Byford Dolphin

Byford Dolphin in dry dock at Invergordon (Scotland, UK) in 2008
History
Name	Byford Dolphin Deep Sea Driller (1974–1978)
Owner	Byford Dolphin Pte. Ltd. (Fred. Olsen Energy)
Operator	Dolphin Drilling
Port of registry	Singapore Panama (1974–2005)
Builder	Aker Group
Yard number	Aker Verdal A/S (695)
Laid down	31 October 1972
Completed	1 February 1974
Identification	Call sign: 9VDG7 DNV ID: 09092 IMO number: 8750584 MMSI no.: 563601000
Status	Operational
Notes
General characteristics
Class and type	DNV class: 1A1 Column-stabilised Drilling Unit UKVS
Tonnage	11,792 GT 3,538 GT
Length	108.2 m (355 ft)
Beam	67.4 m (221 ft)
Depth	36.6 m (120 ft)
Speed	4.5 kn
Capacity	Variable Deck Load: 3,021 t Liquid Mud: 3,981 bbls (534 m3) Bulk Mud/Cement: 547 t / 270 t
Crew	102 berths
Notes

Byford Dolphin is a semi-submersible, column-stabilised drilling rig operated by Dolphin Drilling, a Fred. Olsen Energy subsidiary, and currently contracted by BP for drilling in the United Kingdom section of the North Sea. She is registered in Singapore. The rig has suffered some serious accidents, most notably an explosive decompression in 1983 that killed five workers and badly injured one.

In 2009, it was contracted for three years to BP.

Description

Byford Dolphin drilling rig is an Enhanced Aker H-3 design which was built by Aker Group at the Aker Verdal shipyard in 1974. In 1974–1978, she was named Deep Sea Driller.

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). She has a maximum drilling depth of 6,100 metres (20,000 ft), and she could operate at a water depth of 460 metres (1,500 ft). 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

Diving bell accident

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 decompression chamber system attached by a trunk (a short passage) to a diving bell on the rig, being assisted by two dive tenders. One diver 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 in a fraction of a second. One of the tenders and all four of the divers were killed instantly; the other tender was severely injured.

The compression 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.

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 themselves experienced divers. A third chamber was connected to this system but was not involved. On this day, divers D1 (35 years old) and D2 (38 years old) were resting in chamber 2 at a pressure of 9 atm. The diving bell with divers D3 (29 years old) and D4 (34 years old) had just been winched up after a dive and joined to the trunk. Leaving their wet gear in the trunk, the divers then 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, and D4 was about to carry out step 3 when, for an unknown reason, one of the tenders opened the clamp, resulting in explosive decompression of the chamber. A tremendous blast shot from the chamber through the trunk, pushing the bell away and hitting the two tenders. The tender who opened the clamp was killed, and the other was severely injured.

Divers D1, D2 and D3 were exposed to the effects of explosive decompression and died in the positions indicated by the diagram. Subsequent investigation by forensic pathologists determined D4, being exposed to the highest pressure gradient, violently exploded due to the rapid and massive expansion of internal gases. All of his thoracic and abdominal organs, and even his thoracic spine were ejected, as were all of his limbs. Simultaneously, his remains were expelled through the narrow trunk opening left by the jammed chamber door, less than 60 centimetres (24 in) in diameter. Fragments of his body were found scattered about the rig. One part was even found lying on the rig's derrick, 10 metres (30 ft) directly above the chambers. The deaths of all four divers were most likely instantaneous.

Medical findings

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. This fat was unlikely to be embolic, but must have "dropped out" of the blood in situ. It is suggested the boiling of the blood denatured the lipoprotein complexes, rendering the lipids insoluble.

The rigor mortis was unusually strong. The hypostases (accumulations of blood in internal organs) were light red, and in two cases, there were numerous hemorrhages in the livers. All the organs showed large amounts of gas in the blood vessels, and scattered hemorrhages were found in soft tissues. One of the divers had a large sub-conjunctival bulla (a blister in the tissue of the eye).

Investigation

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 amongst the divers, who often worked 16-hour shifts. Modifications to the "planned use of overtime" policies were made as a result of further investigation into this incident.

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. 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," 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.

Among others, former crew members of Byford Dolphin and NOPEF (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.

Post-investigation

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." The group formed the North Sea Divers Alliance in the early 1990s and now campaigns for compensation for divers killed or injured in the Norwegian Sector of the North Sea.

Subsequent lawsuit

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." The families of the divers eventually received damages from the Norwegian government, 26 years after the tragedy.

Other incidents

• 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.

See also

• Commercial offshore diving
• Piper Alpha oil production platform

Further reading

• Gjerde, Kristin Øye; Ryggvik, Helge (2009). Nordsjødykkerne (in Norwegian). Stavanger: Wigestrand Forlag. Retrieved 14 July 2010. {{cite book}}: Unknown parameter |trans_title= ignored (|trans-title= suggested) (help) – 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