Process safety failures led to the fatal Styrene release in India last month

Today, the Indian government released its investigation findings regarding the fatal Styrene release on May 7, 2020, which killed 12 citizens and hospitalized 585 others.  This incident, like the many before it, came about by a number of failures the facility/company made in the management of their Styrene inventory.  In the light of the root causes discussed, the Committee is of the view that the accident in the Styrene storage M6 Tank can be attributed to:

1. the poor design of the tank,
2. inadequate refrigeration and cooling system,
3. absence of circulation & mixing systems,
4. inadequate measurement parameters,
5. poor safety protocol,
6. poor safety awareness,
7. inadequate risk assessment and response,
8. poor process safety management systems,
9. slackness of management,
10. insufficient knowledge amongst staff,
11. insufficient knowledge of the chemical properties of Styrene, especially during storage under idle conditions.

SAFTENG members can download the full report which contains a fishbone diagram/root cause analysis.  The Committee deliberated on the main causes of the accident and identified the following as the root causes behind the runaway polymerization reaction leading to uncontrolled Styrene vapor release from M6 Tank in LG Polymers Visakhapatnam.

Here is a more detailed discussion of these failures:

1. Tank design was not proper
   1. Poor Maintenance of Tank
   2. the conical roof is supported within the tank interior.
   3. number of idle nozzles NOT kept at a minimum
   4. age of tank exceeded its intended service life
   5. Tank materials of construction was NOT proper
   6. tank neither has a flare system nor a cryogenic system to condense Styrene vapors
   7. Change of Design in the suction and discharge lines of recirculation circuit in M6 Tank
2. Tank Temperature Measurement & Control was woefully inadequate
   1. Wrongful assumption of Bottom Temperature as Temperature of the Whole Liquid Styrene in M6 Tank
3. Recirculation and Refrigeration System
   1. Inadequate Time for Refrigeration and Manual Operation
   2. Improper Cooling of Styrene Monomer due to Design Change in the Refrigeration
   3. Possibility of R-22 contamination of Styrene Monomer in M6 Tank
   4. Insufficient Capacity of the refrigeration unit
4. Inhibitor Addition Protocols
   1. Improper SOP for Inhibitor Measurement
   2. Unavailability of inhibitor Stock
   3. Decrease of TBC Concentration in Styrene
   4. Absence of monitoring of Dissolved Oxygen
5. Lockdown Period

1. The modified piping design carried out by December 2019, within the M6 Tank not only totally disturbed the Styrene recirculation system but also led to significant thermal stratification in the M6 Tank with high-temperature gradient. Hence, the top level of the Styrene monomers in M6 Tank experienced much higher temperatures than the bottom layer.
2. The refrigeration system was operated as a standard practice in LG Polymers from 8:00 a.m. to 05:00 p.m. only on all days manually. There was an inadequate time duration for the Refrigeration and cooling system to maintain the temperature of Styrene monomer below 20°C in the M6 Tank at all levels in the tank.
3. The temperature measurement in M6 Tank is restricted to the bottom zone, while the top and central zones had higher temperatures. Thereby, the temperatures at the top level and the middle level were not available at all to detect the temperature rise in the upper levels. Further, the SOP followed by LG Polymers for the temperature limit of 35°C was improper. The prescribed frequency standards of polymer and TBC measurement were also not followed and the samples of Styrene monomer from the recirculation and refrigeration system viz., bottom of the M6 Tank was analyzed once in 4 days approximately by LG Polymers.
4. The high temperatures at the top levels of the tank led to Thermal Radical Polymerisation. The high temperatures made the limited TBC available (due to Thermal Stratification) at the top layers ineffective.
5. The M6 Tank was an old tank with old design structures. The inner side of the tank was not lined. Further, LG Polymers was complacent in cleaning the tank once in 5 years (last cleaned in 2015) resulting in the accumulation of contaminants, which acted as a catalyst inside the tank, initiating polymerization of Styrene which overwhelmed the inhibition effects of TBC.
6. The company management had ignored the increase of polymer content from 4th April 2020 and the n the sharp rise on 25th April 2020 / 28th April 2020. The management considered polymer content as a quality measure for Styrene rather than a safety measure. The early indications of a runaway reaction shown in the rise in polymer content in the M6 Tank was totally ignored.
7. Onset of the runaway polymerization reaction is the critical parameter in the root causes of the accident. There was only one sensor for temperature which measured only the local temperatures and 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 any potential catastrophic high-temperature hot spots in the tank. Polymerization was ongoing and unnoticed in zones that are not near the lone temperature sensor for the quantity (1937 MT) of Styrene monomer in (in 18 m dia x 12.185 m tall vertical cylindrical fixed roof tank). The uncontrolled Styrene vapor release from the M6 Tank was due to high temperatures, well beyond the company’s protocol temperature of 35°C.
8. The company failed to consider the TBC stratification and measured TBC only from the samples from the bottom layer. Further, there was no stocks of TBC available in the LG Polymers at the time of the accident. The number of high-temperature inhibitors like TDM & NDM was also limited, which got exhausted after a few hours and failed in preventing the runaway reactions.
9. There was no monitoring device or no monitoring system in place to measure the quantum of dissolved oxygen in the Styrene monomer in M6 Tank.
10. As clarified later in this chapter, no process safety management system was followed in LG Polymers.
11. There was a dearth of knowledge and talent among the top, middle, and shift management in LG Polymers. Most of the present shift in-charges / engineers were not qualified engineers. Hence, their knowledge and skills were not adequate when faced with a challenge or an emergency.
12. LG Polymers was closed during the Covid-19 lockdown period as it is a non-essential industry and the minimum staff was given permission to maintain the factory during the lockdown period. However, the LG Polymers management was irresponsible, as they followed the same SOP as applicable for regular steady-state operational circumstances, during the lockdown period as well and did not consider the idling conditions in the M6 Tank. Further, they ignored the early indications in the rise in polymer content.
13. No separate SOP was created for the lockdown and restart operations (PSSR: Pre-Start up Safety Review). Thus, the LG Polymers did not at all consider the idling conditions in all the tanks including M6.

CLICK HERE to download the full report