A missing safety interlock on a North Sea rig rewrote diving rules
In November 1983, a clamp on the Byford Dolphin drilling rig opened while its diving chambers were still pressurised at nine atmospheres. Five men died in an instant. Norway made interlocks compulsory a month later, but the divers' families waited 26 years for compensation and still argue the official inquiry blamed the wrong person.
Byford Dolphin began life in 1974 as Deep Sea Driller, the first of Aker's successful H-3 series of semi-submersible rigs. It was 108 metres long, could drill 6.1 kilometres down in water up to 460 metres deep, and drilled seasonally in British, Danish and Norwegian waters for Dolphin Drilling, part of Fred Olsen Energy. Saturation divers working from it lived in deck chambers held at the pressure of the depths, travelling to the seabed in a diving bell linked to the chambers by a short sealed passage called a trunk.
In the early hours of 5 November 1983, over the Frigg gas field, two divers had just returned in the bell and climbed through into their chamber, while two colleagues rested next door. Separating the bell required closing doors, bleeding the trunk down to surface pressure, and only then releasing the clamp. The clamp opened before the chamber door was shut, and the whole system dropped from nine atmospheres to one almost at once. All four divers and a tender were killed and a second tender badly hurt.
Investigators blamed the tender who released the clamp, though they could not say whether he acted on orders, on his own, or after a misheard instruction; the crew communicated with the chamber through a wall-mounted megaphone amid heavy rig noise, and had worked beyond 12 hours. Engineers saw a deeper fault. The 1975 diving system lacked fail-safe hatches, outside pressure gauges and an interlock that would have made opening the trunk under pressure impossible, something the certifier Norske Veritas already required on paper.
Former crew and the Norwegian union NOPEF called the inquiry a cover-up, saying dispensations granted by the petroleum directorate let the rig run without that equipment. A report obtained by the North Sea Divers Alliance in 2008 pointed to faulty equipment, and the Norwegian government eventually compensated the families. The rig suffered another fatal accident in 2002 and was scrapped in 2019.
Source: Byford Dolphin
