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The '''Byford Dolphin''' is a semi-submersible [[Norwegian]] [[oil rig|oil exploration rig]] converted from a diving rig. It floats in the [[North Sea]] to find and drill [[oil]] deposits. Built on the "Aker H-3" design, the rig is operated by [[Dolphin Drilling]], a [[Fred Olsen]] subsidiary. It is able to manoeuvre with its own [[engine]]s (to counter [[drift]] and ocean currents), but for long-distance relocation it must be moved by specialist [[tugboat]]s. |
The '''Byford Dolphin''' is a semi-submersible [[Norwegian]] [[oil rig|oil exploration rig]] converted from a [[diving rig]]. It floats in the [[North Sea]] to find and drill [[oil]] deposits. Built on the "Aker H-3" design, the rig is operated by [[Dolphin Drilling]], a [[Fred Olsen]] subsidiary. It is able to manoeuvre with its own [[engine]]s (to counter [[drift]] and ocean currents), but for long-distance relocation it must be moved by specialist [[tugboat]]s. |
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As a drilling rig, the Byford Dolphin is near the top of its class. It is equipped with advanced drilling equipment and has to meet very high levels of certification under Norwegian law. However the rig has suffered some notable accidents. The best known accident was an [[explosive decompression]] accident in [[1983]], known as the '''Byford Dolphin diving bell accident''', which resulted in the loss of five lives and badly wounded one other worker. |
As a drilling rig, the Byford Dolphin is near the top of its class. It is equipped with advanced drilling equipment and has to meet very high levels of certification under Norwegian law. However the rig has suffered some notable accidents. The best known accident was an [[explosive decompression]] accident in [[1983]], known as the '''Byford Dolphin diving bell accident''', which resulted in the loss of five lives and badly wounded one other worker. |
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==Diving Bell Accident== |
==Diving Bell Accident== |
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At 4:00 AM on [[November 5]], [[1983]], four divers were in a compression chamber system on board a [[diving bell]] on the rig, being assisted by two dive tenders. One diver was to about to close the door between the chamber system and the trunk when the chamber was |
[[Image:Byford Dolphin Accident.jpg|thumb|300px|right|The compression chamber at the moment the accident occurred. D1 - D4 are divers; T1 and T2 are dive tenders.]] |
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At 4:00 AM on [[November 5]], [[1983]], four divers were in a compression chamber system on board a [[diving bell]] on the rig, being assisted by two dive tenders. One diver was to about to close the door between the chamber system and the trunk when the chamber was [[explosive decompression|explosively decompressed]] from a pressure of 9 [[Atmosphere (unit)|atm]] to 1 atm in a fraction of a second. Five of the men were killed the other was severely wounded. |
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⚫ | The situation just before this accident occurred was follows. Compression chambers 1 and 2 were connected via a trunk to a diving bell. This connection was sealed by a clamp operated by two tenders (T1 and T2), who themselves were 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 3 (29 years old) and 4 (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 had then climbed through the trunk into chamber 1. |
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All six men were qualified and experienced [[diving|deep sea divers]]. |
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At this point, diver D4 would normally go through a procedure to seal off the chamber. However, before he could complete this operation, one of the tenders inexplicably opened the clamp. This resulted in the high pressure within the chamber being released into the atmosphere. A tremendous blast shot from the chambers through the trunk, pushing the bell away and hitting the two tenders. The one who opened the clamp died, and the other was severely injured. |
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⚫ | The situation just before this accident occurred was follows. Compression chambers 1 and 2 were connected via a trunk to a diving bell. This connection was sealed by a clamp operated by two tenders ( |
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Operations a and b had been completed and diver 4 was about to carry out operation c when, for some inexplicable reason, one of the tenders opened the clamp. The result was a free communication between the chamber system with a pressure of 9 atm and the surroundings with a pressure of 1 atm. A tremendous blast shot from the chambers through the trunk, pushing the bell away and hitting the two tenders. The one who opened the clamp died, and the other was severely injured. Unfortunately, the dead tender was not sent to autopsy. The chamber opening was 60cm in diameter. Unfortunately, the door jammed so firmly that it later had to be cut loose with an [[acetylene]] burner. Diver 4 was shot out through the opening and completely disintegrated. Parts of him were found scattered about the rig. One part was even found lying on the Derrick, 10 metres above the chambers. The other three divers in the chambers died on the spot, probably instantaneously. |
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Diver D4 was shot out through the opening. Subsequent investigation by [[forensic pathology|forensic pathologists]] determined that diver D4, being exposed to the highest pressure gradient, exploded with violence due to the rapid and massive expansion of internal gasses. All of his thoracic and abdominal organs, and even his thoracic spinal column, were ejected, as were his legs and left arm. Simultaneously his remains were expelled with force through the narrow trunk opening (less than 60cm in diameter). Chunks of his body were found scattered about the rig. One part was even found lying on the rig's derrick, 10 metres directly above the chambers. Thankfully, his death would have been painless and instantaneous. |
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By remarkable contrast the three other divers remained completely intact although they also died instantly. |
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===Medical Findings=== |
===Medical Findings=== |
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Medical investigations were carried out on the four divers' remains. The most conspicuous finding of the [[autopsy]] was large amounts of fat in large [[artery|arteries]] and [[vein]]s and in the [[Heart|cardiac chambers]], as well as intravascular fat in organs, especially the [[liver]]. This fat was unlikely to be [[embolism|embolic]], but must have "dropped out" of the blood ''[[in situ]]''. It is suggested that the boiling of the blood denatured the [[lipoprotein]] complexes, rendering the [[lipid]]s insoluble. |
