Failure Knowledge Database - 100 Selected Cases

Fire during Ethylidenenorbornene Manufacturing【October 18th, 1973

Kawasaki, Kanagawa, Japan】

Mitsuo Kobayashi (Graduate School of New Frontier Sciences, University of Tokyo)
Masamitsu Tamura (Graduate School of New Frontier Sciences, University of Tokyo)
A series of explosi on and fire accident s related to t he petrochemical industry
occurred in 1973. This a ccident was also one of them. When the course of the accident
is carefully considered, a lesson

will be le arned regarding what to do f

or saf ety

operation of plants developed inside the company.
On October 18th, 1973, a big fire occurred at an in-house developed manufacturing
plant of Nip pon P etrochemicals C o., Ltd ., s oon after the operation was shifted int o acommercial run fr om p erformance run. T wo operators d ied and two operators w ere
injured severely. The construction of the pl ant was completed in July, the performanceruns were carried out i n August, and the r uns were finished with the confirmation ofobtaining the products manufactured to the specification. A total re-adjustment was
carried out in Septem ber, and th e accident

occurred j ust after th e startof thecommercial production i n Octobe r. Fortunately, the install ation site w as located i n alittoral industrial are a, and the pla nt de veloped first was not so big so the dam age
outside of the plant was not large.
The p roduct ethylid enenorbornene (E NB) is form ed fro m cyclop entadiene andbutadiene through many reaction steps, and it is used as the third component for the
manufacture of ethylene-propylen e-diene-monomer (EPDM) rubber . The accident
occurred in the react or where viny lidenenorbornene (V NB), an E NB p recursor, wasbeing synthesized by a Diels-Alder reaction . Operators w ere working f or a temporall y
shutdown of the r eactor because of a failure of the purification section, which is d own
stream of the p rocess. The r eaction was a liquid p hase exothermic r eaction without acatalyst, and it was conducted in a liquid seal type vertical drum with an agitator a nd
a cooling coil. On st opping the reaction, th ey st opped agitation without lowering t hereactor te mperature or changing the c omposition of th e reactio n li quid. The f ire
occurred in the up per p art of the r eactor tw o hours after the agitation was stop ped.
First, a little flame ros e from the reactor, tha t became a comparatively big fire, andthen the reactor and the periphery were wrapped in the fire with a big sound.
The d irect cause of th e accid ent i s to have s topped the agitation thoughtlessly.
Moreover, there were some basic factors leasi ng to th e stopping of the agitation, suchas insufficient operation manual, and transmission of information.

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Failure Knowledge Database - 100 Selected Cases

In the end, the plant was abandoned. Late r, a manufacturing plant using the sameprocess was const ructed at anoth er l ocation with new d esign and new op eration
manuals based on th e experience from the accident. At present, over 50% of the gl obal
production of ENB is manufactured at the plant.
1.

Event
At around 15:19 on October 18th, 1973, there was a fire accident of a reactor in the

Kawasaki li ttoral industrial area t hat wa s accompanied by a sound which seemed toindicate that an explosion occurred as well . The p lant w here th e ac cident o ccurredmanufactured ENB, a substance that is used as the third component of higher grade of
EPDM rubber that sho ws good properties in heat resistance and oil resistance a mong
many grades of EPDM rubber . The plant wa s constructed in Julyfinishing a performance run in August and1973, and after

undergoing re-adjustment in September ,the plant began the co mmercial production few days before the accident. A laboratoryof the parent company Nippon Oil developed

the technol ogy of the process, and thebasic design was carried out in-house. It wa s the s econd or third plant manufacturing
ENB in the world and it was a small type plant with a manufacturing capacity of 3000
ton/year.

