The Weekly Reflektion 30/2021

What is the worst Major Accident we have come across? What criteria should we use to judge the many Major Accidents that we have studied? The consequences in the terms of loss of life, impact on the environment or financial loss? In our view it is more appropriate to judge based on the failure of the systems in place to prevent a Major Accident.

Which principles of inherent safety were not followed at the Texas City refinery? 

The Texas City Refinery explosion in 2005 is one of the worst Major Accidents that we have studied. The explosion occurred when a distillation column used to produce high octane fuel was filled with liquid due to a closed outlet valve. The overfilling caused pressure relief valves to open, and the contents of the column filled a blowdown drum with hot hydrocarbons. This drum then overflowed, and a geyser of hot liquid spouted from the open vent on the drum. The resulting vapour cloud was ignited by a diesel pick-up truck that was parked nearby and still running. The explosion killed 15 people and injured 170.

Principles of inherent safety were not followed at the Texas City refinery and these failures were a significant factor in both the causes and the consequences of the incident.

When the pressure relief valves opened the hydrocarbon liquids and gas flowed to a blowdown drum with an open vent next to the distillation column. Normally a blowdown drum and flare located remotely from the process facilities would be used. The flare would be designed to burn off the gas hereby preventing build up of an explosive mixture. The blowdown drum would be sized to ensure the operators can act before the liquids are discharged. The remote location keeps the hydrocarbon away from people and process systems in the event liquids are emitted from the vent. The installation of a remote flare at the refinery had been identified in several safety studies, however the investment had not been prioritised.

A major shutdown had recently been completed at the refinery and the explosion occurred during the start-up. Temporary containers had been installed near the blowdown drum as office accommodation for the people working on the shutdown. At the time of the explosion the workers were returning to these offices from a free lunch celebrating the completion of the shutdown activities without a recordable incident. No one had informed the workers of the start-up. Start up of a refinery following a maintenance shutdown is one of the most critical operations at the refinery and one where only essential personnel should be on site.

The principles of inherent safety are relatively simple and are worth a refresher every so often. At Texas City refinery the hazard was placed in the middle of the process facilities and then the people were placed next to the hazard. This was irresponsible and unforgivable and one of the reasons we consider this as one of the worst Major Accident.

Keep the people away from the hazards or keep the hazards away from the people. If there is no one there, then no one will get hurt or killed.