Byford Dolphin

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Byford Dolphin in dry dock at Invergordon (Scotland, UK) in 2008
  • Byford Dolphin
  • Deep Sea Driller (1974–1978)
Owner: Byford Dolphin Pte. Ltd. (Fred. Olsen Energy)
Operator: Dolphin Drilling
Port of registry:
Builder: Aker Group
Yard number: Aker Verdal A/S (695)
Laid down: 31 October 1972
Completed: 1 February 1974
Status: Operational
Notes: [1][2]
General characteristics
Class and type: DNV class: 1A1 Column-stabilised Drilling Unit UKVS
Length: 108.2 m (355 ft)
Beam: 67.4 m (221 ft)
Depth: 36.6 m (120 ft)
Speed: 4.5 kn
  • Variable Deck Load: 3,021 t
  • Liquid Mud: 3,981 bbls (534 m3)
  • Bulk Mud/Cement: 547 t / 270 t
Crew: 102 berths
Notes: [1][2]

Byford Dolphin is a semi-submersible, column-stabilised drilling rig operated by Dolphin Drilling, a Fred. Olsen Energy subsidiary, and in 2009 contracted by BP for drilling in the United Kingdom section of the North Sea for three years.[3][4][5] It is registered in Hamilton, Bermuda.[1]

The rig has suffered some serious accidents, most notably an explosive decompression in 1983 that killed four divers and one dive tender, and badly injured another dive tender.[6]


Byford Dolphin drilling rig is an Enhanced Aker H-3 design which was built by Aker Group at the Aker Verdal shipyard in 1974.[7] Between 1974 and 1978, it was named Deep Sea Driller.[1]

Byford Dolphin has a length of 108.2 metres (355 ft), breadth of 67.4 metres (221 ft) and depth of 36.6 metres (120 ft). It has a maximum drilling depth of 6,100 metres (20,000 ft), and it could operate at a water depth of 460 metres (1,500 ft).[8] As a drilling rig, Byford Dolphin is equipped with advanced drilling equipment and has to meet strict levels of certification under Norwegian law. Byford Dolphin is able to maneuver with its own engines (to counter drift and ocean currents), but for long-distance relocation, it must be moved by specialist tugboats.

Byford Dolphin specifications
Operating deck load 3,025 tonne
Crew quarters 102 persons
Operating water depth 460 metres (1,500 ft) maximum
Derrick 49-metre (160 ft) Shaffer top compensator
Mooring system 12 point
Blow-out preventer Hydril 476 mm (18.7 in), 10,000 kPa (1,500 psi)
Sub Sea Handling System Christmas tree
Deck cranes 2 × 40 tonnes

Accidents and incidents[edit]

Deep Sea Driller accident[edit]

On 1 March 1976, the rig ran aground during transit from a block in the North Sea to Bergen. All crew were evacuated in the life boats, but six people died when they fell from their life boat.[9]

Diving bell accident[edit]

On 5 November 1983 at 4:00 a.m., while drilling in the Frigg gas field in the Norwegian sector of the North Sea, four divers were in a diving chamber system attached by a trunk (a short passage) to a diving bell on the rig. The divers were Edwin Coward (British, 35 years old), Roy Lucas (British, 38), Bjørn Giæver Bergersen (Norwegian, 29) and Truls Hellevik (Norwegian, 34). They were assisted by two dive tenders, Crammond and Saunders.[6]

Hellevik was about to close the door between the chamber system and the trunk when the chamber explosively decompressed from a pressure of nine atmospheres to one atmosphere. One of the tenders, 32-year-old William Crammond of Great Britain, and all four of the divers were killed instantly; the other tender, Saunders, was severely injured.[10]

The decompression chamber at the moment the accident occurred. D1–D4 are divers; T1 and T2 are dive tenders. The trunk is the section that joins chamber 1 to the diving bell.[6]

The situation just before this accident was as follows: Decompression chambers 1 and 2 were connected via a trunk to a diving bell. This connection was sealed by a clamp operated by two tenders, who were experienced divers. A third chamber was connected to this system but was not involved. On this day, Coward and Lucas were resting in chamber 2 at a pressure of 9 atm. The diving bell with Bergersen and Hellevik had just been winched up after a dive and joined to the trunk. Leaving their wet gear in the trunk, the divers climbed through the trunk into chamber 1.

