The U.S. Chemical Safety and Hazard Investigation Board (CSB) released its final investigative report on the Nov. 27, 2019, explosions and fires at the TPC Group Port Neches Operations facility chemical plant in Port Neches, Texas.
The incident occurred when a piping section ruptured, releasing highly flammable butadiene that quickly ignited. The resulting pressure wave destroyed parts of the facility and injured two TPC employees and a security contractor. The blast damaged nearby homes and buildings and was reportedly felt up to 30 miles away. Local officials stated that process fluid that continued to escape from ruptured equipment fueled fires that burned for more than a month.
The CSB found that a dangerous substance known as popcorn polymer, which is prone to forming in processes with high-purity butadiene, had accumulated in a temporary “dead leg” in piping that was created when a process pump was taken out of service for several months. During this period, popcorn polymer developed and exponentially expanded until pressure inside the dead leg caused the piping section to rupture, releasing butadiene that then exploded.
CSB Chairperson Steve Owens said, “the incident at TPC was the result of a known safety hazard – popcorn polymer – that was poorly managed and controlled at the facility. The result was a catastrophic incident that caused hundreds of millions of dollars in damage to the facility and nearby homes and business and resulted in a mandatory evacuation being ordered for everyone within a four-mile radius of the facility.”
CSB’s investigation identified four safety issues that contributed to the incident.
- Dead Leg Identification and Control: The TPC facility had a procedure in place to minimize popcorn polymer hazards associated with dead legs. But that dead leg procedure did not identify all potential temporary dead legs within the unit, including the one that eventually ruptured. Further, the American Chemistry Council’s Butadiene Product Stewardship Guidance Manual does not contain information on the potential consequences of dead legs or how companies should identify, control, or prevent them.
- Process Hazard Analysis Action Item Implementation: A 2016 PHA of the butadiene process at TPC recommended that piping associated with out-of-service equipment be flushed monthly. Yet, this recommendation, which could have helped to flush popcorn polymer out of the dead leg piping that ultimately ruptured, was never implemented.
- Control and Prevention of Popcorn Polymer. CSB determined that TPC did not have sufficient internal policies to lead employees to shut down and clean the butadiene unit after it experienced exceedingly high levels of hazardous popcorn polymer. The CSB also determined that additional guidance in ACC’s Butadiene Product Stewardship Guidance Manual providing mitigation strategies that companies should follow when popcorn polymer is identified could help prevent future incidents.
- Remotely Operated Emergency Isolation Valves: CSB found that there were no remotely operated emergency isolation valves installed on equipment that was part of TPC’s butadiene process. Had such valves been installed, the initial release from the ruptured piping could have been minimized and some of the subsequent explosions may have been prevented.
As a result of the incident, CSB made a recommendation to the TPC Group to develop and implement a process to identify and control, or eliminate, dead legs in high-purity butadiene service. This process must include requirements for identifying potential dead legs, implementing preventive design strategies, preventing popcorn polymer buildup, and effective management oversight.
The agency also made recommendations to the American Chemistry Council to revise its Butadiene Product Stewardship Guidance Manual to include guidance on identifying and controlling or eliminating dead legs in high-purity butadiene service, as well as provide guidance on a methodology to help identify what should be considered excessive or dangerous amounts of popcorn polymer in a unit.
CSB Board Member Sylvia Johnson said, “We believe our final report and recommendations will help facilities that handle and store large quantities of butadiene better control popcorn polymer formation and growth within their processes. Doing so can prevent another terrible incident like the one that occurred at TPC.”
The CSB is an independent federal agency charged with investigating incidents and hazards that result, or may result, in the catastrophic release of extremely hazardous substances. The agency’s core mission activities include conducting incident investigations; formulating preventive or mitigative recommendations based on investigation findings and advocating for their implementation; issuing reports containing the findings, conclusions, and recommendations arising from incident investigations; and conducting studies on chemical hazards.
The agency’s board members are appointed by the president subject to Senate confirmation. The board does not issue citations or fines, but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA.