Friday, 19 September 2014

DEATH(S) By Explosive Decompression, (The Byford Dolphin Deep Sea Driller Incident of 1983) – NORTH SEA

Circumstances that led to the deaths of these poor souls were so horrific and could have been prevented…

Byford Dolphin oil exploration rig
in dry dock at Invergordon (Scotland) on 2008
“It was like someone shaking a bottle of pop and opening the top… Talking to people who saw it is virtually impossible because they have been so traumatised by it and can’t speak about it.” – Clare Lucas, daughter of Roy Lucas
The Byford Dolphin Deep Sea Driller is a semi-submersible, column-stabilized drilling rig which has suffered some serious accidents, most notably an explosive decompression in 1983 that killed five workers and badly injured on




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, (see diagram below), being assisted by two dive tenders – Roy Lucas and Billy Crammond. One diver was about to close the door between the chamber system and the trunk when the chamber explosively decompressed. One of the tenders and all four of the divers were killed instantly; the other tender was severely injured.

The accident happened when Mr Lucas’s colleague Billy Crammond opened a hatch to the decompression chamber they were working in.

The chamber lost a huge amount of pressure instantaneously – decompressing from a pressure of nine atmospheres to one atmosphere in a fraction of a second, resulting in the horrendous aftermath.


The situation just before this accident was as follows:

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.
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.
  6. 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.

Roy Lucas and Billy Crammond
died in 1983 along with 3 other men
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 and painless.

More 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 its original place. 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 subsequent investigation of the accident resulted in the following 2 findings:

The accident was due to 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.

Did You Know...

  • 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).
  • The North Sea Divers Alliance, (NSDA), 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 and was awarded a six-figure payout from the Norwegian government, 26 years after the tragedy.
  • In 2001, the Byford Dolphin was left adrift in a storm. The company claimed there was no serious danger to the 71 workers.
  • 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.
  • Saturation divers, divers who work underwater for long periods at a time, are definitely not for the faint-of-hearts and requires a high degree of tolerance and humour. To put things in perspective: Consider divers who work at a chosen depth without the need to continually decompress. They are required to live at the same pressure of the sea bed they are working at. So picture living in a chamber (A metal tube) which is 2.1 metres in diameter and varying in length of 5 to 6 metres. Attached to this is a smaller chamber 2 to 2.5 metres in length (called a transfer lock) which gives access to the diving bell, it also serves as a toilet and shower area. For the whole period of the saturation divers will be confined (sleeping and eating) to this area with up to a further 5 colleagues. To get some idea of the space, measure the area in your office; now imagine 3 bunk beds and a table and 2 bench seats. Now imagine you can’t escape for up to 28 days. Living with up to 5 other guys in a confined space, who all have their own personalities and quirky habits…


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