The Vizag polystyrene plant accident - Analysis and comments - Chemical Weekly
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Special Report
The Vizag polystyrene plant accident – Analysis and
comments
R
eview and learnings for practicing of polymerisation (technically called as
chemical engineers, based on ‘degree’) decides the properties. Styrene
discussions among the B. Chem. – a common product made by petrochemi-
Engg. Batch (1978) of Institute of Chemi- cal industry world over – is itself an aro-
cal Technology (ICT), Mumbai, formerly matic organic chemical, made by catalytic
known as UDCT. reaction of benzene and ethylene to form
ethyl benzene, followed by dehydrogena-
Background and purpose tion. Styrene is liquid at ambient tempera-
The industrial accident on 7th May ture, and is reasonably safe to handle and
2020, at the polystyrene plant of LG transport, though inherently flammable
Polymers India Pvt. Ltd. at Vizag, lead- B. Chem. Engg. batch of 1978, comprising and toxic. The entire Indian requirement
ing to at least 12 deaths and over 2,000 of more than 15 chemical engineers. Their of styrene is imported from China, and
people affected, has been a matter of names are listed at the end of the docu- several other countries.
concern to the Indian chemical industry ment. The collective ownership of this
and engineering fraternity. As alumni of document is with this team. Besides being used to make PS, sty-
ICT, Mumbai, with a life-time of experi- rene is also used as a raw material for some
ence in design, production, technology The material/s perfumery and speciality organic chemi-
and safety of chemical plants, some with Polystyrene (PS) is a common engi- cals. LG Chemicals, the Korean com-
first-hand experience in styrene and poly- neering polymer, used on its own as a plas- pany owns the PS plant at Vizag, Andhra
styrene plants, we felt compelled to dis- tic or in combined forms with other plas- Pradesh. This plant has gone through mul-
cuss and deliberate on this accident and to tics, resins and chemicals. ‘Thermocol’, tiple ownerships, with stepwise capacity
understand its root cause, so that we can polyester resins, Styrene-Butadiene Rub- enhancement over the last fifty years.
shed some light on the key issues facing ber (SBR) are some of the well-known
the chemical manufacturing industry in forms of PS. The accident
India. A major leakage of styrene occurred in
PS is produced by controlled polymeri- the early hours of 7th May 2020 from the
It may be noted that this discussion is sation of styrene. The extent or the degree LG Polymers plant in Vizag. The spread of
not based on any direct investigation car- this gas into the residential areas surround-
ried out at the accident site, or access to ing the plant resulted in at least 12 deaths
the logbooks, or interaction with the ope- and over 2,000 affected people, caused by
rating or management teams. This may Styrene: its inhalation. The immediate corrective
come out in due course, after official in- actions taken by the plant management
vestigation by the authorities. The princi- and the district authorities are claimed
pal purpose of this document is to capture Other Names : Ethylbenzene,Vinylbenzene, to have restricted the human cost of this
a learned view on the accident, so that phenylethene incident.
recurrence of such accidents can be avoid- Chemical Formula : C6H5CH=CH2
Molecular Mass : 104.15 g/mol
ed in future. As professionals trained in It is understood that the plant was
Physical Form : Liquid at NTP
chemical engineering by one of the top- Density : 909 kg/m3 shut down for nearly 40 days, on account
rated chemical engineering institute in Boiling Point : 145°C the COVID-19 pandemic lockdown in
the world, we feel it is our moral respon- Vapour Pressure : 6.4 mmHg at 25°C the country and was scheduled to restart
Flash Point : 31°C
sibility to check on the overall health of around 7th May. The accident apparently
Explosive Limits : 0.90% LEL-6.8% UEL
chemical manufacturing industry and to Toxicity: LD50 : 2194 ppm (mouse, 4 hr) took place during the restart.
