- Piper Alpha
Piper Alpha was a
North Seaoil production platform operated by Occidental Petroleum (Caledonia) Ltd. ["OPCAL’s share 36.5%, Texaco’s share 23.5%, Union Texas Petroleum’s share 20%, and Thomson’s share 20%." CAPLAN, section 1.2] The platform began production in 1976 ["by the end of 1976 and Claymore by the end of 1977", CAPLAN 1.2] , first as an oil platform and then later converted to gas production. An explosionand resulting firedestroyed it on July 6, 1988, killing 167 men. Total insured loss was about £1.7 billion (US$ 3.4 billion). To date it is the world's worst offshore oil disasterin terms both of lives lost and impact to industry. At the time of the disaster the platform accounted for around ten percent of the oil and gas production from the North Sea.
The Kirk of St Nicholas in Union Street, Aberdeen has dedicated a chapel in memory of those who perished and there is a memorial sculpture in the Rose Garden of Hazlehead Park in Aberdeen.
Four companies that later transformed into the OPCAL joint venture obtained an oil exploration license in 1972 and discovered the Piper Field located at coord|58|28|N|0|15|E in early 1973 and commenced fabrication of the platform, pipelines and onshore support structures. Oil production started in 1976 with about 250,000 barrels of oil per day increasing to convert|300000|oilbbl|m3. A gas recovery module was installed by 1980. Production declined to convert|125000|oilbbl|m3 by 1988. OPCAL built the
Flotta oil terminalin the Orkney Islandsto receive and process oil from the fields Piper, Claymore and Tartan, each with its own platform. One thirty inch(0.762 m) diameter main oil pipeline ran 128 miles (206 kilometres) from Piper Alpha to Flotta, with a short oil pipeline from the Claymore platform joining it some twenty miles (32 km) to the west. The Tartan field also fed oil to Claymore and then onto the main line to Flotta. [http://www.dbd-data.co.uk/bb1998/append11.htm pipeline dimensions ] Separate 46 cm diameter gas pipelines run from Piper to the Tartan platform, and from Piper to the gas compressing platform MCP-01 some convert|30|mi|km to the Northwest.
A large fixed platform, Piper Alpha was situated on the Piper Oilfield, approximately 120 miles (193 km) northeast of
Aberdeenin 474 feet (144 m) of water, and comprised four modules separated by firewalls. ["were not designed as blast protection walls and their function was to localise fire" CAPLAN 2.6.1] The platform was constructed by McDermott Engineering at Ardesier and UIE at Cherbourg, with the sections united at Ardersier before tow out during 1975, with production commencing in late 1976.For safety reasons the modules were organised so that the most dangerous operations were distant from the personnel areas. The conversion from oil to gas broke this safety concept, with the result that sensitive areas were brought together, for example the gas compression next to the control room, which played a role in the accident. It produced crude oiland natural gasfrom twenty four wells for delivery to the Flotta oil terminal on Orkney and to other installations by three separate pipelines. It has been said that at the time of the disaster, Piper was about the heaviest platform operating in the North Sea. At the time of the disaster 226 people were on the platform; 167 died and 59 survived. [Hull AM, Alexander DA, and Klein S. Survivors of the Piper Alpha oil platform disaster: long-term follow-up study. The British Journal of Psychiatry (2002) 181: 433-438.]
Timeline of the incident
A new gas pipeline was built in the weeks before the
6 Julyexplosion, and while this work disrupted the normal routine, the platform was operated as normal. The discovery of a small gas leak was normal and no cause for concern. As the platform was completely destroyed, and many of those involved died, analysis of events can only suggests a possible chain of events based on known facts. Some witnesses to the events question the official timeline. [http://news.bbc.co.uk/1/hi/uk/215866.stm Piper Alpha pair 'wrongly blamed']
12:00 p.m.Two Condensate pumps on the platform, designated A and B, compressed the gas for transport to the coast. On the morning of
July 6, Pump A's pressure safety valve (PSV #504) was removed for routine maintenance. The pump's fortnightly overhaul was planned but had not started. The now open Condensate pipe was temporarily sealed with a flat metal disc. Because the work could not be completed by 6:00 p.m., the metal disc remained in place. The on-duty engineer filled out a permit which stated that Pump A was not ready and must not be switched on under any circumstances.
6:00 p.m.The day shift ends and the night shift starts with 62 men running Piper Alpha. As he found the on-duty custodian busy, the engineer neglects to inform him of the condition of Pump A. Instead he places the permit in the control centre and leaves. This permit disappeared and was not found. Coincidentally there was another permit issued for the general overhaul of Pump A that had not yet begun.