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===Investigation=== |
===Investigation=== |
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The committee investigating the accident concluded that it was due to human error. It is not clear wether the tender who opened the clamp before the trunk was depressurized did so by order of the diving supervisor or on his own initiative, due to 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, in the operating procedure. Fatigue from many hard hours of work, also took |
The committee investigating the accident concluded that it was due to human error on part of the dive tender who opened the clamp. It is not clear wether the tender who opened the clamp before the trunk was depressurized did so by order of the diving supervisor or on his own initiative, due to 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, in the operating procedure. Fatigue from many hard hours of work, also took its toll on awareness amongst the divers, who could often work 16 hour shifts. |
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This incident was also an engineering failure, in that the system was not equipped with [[fail-safe]] hatches. Subsequently a law was passed in Norway requiring such systems to have fail-safe seals. |
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Some individuals have alleged that the investigation was a [[cover-up]], and that the accident was due to of a lack of proper equipment including outboard pressure gauges and safe communication system, which had been held back due to dispensations allowed by the Norwegian Petroleum Directorate. |
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==Other incidents== |
==Other incidents== |
Revision as of 22:23, 12 May 2005
Byford Dolphin
Byford Dolphin | |
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Operating deck load | 3025 MT |
Crew quarters | 102 persons |
Operating water depth | 1500 feet maximum |
Derrick | 160 foot Shaffer Top Compensator |
Mooring system | 12 point |
Blow-out preventer | Hydril 18¾ inch, 15,000 PSI |
Sub Sea Handling System | Christmas tree |
Deck cranes | 2 x 40 tons |
The Byford Dolphin is a semi-submersible Norwegian oil exploration rig converted from a diving rig. It floats in the North Sea to find and drill oil deposits. Built on the "Aker H-3" design, the rig is operated by Dolphin Drilling, a Fred Olsen subsidiary. It is able to manoeuvre with its own engines (to counter drift and ocean currents), but for long-distance relocation it must be moved by specialist tugboats.
As a drilling rig, the Byford Dolphin is near the top of its class. It is equipped with advanced drilling equipment and has to meet very high levels of certification under Norwegian law. However the rig has suffered some notable accidents. The best known accident was an explosive decompression accident in 1983, known as the Byford Dolphin diving bell accident, which resulted in the loss of five lives and badly wounded one other worker.
Diving Bell Accident
At 4:00 AM on November 5, 1983, four divers were in a compression chamber system on board a diving bell on the rig, being assisted by two dive tenders. One diver was to about to close the door between the chamber system and the trunk when the chamber was explosively decompressed from a pressure of 9 atm to 1 atm in a fraction of a second. Five of the men were killed the other was severely wounded.
The situation just before this accident occurred was follows. Compression chambers 1 and 2 were connected via a trunk to a diving bell. This connection was sealed by a clamp operated by two tenders (T1 and T2), who themselves were 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 3 (29 years old) and 4 (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 had then climbed through the trunk into chamber 1.
At this point, diver D4 would normally go through a procedure to seal off the chamber. However, before he could complete this operation, one of the tenders inexplicably opened the clamp. This resulted in the high pressure within the chamber being released into the atmosphere. A tremendous blast shot from the chambers through the trunk, pushing the bell away and hitting the two tenders. The one who opened the clamp died, and the other was severely injured.
Diver D4 was shot out through the opening. Subsequent investigation by forensic pathologists determined that diver D4, being exposed to the highest pressure gradient, exploded with violence due to the rapid and massive expansion of internal gasses. All of his thoracic and abdominal organs, and even his thoracic spinal column, were ejected, as were his legs and left arm. Simultaneously his remains were expelled with force through the narrow trunk opening (less than 60cm in diameter). Chunks of his body were found scattered about the rig. One part was even found lying on the rig's derrick, 10 metres directly above the chambers. Thankfully, his death would have been painless and instantaneous.
By remarkable contrast the three other divers remained completely intact although they also died instantly.
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 that the boiling of the blood denatured the lipoprotein complexes, rendering the lipids insoluble.
Investigation
The committee investigating the accident concluded that it was due to human error on part of the dive tender who opened the clamp. It is not clear wether the tender who opened the clamp before the trunk was depressurized did so by order of the diving supervisor or on his own initiative, due to 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, in the operating procedure. Fatigue from many hard hours of work, also took its toll on awareness amongst the divers, who could often work 16 hour shifts.
This incident was also an engineering failure, in that the system was not equipped with fail-safe hatches. Subsequently a law was passed in Norway requiring such systems to have fail-safe seals.
Some individuals have alleged that the investigation was a cover-up, and that the accident was due to of a lack of proper equipment including outboard pressure gauges and safe communication system, which had been held back due to dispensations allowed by the Norwegian Petroleum Directorate.
Other incidents
- In late November 2001, the rig was left adrift without control in a storm. Although 17 of the 71 workers were evaculated by helicopter, the company claimed there was no serious danger.
- On April 17 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 the Byford Dolphin losing a exploration contract with Statoil, who expressed concerns with the rig's operating procedures. The incident cost the company millions of dollars in lost income.
See also
References
The American Journal of Forensic Medicine and Pathology 9(2): 91-101, 1988.