At 10:28 a.m. on Saturday, May 19, 2018, an ethylene release caught on fire at the Kuraray ethylene and vinyl alcohol copolymer (EVAL) plant in Pasadena, Texas. At the time of the incident, 266 employees and contract workers were onsite, according to the final report from the Chemical Safety Board (CSB).
The incident occurred during a chemical reactor system startup following a scheduled maintenance shutdown. High-pressure conditions developed inside the reactor and activated the reactor’s emergency pressure-relief system, discharging flammable ethylene vapor – through horizontally aimed piping – into the ambient air in an area where contractors were working.
These workers were performing various tasks not essential to the startup of the reactor, including welding, which likely ignited the ethylene vapor cloud, causing the fire. Kuraray reported that 2,347 pounds of ethylene released in less than three minutes. When the pressure inside the reactor dropped sufficiently below the activation pressure, the spring-loaded emergency pressure-relief valve closed, extinguishing the fire.
Workers in the immediate area tried to escape from the ethylene release and fire.
While fleeing, some workers suffered injuries as they jumped from the second or third story of the plant structure and ran or otherwise exited from the area, tripping and falling or suffering sprains and other injuries along the way. Other workers were wearing fall protection equipment that physically attached them to structures in the area, which delayed their escape from the fire and increased the severity of their injuries.
Two injured workers were life-flighted from the Kuraray facility. One contract worker remained in critical condition for several days but survived. Emergency responders transported as many as 19 other injured workers to off-site medical facilities for treatment.
CSB determined the cause of the incident was Kuraray’s long-standing emergency pressure-relief system design that discharged flammable ethylene vapor through horizontally aimed piping into the air, near workers. Had Kuraray’s emergency pressure-relief system discharged vapor from the reactor to a safe location, the flammable ethylene gas should not have harmed any workers.
Kuraray’s long chain of weakly implemented management system elements that made up its overall process safety management system also contributed to the incident, the CSB report said. In addition to the management system elements that Kuraray used to manage the EVAL reactor’s emergency pressure-relief system, other elements contributed by allowing high-pressure conditions to develop inside the chemical reactor system (EVAL Reactor 2). The combination of these ineffective management system elements culminated with the reactor’s emergency pressure-relief system activating and discharging flammable ethylene vapor into the air, where it ignited near nonessential workers.
Timeline of key events that led up to the fire at the Kuraray America, Inc. plant in Pasadena, Texas, that injured 23 workers.Source: CSB
Kuraray’s safety management systems also fostered inconsistent practices for keeping nonessential personnel from being physically present within the unit during critical events and activities, such as unit startups or when upset process conditions develop, which contributed to the injuries suffered, the CSB report said.
Kuraray could have prevented these injuries by implementing a policy to exclude workers not involved in the startup. Furthermore, Kuraray could have taken protective actions during upset conditions to prevent worker injuries, the CSB report said. For example, when the reactor’s high-pressure alarm sounded, Kuraray should have stopped work and evacuated the workers from the area.
CSB’s investigation identified and evaluated the following safety issues:
Emergency pressure-relief system discharge design: A chain of process safety management system failures that led to excessive pressure being generated within Kuraray’s EVAL Reactor 2. Kuraray protected this reactor with a safety system that lowered this excess pressure by discharging flammable ethylene vapor into the air. Of all the factors that contributed to injuring the 23 workers, none was more significant than the design of the outlet piping from the reactor’s emergency pressure-relief system, which caused the release to be aimed toward an area where workers were present.
Presence of nonessential workers during startup and upset conditions: At the time of the incident, none of the contract workers near the EVAL Reactor 2 emergency pressure-relief system were essential to the startup, nor were they responding to the upset process conditions that led to the emergency release. When the flammable ethylene vapor discharged from the reactor’s emergency pressure-relief system, many of these nonessential workers were in harm’s way, and the welding work they were performing likely supplied the ignition source that created the fire.
Hazardous location: In the context of the Kuraray incident, hazardous location describes the area with increased fire and explosion risk to workers resulting from the horizontal orientation of the reactor’s emergency pressure-relief system outlet piping. With workers present, activating this safety system created a danger to their safety.
