateas in p u ttoan in s t r u me n tc alle d a c o n t r o lle r wh ic h au to matic ally o p e n s o r c l o s e s a c o n t r o l v alv etomain tain a s p e c i f i e d ( s e tp o in t) f l o wr ate . F O I A Fr e e d o m o f I n f o r matio n A c t
J- 1HA Z O P H azar d an d O p e r ab ility S t u d y gas o i l Amiddle

- b o ilin g po in t r a n g e(450-800 o f ) f

r ac tio n wh ic h is an in te r m e d iatepr o duc t f r o m a c r u d eo il s e p a r atio n o r d i s tillatio n p r o c e s s e s . HD A A p r o c e s s th at r e d u c e s th ele v e l o f ar o matic c o mp o u n d s in d i e s e l tob y r e ac tin g th e m w ith h ydr o g e n . HD N Hyd r o d e n itr o g e n atio n - a h yd r o g e n p r o c e s s th at s e p a r ate s n itr o g e n c o mp o n e n ts f r o m a f e e d st o c k
. HD S Hyd r o d e s u lf u r izatio n - a h yd r o g e n p r o c e s s th at s e p a r ate s s u lp h u r p r o d u c ts f r o m a f e e d st o c k
. HP S Hi g h Pr e ssu r eSe p a r a t o r HRB R o c k w e ll h a r d n e s s n u mb e r , HR u s in g th eR o c k w e ll B s c ale
. Th en u mb e r is d e r i v e d f r o m th en e t in c r e a s ef r o m a te s tin d e n tatio n as a f o r c eo n th ein d e n t e r is in c r e a s e d f r o m a s p e c i f i e d p r e limin ar y te s tf o r c etoa s p e c i f i e d to tal te s tf o r c ean d th e n r e tu r n e d toth e p r e limin ar y te s tf o r c e . I / A F o x b o r oI n te llig e n t A u to matio n d i s t r i b u te d d i g ital c o n t r o l s y s t e m . I s op a r a ffi n Abr a n c h e d h yd r oc a r bon c o n s i s t i n g of s i n g l ec a r bon

- c a r bon bon d s . I I R I s o c ra c k e r I n g e rs o l l R a nd ( h yd ro g e n re c yc l ec o m p re s s o r) L E D A s e mic o n d u c to r d i o d eth at c o n v e r ts ap p lie d v o ltag etolig h tan d is u s e d d i g ital d i s p lay s o n in s t r u me n t s . L P S L o w Pr e ssu r eSe p a r a t o r M T h o us a n d M B P D T h o u s a nd b a rre l s p e r d a y Mg O M a g n e si u m Ox i d e M M M illio n MMSC FD M illio n s tan d a r d c u b i c f e e tp e r d a y Mo Mo l y b d e n u m M O C M a n a ge m e n to f Ch a n ge M T B E M e th y l te r t
- b u t y l e t h e r . A o x yg e n ate d ad d itiv eu s e d toin c r e a s eth eo c tan er atin g o f b l e n de d ga s o l i n e . mu ltip le x e r Ae l e c t r i c al d e v i c ew ith in p u tc a r d s th at c o n v e r t milliv o lt s i g n als f r o m th eth e r mo c o u p l e w i r e s tod i g ital s i g n als wh ic h ar es e n ttoa c o mp u t e r ( d ata lo g g e r ) in th ec o n t r o l r o o m . n i p p l e As h o r tp i ece o f s mall d iame te r p i p e J- 2N T S B U
. S
. N atio n al Tr an s p o r tatio n an d S a f e ty B o a r d
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- te s t Ate r m u s e d tod e s c r i b ep r o d u c t o r s t r e ams th at d on o t me e tman u f ac tu r i n g s p e c i f i c atio n s . ol e f i n As t r a i g h tc h a i n h yd r oc a r bon h a vi n g d o u b l ec a r bon

- c a r bon bon d s . p a r a f f i n A s t r aig h tc h ain h yd r o c ar b o n c o n s is tin g o f s i n g lec a r b o n - c ar b o n b o n d s . PFD Pr o c e ss Fl o w Di a g r a m P HA P r o c e s s H azar d s A n aly s i s P I P lan t I n f o r matio n c o mp u t e r s y s t e m - U s e d f o r man ag e m e n t p u r p o s e s . P & I D P r o c e s s an d I n s t r u me n tatio n D iag r a m P M S P e r f o r man c eM o n ito r i n g S y s t e m . Ac o mp u t e r s y s t e m c o n tin u ally g ath e r s d ata f r o m o v e r 1, 000 in s t r u me n t s in th er e f i n e r y an d dis p lay s c r itic al in f o r matio n too p e r ato r s in dif f e r e n t , o f