7:00 p.m.Like many other offshore platforms, Piper Alpha had an automatic fire-fighting system, driven by both diesel and electric pumps (the latter of which were disabled by the initial explosions). The diesel pumps were designed to suck in large amounts of sea water in order to extinguish any fires. These pumps had an automatic control which would start them in case of fire. However, the fire-fighting system was under manual control on the evening of
July 6. Piper Alpha procedures required manual control of the pumps whenever divers were in the water (as they were approximately 12 hours per day during summer) regardless of their location, to prevent divers from being sucked in with the sea water. (Fire pumps on other platforms were switched to manual control only if the divers were close to the inlet.)
9:45 p.m.Condensate (LPG) Pump B stops suddenly and cannot be restarted.
The entire power supply of the offshore construction work depended on this pump. The manager had only a few minutes to bring the pump back online, otherwise the power supply would fail completely. A search was made through the documents to determine whether Condensate (LPG) Pump A could be started.
9:52 p.m.The permit for the overhaul is found, but not the other permit stating that the pump must not be started under any circumstances due to the missing safety valve. The valve was in a different location from the pump and therefore the permits were stored in different boxes, as they were sorted by location. None of those present was aware that a vital part of the machine had been removed. The manager assumed from the existing documents that it would be safe to start compressor A. The missing valve was not noticed by anyone, particularly since the metal disc replacing the safety valve was located several metres above ground level and obscured by machinery.
9:55 p.m.Condensate (LPG) Pump A is switched on. Gas flowed into the pump, and due to the missing safety valve produced an overpressure which the loosely fitted metal disc did not withstand. ["leakage of condensate from a blind flange assembly at the site of a pressure safety valve" CAPLAN volume 2 chapter 5 Causation 1]
Gas audibly leaks out at high pressure, drawing the attention of several men and triggering 6 gas alarms including the high level gas alarm, but before anyone can act, the gas ignites and explodes, blowing through the firewall made up of 2.5 x 1.5 metre panels bolted together, which were not designed to withstand explosions. The custodian presses the emergency stop button, closing huge valves in the sea lines and ceasing all oil and gas production.
Theoretically, the platform would now have been isolated from the flow of oil and gas and the fire relatively contained. However, because the platform was originally built for oil, the firewalls were designed to resist fire rather than withstand explosions. The first explosion breaks up the firewall and dislodges panels around Module (B). One of the flying panels ruptures a small Condensate pipe, creating another fire.
10:04 p.m.The control room is abandoned. Piper Alpha's design made no allowances for the destruction of the control room and the platform's organisation disintegrates. No attempt was made to use loudspeakers or to order an evacuation.
Emergency procedures instructed personnel to make their way to lifeboat stations, but the fire prevented them from doing so. Instead the men moved to the fireproofed accommodation block beneath the helicopter deck to await further instructions. Wind, fire and smoke prevented helicopter landings and no further instructions were given with smoke beginning to penetrate the personnel block.
As the crisis mounted, two men donned protective gear in an attempt to reach the diesel pumping machinery below decks and activate the firefighting system. They were never seen again.
The fire would have burnt out were it not being fed new oil from both Tartan and the Claymore platforms, the resulting backpressure forcing fresh fuel out of ruptured pipework on Piper, directly into the heart of the fire. The Claymore continued pumping until the second explosion because the manager had no permission from the Occidental control centre to shut down. Also, the connecting pipeline to Tartan continued to pump, as its manager had received this directive from his superior. The reason for this procedure was the exorbitant cost of such a shut down. It takes several days to restart production after a stop, with substantial financial consequences.
Gas lines of 140 to 146 cm in diameter ran close to Piper Alpha. Two years earlier Occidental management ordered a study, which warned of the dangers of these gas lines. Due to their length and diameter it would take several hours to reduce their pressure, so that it would not be possible to fight a fire fueled by them. Although the management admitted how devastating a gas explosion would be, Claymore and Tartan were not switched off with the first emergency call.
10:20 p.m.Tartan's gas line (pressured to 120 Atmospheres) melts and bursts, releasing 15 - 30 tonnes of gas every second, which immediately ignite. A massive fireball of 150 metres in diameter engulfs Piper Alpha. From this moment on, the platform's destruction is assured.
10:30 p.m.The Tharos, a large fire fighting and rescue platform, draws alongside Piper Alpha. Attempts are made to extend its rescue walkway the 30 metres to the deck. A woeful design flaw in Tharos becomes apparent as the walkway extends too slowly to be able to reach the platform before 22:50.
10:50 p.m.The second gas line ruptures, spilling millions of litres of gas into the conflagration. Huge flames shoot over three hundred feet in the air. The Tharos is driven off due to the fearsome heat, which begins to melt the surrounding machinery and steelwork. It was after this second explosion that the Claymore stopped pumping oil. Personnel still left alive are either desperately sheltering in the scorched, smoke-filled accommodation block or leaping from the deck some convert|200|ft|m|abbr=on into the cold, rough North Sea.
