Piper Alpha oil rig tragedy was sparked by human error
WHEN a maintenance crew failed to tell an oil rig control room about a missing safety valve it brought about one of the worst oil rig disasters in history
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ITwas a summer evening on the Piper Alpha oil and gas platform in the North Sea, about 190km northeast of Aberdeen, Scotland. A night shift crew of 60 were working, while the rest of the workers were relaxing or sleeping before their next shift.
Earlier in the day a safety valve had been removed from condensate pump A (one of two pumps for pipes that carried raw natural gas) and recapped. In the shift changeover, the night shift was not informed that the valve was missing.
At 9.45pm a control room attendant saw an alarm flash saying that condensate pump B had shut down, because of a blockage. So at 9.55pm he transferred the flow to pump A, not realising that the safety valve had been removed.
The temporary cap was unable to hold back the pressure, causing a gas leak and a series of explosions that tore the platform apart. The disaster, which happened 30 years ago today, was one of the worst oil rig disasters in history in terms of the deaths, damage and disruption costs.
The area of the North Sea off Scotland containing the Piper oilfield was first explored in 1972; oil was discovered in 1973. In preparation for drilling, a steel platform with dozens of well slots and room for two drilling rigs was built in the middle of the oilfield in 1975. Piper Alpha was ready for production by October 1976.
The platform was owned and run by a consortium of oil companies operated by American company Occidental Petroleum. Initially the platform only handled oil but it was later converted to also handle natural gas and connected by pipeline to the Orkney Isles.
But while adding the gas equipment the builders departed from the original plan of keeping the most dangerous parts of the platform distant from staff areas. By the time of the disaster employees were working close to the gas compression areas.
In 1988 Piper Alpha was producing more than 300,000 barrels of oil, more than any other platform in the world. It had a workforce of 226 people, working rotating shifts. The pressure to keep the station going was intense, which made maintenance work that much more important. In 1988 Occidental began major construction and maintenance works on the platform.
The explosions on July 6, 1988, that resulted from the slip-up in safety procedures, killed many of the crew while those who survived the initial explosions were confronted by a series of other problems.
The gas explosion destroyed firewalls designed to only withstand an oil fire. Workers also tailed to shut off the gas flow from a nearby platform, because such an order had to come from Occidental’s control centre, due to the huge cost of a shutdown and the time it took restart the flow.
An automatic fire fighting system that pumped seawater on to the platform, had also been deactivated because divers had been working in the water around the platform earlier.
The control room, built too close to the gas compression area, had to be abandoned and there was no warning to evacuate on the platform’s loudspeakers. Survivors were told to head for the lifeboats but many were already destroyed or fire prevented them getting near the lifeboat stations.
While about 100 people waited for rescue in a fireproof area, many of the crew began jumping into the ocean to escape. The heat and flames prevented helicopters from extracting anybody from the deck of the rig, so the only survivors were those who risked the 50m drop into the water, many of whom were badly burned by the boiling waters.
Two crewmen aboard rescue vessel Sandhaven and the six Piper Alpha employees they had rescued, were killed when their boat got too close to the platform and was caught in an explosion. Dozens more died as Piper Alpha finally crumpled and fell into the North Sea.
The final death toll was 167, only 61 survived. The cost of the damage and the interruption to fuel supplies was calculated at around £1 billion ($1.8 billion).
The fire raged for three weeks until it was finally extinguished by a crew led by the legendary American oil firefighter Paul “Red” Adair. He had to perform the difficult task in high winds and rough seas.
A commission of inquiry under Scottish judge William Cullen recommended a list of 106 changes to safety procedures, all of which were later adopted. Occidental later made payouts of around £66 million ($118 million) to the families of those who died, but the company was not blamed.