help improve its image in society. 5543 ppm (rat, 4 hr)
It is important to note that accidents in
The note is based on the discussions Ref.:https://en.wikipedia.org/wiki/ styrene plants, storage and transit, caus-
Styrene#Health_effects
among the WhatsApp Group of the ing styrene leak and associated damages,
Chemical Weekly May 26, 2020 137Special Report
Table 1: Selected thermal runaway incidents related to the styrene process is currently imported, mainly from the
Consequences Middle East, North East and South East
Date Location Asia. A styrene production plant requires
Injury Fatality
significant investment to set up and run;
07/05/1994 Kaohsiung, Taiwan 0 1 and it does not seem economical for
01/26/1996 Chiayi, Taiwan 1 0 Indian users of styrene to have their own
01/21/1998 Kaohsiung, Taiwan 4 0 production plants in India. This may have
led to current Indian users being less
12/24/1998 Kanagawa, Japan 0 0 informed on the practical aspects of
06/27/1998 Channahon, IL, US 1 0 handling styrene.
06/23/1999 Pasadena, TX, US 21 2
Styrene tends to self-polymerise,
10/06/1999 Chiayi, Taiwan 1 0
even at ambient temperature, albeit at
03/27/2000 Pasadena, TX, US 71 1 very slow reaction rates. However, even
04/02/2003 Addyston, OH, US 0 1 the slow rates of self-polymerisation
04/08/2004 Jiangsu, China 8 6 cause major operating issues, because
of heat liberation, blockages in the tank,
06/30/2005 Mesa, AZ, US 0 1 pipelines and pumps due to the formation
Ref.: Lin Zhao et al, ACS Omega, 2019 4 (5), 8136-8145
of a solid polymer. The rate of this reac-
fatalities and non-fatal human damages M/s. Polychem, operated in Mumbai from tion doubles every 10°C. Such polymeri-
are not uncommon. In fact over last 25 the 1956 to around 2005. This was based sation can lead to quality deterioration
years, there have been 11 accidents – four on technology sourced from M/s. Dow and operating issues. The combination of
in Taiwan, one in Japan, one in China and, Chemical – initially 7,500-tpa (tonnes polymerisation – heat liberation – tem-
four in USA – collectively accounting for per annum) capacity, single-line, which perature rise – and further polymerisation
12 fatalities and 107 injuries (Table 1), the was later doubled. The PS was used to can lead to rapid reaction and heating;
most recent being from the styrene-car- make general-purpose PS (GPPS) and this is known as a ‘run-away reaction’.
rying railway tanker at Cincinnati, USA, high-impact PS (HIPS), the latter through As the temperature rises, styrene starts
in Aug. 2005. In fact, EPA came out with addition of polybutadiene rubber. The vaporising. The pressure in the storage
an Emergency Response Guideline Book Polychem plant was closed around for tank may progressively increase, and the
with scientifically validated approach list- environmental and economic reasons safety valves provided on the tanks may
ing chemicals which undergo self-poly- around 2005, and its assets were sold to open. The styrene storage tanks are there-
merisation. (Ref.: https://www. aristatek.com/ Supreme Industries Ltd. fore fitted with secondary containment
Newsletter/OCT08/TechSpeak.pdf). facility, to prevent any leakage to the
The entire Indian requirement of sty- environment. The tanks are also provided
Technical background of PS reaction rene – about 850,000-tonnes in 2018-19 – with cooling/chilling circuits, which can
PS is made from styrene by thermal
initiation process; i.e. styrene is initially Self-Polymerisation of styrene
heated to start up the reaction, following
which the inherent exothermic (i.e. heat-
liberating) nature of the resulting poly-
merisation reaction causes the temperature n H
to rise rapidly. The temperature rise cannot
be left uncontrolled, and the heat gene- C C
rated, is removed by circulating a thermic H H n
fluid (Dowtherm DTA), so that the reactor
operates at the desired temperature around Enthalpy of polymerisation: 49-160 kcal/kg
450°C. The polymer formed is in the mol- TBC (Inhibitor) slows down the reaction rate; does not inhibit polymerisa-
ten form; it is extruded into strands, cut tion totally.
into granules and despatched to customers. Rapid temperature rise starts at 100-105°C, under adiabatic conditions.
A plant for making PS, named as Ref.: https://pubs.acs.org/doi/10.1021/acsomega.9b00004
138 Chemical Weekly May 26, 2020Special Report
bring down the temperature and control Uncontrolled polymerisation during the probability of such failures occurring
the reaction. prolonged storage is low.