ENB is for med by tran sferring the position of the double bond of V NB, which wassynthesized first. Th e accident oc curred in th e r eactor w here V NB was synthesized .
ENB is synthesized fro m two kind s of raw material: cycl opentadiene and butad iene.
When the t wo raw materials are m ixed in th e liquid phase, one d iene combines wi th
the other d iene, and va rious d imers and tri mers ar e obtained, in cluding V NB. F or
improving the VNB yield and decreasing the fo rmation of substances that are d ifficult

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Failure Knowledge Database - 100 Selected Cases

to separate, the operation conditions were set at 115℃ and 2.1MPaG. The reactor wa s
a liquid seal type for preventing the reagents from making contact with air, and it was
equipped wi th an agitator and a coolingcalled thecoil f or mixing a nd cooling. This reacti on,

Diels-Alder (DA) reaction, isa non-catalytic reaction, and theonlycontrolling elements are temperature and composition.

On the day of the accident, the DA reactor for the VNB synthesis was stopped due toproblems of the CPD separation section. The outline of the process is s hown in Fig . 2.
Agitation was stopped soon after

the supply of raw mat

erials was stopped. Thepressure control valve at the r eactor outlet was clos ed manually. The reactor pressurerose after temporally falling as a result of the supply stop, and then the pressure w asreleased by op ening th e byp ass va lve of th e c ontrol valve . T he sam e op eration was
repeated. Soon after the operation, the reactor pressure rose suddenly, and the safet yvalve mounted in the upper part of the reactor operated. A fire was soon occurred in theupper part of the reactor. First a flame spouted out suddenly from the safety valve inlet
flange. In addition, a sli ghtly larger flame rose with a small sound in the upper part of
the reactor. After few s econds, a large fl ame sudde nly wrappe d the re actor. At tha t
moment a slightly larger sound was heard, bu t it was not recogniz ed as an explosion,
because there was no damage to the slate roof or window glass of the nearby building.

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Failure Knowledge Database - 100 Selected Cases

2. Course
At 11:30, the decision was made to stop the VNB reactor in the afternoon because of
the failure in the CPD separation. The shutdown operation st

arted at 13:05. The

following st eps wer e carried out during the shutdown o peration: st opping of t hefeedstock s upply to th e r eactor, s topping of the st eam of the p re-heater, et c. The
shutdown proc edure of the reacto r finished at 13:30. So on after , th e agitator was
stopped and the p ressure c ontrol v alve outl et block valve of the react or outlet wasclosed. The liquid in the reactor was perfectly enclosed as a result of this operation.
The re actor pre ssure d ropped te mporally after the fe ed was stop ped, but after awhile it inc reased grad ually and soon exceeded the no rmal op eration p ressure of 2.1
MPaG. The pressure wa s released at 14:10 by op ening the block valve of the cont rol
valve. The same operation was repeated at 14:15.
The pressure started to rise from 14 :50, and rea ched to 2.1MPaG at around 14:5 5
and 2.2 MPaG at around 15:10.

After that p oint, the pressure ro se rapidly , and it

reached 3.5MPaG in 10 minutes. The temperat ure chart w ent off the s cale, indicatingthat the temperature in the reactor was higher than 150℃.
At around 15:20, a soun d like the operation of the safety v alve mount ed on thereactor was heard , and the te mperature of th e outl et valv e of th e saf ety valve w as
observed to be extremely high. S oon after , a fire oc curred. Th e p ublic fire bri gade4