The normal procedure would have been:

  1. Close the bell door.
  2. The diving supervisor would then slightly increase the bell pressure to seal this door tightly.
  3. Close the door between the trunk and chamber 1.
  4. Slowly depressurize the trunk to 1 atmosphere.
  5. Open the clamp to separate the bell from the chamber system.

The first two steps had been completed when, for an unknown reason, one of the tenders (Crammond) opened the clamp before Diver 4 (Hellevik) could close the door to the chamber. This resulted in the explosive decompression of the unsealed chamber. Air rushed out of the chamber with tremendous force, jamming the interior trunk door and pushing the bell away, striking the two tenders. The tender who opened the clamp was killed while the other was severely injured.[6]

Medical findings[edit]

Medical investigations were carried out on the four divers' remains. The most conspicuous finding of the autopsy was large amounts of fat in large arteries and veins and in the cardiac chambers, as well as intravascular fat in organs, especially the liver.[6] This fat was unlikely to be embolic, but must have precipitated from the blood in situ. It is suggested the rapid bubble formation in the blood denatured the lipoprotein complexes, rendering the lipids insoluble.[6] Death of the three divers left intact inside the chambers would have been extremely rapid as circulation was immediately and completely stopped. The fourth diver was dismembered and mutilated by the blast forcing him out through the partially blocked doorway and would have died instantly.[6]

Coward, Lucas, and Bergersen were exposed to the effects of explosive decompression and died in the positions indicated by the diagram. Investigation by forensic pathologists determined that Hellevik, being exposed to the highest pressure gradient and in the process of moving to secure the inner door, was forced through the 60 centimetres (24 in) diameter opening created by the jammed interior trunk door by escaping air and violently dismembered, including bisection of his thoracoabdominal cavity, which resulted in expulsion of all of the internal organs of his chest and abdomen, except the trachea and a section of small intestine, and of the thoracic spine. These were projected some distance, one section being found 10 metres (30 ft) vertically above the exterior pressure door.[6]


The committee investigating the accident concluded that it was caused by human error on the part of the dive tender who opened the clamp. It is not clear whether the tender who opened the clamp before the trunk was depressurized did so by order of his supervisor, on his own initiative, or because of miscommunication. At the time, the only communication the tenders on the outside of the chamber system had was through a bullhorn attached to the wall surface; with heavy noise from the rig and sea, it was hard to listen in on what was going on. Fatigue from many hard hours of work also took its toll among the divers, who often worked 16-hour shifts.[citation needed]

This incident was also attributed to engineering failure. The obsolete Byford Dolphin diving system, dating from 1975, was not equipped with fail-safe hatches, outboard pressure gauges, and an interlocking mechanism, which would have prevented the trunk from being opened while the system was under pressure.[11] Prior to the accident, Norske Veritas had issued the following rule for certification: "Connecting mechanisms between bell and chambers are to be so arranged that they cannot be operated when the trunk is pressurized,"[12] therefore requiring such systems to have fail-safe seals and interlocking mechanisms. One month after the accident, Norske Veritas and the Norwegian oil directorate made the rule final for all bell systems.[citation needed]

Among others, former crew members of Byford Dolphin and NOPEF (a Norwegian oil and petro-chemical union) have come forward and claimed the investigation was a cover-up. They claimed that the commission investigating the accident did not mention in their report the irresponsible dispensations on vital equipment requested by Comex and authorized by the diving section to the Norwegian Petroleum Directorate, which played a vital role in the accident's occurrence. They also alleged the accident was due to a lack of proper equipment, including clamping mechanisms equipped with interlocking mechanisms (which would be impossible to open while the chamber system was still under pressure), outboard pressure gauges, and a safe communication system, all of which had been held back because of dispensations by the Norwegian Petroleum Directorate.[13]


The conclusions of the investigation were disputed, and a group of divers gathered evidence with the intention of "find[ing] justice for all of the crew of Byford Dolphin."[14] The group formed the North Sea Divers Alliance in the early 1990s and now[when?] campaigns for compensation for divers killed or injured in the Norwegian Sector of the North Sea.[15]


The North Sea Divers Alliance, formed by early North Sea divers and the relatives of those killed, continued to press for further investigation and, in February 2008, obtained a report that indicated the real cause was faulty equipment. Clare Lucas, daughter of Roy Lucas, said: "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."[16] The families of the divers eventually received compensation for the damages from the Norwegian government 26 years after the incident.[17]