It is understood that the PS plant was
In order to avoid such polymerisation, closed during the COVID-19 lockdown Non-adherence to standard operating
styrene is mixed with a polymerisation and was being restarted after relaxation procedures (SOPs)
inhibitor – 4-tert-butylcatechol (TBC) – at of lockdown conditions. The accident All plants are slated to follow set
controlled concentrations. This prevents took place during the restart operations. SOPs. There are well-defined SOPs even
polymerisation during high sea or road Was the right level of TBC added to the for shut-down and start-ups, including
transit, as well as during storage. Before styrene stored, given that the ambient for warm-shutdown and warm-start up
utilising the styrene for PS synthesis, the temperature in March to May can be very (which means stopping a running plant
TBC needs to be removed. Provision to high (≥40°C). The styrene in the storage and restarting the same with materials held
remove the TBC is an integral part of tank could thus have experienced such up in the plant). For the mature technology
styrene storage facility. Use of TBC is high temperatures for almost forty days used in PS plants all over, such procedures
practised especially by those users who during the shutdown, resulting in uncon- are followed globally and any abnormal
handle and store large quantities of sty- trolled polymerisation inside the storage temperature/pressure in the styrene stor-
rene. Users of small quantities or those tank; and temperature/pressure rise could age tank would have been detected before
who make immediate use of styrene within cause the styrene to evaporate, build up re-starting up the plant. All failure condi-
minimal storage time, may not use/add TBC. pressure and escape through vent. tions are expected to surface through a
structured pre-start audit procedure. Since
In the event of styrene vapours escap- Failure of the temperature control the plant shutdown was likely to have been
ing from the tank/premises, it is required system on styrene storage tank done at a short notice, due to COVID-19
to know how far the vapours can spread; In case polymerisation commenced lockdown order, the SOP for warm shut-
and how many people/animals/farms in the storage tank, it is possible that the down, which should have been followed
may get affected. The regulatory au- temperature control system based on the as a rule (covering, for example, emptying
thorities have made it mandatory for the circulation of coolant fluid/chilled water transfer line, mixing additional dosages of
producers to evaluate the spread of the may have failed. Good design practice polymerisation inhibitor, recording of tank
vapour and its human impact on mathe- – as shown in Figure 1 – generally provides temperature during shutdown, etc.) may
matical diffusion models, accounting for for interlocks which does not permit such not have been fully followed as per com-
external factors like wind direction and failure to occur, because alarm systems get pliance requirements.
speed, ambient temperature, season and activated well in advance of failure. In a
time of the day, and the location of human well-designed & well-maintained plant, Chemical engineers in this WhatsApp
population in a 360 degree radius of the
STYRENE TANK
plant. Permitted quantities for storage,
the primary and secondary containment CIRCULATION IN PROGRESS
measures, disaster management facili-
SET POINT (LO)#COM 0 C
ties mandated and the consent to operate SET POINT (H1)#COM 0 C
are planned based on these modelling
studies. The consent to operate are also
audited periodically by statutory authori-
ties and by plant management audits, to
assure total compliance. LT-sty
CHWR
Strict adherence to the above guid- HE-7
#COM
ance assures safety in styrene handling, #COM CHWS
transit, storage and PS production facili-
#COMMT
Ch water supply valve Interlock
#COMxg
Set [point Ch water
ties. #COMMT TO BL1
#com c < #com c
#COMCM
TO BL3
Possible causes of the accident STYRENE STYRENE
TO BL5
With the above technical background,
we discussed the possible causes of the
accident, which are summarised here. Fig. 1: Styrene storage tank safety system
Chemical Weekly May 26, 2020 139Special Report
group, with considerable experience in A supply of TBC must always be Green tag system and Lock out Tag out
start-up and shut-down of similar plants available in the plant raw material (LOTO) system is also rigorously fol-
(such as LPG, hydrogen sulphide, and stores for emergencies. lowed. For a non-routine operation (like
other reactive monomers), have high- It may be noted that even technically drilling exploration or High-Pressure
lighted the need for total rigour in follow- empty styrene tanks are prone to con- High Temperature well), DWOP (Drill-
ing procedures for shutdown and restarts tain solid deposits of polymer, which ing Well On Paper) exercise is carried
in order to avoid accidents. can often be found on, and inside, the out and hazard analysis is undertaken in
casing of submersible pumps. This detail, including severity matrix and miti-
Considering that the plant and tech- may be attributed to the polymerisation gation methods. This makes the people
nology is well established, and several of residual styrene, traces of which can and management prepared for any even-
shutdowns and start-ups may have been accumulate inside sumps and pumps, tuality by revising the basics of process
done, SOP must have been available for causing jamming of the pump impel- safety.
