Byford Dolphin

• 1. Introduction

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  Six men were working the diving chamber system aboard Byford Dolphin, a drilling rig in the North Sea. One morning in 1983, a routine decompression step went catastrophically wrong. A mechanical failure in the chamber system would make it one of the deadliest days in offshore diving history. What exactly failed, who investigators blamed for it, and what became of the rig afterward are the questions this account follows.

• 2. Built For The North Sea

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  Dolphin Drilling operated Byford Dolphin, a semi-submersible, column-stabilised drilling rig, as a subsidiary of Fred Olsen Energy, and registered it in Hamilton, Bermuda. It drilled seasonally across the British, Danish, and Norwegian sectors of the North Sea for decades.

  Aker Group designed the rig, first named Deep Sea Driller, as the lead vessel in the Aker H-3 series. Workers completed it at the Aker Verdal shipyard in 1974, and the H-3 class went on to become highly successful.

  At 108.2 meters long, 67.4 meters wide, and 36.6 meters deep, the rig could drill to a depth of 6.1 kilometers. It could also operate in water as deep as 460 meters.

  Norwegian law initially certified Byford Dolphin to strict safety standards. Regulators later banned it from Norwegian waters, though it could still maneuver on its own engines to counter drift and ocean currents. For long-distance moves, though, it needed specialized tugboats.

  Its operating deck could carry 3,025 tonnes, and crew quarters held as many as 102 people. Equipment included a 49-meter derrick, a 12-point mooring system, and a blowout preventer rated to 10,000 kilopascals.

  That drilling depth and those safety certifications would be tested within a decade, when the rig's diving system faced a very different kind of pressure.

• 3. Nine Atmospheres

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  On Saturday, the 5th of November 1983, four divers were working the Frigg gas field in the Norwegian sector of the North Sea. Edwin Arthur Coward, a 35-year-old Briton, and Roy P. Lucas, 38 and also British, were resting in decompression chamber 2 at a pressure of nine atmospheres. Bjørn Giæver Bergersen, a 29-year-old Norwegian, and Truls Hellevik, 34, had just been winched up in the diving bell after a dive. They joined the chamber system through a connecting trunk, leaving their wet equipment behind and climbing into chamber 1. Outside, two tenders, William Crammond, 32 and British, and Martin Saunders, managed the clamp sealing that connection.

  Standard procedure called for five careful steps. Tenders were to close the diving bell door, then slightly raise pressure inside the bell to seal it tight. Next came closing the chamber 1 door, slowly depressurizing the trunk down to 1 atmosphere, and only then opening the clamp. The crew had completed the first two steps when a mechanical failure struck.

  The clamp sealing the trunk sprang open before Hellevik had closed the door to chamber 1. Both chambers depressurized in an instant, dropping from nine atmospheres to the outside pressure of 1 atmosphere. Escaping air rushed out with tremendous force, jamming the interior trunk door and slamming the diving bell into the two tenders outside. All four divers were killed instantly, along with Crammond; Saunders survived but was severely injured.

  Investigators and pathologists would later reconstruct exactly how that instant of decompression affected each man's body.

• 4. What The Postmortem Found

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  Medical examiners studied the remains of the four divers and found large amounts of fat in major arteries, veins, and the heart's chambers. Intravascular fat also showed up in their organs, especially the liver.

  This fat was unlikely to be embolic; pathologists concluded it had instead precipitated directly from the blood. Their working theory held that bubble formation in the blood denatured the divers' lipoprotein complexes, turning previously soluble lipids insoluble. Those now-insoluble lipids likely blocked circulation and caused death for three of the men.

  Truls Hellevik, the fourth diver, died differently than the other three. He was in the process of securing the inner door when the pressure surge forced his body through the narrow gap left by the jammed trunk door, an opening measuring 60 centimeters. The force of the blast caused fatal, catastrophic trauma, and investigators later found part of his remains as far as 10 meters above the exterior pressure door.

  Coward, Lucas, and Bergersen died in the positions investigators later diagrammed, each exposed to the effects of explosive decompression.

  Those postmortem findings would shape how investigators explained what went wrong mechanically inside the trunk itself.

• 5. Human Error Broken Design

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  A committee investigating the accident concluded that human error by the tender who opened the clamp was to blame. The trunk door itself had a centre-hinge design similar to a butterfly valve disc, and it had rotated too far to the left. That left the rim of the interior hatch lodged against the door opening, similar to a manhole cover left ajar but held partly in place. The resulting gap measured 24 inches across horizontally.

  Investigators could not determine whether the tender who opened the clamp did so on orders, on his own initiative, or because of a miscommunication. At the time, tenders outside the chamber could only communicate through a wall-mounted megaphone, and heavy rig and sea noise made it hard to hear. Fatigue may also have played a role; the crew had already been working for more than 12 hours.

  Investigators also pointed to engineering failure: the diving system dated to 1975 and lacked fail-safe hatches, outboard pressure gauges, and an interlocking mechanism. An interlock would have physically prevented the trunk from opening while still under pressure. Before the accident, Norske Veritas had already issued a rule requiring such connecting mechanisms to be impossible to open while the trunk was pressurized. One month after the accident, Norske Veritas and the Norwegian oil directorate made that rule final for all bell systems.

  Former crew members of Byford Dolphin and NOPEF, a Norwegian oil and petro-chemical union, later came forward and called the investigation a cover-up. They claimed the commission's report never mentioned dispensations on vital safety equipment that Comex had requested and the diving section had authorized through the Norwegian Petroleum Directorate. They also alleged the rig lacked interlocking clamps, outboard pressure gauges, and a safe communication system, all withheld because of those same dispensations.

  Those cover-up allegations would resurface years later, when the case reached a Norwegian courtroom.

• 6. A Government Accused

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  The North Sea Divers Alliance formed from early North Sea divers and the relatives of the men killed in 1983, pressing for a fuller investigation. In February 2008, the Alliance obtained a report indicating that faulty equipment, not human error, was the real cause of the accident.

  Clare Lucas, daughter of diver Roy Lucas, offered a blunt assessment. "I would go so far as to say that the Norwegian Government murdered my father because they knew that they were diving with an unsafe decompression chamber," she said.

  The divers' families eventually received compensation from the Norwegian government, 26 years after the accident.

  The settlement closed one chapter of accountability, but the rig's crew would face an entirely different tragedy on deck in the years that followed.

• 7. A Second Tragedy

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  On the 17th of April 2002, a 2-year-old Norwegian child on the rig was struck on the head and killed in an industrial accident. The death cost Byford Dolphin its exploration contract with Statoil, which raised concerns about the rig's operating procedures. That lost contract alone cost the company millions of US dollars in lost income.

  Dolphin Drilling kept the rig working in the North Sea for years afterward, before finally scrapping Byford Dolphin in 2019.