Piper Alpha event

This case study concerns the events leading up to the hydrocarbon explosion which was the starting point for the Piper Alpha offshore disaster. It describes the investigation of the incident using the sequentially timed events plotting (STEP) technique. Based on the STEP work sheet developed, the critical events involved in the incident are identified and analyzed in order to identify their root causes. 

The case study has documented the investigation and root cause analysis process applied to the hydrocarbon explosion that initiated the Piper Alpha incident. The case study serves to illustrate the use of the STEP technique, which provides a clear graphical representation of the agents and events involved in the incident process. The case study also demonstrates the identification of the critical events in the sequence which significantly influenced the outcome of the incident. Finally the root causes of these critical events were determined. This allows the analyst to evaluate why they occurred and indicated areas to be addressed in developing effechve error reduchon strategies. 

Ever since the inception of the petroleum industry the level of fires, explosions and environmental pollution that have precipitated from it, has generally paralleled its growth. As the industry has grown so has the magnitude of its accidental events. Relatively recent events such as the Flixborough incident (1974), Occidental s Piper Alpha disaster (1988), and Exxon s Valdez oil spill (1989) have all amply demonstrated the extreme financial impact these accidents can produce. 

If instmments are placed on manual, particularly emergency instruments, then a common cause event has been created. For example, one of the contributing factors in the Piper Alpha disaster was that both firewater pumps were on manual. They had been placed in that state to ensure that any divers in the water were not sucked into the firewater intake in the event of an automatic start of the pumps. Unfortunately, the fire on the platform prevented operators firom getting to the pumps to turn them on. The lack of firewater capability materially contributed to the magnitude of the disaster. 

The stories we tell should have a resolution. In the case of major events such as Piper Alpha or Deepwater Horizon, the resolution could be new ways of managing safety (Safety Cases) or the introduction of new regulations (SEMS). Even less dramatic stories should always provide guidance to better behaviors or improved management systems. 

Maitland, G. (2011) Offshore Oil and Gas in the UK An Independent Review of the Regulatory Regime. Report by Chairman Geoffrey Maitland, FREng, December 2011 (hereinafter, Maitland Review). Lord Cullen (1990) The Public Inquiry into the Piper Alpha Disaster. Report by the Chairman The Hon. Lord Cullen, Cm. 1310, 1990. HMSO London (hereinafter, Cullen Report). The events and responses surrounding the Piper Alpha disaster are beyond the scope of this work. For further discussion on this, see Chapter 6 in this volume. 

Major organizational accidents such as the destruction of the space shuttle Challenger in 1986, the explosion of the Chemobyl s nuclear power plant in 1987, the accident with off-shore platform Piper Alpha in 1988 or the destmction of the space shuttle Columbia in 2003, highlighted the relevance of hmnan contributions to organizational safety. Investigations traditionally considered technical and human factors in the development and prevention of these negative events but, in spite of such operational perspective, statistics have revealed the preponderance of human factors in up to 60-70 percent of the situations (e.g., Deldcer, 2002). 

There is sufficient evidence from well-known historical events to indicate that safety culture (Piper Alpha), human error (Kegworth) and violations (Herald of Free Enterprise) all play major roles in the occurrence of incidents. Coupled with the increasing importance being afforded to the human factors causes of incidents, organisations have a very convincing case for the development of an integrated suite of tools for incident investigators. 

Although the Piper Alpha disaster has a much higher profile, the Alexander L. Kielland event that occurred in 1980 was almost equally serious. However it did... 

The Piper Alpha platfomi was a large, fixed structure platform located about 110 miles northeast of Aberdeen in 474 feet of water. It handled both oil and gas. Equipment on board separated the incoming oil and gas streams and created (hydrocarbon) condensate product. The oil and condensate were then exported from Piper Alpha through a 30-inch line to the onshore Flotta terminal. Piper Alpha contributed about 10 percent of the oil production from the U.K. sector of the North Sea. The explosion and fire that occurred in 1988 is one of the most important process-safety events that has ever occurred either onshore or offshore. 

Critically important to an understanding of this event is the fact that Piper Alpha was a hub platform. Not only did the platform have its own risers, it also received gas from the Tartan A platform, which was located about 11.5 miles away. The gas flowed to Piper Alpha through a subsea 18-inch pipeline. This gas stream was combined with Piper s own gas, compressed, and sent to the MCP-01 platform, some 33.5 miles away. Some of the gas was also used as lift gas and as fuel for the onboard generators (the gas could also be flared). In addition, another platform—Claymore—could also feed gas to Piper Alpha. All of the platforms were operated by the same company—Occidental. 