these operations. ler. When this was observed in a sty-
rene storage system a few years ago, Industry-specific safety measures (if
Practices in MNCs using styrene as raw the Plant Safety Audit Committee re- not available) must be developed and
material commended removing and overhauling rigorously followed by all sectors of the
The members of this WhatsApp group of the submersible pump at the end of chemical industry. There are no short
with considerable expertise in handling each production campaign. Jamming cuts to safety and safety has no holiday.
styrene wish to share the following good of submersible pump can also hap-
manufacturing practices: pen with a fresh lot of styrene due to The recent circular from the Ministry
the inherent fine clearance between of Industries (issued post the LG Polymers
When styrene is used in small quan- the pump shaft sleeve and the bush- accident) regarding safe restart procedures
tities with short storage times, the ing mounted inside the hollow vertical to be followed is a glaring example of
polymerisation inhibitor needs to be pipe of submersible pumps. the lack of serious thought.
monitored to avoid depletion. Many Normal production campaigns gene-
medium/small users of styrene do not rally run continuously round the clock Partial failure of knowledge transfer
check the levels of this vital inhibitor and situations involving cold/warm It is observed that for many mature
(LG is a large company though). We start-up and shut-down are very rare. technologies transferred to the develop-
understand that after the accident, LG As such, plant operating personnel ing world, the effectiveness of know-
Polymers urgently purchased the in- have little or no practical experience of ledge transfer between generations of
hibitor to save the remaining quantity these kind of start-ups and shut-downs. engineers is not robust. With the comfort
of styrene. of good safety track records of such mature
A spare or standby storage tank hav- All the above learnings from different technologies, the current generation of
ing the same capacity as the styrene plants around the world must become an plant engineers often do not possess the
tank under consideration must always integral part of the knowledge base of any necessary practical understanding and
be available in case of emergency, so styrene handling facility globally. insights, which the earlier generations of
that styrene can be transferred from engineers – who were involved in plant
the regular storage tank if the storage Hazard & Operability Analysis (HAZOP) design and construction – possessed.
system fails. Oilfield operations involve many During the transfer of knowledge bet-
As far as possible, it is desirable to start-ups/shut-downs and so-called ad ween generations, a lot of key messages
continue running the production plant hoc operations. It is common practice gets inadvertently obscured.
until all the styrene is completely to undertake a complete HAZOP before
used up, and then organise the shut- any operation. Oil rig operations involve We observe that, despite its invalu-
down. This will eliminate the need to highly flammable materials and are able role in the success of chemical manu-
store and monitor styrene. hazardous. Even in the case of routine facturing industry, technology transfer
It is also good practice not to store operations, a ‘permit to work’ system is remains a non-standardised process. It
styrene over extended periods of in place and is strictly adhered to. remains a one-time activity, when the
time. technology is purchased, or transferred
Stored styrene must preferably be Toolbox talk is mandatory to create from lab to plant, and no formal process
under nitrogen blanketing all the the ethos, to revise well-known practices, for technology transfer is standardised in
time. and to warm-up for a safe operation. the later life of a plant. It is required to
140 Chemical Weekly May 26, 2020Special Report
develop, follow and execute a technical ruthlessly and improved, based on the work. The severity of such accidents man-
standard for the same. experience, in line with the word and dates that chance of errors should be mini-
the spirit of the audit, by honest audit- mized through automation, interlocks, and
Audit failure ing agencies. (Ref.: https://www.nistinsti- controls.