Other incidents[edit]

On 17 April 2002, a 44-year-old Norwegian worker on the rig was struck on the head and killed in an industrial accident. The accident resulted in Byford Dolphin losing an exploration contract with Statoil, which expressed concerns with the rig's operating procedures. The incident cost the company millions of dollars in lost income.[17]

See also[edit]

  • Commercial offshore diving – Professional diving in support of the oil and gas industry
  • Saturation diving – Diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas
  • Piper Alpha oil production platform
  • Pioneer – 2013 Norwegian thriller film by Erik Skjoldbjærg, a fictional film set in the 1970s Norwegian oil industry, and which features a fatal decompression chamber accident and its cover-up


  1. ^ a b c d "Byford Dolphin (09092)". DNV GL Vessel Register. Det Norske Veritas. Retrieved 14 July 2010.
  2. ^ a b "Byford Dolphin". Fred.Olsen Energy ASA. 24 February 2008. Retrieved 14 July 2010.
  3. ^ "Byford Dolphin gets Senergy extra-time". Upstream. NHST Media Group. 2009-05-19. Retrieved 2010-05-23.
  4. ^ "Fred Olsen upgrading fleet for drilling upturn". Offshore Magazine. PennWell Corporation. 2010-02-17. Retrieved 2010-05-23.
  5. ^ Kolstad, Elisabeth (2009-12-18). "Byford Dolphin-agreement". International. Offshore Media Group. Archived from the original on 2013-02-23. Retrieved 2012-11-05.
  6. ^ a b c d e f g h Giertsen JC, Sandstad E, Morild I, Bang G, Bjersand AJ, Eidsvik S (June 1988). "An explosive decompression accident". American Journal of Forensic Medicine and Pathology. 9 (2): 94–101. doi:10.1097/00000433-198806000-00002. PMID 3381801.
  7. ^ "Rig Data: Byford Dolphin". Rigzone. Retrieved 2010-05-23.
  8. ^ "Byford Dolphin" (PDF). Fred. Olsen Energy. Archived from the original (PDF) on 20 July 2011. Retrieved 2010-05-23.
  9. ^ Deep Sea Driller-ulykken Store norske leksikon. Retrieved 29 September 2014
  10. ^ Limbrick, Jim (2001). North Sea Divers - a Requiem. Hertford: Authors OnLine. pp. 168–170. ISBN 0 7552 0036 5.
  11. ^ Norges offentlige utredninger NOU 1984: 11 Dykkerulykken på Byford Dolphin ISBN 82-00-70889-6
  12. ^ 'Rules for certification of diving systems Sec 3 B305, 1982'
  13. ^ Ringheim, Gunnar (22 March 2008). "Historiens verste dykkerulykke" [History's worst diving accident] (in Norwegian). Oslo: Retrieved 2009-11-18.
  14. ^ Wingen, Tom. "Byford Dolphin Disaster". Pioneer Divers in the Norwegian Sector of the North Sea. North Sea Divers Alliance. Archived from the original on 27 July 2011. Retrieved 2009-10-26.
  15. ^ Wingen, Tom. "Norwegian Sector Divers - Fighting the Norwegian Government over Human Rights Abuses". Pioneer Divers in the Norwegian Sector of the North Sea. North Sea Divers Alliance. Archived from the original on 3 January 2010. Retrieved 2009-10-26.
  16. ^ Lister, David (2008-03-25). "Families of British divers killed in North Sea oil boom sue Norway". The Times. London. Retrieved 2009-11-18.
  17. ^ a b Staff writers (20 October 2009). "Norwegian government finally pays out for 1983 Byford Dolphin diver death". cDiver. Retrieved 14 July 2010.

Further reading[edit]

  • Gjerde, Kristin Øye; Ryggvik, Helge (2009). Nordsjødykkerne [North Sea divers] (in Norwegian). Stavanger: Wigestrand Forlag. Retrieved 14 July 2010. – A documentation of offshore diving and pioneer divers on the Norwegian continental shelf; contains a section on safety and responsibility
  • Haddow, Iain (27 March 2008). "Norway's underwater 'guinea pigs'". BBC News Magazine. British Broadcasting Corporation. Retrieved 14 July 2010. – News report on Byford Dolphin and other incidents in the North Sea