Safety Cases: Are They Appropriate for Most Offshore Platforms?
Authors: Arnold K.E. 
Published: December 2007

E&P Exchange

A safety case is a written presentation of a formal safety assessment of major hazards that evaluates the safety management systems of both the company and its installation and demonstrates that both the design and the operation of the facility meet the desired level of safety. Thus, a safety case establishes that potential major hazards and risks to operating personnel have been identified and that suitable controls have been provided. Further, a safety case shows that, in the event of a major emergency, provisions exist for personnel evacuation, escape, and rescue.

While quantification of risks is not required in a safety case, application of safety cases to North Sea platforms has led to the belief that a safety case must contain a quantitative risk assessment to demonstrate acceptable risk levels.

Piper Alpha

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 that claimed 165 lives. The report criticized the operating company's management:"They adopted a superficial attitude toward the assessment of risk of major hazard. The safety policies and procedures were in place, the practice was deficient." The initial fire was determined to result from an improper"tag out" procedure, although an argument can be made that it resulted from improper analysis of what constitutes a safe design. (Relief valves were designed to be removed and bench-tested annually instead of being tested in place using a locked-open valve. Some operators believe the latter method provides 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. Many people remained in the living quarters, which were destroyed and became a deathtrap. From this tragedy, the need for a temporary safe refuge (TSR) and analysis of the integrity of the TSR were identified as integral parts of any safety case for a North Sea platform. The TSR serves as a safe gathering place for personnel while the emergency is assessed and mitigated, control methods are activated, and preparations are made for evacuation. The frigid North Seawaters present an immediate danger to personnel, necessitating such evacuation measures as insulated survival suits, fast rescue craft, and totally enclosed survival craft. A typical safety case analysis for a large North Sea platform can cost in excess of $1 million.

Applicability in Mild Climates

To evaluate the need for safety cases in relatively mild climate areas like the Gulf of Mexico, the west coast of Africa, and Southeast Asia, the following points should be considered.Possibility of event escalation before personnel can escape. The climate in the northern North Sea dictates enclosed production facilities. A typical design includes several walled modules with powered ventilation and heating systems. This walled design limits the escape routes and leads to relatively high overpressures if a gas leak is ignited. Additionally, smoke could easily fill an enclosed, unventilated module, hampering escape.On platforms in milder climates, equipment is placed on open decks. Gas leaks are more easily dispersed by natural ventilation, lessening the chance of ignition, and smoke accumulation is less likely. Open design also decreases the chance of overpressure should ignition occur and affords more paths of egress.Ability to escape the platform. In milder climates, escape from the platform to boats or directly to the sea is possible in an emergency. Thus, the need to provide a TSR to allow helicopter evacuation or evacuation by self-launching lifeboats is lessened.Platform size. In milder climates, platforms tend to be smaller than in the North Sea. On these platforms, the proper fire control strategy may be to attempt to control an incipient fire with hand-held extinguishers. The strategy for blowouts and large fires may be to shut in production, to abandon the platform immediately, and to allow the fire to burn out. In this case, only minimal active fire control is provided, and provision of a TSR and elaborated eluge system may not be warranted.

Assuring Adequate Safety Levels

The vast majority of platforms are relatively small and in mild climates. If safety cases are not performed on these platforms, how can the operator be certain that they are designed and operated in a manner that ensures maintenance of adequate safety levels?

Luckily, there is a long history of operating platforms in the Gulf of Mexico with an extensive database. Since the early 1970's, when the U.S. Mineral Management Service rules and the API 14 series specification and recommended practices for safe design were first developed, the safety record for 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 Environmental Management 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 mild climates. These documents have been awarded the 1994 Safety in Seas Award by the Natl. Ocean Industries Assn.

API RP 14J provides guidance for safe design according to well-established industry practice. It details recommended safety information required to ensure safe 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 manage safety. It provides guidance on the necessary policies and procedures and the management systems required to ensure that the practice of these procedures is not deficient. Thus, it directly addresses Lord Cullen's primary concern about Piper Alpha quoted above.

Conclusion

API RP 75 and 14J are designed to meet Lord Cullen's basic objective that adequate design and operating procedures are not only in place but are being adequately practiced. This is accomplished with a minimum of paper work. For the majority of platforms, adherence to these documents will ensure as high a level of safety as would be derived from developing individual safety cases at a fraction of the cost.

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