Norway’s worst diving accident

This incident cost five people their lives, while one was seriously injured. Since oil operations began in the mid-1960s, about 30 divers had died in the North Sea basin as a whole. That made diving the riskiest occupation in the offshore business. The special feature of the Byford Dolphin accident was that it occurred above water while connecting the diving bell to the pressure chamber.

A Norwegian-registered semi-submersible built to the Aker H3 design, Byford Dolphin had been chartered by Elf Aquitaine.[REMOVE]Fotnote: Byford Dolphin was the first rig built to the internationally-acclaimed Aker H3 design. Originally named Deep Sea Driller, this unit was delivered in 1973 and became notorious in Norway under that name when it was wrecked off Bergen in the 1970s with the loss of six lives. The rig was working on the drilling and completion of six production wells on North-East Frigg. Comex Norge A/S was the diving contractor, and owned and operated the diving system on board.[REMOVE]Fotnote: NOU 1984: Dykkerulykken på Byford Dolphin, p 5

The accident occurred when the bell had just been recovered on board after two Norwegian divers had performed various jobs on the production template for North-East Frigg. They had been in the water for almost 2.5 hours. Two British divers were resting in the pressure chamber after a nine-hour shift. The British divers who were helping on deck outside the bell had been working for a total of 12 hours and 48 minutes when the accident happened.[REMOVE]Fotnote: Five divers killed on oil rig, The Observer, 6 November 1983.

An internal report describes the sequence of events on a minute-by-minute basis. At 04.01, the bell was connected to the chamber. A diver on deck reported to the diving supervisor that the locking mechanism was in place. The door between the tunnel and the chamber system was then opened, and the divers began transferring equipment to the living quarters. The two others were asleep. Pressure in the chamber corresponded to a working depth of 90 metres. At 04.08, the second of the divers left the bell and the diving supervisor slightly increased the pressure in the bell in order to secure a seal on the door. Five minutes later, the fatal incident occurred.

The locking mechanism failed and the bell was blasted with great force away from the chamber. Pressure was lost in the chamber system within seconds, and all four divers inside were killed instantly. The two diving assistants standing by the locking mechanism when it failed were both badly hurt. One died on the way to Haukeland Hospital.[REMOVE]Fotnote: NOU 1984: Dykkerulykken på Byford Dolphin, pp 39-42.

The question addressed in the wake of the accident was why the locking mechanism failed. Following an investigation, the Norwegian Petroleum Directorate concluded that the direct cause of the accident was that the locking device connecting the bell with the chamber system was unlatched while the system was still under pressure. Nor were all the internal doors locked. The accident was caused not by a mechanical fault in the locking device, but by a failure in routines. As a critical phase in this stage of a diving operation, the locking procedure made special demands for good and safe interaction between the diving supervisor and personnel operating the locking mechanism.

The diving supervisor should not have reduced pressure in the connecting tunnel until the divers had reported that they were finished and that the door between chamber and tunnel was closed. Once pressure in the tunnel had reached one atmosphere, the supervisor could have given orders for the connecting lock to be removed. But that interaction failed in this case. The diving supervisor and the diving assistant left out several stages in the normal procedure. The locking device was opened (screwed off) before the door into the chamber had been closed and pressure in the tunnel was reduced. It was not possible to determine why this had happened, since one of the diving assistants died in the accident.

Per Otto Selnes, who participated in Elf’s internal inquiry, believes that the blame lay with unclear orders and a poor culture.[REMOVE]Fotnote: Per Otto Selnes in conversation with KØG, 16 December 2005.

The official inquiry report (NOU) suggested that the divers had been subject to an inappropriate burden of work over the period immediately before the accident. Between 15 August and 5 November, 38 per cent of the bell excursions exceeded the maximum permitted time of eight hours. A bell excursion is measured between disconnection from and reconnection to the pressure chamber. Nor was a shift plan in place during the period in which the accident occurred, and no log of working hours had been kept for the divers.[REMOVE]Fotnote: NOU 1984: Dykkerulykken på Byford Dolphin, p 21.

The accident was reported to the police, with the result that fines were imposed on a senior executive in the diving company and on a senior Elf executive.[REMOVE]Fotnote: Direktører bøtelagt efter dykkerulykke, Aftenposten, 26 November 1986. Charges against the Elf executive were later dropped. Another consequence of the accident was that the Norwegian Petroleum Directorate emphasised that applicable procedures had to be observed, and ordered operators and diving contractors to review the operational and technical aspects of the transfer phase between diving bell and pressure chamber.[REMOVE]Fotnote: Safety report, Norwegian Petroleum Directorate, 2/83