Recognized and generally accepted good engineering practices: Kuraray should have thoroughly evaluated whether its EVAL Reactor 2 emergency pressure-relief system met existing good engineering practices. The horizontally aimed discharge piping from this emergency pressure-relief system deviated from industry standards.
Process hazard analysis safeguards: In 2015, Kuraray’s process hazard analysis (PHA) team identified three existing safeguards that should have controlled high-pressure conditions inside EVAL Reactor 2 without activating the emergency pressure-relief system. On the day of the incident, however, none of these safeguards were effective in preventing the EVAL Reactor 2 emergency pressure-relief system from activating.
Process hazard analysis recommendations: Safety recommendations stemming from a PHA must be resolved and documented. In 2015, Kuraray’s PHA team developed a safety recommendation addressing worker safety concerns related to potential ethylene releases from emergency pressure-relief systems. Implementation of this safety recommendation could have led Kuraray to prevent the May 19, 2018, incident.
Warning signs: In its investigation of the May 19, 2018, ethylene release and fire, CSB found several pre-incident warning signs. For example, dangerous releases of flammable ethylene from emergency pressure-relief devices at the EVAL plant had previously occurred. In addition, Kuraray’s own hazard review team had cautioned that ethylene vapor cloud explosions could occur when some of these safety systems discharged flammable ethylene vapor into the air.
Equipment design: Based on equipment design pressures, each of Kuraray’s four EVAL reactors had an emergency pressure-relief system designed to activate at a pressure of 1,150 pounds per square inch (psi), except for EVAL Reactor 2. Kuraray designed the EVAL Reactor 2 emergency pressure-relief system to activate at 740 psi, which was 410 psi lower than the designed activation pressure of the other three reactors.
Operating procedures: Kuraray management supplied its operations team with nightly operating instructions that conflicted with the company’s written operating procedures and resulted in unmanaged changes during the reactor startup. Kuraray’s operators followed some nightly management instructions that deviated from the written operating procedures during the EVAL Reactor 2 startup, which contributed to the incident.
Operator training: Critical gaps in Kuraray’s operator training contributed to the incident. For example, Kuraray’s operator training program did not cover alarm setpoints or actions that operators should take in response to specific process alarms, such as high-pressure conditions inside an EVAL Reactor.
Abnormal operating conditions: During the startup, ethylene vapor condensed and started flowing into EVAL Reactor 2, forming an inventory of liquid ethylene and creating a low- temperature condition. Kuraray’s response to these abnormal operating conditions included heating the reactor’s contents, causing some of the liquid ethylene to change to ethylene gas, which in turn generated high pressure inside the reactor and led to the incident.
Safety interlock disabling: During the EVAL Reactor 2 startup, Kuraray operators disabled the reactor’s abnormal condition safety interlock while troubleshooting a problem that stemmed from a misaligned valve.
Alarm management: At the time of the incident, Kuraray had not completed its process alarm management efforts to improve the quality and reduce the frequency of alarms that the company tasked its board operators with responding to during upset or abnormal conditions.
Process alarm response: Kuraray’s operating procedures did not include alarm information or operator guidance for responding to process alarms. The response that Kuraray’s board operators took to active high-pressure alarms during the startup did not bring the reactor pressure back below the alarm limits.
Safe operating limits: Kuraray’s safe operating limits management system did not prevent high-pressure conditions from developing inside the reactor. Kuraray also set the safe operating limits for EVAL Reactor 2 too high – at the reactor’s mechanical design conditions – to effectively prevent activating the EVAL Reactor 2 emergency pressure-relief system.
Environmental permit: Kuraray had an environmental permit that limited the amount of volatile organic compounds (VOCs), including ethylene, the company was allowed to send to its flare. As the pressure within the EVAL Reactor 2 steadily increased during the startup, Kuraray’s board operators limited the flow of ethylene vapor to the flare to avoid exceeding these permit limits.
Safety management system self-assessment audits: The investigation of the incident on May 19, 2018, revealed weak process safety management systems at Kuraray. Although the problems with these management systems were identifiable and correctable, Kuraray’s self-assessment audits did not achieve the level of detail required to address the process safety management system failures that contributed to the incident.
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