ARE YOUR CRITICAL ALARMS SET CORRECTLY?

On March 14, 2023, at 11:40 a.m., approximately 1,000 pounds of flammable hydrocarbons were accidentally released from a pump seal and ignited (autoignition) at a Refinery in Texas, causing a fire.      The company estimated the property damage from the incident to be over $1 million.                        

During the unit startup approximately five days before the incident, the pump (a centrifugal pump) had operated with low suction (inlet) pressure for nearly two hours due to a low liquid level in the upstream equipment. The low suction pressure caused the pump to cavitate, which vibrated the pump and damaged the pump’s bearings. Five days later, on March 14, the damaged bearings and the resulting stress on the pump’s mechanical seal caused the seal to fail. The hot hydrocarbons within the pump were released into the atmosphere and ignited, causing a fire. The material was released at 590 degrees Fahrenheit (°F) and had an autoignition temperature of 484 °F.
 In addition, on March 11, two days after the unit startup, vibration from the damaged pump triggered a “High Priority Alarm.” The refinery’s usual responsive action to high-priority vibration alarms was to switch pumps. However, the company did not have another pump available and continued to operate the installed pump, as refinery employees believed the pump was still safe to operate. Employees anticipated that a replacement pump would be available on March 13, but the pump was not replaced before the incident on March 14.
Although the pump vibrations continued and worsened, they never triggered the “Critical High High” vibration alarm threshold because the alarm was programmed incorrectly. Had the vibration alarm been programmed correctly, the “Critical High High” alarm should have activated on March 12, two days before the incident.
The company's investigation found that the refinery operators mistrusted the pump vibration alarms due to past nuisance alarms, causing employees to normalize these alarms.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release and ignition of hydrocarbons from a failed pump that had been damaged after it cavitated during a unit startup. Contributing to the incident were unit startup conditions that damaged the pump, incorrectly programmed alarms, and employee mistrust of alarms.

Source: CSB.gov