The long-term effects of the Piper Alpha event were profound. The formal investigation into the Piper Alpha tragedy was headed by Lord Cullen, a Scottish High Court judge. In 1990 his committee published the The Public Inquiry into the Piper Alpha Disaster, a document that is usually referred to simply as The Cullen Report. 

Chemical Safety Board) had not been published, so further conclusions and insights are to come. However, there is no doubt that this event has had an impact on the offshore oil and gas industry equal to that of Piper Alpha. 

Chapter 6 of this book describes the safety case approach to managing risk. One of the reasons that this approach was not followed in the Gulf of Mexico following the Piper Alpha event is that there are thousands of platforms in the Gulf, many of them small, unmanned, and very similar to one another. It would not be feasible to develop a safety case for each of these. 

Piper Alpha This event cannot be attributed to tailure to follow regulations. Indeed, The Cullen Report led to major developments in technical safety and formal safety analyses and ot regulations built around the Safety Case concept. 

On an offshore platform, however, the persons who are not working are still present on the platform and they may be killed or injured in the event of a catastrophe. Many of the deaths on the Piper Alpha platform, for example, were off-duty crew who were sleeping and who could not escape from the living quarters. 

With regard to offshore operations, the development of Safety Cases in the UK sector of the North Sea received a major impetus following the Piper Alpha catastrophe. Although Safety Cases had been used before that event, it is probably not an exaggeration to say that the modem Safety Case for offshore work came into being following the publication of The Cullen Report. 

Bow tie analysis is a tool that has become very popular in the last few years, especially because of the ease in which it can display cause-consequence of a particular hazardous condition. It is a qualitative tool that combines the fault tree to determine the causes and how the fault could occur, with the event tree, which documents the consequence of the hazardous condition. It became much better known in the mid-1990s when Royal Dutch/Shell used it to better understand the Piper Alpha disaster. The process industry uses it not only to assess the hazards and risks but also as a very effective communication tool to illustrate the cause-consequence-control and how it can impact a hazardous condition. In reality, it really isn t a new analytical tool, but rather, a very good visualization tool. 

In the Piper Alpha Enquiry [1], Cullen reviewed evidence from survivors and experts and tried to reconstruct events. This was difficult because many of the people most directly involved in events had died. Cullen concluded that the most likely cause of the explosions and fire was because a member of the nightshift operations team, George Vernon, had started up a condensate (light hydrocarbon) pump, here called pump A, when it was still under maintenance with an outstanding Permit to Work, and was therefore not in a safe condition. George Vernon died in the accident. 

For example, accidents such as the Piper Alpha disaster [1] clearly illustrate that a highly complex sociotechnological system performance is dependent upon the interaction of human, technical, organizational, social, environmental, and managerial elements. More clearly, all these factors or elements can be very important cocontributors to incidents that could result in catastrophic events. Thus, this chapter presents various important aspects of human factors contribution to accidents in the oil and gas industry and fatalities in the industry. 

On an offshore platform, however, the persons who are not on duty are still present and they may be killed or injured in the event of a catastrophe. Many of the deaths on the Piper Alpha platform (Chapter 2), for example, were of off-duty crew who were sleeping, and who could not escape from the living quarters. By contrast, 25 years later, when the explosion and fire occurred on the Deepwater Horizon platform, 11 men died instantiy, but the other 135 persons on board survived the blast and subsequent fire. This is an indication that the safety measures that have been designed into rigs and platforms in the years following Piper have had a positive effect on safety improvement. 

The Deepwater Horizon (DWH) event occurred in April 2010 in the GoM. At the time of writing some of the investigation reports (such as that from the Chemical Safety Board) had not been published, so it is Important not to draw too many conclusions until those reports and their associated findings are made available. However, it is already clear that this event will have an impact on the offshore oil and gas industry as large as that of Piper Alpha. 

The previous seven chapters of this book have demonstrated how much the offshore safety management business has changed and matured in the quarter century since the Piper Alpha accident. Yet, as the Deepwater Horizon and Montara events illustrate, more progress needs to be made, particularly with respect to process and technical safety. The industry has not yet arrived. No doubt ongoing application of the Safety and Environmental Management Systems (SEMS) and safety case techniques will lead to further improvement, yet there may also be a need to make a step change, and to find new ways of improving safety. 

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