11:20 p.m.The pipeline connecting Piper Alpha to the Claymore Platform bursts and the disaster claims its final victims.
11:50 p.m.The generation and utilities Module (D), which includes the fireproofed accommodation block, slips into the sea. The largest part of the platform follows it.
July 7The entire platform has gone. Module (A) is all that remains of Piper Alpha.
There is controversy about whether there was sufficient time for more effective
emergency evacuation. People were still getting off the platform several hours after the initial fires and explosions. The main problem was that most of the personnel who had the authority to order evacuation had been killed when the first explosion destroyed the control room. This was a consequence of the platform design, including the absence of blast walls. Another contributing factor was that the nearby connected platforms Tartan and Claymore continued to pump gas and oil to Piper Alpha until its pipeline ruptured in the heat in the second explosion. Their operations crews did not believe they had authority to shut off production, even though they could see that Piper Alpha was burning. [http://home.versatel.nl/the_sims/rig/pipera.htm Piper Alpha]
The nearby support vessel Lowland Cavalier reported the initial explosion just before 22:00, and the second explosion occurred just twenty two minutes later. By the time civil and military rescue
helicoptersreached the scene, flames over one hundred metres in height and visible as far as one hundred km (120 km from the Maersk Highlander) away prevented safe approach. " Tharos", a specialist firefightingvessel, was able to approach the platform, but could not prevent the rupture of the Tartan pipeline, about two hours after the start of the disaster and was forced to retreat due to the severity of the fire. Only after Tartan stopped pumping gas into the inferno could "Tharos" once again come alongside. "Tharos" recovered no one that night.
Two crewmen from the designated standby vessel were killed when an explosion on the platform destroyed their "Fast Rescue Craft", which had recovered several survivors from the waters underneath the platform.
The blazing remains of the platform was eventually extinguished by a team led by famed firefighter
Red Adairin which he claims he had to battle convert|80|mi/h|km/h|abbr=on winds and convert|70|ft|m|sing=on waves. [ [http://news.bbc.co.uk/2/hi/americas/2281867.stm BBC news] ]
Legacy of Piper Alpha
Cullen Enquirywas set up in November 1988 to establish the cause of the disaster. In November 1990, it concluded that the initial condensate leak was the result of maintenance work being carried out simultaneously on a pump and related safety valve. The enquiry was critical of Piper Alpha's operator, Occidental, which was found guilty of having inadequate maintenance and safety procedures. But no criminal charges were ever brought against it. [http://scotlandonsunday.scotsman.com/spectrum/The-night-the-sea-caught.4184800.jp The night the sea caught fire: Remembering Piper Alpha]
The second phase of the enquiry made 106 recommendations for changes to North Sea safety procedures, all of which were accepted by industry. [http://www.timesonline.co.uk/tol/news/uk/scotland/article4272717.ece Twenty years on, Piper Alpha survivor tells of fleeing fireball] Most significant of these recommendations was that the responsibility for enforcing safety in the North Sea should be moved from the Department of Energy to the
Health and Safety Executive, as having both production and safety overseen by the same agency was a conflict of interest. [http://media.newscientist.com/article/mg12817431.100-piper-alpha-rewrites-the-rules-on-offshore-safety-.html Piper Alpha rewrites the rules on offshore safety]
Survivors and relatives of those who died went on to form the Piper Alpha Families and Survivors Association, which campaigns on North Sea safety issues. [http://news.bbc.co.uk/1/hi/scotland/north_east/7483428.stm Widows hope deaths not in vain]
The wreck buoy marking the remains of the Piper is approximately 120 metres from the south-east corner of the replacement
Piper Bravoplatform. A lasting effect of the Piper Alpha disaster was the establishment of Britain's first "post- Margaret Thatcher" trade union, the Offshore Industry Liaison Committee.
A memorial sculpture, showing three oil workers, can be found in the Rose Garden within Hazlehead Park in Aberdeen. [http://www.timesonline.co.uk/tol/news/uk/article4282147.ece Piper Alpha North Sea oil rig disaster remembered 20 years on] The sculptor is
Sue Jane Taylor.
*National Geographic "Seconds From Disaster" episodes
* cite web
title=Appendix to Opinions (Lord Caplan) pgs 560-739 0/1261/5/1990
* cite web
title=Appendix to Opinions (Lord Caplan) volume 2 chapter 5 Causation 1
* cite web
author=Department of Trade and Industry (dti)
title=Oil and Gas Resources of the United Kingdom Volume 2 1998
* cite web
author=Department of Trade and Industry (dti)
* cite web
title=On This Day
* cite web
title=Piper Alpha Disaster - 20 Year Anniversary of Tragedy
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