The decompression of diving chambers on a Norwegian oil rig in 1983 would have been avoided with modern safety interlocks.
The Byford Dolphin was a semi-submersible oil rig located in the Frigg gas field in the North Sea, approximately 200 km off the coast of Norway.
By 4 o’clock in the morning on 5 November 1983, two workers, Edwin Arthur Coward and Roy P. Lucas, had returned from a dive and entered a system of decompression chambers on the rig’s deck. These chambers served as living quarters during saturation diving operations, where workers would live and sleep in heavily pressurised environments between shifts.
Another pair of divers, Bjørn Giæver Bergersen and Truls Hellevik, rested in one of the chambers at a pressure of 9 atmosphere (atm). The chambers were connected to the diving bell by a short passage known as the trunk. Two dive tenders, William Crammond and Martin Saunders, sealed the connection from outside with a clamp.
The usual procedure for decompression, as outlined by a medical investigation into the accident published in The American Journal of Forensic Medicine and Pathology, would be to:
- Close the diving bell door
- Slightly increase the bell pressure to seal the door
- Close the door between the trunk and chamber 1
- Depressurise the trunk to 1 atm
- Open the clamp to separate the bell from the chamber system
The first two steps had been completed when the clamp sealing the tunnel off from the diving bell was released, causing the highly pressurised chamber system to drop from 9 atm to 1 atm instantaneously.
Coward, Lucas and Bergersen died instantly during a rapid decompression. The autopsy identified the effects on their bodies.
“The most conspicuous finding was large amounts of fat in the large arteries and veins and in the cardiac chambers, as well as intravascular fat in the organs, especially the liver,” the autopsy report said. “It is suggested that the boiling of the blood denatured the lipoprotein complexes, rendering the lipids insoluble.”
Hellevik, standing by the door to the chamber, was exposed to the highest pressure. His body pushed through the partly opened door, which became jammed so tightly it was later opened with an acetylene burner.
Outside the chambers, the diving bell swung wildly, fatally colliding with Crammond and severely injuring Saunders.
Out of date
Modern safety interlocks are designed to prevent disasters such as this, but outdated equipment on the Byford Dolphin precluded this possibility.
The direct cause of the explosive decompression was the coupling lock connecting the diving bell to the chamber system being opened prematurely, while the system was still pressurised and with all internal doors open.
The Byford Dolphin diving system was based on rules set in 1975, which did not outline any specific requirements for the locking arrangement. This had since been superseded by updates made in 1982. Among other things, these new requirements mandated that the coupling mechanisms between bell and chamber should be constructed so that they can’t be opened while the connection tunnel is under pressure. Critically, such a modification had not yet been implemented on the Byford Dolphin’s system.
Further, a Norwegian Official Report into the incident identified an operational error involving premature unlocking. Specifically, the coupling lock was unscrewed and opened before pressure in the connecting tunnel was released and before the chamber door was closed.
The detailed procedural steps for transferring divers, which were not correctly followed during this critical phase, emphasise the high risks inherent to such operations, according to the report. It attributes the direct cause to human error relating to the dive leader’s and lock operators’ failure to maintain proper sequence and safety checks. However, the report concludes that, due to the deaths of key personnel involved in the locking phase, the exact sequence is difficult to reconstruct completely.
New controls
The Byford Dolphin incident transformed how diving safety is approached, particularly in the context of saturation diving.
The Norwegian Official Report outlined measures designed to prevent similar accidents from occurring. These emphasised the need for improved technical safety features and procedural controls in diving systems, especially saturation diving setups. The recommendations included:
- The installation of fail-safe interlocking mechanisms on connections such as the diving bell and chambers so they can’t be opened when the system is under pressure
- Upgrading equipment to include outboard pressure gauges for continuous, visible pressure monitoring
- Improvements in communication systems to provide clear and reliable contact between divers, supervisors and surface control
- Developing and enforcing strict operational procedures and training to minimise human error during critical operations like transfer under pressure
- Rebuilding diving systems to meet the latest safety regulations, even if older systems are not initially subject to retrospective orders
- Mandatory inspections and certifications by relevant authorities to ensure compliance with updated safety standards
- Specific attention to the control of “transfer under pressure” operations, including mandatory closing of all internal doors during transfers or installation of automatic door-closing devices in the event of pressure loss
The Norwegian Government paid undisclosed compensation to the families of the six divers involved in the incident in 2009. The Byford Dolphin rig continued to be in service until 2016.
Risky business
The Byford Dolphin disaster was not the first time death had greeted North Sea divers, who often worked in extremely high-risk environments. It was also not the last.
British diver Bradley Westell died in 1995 when his lifeline was caught in the propellers of the Stena Orelia, a diving support vessel operating off the Norfolk coast.
The incident led to the imprisonment of the diving supervisor for perverting the course of justice during the investigation, a first for the offshore oil industry in the North Sea.
This story was originally published in the February 2026 edition of create with the headline “Under pressure”.
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Sources
Giertsen et al., “An Explosive Decompression Accident”, The American Journal of Forensic Medicine and Pathology, 1988
The Byford Dolphin Diving Accident, Norwegian Official Report, 1984
