At 4:00 a.m. on 5 November 1983, 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.[1] One diver was about to close the door between the chamber system and the trunk when the chamber was explosively decompressed from a pressure of nine atmospheres to one in a fraction of a second. Five of the men were killed; the other was severely injured.
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: (a) close the bell door, (b) the diving supervisor would then slightly increase the bell pressure to seal this door tightly, (c) close the door between the trunk and chamber 1, (d) slowly depressurize the trunk to 1 atmosphere, and (e) 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 (c) when, for some reason, one of the tenders opened the clamp. This resulted in explosive decompression. A tremendous blast shot from the chambers through the trunk, pushing the bell away and hitting the two tenders. The tender who opened the clamp died, and the other was severely injured.