The rigour and discipline of audits tute.com/hse-audit-for-process-chemi-
(plant audits, safety audits, management cal-industries.php). Timely legal/punitive action
audits) is supposed to take care of pro- Prima facie it looks like there was
cedural lapses and bring back the disci- Seriousness in execution of warm gross negligence on somebody’s part
pline. Audits, if conducted seriously, can shut-down and warm restart while preparing to restart the closed plant.
help correct many such lacunae. This In the case of LG Polymers, we un- The main reason for such casual attitude
WhatsApp Group strongly feels that derstand that this was not a normal shut- is lack of concern for safety of fellow be-
most audits are now conducted with the down. It was unplanned shut down. Com- ings – both inside and outside the plant.
intent of securing certification, which pany could have approached government The Bhopal accident is a glaring example
are mandated by statutory authorities or and continued some operations, till it of how no one was deemed liable and the
the customer, and miss out on compre- was safe to shut down. The inventory guilty escaped unpunished. We sincerely
hensive corrective actions. This needs to could have been reduced to safest levels. hope that those liable in this case are
be redressed as a matter of priority. The intermediate tank, after removal of brought to account. Timely punitive action
polymerisation inhibitor, should have (including stringent actions as cancellation
The team feels that the following sprinkling system fitted to keep material of qualification/licence, ban on similar fu-
good practices need to be seriously put cooled during shut-down. There must be ture employment, financial liability etc.)
to implementation: round-the-clock monitoring of such tanks can prove to be strong deterrents to casual
Management commitment to conduct for temperature and pressure. The opera- approaches which some plant personnel
business in safest and sustainable way. ting personnel need to be adequately seem to take.
Repeated and consistent training to trained, specifically for shut-down and
employees on process sensitivities, in- recommissioning. Change management
cluding safety awareness. There are many changes made dur-
Regular, frequent and comprehensive It is observed that most managements ing normal running and shutdown. These
safety drills. normally do not give the necessary atten- changes must be authorised by expert
Sustained campaign on safety aspects tion to recommissioning; and push for rapid members of senior leadership team, and
for all operations in business. production. The restart of a plant after operating personnel must be well trained
Adequate funds and skilled manpower shutting down is most difficult, even more and informed about the changes made.
to accomplish the tasks. difficult than the initial commissioning. There must be a documented system
Recognising and rewarding emplo- This is due to the presence of a big team for the same, and changes should be re-
yees who follow practices, and puni- to supervise first commissioning of a plant viewed by top management. It is very im-
tive actions against those found to be (Design, R&D, Projects, Instrumentation, portant to get HAZOP done before these
non-compliant. Maintenance etc). But in the case of plant changes are implemented.
Comprehensive & brutally honest restart, it is only the core production team
audits (safety audit, systems audit & that is involved. The restarting team rarely Learnings
overall management audit). In our know the amount of energy they are hand- Since the purpose of this analysis is
opinion, the ‘big rot’ lies here and must ling and hence can be negligent. Many a not to find the specific causes of the Vizag
be corrected as a matter of urgency. times, auditors can find vital alarms being accident, but to capture and consolidate
Good audit practices, such as: not us- bypassed. Training and commitment to the learnings so that such accidents can be
ing the same auditor/auditing agency SOP are critical. avoided in the future, the team has listed
for more than two years; no sample the main learnings. These may serve as
audit, but comprehensive audit of all Human errors useful for practising chemical engineers,
aspects, every two years; financial Human errors cannot be the excuse designers and students of chemical engi-
liability of auditors individually and as for industrial accidents. Experience shows neering and process safety, alike.
agencies, for auditing failures; audit of that human errors can be minimised
audits, etc., need to be implemented. through multiple, interlocked actions such Continuous, comprehensive & rigorous
NIST/ISO standards available for as efficient supervision, pre-job safety training
such purpose need to be implemented meetings, and comprehensive permit to The plant personnel at all levels
Chemical Weekly May 26, 2020 141Special Report
should be repeatedly trained in all as- properly – whether for process, safety, datory for recording and monitoring of
pects of the process and tested repeatedly. environment, quality, finance, or man- critical areas of plant operation includ-
Training should be meant for all – from agement. Never look at audits as a mere ing storage systems. Obsolete persona-
plant management to the plant cleaning & means to get certification, or awards. lised system of monitoring, which is a
security personnel. Never interfere with the auditors’ work; routine practice followed in old plants,
demand a thorough audit; do not be de- must be replaced.