Failure Knowledge Database - 100 Selected Cases

arrived at around 15:25, and th ey sprayed water for cooling t he site. Confirmation thatthe fire had been extinguished was made at 19:36.
3. Ca use
The cause of the fire was concluded to be an increase of the temperature andpressure in the reactor as the result of a runaway reaction. High-temperature gas andliquid spouted out through the flange, which used a thermally weak Teflon gasket wasused.
Agitation of the reactor had been stopped though the reactor still had the potential
for an exothermic reaction. In other words, the contents of the reactor were still rich inmonomer, the reactor temperature had not been lowered enough to the temperature atwhich the reaction would not occur, the reactor liquid had been enclosed in the reactor
by closing the outlet block valve of the control valve, which is usually used for releasing
the liquid from th e reactor wh en th e p ressure r oses. Th ese factors are considered t ohave caused the fire.
The causes mentioned above are only outward factors, and not true causal factors.
In a non-c atalytic exo thermic r eaction c ontrolled onlyby the te mperature a ndcomposition in the reactor , the exothermic reaction continues if a monomer remains,
and the tem perature is sufficiently high. Furth ermore, if a gitation is stop ped, removalof the reaction heat is not p ossible, s o th e t emperature rises andeventually t hereaction becomes a runaway reaction. This fact should be common knowledge for many
chemists an d chemical engine ers i n the che mical ind ustry. How ever, this comm on
knowledge was not described either in the operation manual or in the directions for the
shutdown p rocedure on the d ay o f theaccident. Th e management staff of the

manufacturing secti on or the staff of the te chnical section should have checked thisimportant point. Accord ing to a che mist who w as a membe r of the R &D team of t his
research th e info rmation on r eaction hazar ds had be en t ransferred fr om t heresearchers to the headquarters or the engi neering d epartment of the factory. Th ere
might be i nsufficient communication in th e company or the p ersons who g ot the
information might not take it s eriously. If th e researchers had prepared the basic partof the safet y manual a bout the reaction, an d had cle arly explained the de tails to thefactory staff and, the accident might not have occurred.
Besides, the p ressure in creased in s pite of the o peration of the safety valve. The
initial bow-off quantity is det ermined acco rding to a saf ety valve ca pacity, and thiscapacity should be large enough t o prevent a r unaway reaction. If the setting of theblow-off p ressure of th e safety valve is below the critical p ressure, c ooling of th e

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Failure Knowledge Database - 100 Selected Cases

reaction liquid may be possible thr ough th e r elease of the heat of evaporation of the
butadiene in the react or. The s etting of th e blow-off quanti ty and blow -off pressure of
the safety might be one of the causes of the accident.
4.

Process of cause elucidation
The danger of a runaway reaction should have been known in the research phase. A

rise in tem perature an d pressure could ha ve been c onfirmed by sim ulations on thepremise of the homogenous condition in p erfect hear insulation. From the records thathave remained in th e control room and the inv estigation of the ac cident site, evidenceof the t emperature act ually rose i n the reactor was found, providing that a runaway
reaction occurred. Th e Teflon gask et at th e sp ot wher e th e safety valve was mou nted
disappeared almost c ompletely. F urthermore, the gasket of the ma nhole wher e th eagitator was mounted was also damaged. Acco rding to the estimation of the remaining
gasket by the gasket manufacturer, it appears that the gasket at the manhole had beenheated to 3 60-370℃ and that the gasket at the mounting sheet of the agitator was
exposed to a high temperature of over 450℃.
5.

Countermeasure
In the accident investigation report , it was indicated thatthe plant w here theaccident o ccurred was the ne wly d eveloped and that the re were pro blems re lated totechnology development. Th

e p roblems included those related to the safetymanagement system, education, and technica l details. The problems of the way oftechnology development are shown below.
“It is necessary to establish a technique for safety assessment in a developing newtechnology. It is also necessary to ha ve sufficient consideration for ensuring the process
safety through all stages suchas res earch and de velopment st age in a laboratory ,process design stage, p lant detailed design stage, c onstruction stage, p erformance run
stage, and commercial run stage. Moreover, it is also important to establish the rule ofthe info rmation ex change fr om on e stage t o th e foll owing stage and t o establish thefollow-up system for t

he f ollowing stage.