te n d i s tan t, p a r t s o f th er e f i n e r y . U s e s a F o x b o r oS p e c t r u m M o n ito r tod i s p lay
. p p m p a r t s p e r millio n ps i , ps i a , ps i g un i to f pr e s s u r e : po un ds pe r s qua r ei n c h , po un ds pe r s qua r ei n c h a b s o l u t e , a n d po un ds pe r s q u a r ein c h g a u g e . A b s o lu tep r e s s u r ein c l u d e s th ep r e s s u r eo f th eamb ie n tatmo s p h e r e wh i l ega ugepr e s s u r edo e s n o t . Pr e ssu r e c o nt ro l l e d A u to matic c o n t r o l o f a p r o c e s s s t r e am th at u s e s a me as u r e d p r e s s u r etoc o n t r o l an o t h e r p r o c e s s v a r iab les u c h as h e at o r f l o wr ate . Th ep r e s s u r eis in p u ttoan in s t r u me n tc alle d a c o n t r o lle r wh ic h au to matic ally o p e n s o r c l o s e s a c o n t r o l v alv etomain tain a s p e c i f i e d ( s e t po i n t ) pr e s s u r e . PSM Pr o c e ss Sa f e t y Ma n a g e m e n t
r e ac tio n k i n e tic s Q u an titativ es t u d y o f th er ateat wh ic h a c h e mic al r e ac tio n o c c u r s , th ef a c t o r s o n wh ic h th is r ated e p e n d s , an d th emo le c u lar ac ts in v o l v e d in th ec h e mic al r e ac tio n . S C B A S e lf

- C o n tain e d B r e ath in g A p p a r atu s
s c f S tan d a r d c u b i c f o o t
- v o l u m eo f an id e al g a s at s tan d a r d c o n d itio n s o f 1 4
. 7 p s ia an d 6 0 o F (pe t r o l e u m a n d ga s i n dus t r y)
. S C F /bbl S t a n d a r d c u bi c footof r e c yc l eg a s p e r ba r r e l of oi l fe e d S C F D S t a n d a r d cu b i c f eetp e r d a y sk i n te mp e r atu r e Te mp e r atu r eo f e x te r i o r me tal s h e ll o f v e s s e l.
S O P S tan d a r d O p e r atin g P r o c e d u r e

J- 3S u lf id in g Fr e s h o r r e g e n e r ate d c ataly s tmu s tb eac tiv ate d b y s u lf id in g p r io r toits u s e . S u lf id in g in v o l v e s h e atin g th ec ataly s tat a c o n t r o lle d r atewh ilec o n tac tin g it w ith h yd r o g e n s u lf id e wh ic h c o n v e r ts th eme tal o x id e s tome tal s u lf id e s , th ef o r m mo s tac tiv ef o r h yd r o g e n atio n . Te mp e r atu r e c o nt ro l l e d A u to matic c o n t r o l o f a p r o c e s s s t r e am th at u s e s a me as u r e d te mp e r atu r etoc o n t r o l an o t h e r p r o c e s s v a r iab les u c h as h e at o r f l o wr ate . Th ete mp e r atu r eis in p u ttoan in s t r u me n tc alle d a c o n t r o lle r wh ic h au to matic ally o p e n s o r c l o s e s a c o n t r o l v alv etomain tain a s p e c i f i e d ( s e t p o in t) te mp e r atu r e . Te mp e r e m b r ittle me n t Ac o n d itio n in wh ic h th ic k w alle d v e s s e ls ar es u b j e c ttoh i g h s t r e s s d u r in g r a p i d te mp e r atu r ec h an g e . Un d e r th e s ec o n d itio n s th es t e e l is b r ittlean d may f

r ac tu r e . Th e e f

f e c tis mo r es e v e r eat lo w te mp e r atu r e s an d w ith th ev e s s e l u n d e r p r e s s u r e . th e r mo c o u p l e Ath e r mo e l e c t r i c d e v i c ef o r me as u r in g te mp e r atu r e , c o mp o s e d o f a tw ow i r e s o f d i s s imilar me tal in a c i r c u it. Th ee l e c t r i c al p o te n tial d i f f e r e n c eg e n e r ate d b e tw e e n th ep o in ts o f c o n tac t ( 2 j u n c tio n s ) o f th ew i r e s is u s e d as a me as u r eo f te mp e r atu r ed i f f e r e n c e . th e r mo w e ll Ame tal tu b ein towh ic h a th e r mo c o u p l eo r th e r mo me te r c a n b ein s e r t e d f o r me as u r in g th e te mp e r atu r ein a p i p eo r v e s s e l. Th etu b eis c l o s e d at o n ee n d an d e x te r n ally th r e ad e d o r f lan g e d at th eo t h e r e n d s oit c a n b ef itte d toa c o u p lin g in th ep i p eo r v e s s e l. TRI S y s t e m To s c or e liab ility s y s t e m . TRI w a s a to o l f o r s c h e d u lin g , p lan n i n g , tr ac k i n g , an d d o c u me n tin g p lan t s y s t e m s an d e q u i p m e n t main te n a n c e . Th eTRI s y s t e m h a s b e e n r e p lac e d b y a n e w s y s t e m c alle d I MPAC T
. tu r n a r o u n d M aj o r main te n a n c eo f e q u i p m e n t f o llo w i n g s h u t d o w n o f o p e r atio n s f o r an e x te n d e d p e r i o d o f

time
. U S EP A U .S . En v i r o n m e n tal P r o t e c tio n A g e n c y W C A T W e i g h te d C ataly s tA v e r ag e d Te mp e r atu r e
ze o lite A ty p eo f c ataly s tmad ef r o m alu min u m - s ilic ateb a s e d mate r ials c h ar ac te r ize d b y a v e r y po r o us s t r u c t ur e .

J- 4