July 13, 2023

CSB: Valve Design, Lack of Training Led to Deadly Acid Release

A final report (PDF) published recently by the U.S. Chemical Safety and Hazard Investigation Board details the agency’s investigation of the release of an acetic acid mixture that fatally injured two workers and seriously injured two others on July 27, 2021, at the LyondellBasell La Porte complex in La Porte, Texas. CSB determined that the release occurred when three contracted workers employed by Turn2 Specialty Companies inadvertently removed the bolts that secured a pressure-retaining valve cover when attempting to repair a leaking pipe. The design of the valve and inadequate training provided to the workers by LyondellBasell and Turn2 contributed to the release, the agency found.

CSB’s press release states that a LyondellBasell technician had discovered a small leak in a pipe upstream of the complex’s acetic acid reactor. When the acetic acid unit was shut down a few days later, LyondellBasell employees developed a plan to isolate and repair the leaking pipe that involved removing the mechanical device used to operate the valve, or actuator, between the pipe and the acetic acid reactor. LyondellBasell personnel informed Turn2’s superintendent and night foreman of the plan. However, “LyondellBasell did not have a procedure detailing how to remove the actuator, and neither LyondellBasell nor Turn2 trained the Turn2 personnel on how to remove the actuator,” according to CSB’s report.

Later that evening, the Turn2 night foreman returned with two Turn2 pipefitters and began to remove the bolts they believed would allow them to take off the actuator. Instead, they mistakenly removed the bolts that secured the pressure-retaining cover of the valve. The valve cover and plug ejected, and all three Turn2 workers were sprayed with the contents of the reactor mixture—about 164,000 pounds of acetic acid mixture at a temperature of 238 degrees Fahrenheit. The foreman and one pipefitter were fatally injured from chemical burns and inhalation of acetic acid and methyl iodide. The second Turn2 pipefitter and a LyondellBasell employee responding to the accident were seriously injured. Twenty-nine workers who were in an adjacent unit at the time received medical evaluation and treatment.

CSB identified four other incidents in which workers were killed or seriously injured by toxic chemicals after inadvertently removing pressure-retaining parts of valves. According to CSB’s press release, “[t]he recurrence of these types of incidents points to the need to further redesign plug valves so that it is more difficult to remove pressure-retaining components while attempting to remove actuating equipment.” The report recommends that the American Society of Mechanical Engineers and the American Petroleum Institute revise their standards for valve design, as well as work with the Valve Manufacturers Association of America to ensure a consistent plug valve design and method for marking pressure-retaining components.

CSB also recommends that LyondellBasell develop procedures for properly removing equipment from plug valves and that both LyondellBasell and Turn2 ensure employees and contract workers are trained to safely perform all required work.

More information can be found in CSB’s press release.