Finally, it is necessa ry to

prepare theoperation manual based on the consideration of all possible cases.”
When we a pply the items ind icated in the re port in gen eral exp ression to this
accident as well as to other similar accidents from the aspect of operation and facilities,
the countermeasures can be expressed as follows.
a. In the op eration asp ect, the wo rk procedure s hould be d ecided based on fullconsiderations of the possibility of a runaway reaction. For example, stopping of6

Failure Knowledge Database - 100 Selected Cases

the agitation of a reactor should be absolutely forbidden, until the temperature in
the reactor is lowered to the point at which the reaction cannot occur.
b. Facilities f or controlling a runaw ay reacti on in the initial stage or

before thatshould be installed. The cooling capacity of the coil or jacket should be increased
about 150% or 200% to meet thepotential demand in the case of

emergency .

Another cooling function without

using co oling water should be given. If thecooling using the latent heat of vaporization of the reaction liquid in the reactor ispossible, it is desirable to use it . More over, a t otal blowdown system should beinstalled as a last resort.
c. Duplication of the power supply should be considered.
6. Knowledge
a. Even if the side having information s ends the information, it is not sure whether
information is transmi tted. Whet her th e inf ormation is transmitted or notcompletely depends on the receiver side. For transmission of critical information,
the side having the information must send the information many times and check
both the re ceiver’s acti on and the results of t he action . F or example, effectiv etransmission of critical information can be confirmed by ch ecking the content of
the operation manual.
b. Fo r newly de veloped e quipment, sufficie nt time should be taken to ensure thecomplete safety of the equipment. A performance run of abou t one or two months
is not enough for all of the weak points of the plant and possible omissions during
R&D and process desig n to be f ound. The foll ow-up system including all the
related person must be necessary.
7.

Influence of failure
As for the human damage, two persons died and two persons were injured severely.

As for the p hysical damage, the rea ctor and ne arby objects were co mpletely destroyed,
and the monetary damage was esti mated to be about 300 million yen. The plant wasclosed d own and re-c onstructed in the d ifferent location after s everal years. The total
damage was enormous considering the loss of business and new plant investment.
8. On the side
Later, the operation manual was gr eatly revised, and the plant with st rengthened
safety equipment was constructed. Recentl y, the same plant with the same design was
also constructed in the U.S.A., and over 50% of the world share of E NB production is7

Failure Knowledge Database - 100 Selected Cases

occupied by the plants. Therefore, this is an example in which the facilities and a modeof operation were successfully changed by utilizing experience from the failure.
A “runaway reaction” is an uncontrolled exothermic reaction, and it finally results
in an explosion and fire. In short, a runa

way reaction should be prevented by the

suppression of th e reaction. Conceivable methods are cooling down the reaction liquid
to decreas e the reaction rate, removal of a catalyst, and removal of a reactant. It isreported that when the reactant temperature rises by 10℃, the reaction rate is doubled.
The effective m easures for sup pressing the reac tion are d etermined by the mat erial
and other fe atures of th e reaction. For example, a runaway re action can be stopped byusing a larger heat exchanger. Alternatively, the latent heat of vaporization can be used
for cooling, all of the liquid can be drawn

off by blowd own or high-p ressure nit rogencan be used for the fixed bed catalytic reaction.
References
・The Kanagawa Labor Standards Bureau. “investigation report of fire accident at
ethylidenenorbornene manufacturing plant”(1974)
・The high pressure gas association. Safety research report of Kawasaki and Yokohama
complex, 88-89 (1983)
・Tetsuzo Kitagawa, “Fire during vinylidenenorbornene manufacturing”, “Analysis of
the explosion”. p251-253, Nikkan Kogyo(1980)
・Masamitsu Tamura, Masahide Wakakura, “Ignition under ethylidenenorbornene
manufacturing”, “Reaction hazards- Accident case and analysis”

p35, Seisaku

Kenkyu Center(1995)
・Safety Research Association on hazards

materials in Kawasaki City “Accident casesof hazardous facilities with FTA immediately useful” p.17-19 (1997)
・Chemical Industries Association, “The accident disaster case

Fire and explosion of

ENB plant”, “Safety countermeasure technology of the chemical plant. 4, Accident
disaster cases and countermeasure”, p323-324, Maruzen (1979)8