Piper Alpha

Location of Piper Alpha in the North Sea

The Piper Alpha was a large drilling platform in the North Sea in the Piper oil field about 170 km northeast of Aberdeen . It was owned by Occidental Petroleum (78%) and Texaco (22%).

The platform was designed and built as an oil rig and began production in 1976; Occidental and Texaco converted them to gas in 1980. Piper Alpha brought about 10 percent of the total oil and gas production in the North Sea to the surface. A fire destroyed the Piper Alpha on July 6, 1988. With 167 fatalities it was the worst accident on an oil rig. Only 61 people survived.

Construction of the oil rig

The drilling rig consisted of four modules that were separated from one another by fire walls . In accordance with the safety requirements, the modules were arranged in such a way that the most dangerous work took place as far away as possible from the crew rooms. The conversion from oil to gas in 1980 broke this concept and resulted in some sensitive areas having to be arranged right next to each other. For example, the gas compression unit - the unit in which the condensate was separated from the natural gas - was placed next to the control room, which had a decisive influence on the course of the accident.

Since the drilling platform was originally built as an oil platform, the fire protection walls were not designed to inhibit explosions. The fire was able to spread down along the fire protection walls and destroyed some oil pipes.

Gas lines several meters in diameter ran near the Piper Alpha. Two years earlier, Occidental's management had commissioned a study warning of the dangers posed by these gas lines. Relieving the pressure contained therein would take several hours due to the length and diameter of the pipes, so that a fire on these pipes would be practically impossible to fight. Although management was aware of the risk of a devastating gas explosion, the Claymore and Tartan platforms were not switched off on the first emergency call.

Prehistory of the fire

The misfortune developed gradually. Within the first hour there were some critical moments in which the right decisions could have prevented the disaster or at least significantly mitigated its effects.

In the weeks leading up to July 6, 1988, a new gas pipeline was built. This work led to deviations from the usual routine, but the platform was still operated as usual. Finding a few small gas leaks was also normal and not a cause for concern.

There were two large condensate pumps on the platform, labeled A and B. These machines carried the condensate, a mixture of liquefied gases, to the coast. On the morning of July 6th, the pressure relief valve on pump A was removed for overhaul. In addition, the pump was scheduled for a fortnightly general overhaul, which had not yet started. The open end of the line was temporarily closed with a metal plate. Because the work could not be completed by 6:00 p.m., the metal plate remained in place. The engineer on duty filled out a form stating that the pump was not operational and should not be switched on under any circumstances.

In addition, the automatic extinguishing system was switched off at the time of the accident. Extinguishing pumps should switch on fully automatically in the event of a fire and pump water onto the drilling rig. When divers were working on the Piper Alpha, the pumps were switched to manual mode and could only be restarted from a single point. On other platforms, manual operation was only switched to when the divers were near the inlet ports to prevent them from being sucked in with the seawater. On the Piper Alpha, however, the automatic extinguishing system was always switched to manual operation whenever divers were in the water, regardless of where the divers were. On the evening of July 6, 1988, the extinguishing system could only be put into operation by hand.

The laying of rubber mats on the descent platform to the sea, which was located on the underside of the drilling platform, also had serious consequences. The mats were used to protect divers from injury from the sharp-edged metal grid floors of the platform and were only laid out on the day of the disaster because of the diving work. The gas supply lines to the Tartan and Claymore oil platforms were located directly above these mats.

chronology

6:00 p.m.: Because he found the overseer on duty busy, the engineer failed to personally inform him of the condition of condensate pump A.
9.45 p.m.: Condensate pump B suddenly stopped and could not be started, the power supply to the drilling platform threatened to collapse within a few minutes.
9:52 pm: Condensate pump A started up; the responsible persons were not aware that the high pressure valve was missing, as the corresponding form was separate from the notification of the general overhaul.
9:57 pm: The gas condensate flowing through pushed the metal plate out of its holder and flowed out. This could have been prevented if the retaining screws of the plate had not only been screwed hand-tight, but also properly tightened with a suitable tool. An initial explosion likely killed two workers and the fire spread across the platform. The overseer stopped the oil and gas production on the platform by emergency stop, but oil and gas continued to flow in through connected lines from the Tartan and Claymore platforms.
10:04 pm: The crew gave up the radio room, which was intended for coordination during an accident. Organized work to contain the disaster collapsed.
10:20 pm: Burning oil flowing down, which would normally have flowed through the metal grid floors into the sea without any further consequences, had collected in the past few minutes on the rubber mats laid out, creating a source of secondary fire in a previously largely undisturbed part of the oil rig. The overlying gas line from the tartan platform broke as a result of the heat. Between 15 and 30 tons of gas leaked and burned every second. One and a half times the UK's gas consumption was flared in an area of just 75 m² . From that point on, the disaster could no longer be stopped.
10:50 pm: The second gas pipe burst and exploded. Claymore also stopped funding.
11:50 pm: The supply block slid into the sea, and most of the platform followed it.

crew

During training, the men had been instructed to go to the lifeboat stations and wait there for further instructions. Because of the fire, the men could no longer reach the prescribed stations. As usual in such cases, they gathered at the alternative assembly point in the fire-protected supply block directly below the helicopter deck. There they waited for rescue from the air. Because the wind was blowing from an unfavorable direction and fire and smoke blew over the helipad, however, no helicopter could land. The men received no further instructions, and the supply block slowly filled with smoke, since the living areas were not, as is common today, protected by increased air pressure and internal breathing air treatment.

