CSB Publishes PEMEX H2S Release Investigation Report
Yesterday the Chemical Safety Board announced the publication of incident investigation report for the October 2024, fatal hydrogen sulfide leak at the PEMEX facility in Deer Park, TX. During the incident 27,000-lbs of H2S were released when contractors opened the wrong line during a maintenance procedure. Two workers were killed and 13 were transported to local hospitals for exposure to H2S. The report identified four key safety issues and the Board made four safety recommendations to prevent future such accidents.
This closed investigation leave just eight CSB open investigations. The four new recommendations brings the total number of CSB recommendations to date to 1,026 with 118 open recommendations.
Incident Summary
The Executive Summary for the report describes the incident:
“The release occurred when contract workers from Repcon, Inc. (Repcon) opened piping containing hydrogen sulfide gas. Instead of opening a pipe flange on empty piping, the workers mistakenly opened an identical piping segment 5 feet away, releasing pressurized hydrogen sulfide gas and fatally injuring one of the Repcon workers. The released hydrogen sulfide traveled downwind to the adjacent unit, where a worker from ISC Constructors, who was unaware of the release, inhaled the toxic hydrogen sulfide and also was fatally injured. The release continued for nearly an hour until PEMEX Deer Park emergency responders reassembled the leaking flange, stopping the release. Thirteen additional contract workers were transported to nearby medical facilities to be evaluated for hydrogen sulfide exposure”
Safety Issues
The four key safety issues were:
Positive equipment identification,
Work permitting and hazard control,
Turnaround contractor management, and
Conduct of operations.
CSB Recommendations
The CSB report assigns one recommendation to the American Society of Chemical Engineers:
2024-05-I-TX-4 Develop written guidelines for marking equipment for opening. The guidelines should define a standard practice for equipment marking that includes clear identifiers of the area to be opened and means to remove the markings at the conclusion of the work.
The three remaining recommendations were assigned to the PEMEX Deer Park facility management:
2024-05-I-TX-1 Label all piping in ARU6 and ARU7 in accordance with ANSI/ASME A13.1 Scheme for the Identification of Piping Systems.
2024-05-I-TX-2 Develop procedures to ensure that any craftworkers introduced to or removed from a unit in Positive Isolation Status receive instructions that define the hazards, safeguards, and requirements of the unit associated with the work. The procedures should require each craftworker to receive clear communication on the identified hazards, control measures, and all other requirements before commencing work in a new area.
2024-05-I-TX-3 Establish a conduct of operations system that establishes and enforces behavioral and performance metrics in accordance with CCPS’s Conduct of Operations and Operational Discipline.
Commentary
One of the reasons that the H2S release lasted so long was that operators had difficulties accessing and closing manual valves to isolate the leaking flange while wearing time-limited escape bottles for their air supplied respirators. In a number of previous incidents, the CSB took facilities to task for not having automated isolation valves on critical systems. There may be a completely legitimate reason why such valves were not in place at this facility, but the issue is not discussed in the report. It would seem to me that any system that handled large volumes of hazardous chemicals should have automated valves near the sources and destinations of any process piping transporting those chemicals.