Extra focus on non-routine situations fensive; do not take short-cuts with audi-
and change management tor’s comments and recommendations, Government of India must restrict the
Even situations which are extremely even if it takes time for implementation. expansion of plants over 50 years old,
uncommon, but possible, should be co- Change the auditors/audit team periodi- which are already depreciated. These
vered in these trainings. The comfort and cally, lest both parties develop a comfort plants pose serious dangers to human
familiarity developed by operating per- with each other, and compromise on the health, whenever actions fall short of ope-
sonnel through long stretches of no-loss- audit quality. An auditor who agrees that rational standards. Environmental emis-
time runs, which the plant must be rightly everything is okay in your plant is most sion standards must also be comparable
proud of, should be questioned. Change likely not to be doing his/her job to the with new plants elsewhere.
management is a critical aspect of non- right extent of professionalism. Let the
routine operations: it must be system auditors know that you want them to Government of India must also re-
based, with proper authorisation, assign- be brutally honest. Auditors are critical strict/ban and impose financial disincen-
ment of responsibility, and interlocks for watchdogs for longer-term success. tives on organisations importing tech-
checklist. Such change management pro- nologies older than, say, 25 years for
cedures need to be emphasized periodi- Combination of punitive actions and manufacturing chemicals in India.
cally and revised on any plant upgrades, rewards
overhauls etc. Standard safety pyramid There will always be situations where List of contributors
data based on near-misses to fatalities, compromises are made in the interest of The following ICT alumni contri-
should be captured, analysed and shared. short-term gains (such as meeting daily buted to the discussion (in alphabeti-
Data and learnings from external plants volumes, costs). Management may ap- cal order of names): Amberkar Vivek,
engaged in similar processes/products preciate a production team for such Bhirud B.V., Dharmadhikari Rajendra,
must be captured and shared for learning. achievements, but simultaneously repri- Gulati R.S., Kakade Vikas, Katti Sanjeev,
mand them for the shortcuts taken and Kulkarni Nandkumar D, Kulkarni Sad-
Never underestimate a chemical/ negligence. They should get a weighted guru, Kulkarni S.R., Mehta V.P., Mhatre
material average of both these actions! Set up a Mangesh, Narvekar Ravindra, Niranjan K,
Plant operating personnel must never system to take timely punitive action on Pai Raiturkar Avadhut, Phalak Kiran and
become complacent and feel that ‘we such behaviour; and reward those who other members of the WhatsApp group:
have handled this chemical/material for honour and implement the correct way of UDCT B. Chem. Engg. 1978.
years, so nothing will happen.’ Treat working. Let this message be made loud
every chemical/material with the due and clear to all. Coordinated and edited by Sadguru
respect it deserves. Kulkarni and K Niranjan.
Additional suggestions
Know-what, Know-how, know-why A few more suggestions: Contact for communication: sadguru.
Establish a system for knowledge Styrene is handled in India by seve- kulkarni@gmail.com
transfer; and ensure that people con- ral PS manufacturers since 1956, but no
cerned have the know-what (what they accident has occurred so far. The Vizag Disclaimer
are supposed to do), know-how (how plant is over 50-year-old and was taken The authors do not claim to have
they are supposed to do it) and know-why over by the Korean MNC LG Chemi- first-hand knowledge of the LG Polymers
(why they have to do it that way). The cals, who are a knowledgeable in the accident. The information and comments
responsibility with which people will manufacture of PS. It is necessary for made above are based on their profes-
work, goes up by orders of magnitude the current owners to bring state-of-the- sional experience as practising chemi-
when they know-what-how-&-why. art technology, SOP for safety standards, cal engineers. ICT is not associated with
and technical audits while operating and this article and does not stand liable. The
Brutally honest audits further expansion in plant capacity. Up- authors do not stand liable for the use of
Ensure that companies use auditors grading technology must be made man- the information given in this document.
142 Chemical Weekly May 26, 2020You can also read
