Lapses in managing styrene monomer gas in the plant and lack of timely emergency response measures led to the styrene gas leak
This is the first section in a two-part series.
Gross negligence by LG Polymers Pvt Ltd in the management of their chemical plant in Andhra Pradesh’s Visakhapatnam led to a gas leak that killed 12 and hospitalised 585 May 7, 2020, said a government report.
Lapses in managing styrene monomer gas in the plant, non-adherence of safety protocols, lack of timely emergency response measures and plans in place resulted in the accident, which also caused a loss of livestock and vegetation.
The report, The High-Power Committee on The Styrene Vapour Release Accident at M/s LG Polymers India Pvt Ltd, was prepared under a joint committee chaired by Neerabh Kr Prasad, Special Chief Secretary of the state forest department and submitted July 6.
Important aspects — including reasons for the release of styrene gas from the plant, lack of emergency response and aspects related to negligence and liability — were described by the report.
The short- and long-term impacts of the gas leak, suggestions related to LG Polymers, industries that use styrene and other hazardous chemicals located close to residential areas were detailed as well.
The report also listed recommendations related to new administrative structures, something that will be discussed in the second part of this series.
Reasons for the gas leak
The entire fact-finding exercise undertaken by the high-level committee included studying all the aspects of the LG Polymers plant. This included the study of the M6 tank from which the gas leaked, extensive discussions with all stakeholders and inspecting available records.
Reports of technical experts of the Chemical, Biological, Radiological and Nuclear department of the National Disaster Response Force (NDRF), the Council of Scientific and Industrial Research and National Environmental Engineering Research Institute and the Andhra Pradesh Pollution Control Board were also studied.
The fact-finding included several other studies done in different areas related to the gas leak. The committee identified a runaway reaction within the M6 tank that held the styrene monomer, as the main cause of the gas leak. A runaway reaction is a thermally unstable reaction system that exhibits an uncontrolled and accelerating rate of reaction that leads to rapid increases in temperature and pressure.
Such a reaction is a factor of heat generation within a system. This resulted in the auto-polymerisation of the styrene monomer in the tank.
The same was verified through different assessments and studies by the committee. It showed an increase in temperature to the boiling point of the styrene monomer — 145 degrees Celsius (°C) — which led to the boiling of the liquid styrene within the M6 tank, causing it to vaporise.
This temperature was reached as the reaction leading to the polymerisation of styrene monomers was highly exothermic, that is, it generated heat at around 71 Kilojoules per mole–1.
The heat that was generated due to polymerisation ultimately led to the runaway reaction. A further increase in temperature led to increase in the pressure of the vapour that led to uncontrolled release of vapour from the vents into the atmosphere since the storage take had structural issues.
The report attributed the onset of runaway polymerisation reaction of the styrene monomer to several lapses in the overall functioning of the plant. These included:
Total breakdown of emergency response procedures
Another aspect was the list of parameters that influenced increase of temperature of styrene in the tank, including tank design, tank temperature measurement and control, recirculation and refrigeration system, inhibitor addition protocols and polymerisation and runaway reaction.
The modification in the piping design within the M6 tank disturbed the styrene recirculation system causing thermal stratification with high temperature gradient, with higher temperatures at the top of the tank than its bottom.
Indulging in the unscientific malpractice of switching on and switching off of the refrigeration and air conditioning system of the tank on a daily basis was done as well.
There was also non-uniform temperature measurement within the M6 tank. An improper statement of purpose (SoP) was also followed by LG Polymers, according to the report. This included controlling the temperature limit of 35°C.
The frequency of measurement of the polymer and p-tert-butyl catechol (TBC) was not followed either. The samples of styrene monomer from the recirculation and refrigeration system at the bottom of the tank analysed only once in four days approximately, the report said.
Limited TBC available at the top layers of the tank was rendered ineffective due to high temperatures. The tank also had old design structures, with a complacency in cleaning the tank resulting in the accumulation of contaminants.
This acted as a catalyst for initiating polymerisation and overwhelmed inhibition effects of TBC, according to the report. The company management also ignored the increase in polymer content from April 4 and a subsequent sharp rise on April 25 / April 28, said the report.
The polymer content is a quality measure for styrene rather than a safety measure.
Early indications of a runaway reaction shown in the rise in polymer content in the M6 tank was ignored, with only one temperature sensor measuring only local temperatures. This did not indicate the temperatures at the higher level of the tank as the contents were not well mixed.
The measured temperature reported by LG Polymers did not reflect the potential catastrophic high temperature hotspots in the tank.
Polymerisation was ongoing and unnoticed in zones that were not near the lone temperature sensor, with a failure to consider TBC stratification. TBC was measured only from bottom layer samples and was not stocked in the plant at the time of accident.
The quantity of high-temperature inhibitors like Tertiary Dodecyl Mercaptan (TDM) and n-dodecyl mercaptan (NDM) were also limited and exhausted after a few hours.
There was no monitoring device / monitoring system in place to measure the quantum of dissolved oxygen in the styrene monomer and no process safety management system was followed either, according to the report.
