The Piper Alpha Cullen Report
The inquiry into the Occidental Petroleum Piper Alpha Disaster was commissioned by the Department of Energy, their being the UK Government Body responsible for the operation and safety of offshore oil and gas installations. They appointed Lord Cullen, a very experienced Scottish Jurist, to conduct the Public Inquiry into the cause of the disaster. The subsequent inquiry began in January 1989 and was to last 6 months, with 260 witnesses giving evidence.
The inquiry, published in 1990, was divided into two parts;
- The Cause of the Piper Alpha Oil Rig Disaster
- Lessons to be Learned and Recommendations
The Cause of the Piper Alpha Oil Rig Disaster
The cause has been explained in detail the preceding section, therefore only salient points raised from the inquiry are noted below.
The initial cause was the escape of gas following the starting of the standby Condensate Pump A, regardless of a current PTW being in force (the PTW was never found). It was suggested by a witness that that because the PTW was for the removal of the PSV (this being a separate component from the pump), the permit therefore may have been stored in the Safety Office and not in the pumps PTW section in the control room.
The adherence to the Permit to Work System had become too relaxed, with no verbal confirmation taking place at shift handovers. This was noted in Lord Cullen’s criticisms of Occidental Petroleum’s Management of Maintenance Safety Systems.
Firewalls were not upgraded to blast walls; therefore they disintegrated on the gas explosion, penetrating gas and oil pipe work and machinery, adding to the fire.
- The Tartan and Claymore Platforms
These platforms continued to supply oil and gas, despite the flames from Piper being visible to them. If they had shut down the supplies to Piper, the fire and subsequent explosions would have been much less severe and may have been have been limited to the Gas Module. Although the explosion and fire caused by the escape of gas from the PSV blinds was the initial cause of the disaster, the failure and rupture of the gas risers were responsible for Piper's destruction and preventing the crewmembers evacuation.
Recommendations and Lessons Learned
Lord Cullen made over 100 recommendations following an extensive and well warranted Inquiry.
Once conversion to gas had taken place, the firewalls between modules should have been replaced or upgraded to blast walls. These would have withstood the initial explosion containing the resultant fire to Module C.
- Emergency Shutdown Valves (ESD Valves)
It was recommended that ESD valves be located on the deck as well as subsea locations on hydrocarbon risers, with the ESDs on the deck being installed within a blast-proof container.
- Limitation of Supply of Hydrocarbons
Lord Cullen recommended that in future the design of offshore installations should limit the supply of hydrocarbons to the installations, and not use them as a “hub."
Lord Cullen noted that many of those killed had died from asphyxiation in the accommodation. He recommended the installation of a gas, fire, explosion, and smoke-proof temporary shelter for the crew on offshore installations, for use until evacuation is arranged.
It was recommended that the HVAC systems be upgraded to prevent ingress of smoke to accommodation modules, pressurizing them and providing air locks to prevent smoke/toxic fumes entering these areas.
- Maintenance Safety Procedures
Lord Cullen was critical of Occidental Petroleum’s Management of Maintenance Safety Procedures, finding them guilty of negligence in this department and recommending their revision in line with the offshore oil and gas installation governing body.
- Offshore Oil and Gas Responsible Body
This was by far the most important change to come out of the Piper Alpha Disaster Inquiry.
The responsibility for the safety of offshore oil and gas installations would be removed from the Department of Energy, a Government Body, and become the responsibility of the Health and Safety Executive (HSE) an independent body with wide-ranging powers.
It would soon introduce radical safety measures such as requiring a “Safety Case." This involved the presentation of a full management safety statement from offshore oil and contractors before any platforms were installed in British waters.
This report was to be compiled by an independent expert and paid for by the oil/gas company.
I saw many changes during my employment as Engineer at the former Brown, Root, and Wimpey offshore construction yard at Nigg in the North of Scotland. Our yard was just across the Firth from McDermott’s facility where Piper Alpha was built. In fact McDermott’s were our major competitor when bidding for the offshore installations construction contracts. We ended up amalgamating with them and being known as BARMAC (Brown and Root, McDermott).
The changes I saw after the Piper Inquiry included:
- Regular production Quality Assurance audits at the yard, high level of NDT inspections of pipe welding and piping pressure testing.
- Heavy gauge steel blast and firewalls fitted to all vulnerable areas and similar enclosures around ESD Valves.
- HVAC design upgraded such as the number of fire-dampers fitted and rooms pressurized to prevent ingress of smoke or gas fumes.
- The introduction of “free-fall" fully totally enclosed lifeboats. Once all survivors were aboard and strapped in, the lifeboat could be launched from inside the lifeboat. Once launched these hit the sea at an angle and force that allowed the lifeboat to travel underwater for a distance to emerge clear of any fires at sea level. There was also an increase in the number and locations of self-inflating life-rafts, ladders and lifebuoys installed at all deck levels.
- The main firewater pumps could still be switched from automatic control room operation to manual local operation from the fire-pump room. This may have changed since I retired, but if not, it still requires to be investigated as I did not see any recommendation regarding this in the Cullen Report. The seawater pumps could be used to supply the firewater ring main, but again these are down-hole pumps and would cause the same problems to the divers.
Perhaps a large steel mesh cage around the pump suction (the pump is submerged being at the bottom of the caisson) would be adequate protection for divers.
A typical firewater pump used on oil and gas production platforms is shown below.