For months, a “dangerous substance” called popcorn polymer accumulated and expanded within an out-of-service piping section, eventually causing a catastrophic explosion at the TPC Group Port Neches Operations in 2019, the U.S Chemical Safety and Hazard Investigation Board (CSB) concluded in its final investigation report released on Dec. 19.
Popcorn polymer is prone to forming in processes with high-purity butadiene. The substance accumulated in piping at the Port Neches facility when the company took a process pump out of service for several months. During this time, popcorn polymer developed and “exponentially expanded until pressure inside the dead leg caused the piping section to rupture, releasing butadiene that then exploded.”
Among its findings, CSB determined that TPC failed to conduct a monthly flushing of piping associated with out-of-service equipment, known as “dead legs” as the agency had recommended during a 2016 process hazard analysis. The agency also suggested that the American Chemistry Council (ACC) revise its guidance on butadiene product stewardship because it lacks information on the potential consequences of dead legs or how companies should identify, control or prevent them.
CSB recommended that TPC Group develop and implement a process to identify and control or eliminate dead legs in high-purity butadiene service, including implementation of preventive design strategies, preventing popcorn polymer buildup and effective management oversight.
The agency also determined that ACC should include additional guidance in its Butadiene Product Stewardship Guidance Manual on mitigation strategies to help prevent future incidents. This includes guidance on identifying and controlling or eliminating dead legs in high-purity butadiene service, as well as methods to help identify when popcorn polymer is excessive or dangerous in a unit.
The explosion, which occurred on Nov. 27, 2019, 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.