On August 12, 2016, hot work was being conducted by a contractor at a crude oil terminal on a section of pipe that contained residual crude oil. Using an isolation device, the pipe segment was plugged on both ends by a sub-contractor (hired by the primary contractor). During the welding operation on the inside surface of a flange, vapor inside the pipe gathered between two of the installed isolation devices and ignited. The ignition caused a build-up in pressure, which led to a violent explosion at either end of the isolated pipe, resulting in burn injuries to seven (7) workers.
NOTE: A contractor issued the HW permit to the contractor performing the HW. The report states this was done on behalf of the host.
The host and primary contractor developed plans and procedures to guide employees on how to conduct hot work operations safely. Still, the CSB found that guidance was inadequate to prevent the fire and explosion. Specifically, the investigation found that the pipe involved in the incident contained residual flammable crude oil, which was not adequately cleaned or inerted before commencing hot work.
The CSB concluded that the host’s hot work procedure did not adequately state that hot work on equipment that currently or previously contained flammable material, was not permitted by OSHA or NFPA 51B. Additionally, the procedure did not clearly explain how to ensure that equipment was to be cleaned or inerted to conduct hot work safely. Therefore, the host and the primary contractor did not implement adequate mitigation strategies to prevent a fire or explosion during hot work activities.
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