On March 22, 2021, at approximately 12:30 p.m., an explosion and fire occurred at a Refinery in California. The explosion and fire seriously injured one contract worker.Leading up to the incident, the refinery was shut down for turnaround maintenance. The planned maintenance work included removing a section of carbon steel piping in the Fluidized Catalytic Cracking (FCC) unit that typically contained gasoline. Two days before the incident, on March 20, 2021, 50 gallons of chemical cleaning water containing hydrocarbons were released when workers opened a flange to install a blind (metal plate) to isolate a section of 18-inch piping.
On March 22, 2021, the day of the incident, the 18-inch piping was isolated with the blind at one end and the other end transitioning to a section of 10-inch piping open to the atmosphere with drain piping between the blind and the open 10-inch end. To remove the piping, Phillips 66 tasked a crew of contract workers to cut the 18-inch piping at the location shown in Figure.
Before the cutting began, an operator performed flammable gas testing at the work area, showing no flammable gas was present. Operators also walked the job with the contractor’s supervisor. After this, the operators issued a work permit authorizing the contractors to use an electric angle grinder with a cutting wheel to cut the piping. The permit stated that the piping was isolated, vented, depressured, and chemically cleaned. Because the work area was elevated about 10 feet above ground, fire blankets were installed, creating an enclosure to contain sparks created during the pipe-cutting work.
As the lower portion (from the four to six o’clock position) of the piping was being cut, liquid flowed out, and the worker stopped cutting. The drain piping was unplugged using a wire, allowing the fluid to drain. The contractors contacted operations personnel to evaluate the piping. The operators rechecked the piping and confirmed that no flammable gas was present. One of the contract workers invoked his stop-work authority and refused to continue cutting on this piping because the liquid smelled like gasoline. One of the operators described the odor as pine and attributed it to the substance used during chemical cleaning. Ultimately, two operators and a contractor supervisor agreed that the liquid was primarily water. At approximately 12:30 p.m., two hours after the work was stopped, another contract worker was sent to finish cutting the pipe. When the worker started the angle grinder, an explosion and fire occurred. The contractor suffered serious burn injuries from the combustion event and was transported and admitted to a hospital for treatment.
The company's investigation determined that the piping contained flammable hydrocarbons because the plugged drain prevented the piping from being flushed and cleared as intended. The flammable gas testing performed at the work area did not identify the flammable vapor inside the piping. In addition, the company’s investigation concluded that when the contract worker used his stop-work authority and refused to cut the piping, his safety concerns should have been elevated to operations and maintenance supervisors for help ensuring the job was safe before resuming work – but they were not. The company estimated that less than half a gallon of gasoline was released.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was that the piping segment was not effectively flushed and drained before the contract workers were authorized to cut the piping. Not recognizing the presence of flammable gas contributed to the incident.
Source: CSB.gov
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