IMPROPER OPERATION READINESS REVIEW DUE TO HUMAN FACTORS CAUSED AN INCIDENT

 On February 23, 2023, at 8:15 p.m., an accidental release of approximately 164 pounds of hydrocarbons (pentane and heavier hydrocarbons) occurred at a Refinery in Texas. The hydrocarbons were released from an open bleed valve on a crude unit heat exchanger during startup. The hot hydrocarbons ignited (autoignition), causing a fire that damaged nearby equipment. The company estimated the property damage from the incident to be $2.3 million.

On February 12, 2023, the crude unit heat exchangers were shut down for cleaning. Ten days later, on February 22, refinery operators prepared to put the heat exchangers back into service after the cleaning. During the day shift on February 23, they purged air from the heat exchangers to prepare it for startup.

Night shift operators then continued readying the heat exchangers for startup. They obtained the energy isolation drawing, which was used to document which valves had been locked in the open or closed position to allow for safe cleaning of the heat exchangers.
The operators walked down the equipment, removed the locks indicated on the energy isolation drawing, and ensured the valves were lined up in the correct position for startup. The operators believed they had addressed all the valves documented on the energy isolation drawing. Unknown to the operators, however, a bleed valve on top of the heat exchangers remained locked open when the lock should have been removed, and the valve should have been closed. The company's investigation report noted that the open bleed valve was not easy to locate visually, and the operators’ ability to see it may have been further impaired when it was dark outside.
As the startup sequence progressed, hot hydrocarbons sent to the heat exchangers flowed through the open bleed valve into ambient air and ignited. The material was released at 562 degrees Fahrenheit (°F) and had an autoignition temperature of 482 °F.
The company stated that the energy isolation drawing was destroyed in the fire; so it is unknown if the locked open bleed valve was shown on the drawing.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release and ignition of flammable hydrocarbons when a bleed valve was inadvertently left open during an equipment startup. Contributing to the incident was a lack of a system, such as leak testing, to ensure all valves were in the correct position before the equipment was started up.

Source: CSB.gov