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

 

 

THE IMPORTANCE OF OPERATION READINESS REVIEWS

 On January 17, 2023, at 10:45 p.m., 670 gallons of hot water were accidentally released and pooled at a facility in Louisiana. One employee was seriously injured after stepping into the pool of hot water.

The investigation of the events leading up to the incident began on January 9, 2023, when the facility planned maintenance work on a control valve in the boiler feedwater piping system. Operators observed water leaking past two valves in series, upstream of the control valve, when in the closed position. To allow for control valve maintenance, site personnel developed and executed a plan to route leaking boiler feedwater out of the system by opening two bleed valves (in series) between the leaking valves. Site personnel attached a hose to the bleed valve piping to route the leaking hot boiler feedwater to a nearby sump.
On January 17, 2023, after maintenance work on the boiler feedwater control valve was completed, operators were tasked to recommission the control valve. At about 8:00 p.m., operators lined up valves in the piping system so the control valve could be returned to service. The operations personnel did not use the site’s operational readiness checklist, which included requirements for personnel to evaluate or “walk down” the piping and valve lineup to ensure correct positioning before startup. As a result, when hot feedwater was re-introduced to the piping, the bleed valves remained open, and the temporary hose remained connected to the piping. Hot boiler feedwater began releasing through the open bleed valves and hose.
At 10:46 p.m., the control board operator observed a low boiler feedwater pressure alarm and requested an outside operator to investigate. Personnel identified that the boiler feedwater piping was the source of the low-pressure alarm and, realizing there was a leak, closed an upstream valve to stop the leak. About 670 gallons of hot water were released. At about 11:45 p.m., an outside operator attempted to close the two open bleed valves and inadvertently stepped into a pool of the hot boiler feedwater that had accumulated in a depression. The high-pressure boiler feedwater release may have created or enlarged this hole. The operator was seriously injured when his lower leg was submerged in the hot water above the top of his rubber boot, and the hot water contacted his lower leg and foot.

Probable Cause
Based on the comapny's investigation, the CSB determined that the probable cause of the incident was starting up the boiler feedwater piping system with open bleed valves connected to an open-ended hose, allowing hot water to release and accumulate. An operator subsequently stepped into the pooled hot water, receiving burns to his lower leg and foot. The ineffective application of the operational readiness checklist contributed to the incident by not ensuring that the bleed valves were closed and the hose was removed before the startup.

Source: CSB.gov