At the time of the event, contract workers were disassembling a 2-inch flange to remove a blind (a solid metal plate used to isolate equipment) before reinstalling a section of piping that had been removed and cleaned. This type of equipment opening is commonly referred to as a “line opening” or “performing a line break.”
The contract workers performing the line opening wore personal protective equipment (“PPE”), including full-face respirators, chemical gloves, and fall protection. The contractor’s pre-job safety analysis form did not require the use of chemical suits or rubber boots because the piping system had been dismantled the previous day for cleaning. This additional protective equipment was required under the facility’s Safe Work/Line Break permit, which authorized the contractor to perform the line-opening work. As the workers disconnected the flanged connection bolts, they were splashed with corrosive liquid silicon tetrachloride that had leaked past an isolation valve and pressurized the piping, seriously injuring the two contract workers with chemical burns.
OSHA investigated the event and cited the contractor for not ensuring workers used the chemical suits and rubber boots required by the safe work permit. OSHA’s investigation file noted confusion between the contractor and the facility regarding line-opening work and who was authorized to perform it. The contractor informed OSHA that the company had performed numerous similar equipment-opening tasks at the facility. The facility, however, told OSHA that only facility employees were permitted to perform this type of line-opening work.
The scope of the facility’s investigation was narrow and insufficient. The investigation found that the contractor was responsible for the incident because the contractor:
(1) had performed this line-opening work and
(2) did not use suitable PPE during that work—violations of site policies and administrative controls.
However, the investigation did not evaluate the facility’s role in the incident’s causation. For example, facility personnel authorized these contractors to perform the line-opening work, which the company stated its policies require to be performed by its employees. In addition, the facility did not ensure that the piping was effectively isolated, flushed, and drained to remove silicon tetrachloride before assigning the contract workers to perform the line-opening work. Furthermore, the facility’s policies required the facility manager to confirm that personnel performing the line-opening work had the required PPE, but this was not done.
Probable Cause
Based on factual investigative information obtained from the facility and OSHA, the CSB determined that the probable cause of the accidental release of silicon tetrachloride was the facility’s failure to effectively isolate, flush, and drain the piping system before turning it over to the contract workers for disassembly. Failure to use PPE that could protect workers from splashes of corrosive silicon tetrachloride contributed to the severity of the incident.
Source: https://www.csb.gov/assets/1/6/csb_incident_reports_volume_one_2025-01-14.pdf