The fire-resistant lining was so efficient that most of the men in the supply block were still alive after the first gas explosion. The situation became more and more threatening because of the increasing smoke, so that some men began to take their fate into their own hands. Even though they had been warned that it would mean certain death, they found their way down from the supply block and risked the 30-meter plunge into the sea.

The Tharos, a large life raft, happened to be anchored in close proximity to the Piper Alpha. Occidental had built this mobile island especially for such an emergency. But here too the technology failed. At first the Tharos extended the fire hoses too quickly. The system shut down and the island crew lost ten minutes to get it going again. The retractable gangway moved slowly and took over an hour to extend to the full length of 30 meters.

The second explosion threw the Tharos back, their crew could only watch as the platform slowly melted and collapsed.

Failure during the accident

The Claymore platform pumped oil through the pipeline until the second gas explosion because the Occidental control center manager did not get permission to shut down the rig. Tartan also continued to pump, the manager of which had received this directive from his superior. The reason for this procedure lay in the exorbitant costs associated with switching off a platform. It takes several days to bring production back to normal after a standstill. Therefore, this decision could not be made easily by the managers of the platforms. Because they should have expected significant sanctions from their employer, they preferred to take out reinsurance with Occidental.

consequences

Memorial to the Victims in Hazlehead Park , Aberdeen

At the time of the accident on July 6, 1988, there were 226 (other sources 229) men on board, 166 of whom died on the platform, another worker died later in the hospital. Those who survived had jumped into the sea from a height of 30 m, contrary to the applicable regulations.

Occidental Petroleum's management relied on the fact that it was the first accident on one of its platforms in the North Sea. Those responsible did not mention that there had been a fatal accident on the Piper Alpha four years earlier, in which a worker died. Occidental destroyed the bent remains of the platform and gave up all activities in the North Sea within a year. It is estimated that the Occidental disaster cost over $ 15 billion.

The Piper Alpha burned for three weeks before they could put Red Adair and his crew out. They brought the big fire under control by pumping cement into the boreholes and then cutting them.

Of those killed, 135 (or 137, the sources are not uniform) were later recovered, the remaining bodies remained missing. The majority of the victims had died of smoke inhalation, only a few from burns.

The extensive investigation by the Cullen Commission revealed the deficiencies in the management and in the operations of Occidental. In its report, the commission made 106 proposals to improve safety on oil rigs. The oil industry accepted all of the proposals. They related to improvements in the documentation of work on the machines (permit to work), more favorable placement of the safety valves on the lines, the thermal insulation of submarine lines, improvements to the evacuation systems, a reduction in the risk of smoke and the introduction of safety audits.

This report had no criminal consequences, there was only - after a lengthy civil process - certain compensation payments for the surviving dependents.

New security concepts

As a result of the disaster Health, Safety and Environment (HSE) Management System (dtsch. Were health, safety and environmental management systems ) and developed as a safety culture in the organization OGP (International Association of Oil and Gas Producers, see. EPSG ) introduced. In the application of the security concept it is also provided that the management distributes its power and a "pull" of the bottom-up instead of the old "push" of the top-down ( bottom-up 'pull' rather than top-down 'push ' ): Reports on safety deficiencies in the workplace (see Swiss cheese model ) and suggestions "from below" are now being promoted ("pull") instead of instructions from the management level "from above" being pushed through ("push"). The concept is also called HSE culture ladder, "Hudson Ladder" .

Web links

Commons : Piper Alpha - collection of images, videos and audio files

Individual evidence

↑ Investigation report, Chapter 3.5.1
↑ Investigation report, Chapter 3.1
↑ "Double Indemnity"
↑ Patrick Hudson: Implementing a safety culture in a major multi-national . In: Safety Science . tape 45 , no. 6 , July 2007, p. 697-722 , doi : 10.1016 / j.ssci.2007.04.005 . (PDF 832 kB, read online )

[1] Investigation report, Chapter 3.5.1

[2] Investigation report, Chapter 3.1

[3] "Double Indemnity"

[4] Patrick Hudson: Implementing a safety culture in a major multi-national . In: Safety Science . tape 45 , no. 6 , July 2007, p. 697-722 , doi : 10.1016 / j.ssci.2007.04.005 . (PDF 832 kB, read online )