Safety Cases: Are They Appropriate for Most Offshore Platforms?
- K.E. Arnold (Paragon Engineering Services Inc.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- November 1994
- Document Type
- Journal Paper
- 954 - 954
- 1994. Society of Petroleum Engineers
- 7.2.1 Risk, Uncertainty and Risk Assessment
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- 138 since 2007
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A safety case is a written presentation of a formal safety assessment ofmajor hazards that evaluates the safety management systems of both the companyand its installation and demonstrates that both the design and the operation ofthe facility meet the desired level of safety. Thus, a safety case establishesthat potential major hazards and risks to operating personnel have beenidentified and that suitable controls have been provided. Further, a safetycase shows that, in the event of a major emergency, provisions exist forpersonnel evacuation, escape, and rescue.
While quantification of risks is not required in a safety case, applicationof safety cases to North Sea platforms has led to the belief that a safety casemust contain a quantitative risk assessment to demonstrate acceptable risklevels.
Safety cases emerged as an issue for offshore platforms as a result of LordCullen's report on the 1988 Piper Alpha catastrophe in the North Sea thatclaimed 165 lives. The report criticized the operating company's management:"They adopted a superficial attitude toward the assessment of risk of majorhazard. The safety policies and procedures were in place, the practice wasdeficient." The initial fire was determined to result from an improper"tag out" procedure, although an argument can be made that it resultedfrom improper analysis of what constitutes a safe design. (Relief valves weredesigned to be removed and bench-tested annually instead of being tested inplace using a locked-open valve. Some operators believe the latter methodprovides a higher level of safety.)
Most victims died from inhalation of smoke and fire; few died of burns.Numerous deaths were attributed to escape routes made impassable by smoke. Manypeople remained in the living quarters, which were destroyed and became a deathtrap. From this tragedy, the need for a temporary safe refuge (TSR) andanalysis of the integrity of the TSR were identified as integral parts of anysafety case for a North Sea platform. The TSR serves as a safe gathering placefor personnel while the emergency is assessed and mitigated, control methodsare activated, and preparations are made for evacuation. The frigid North Seawaters present an immediate danger to personnel, necessitating such evacuationmeasures as insulated survival suits, fast rescue craft, and totally enclosedsurvival craft. A typical safety case analysis for a large North Sea platformcan cost in excess of $1 million.
Applicability in Mild Climates
To evaluate the need for safety cases in relatively mild climate areas likethe Gulf of Mexico, the west coast of Africa, and Southeast Asia, the followingpoints should be considered.
1. Possibility of event escalation before personnel can escape. The climatein the northern North Sea dictates enclosed production facilities. A typicaldesign includes several walled modules with powered ventilation and heatingsystems. This walled design limits the escape routes and leads to relativelyhigh overpressures if a gas leak is ignited. Additionally, smoke could easilyfill an enclosed, unventilated module, hampering escape.
On platforms in milder climates, equipment is placed on open decks. Gasleaks are more easily dispersed by natural ventilation, lessening the chance ofignition, and smoke accumulation is less likely. Open design also decreases thechance of overpressure should ignition occur and affords more paths ofegress.
2. Ability to escape the platform. In milder climates, escape from theplatform to boats or directly to the sea is possible in an emergency. Thus, theneed to provide a TSR to allow helicopter evacuation or evacuation byself-launching lifeboats is lessened.
3. Platform size. In milder climates, platforms tend to be smaller than inthe North Sea. On these platforms, the proper fire control strategy may be toattempt to control an incipient fire with hand-held extinguishers. The strategyfor blowouts and large fires may be to shut in production, to abandon theplatform immediately, and to allow the fire to burn out. In this case, onlyminimal active fire control is provided, and provision of a TSR and elaboratedeluge system may not be warranted.
Assuring Adequate Safety Levels
The vast majority of platforms are relatively small and in mild climates. Ifsafety cases are not performed on these platforms, how can the operator becertain that they are designed and operated in a manner that ensuresmaintenance of adequate safety levels?
Luckily, there is a long history of operating platforms in the Gulf ofMexico with an extensive database. Since the early 1970's, when the U.S.Mineral Management Service rules and the API 14 series specification andrecommended practices for safe design were first developed, the safety recordfor these operations is well documented to be at "acceptable"levels.
In 1993, API issued two documents that should improve this safety record.API RP 75, Recommended Practice for Development of a Safety and EnvironmentalManagement Program for Outer Continental Shelf (OCS) Operations and Facilities,and API RP 14J, Design and Hazards Analysis for Offshore Production Facilities,represent, in effect, a generic safety case for open platforms in mildclimates. These documents have been awarded the 1994 Safety in Seas Award bythe Natl. Ocean Industries Assn.
API RP 14J provides guidance for safe design according to well-establishedindustry practice. It details recommended safety information required to ensuresafe operations and explains how to perform a hazard analysis of the design.API RP 75 explains the elements that should be considered in a system to managesafety. It provides guidance on the necessary policies and procedures and themanagement systems required to ensure that the practice of these procedures isnot deficient. Thus, it directly addresses Lord Cullen's primary concern aboutPiper Alpha quoted above.
API RP 75 and 14J are designed to meet Lord Cullen's basic objective thatadequate design and operating procedures are not only in place but are beingadequately practiced. This is accomplished with a minimum of paper work. Forthe majority of platforms, adherence to these documents will ensure as high alevel of safety as would be derived from developing individual safety cases ata fraction of the cost.
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