The U.S. Chemical Safety and Hazard Investigation Board (CSB) called for new plug valve designs and improved employee training following an accident at LyondellBasell’s La Porte, Texas, complex in 2021.
On July 27, 2021, workers at the plant inadvertently removed pressure-retaining nuts from a plug valve during a maintenance operation, rapidly releasing about 164,000 pounds of acetic acid mixture at 238 °F from the open, unplugged valve. The accident killed two contract workers, seriously injured two others and caused $40 million in damages, according to the CSB’s final report released on May 25.
Technicians at the plant were trying to repair a leak on methanol piping upstream from an acetic acid reactor. To isolate the leaking pipe, workers decided to remove an actuator connected to the valve, so they could use the valve as an energy-isolation device. The CSB notes that there have been at least four other incidents in which workers mistakenly removed pressure-retaining components from plug valves while disconnecting actuating equipment.
Plug Valve Redesign Recommendations
The repeated incidents point to a need for valve redesign, including the use of markings that clearly identify pressure-retaining components to prevent their inadvertent removal, the CSB notes in its investigation. CSB called on the American Society of Mechanical Engineers, the American Petroleum Institute and the Valve Manufacturers Association of America Technical Committee to update their standards and recommendations on plug valves using Prevention through Design principles.
The National Institute for Occupational Safety and Health defines Prevention through Design as “…anticipating and designing out or eliminating safety and health hazards in facilities, work methods, and operations, processes, equipment, tools, products, new technologies and the organization of work,” according to the final CSB report. The agency suggests that the industry could develop plug valves with recessed bolts covered with a sign warning that the bolts shouldn’t be removed in pressurized service.
After the incident, Lyondell installed tamper-resistant mechanisms and tags on the valve cover fasteners of actuated plug valves within the unit, according to the CSB report.
Procedural Changes for Valve Removal
CSB also called for enhanced training to prevent future incidents involving plug valves. The agency determined that Lyondell and its contractor didn’t provide the work crew with any procedure or training to perform the task and failed to adequately assess the potential risk of the operation prior to beginning the work. The agency found that Lyondell and its contractor, Turn2 Specialty Companies, viewed actuator removal as a simple task with minimal risks. During the CSB investigation, one Turn2 worker stated that having a written procedure for the task “would have been pretty helpful.”
CSB offered the following procedural recommendations for future removal of plug valve actuating equipment:
- A risk assessment of all plug valve actuator removal work
- Written procedures detailing actuator removal steps for the specific valve design
- Worker training on the procedure before conducting the actuator removal work
“As this tragic incident shows, even a simple task can turn deadly if it is not performed properly,” said CSB Chairperson Steve Owens in a prepared statement. “There have been similar incidents around the country involving plug valves being inadvertently taken apart when removing connected equipment. It is time to improve the design of these valves and take other protective actions, such as signage and training, before more workers are killed or injured.”
