Esso Longford gas plant explosion

The gas plant that was destroyed had been initially commissioned in 1969. It had not undergone a mechanical inspection for six years. Shutdowns were initially scheduled at three-year intervals, but this interval was extended to five years. The plant had not been retrofitted with modern instrumentation. Pen recorders were prevalent in the control room and operating problems had been encountered with several control valves. Three months before the incident, ice plugging in lines caused several process upsets that were not fully investigated. A defective bypass valve had leaked gas to the atmosphere and had been awaiting maintenance up until one day before the accident. 

On the day of the incident, a pump that supplied hot lean oil to a large heat exchanger on the absorber column tripped. A chart recorder that should have indicated the upset was out of ink. The temperature in the exchanger dropped because of cold condensate flowing through the tubes. After several hours, two supervisors discovered the problem and restored hot lean oil flow to the exchanger to warm it up. This act was car- 

The system that experienced the failure had been modified within the previous decade. Instrumentation and control changes made it difficult for field crews to diagnose and troubleshoot operating problems. Process safety information had not been properly documented and there was litde evidence that the changes had been formally evaluated. A few days before the incident, a tag was installed on a faulty letdown valve instructing that a bypass must not be used. No explanation was given for this instruction. 

There were no formal operating procedures for dealing with the upset conditions that preceded the pump trip. The investigation revealed that fundamental operating practices were violated. Included were failures to monitor plant conditions, respond appropriately to alarms, report process upsets to supervisors, and undertake appropriate checks before making operating adjustments. 

Since 1991, significant staff cuts had taken place. These were particularly noticeable among the supervisory ranks with a 75% reduction in supervisors over the previous three years. The engineering and technical staff had been relocated to a central office in the city of Melbourne 100 kilometers from the plant. The resident plant staff was not experienced and knowledgeable in dealing with upset conditions. This lack of skill and experience contributed significantly to the incident. 

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