October marks the fifth anniversary of publication of Lord Cullens report on the Piper Alpha platform blast that occurred in the U.K. North Sea. Cullens report on the fatal 1988 accident was the basis for new legislation that requires U.K. offshore operators to have an approved safety program, known as a safety case, for each installation or close it down (OGJ, Feb. 14, 1994, p. 25). The safety case deadline is Nov. 30. But U.K. operators are confident they will get remaining approvals through in time to avoid platform shutdowns. Roderick Allison, chief executive of the offshore safety division at the U.K. Health & Safety Executive (HSE), reminded delegates at Aberdeens Offshore Europe conference on Sept. 7 of how far U.K. safety has advanced since 1988.
Revisions
Allison said, Management on Piper Alpha had not dealt adequately with such fundamental matters as weaknesses in the permit to work arrangements, problems with deluge systems, and emergency training and preparedness. They had made no systematic assessment of the risk of explosion leading to the failure of gas risers, which resulted in a catastrophic fire. And the legislative regime did not require such assessment. Since the blast, operators and government have totally revised their safety regimes. Many of the U.K.s 216 offshore installations have had to be modified drastically to improve protection of crews from blasts and fires. Allison gave examples of two approaches to gaining a safety case, which he described as hardware and software. The former involves replacing or reconfiguring an installation. Where this was too costly, a software approach is taken, involving changes to work practices. First, a hardware example, Allison said. A 1970s platform had been modified to receive a riser from another field. Assessment of the safety case showed the riser design was flawed. The design, a concentric conductor around a riser, was capable of withstanding only half the well shut-in pressure. To obtain safety case approval from HSE, the operator was required at an estimated cost of 6-8 million ($9-12 million) to modify the riser to cope with maximum pressure.
Alternative approach
A mid-1970s platform, said to have been one of the most difficult cases to assess, demonstrated the software approach. Replacing problem equipment was too costly, so HSE agreed with the operator to keep hazardous work away from the danger area. Alllison said the operator had to: reduce hot work by 80% from 1991 levels, move the crew out of accommodation space at times of high risk such as during maintenance, adopt a new pipeline checking procedure, limit vessel activity on the side of the platform nearest a vulnerable riser, and adopt new inspection techniques for main oil risers. Even when all U.K. installations have safety cases, Allison said, there will be plenty of safety challenges ahead for operators. First challenge is to ensure that operators cost-cutting programs do not compromise safety. Then there is the need to meet current safety levels in new areas such as West of Shetland, where water is deep, currents are strong, and there are high winds and heavy swells. Finally, there will be the task of abandoning structures safely.
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