A lack of knowledge and talent was in the top, middle and shift management was pointed out by the report. It cited unqualified shift in-charges / engineers, whose knowledge and skills were not adequate when faced with a challenge or emergency.
The LG Polymers management was irresponsible because it followed the same SoP — used under regular operational circumstances — for re-opening the plant post-lockdown, said the report.
The management did not consider idling conditions in the M6 tank either, with process safety management systems not implemented and safety protocols not followed.
LG Polymers also failed to submit a hazard and operability study and risk assessment reports.
The onsite emergency plan did not take into account any likely scenarios of styrene vapour release from the storage tank and such a case was never considered for emergency mock drill, the report pointed out.
An offsite emergency plan was not followed. This included not activating the siren, which was in working condition and had multiple activation points, including near the factory gate.
Abysmal safety protocols
The gas release also brought to light the lack of safety protocols by LG Polymers. There was a failure in providing and ensuring information, instructions, training and supervision for the health and safety of all workers during operational start-up.
Restarting the industry was not carried out and there was failure to provide and maintain safety within the plant, said the report, citing standard guidelines. No pre-startup safety review was undertaken, leading to unmanaged identified hazards before starting operations, according to the report.
The storage tank was not subject to any mechanical integrity assessment study and the plant did not implement a Life Extension Programme (LEP). There was also serious non-conformance as the tanks and pipelines were made of mild steel, said the report.
The operations and maintenance of the styrene tanks was also improper, with permissible limits of exposure of Styrene monomer exceeding, the report added.
Workers were not trained on aspects related to styrene, such as its properties, potential for physical hazards and health impacts including primary routes of entry into the body, protection to limit contact, safe work and good housekeeping practices.
They were not informed of the signs and symptoms of styrene exposure, the action that should be taken, which resulted in the aggravation of medical conditions after they were exposed to the gas, said the report.
Workers were not informed of the Dos and Don’ts to be followed in the usage, handling, storing and transporting of styrene.
There was also no information given on the SoPs for emergencies like leaks, spills and fires, etc. The safety report of the plant was not prepared either: This should have been made available according to Rule 10 of the Manufacture, Storage and Import of Hazardous Chemicals (MSIHC) Rules, 1989.
LG Polymers did not have any process safety management system.
On the whole, LG Polymers did not have proper safety protocols and was, in fact, found in violation of a number of them, said the report.
Complete breakdown of emergency response plans
In terms of the emergency response, the report labelled LG Polymers’ management to be inept because a 12-hour delay on their part caused the runaway reaction to take place.
Apart from this, sufficient stocks of chemicals like TDM and NDM were not maintained. Available chemicals like Ethylbenzene were not utilised for terminating runaway reactions.
The report also pointed out other problems, including management lying about the reporting time of their heads of safety, operations, maintenance and production on reaching the spot.
There was no help and support towards rescue and evacuation operations in the affected areas either, with on-site emergency plans not capturing aspects like release of toxic gas cloud / vapours from the storage tanks as an emergency scenario.
There was no proper protocol on existing onsite emergency plan of the plant and non-operational Manual Call Points to communicate the emergency, the report said. Team members also lacked emergency response training and the Emergency Control Centre was not made functional according to the guidelines.
Plant personnel onsite failed to switch on the siren and safety personnel were unable to execute their duties, said the report. Ineffective mock drills had been performed to handle emergencies of this kind, with offsite mock drills not being conducted yearly as stipulated.
The incompetence of management in handling emergencies highlighted the major flaws in the onsite management plan.
The plant depended on the district administration, even for onsite control of the accident, according to the report.
Off-site management plans were also a complete disaster as the management of the plant failed to undertake basic activities like conducting awareness in the neighboring areas about possible hazards and emergencies that can occur, especially being well-aware of the residential areas around the plant.
The report highlighted a list of 21 points of gross negligence by the plant management, as well as 18 counts of violations by the LG Polymers plant and its representatives.
These violations were under the Factories Act, 1948, MSIHC Rules, 1989 and the Chemical Accidents (Emergency Planning, Preparedness and Response) Rules, 1996.
LG Polymers also faces additional liabilities under:
Issues over environmental clearance
One issue that emerged from the report was LG Polymers continuing operations without any Environmental Clearance (EC).
Even though the plant was set up before the first EIA Notification in 1994, the committee noted that an EC under provisions of Schedule 5 (e) of the new EIA Notification, 2006 was applicable.
The same was also accepted by LG Polymers. There was, however, lack of concrete and urgent action.
The report also highlighted the lapse of Andhra Pradesh’s State Environmental Impact Assessment Authority (SEIAA) for accepting LG Polymers’ EC application.
The SEIAA took 18 months to process a violation case application before forwarding it to the Union Ministry of Environment, Forest and Climate Change (MoEF&CC) and not rejecting or forwarding the application to the MoEF&CC as soon as they noticed a Category A project.
The report also took note of the plant not filing for an EC even after seeking consent to operate in 2007 from the Andhra Pradesh State Pollution Control Board. The plant also did not file for EC until April 2018, and filed an application in the SEIAA portal instead of the MoEF&CC portal causing delays in the EC process.
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