Process safety management program deficiencies ultimately led to the June 2013 explosion and fire at the Williams Olefins Plant in Geismar, La., which killed two employees.
According to a final report [download PDF] released by the U.S. Chemical Safety Board (CSB), the deficiencies at the Williams Geismar facility during the 12 years leading to the incident allowed a type of heat exchanger — a reboiler — to be unprotected from overpressure and ultimately rupture, causing the explosion.
The Williams Geismar facility produces ethylene and propylene for the petrochemical industry and employs approximately 110 people. Approximately 800 contractors worked at the plant at the time of the incident on an expansion project aimed at increasing the production of ethylene.
The explosion and fire in June 2013 occurred during non-routine operational activities that introduced heat to the reboiler, which was offline and isolated from its pressure-relief device. The heat increased the temperature of a liquid propane mixture confined within the reboiler, resulting in a dramatic pressure rise within the vessel. The reboiler shell catastrophically ruptured, causing a causing a boiling liquid expanding vapor explosion (BLEVE) and fire. Two workers were killed and 167 others were injured.
The CSB investigation found that process safety management (PSM) program weaknesses at the Williams Olefins plant included the failure to implement management of change (MOC), pre-startup safety review (PSSR) and process hazard analysis (PHA) programs. Specifically, the CSB cites these failures as causal to the incident:
- Failure to appropriately manage or effectively review two significant changes — the installation of block valves that could isolate the reboiler from its protective pressure-relief device, and the administrative controls Williams relied on to control the position (open or closed) of the block valves. These changes introduced new hazards involving the reboiler that ruptured.
- Failure to effectively complete a key hazard analysis recommendation intended to protect the reboiler that ultimately ruptured.
- Failure to perform a hazard analysis and develop a procedure for the operations activities conducted on the day of the incident that could have addressed overpressure protection.
The CSB case study notes the importance of:
- Using a risk-reduction strategy — the hierarchy of controls — to effectively evaluate and select safeguards to control process hazards. This strategy could have resulted in Williams choosing to install a pressure-relief valve on the reboiler that ultimately ruptured instead of relying on a locked open-block valve to provide an open path to pressure relief. The locked open-block valve is less reliable due to the possibility of human implementation errors.
- Establishing a strong organizational process safety culture. A weak process safety culture contributed to the performance and approval of a delayed MOC that did not identify a major overpressure hazard and an incomplete PSSR.
- Developing robust process safety management programs, which could have helped to ensure PHA action items were implemented effectively.
- Ensuring continual vigilance in implementing process safety management programs to prevent major process safety incidents.
Following the incident, Williams implemented improvements to better manage process safety at the Geismar facility. The changes included redesigning the reboilers to prevent isolation from their pressure relief valves, improving its management of change process to be more collaborative, and updating its process hazard analysis procedure.
To prevent future incidents and further improve process safety at the Geismar plant, the CSB issued several recommendations:
- Implement a continual improvement program to improve the process safety culture at the Williams Geismar Olefins Plant.
- Develop and implement a permanent process safety metrics program that tracks leading and lagging process safety indicators.
- Develop and implement a program that demands robust and comprehensive assessments of the process safety programs at the Williams Geismar facility.
The CSB also identified gaps in a key industry standard by the American Petroleum Institute (API) and issued recommendations to API to strengthen its pressure-relieving and depressuring systems requirements to help prevent future similar incidents industry-wide.