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Monday, March 24th 2008

A Remarkable Case of Explosive Decompression

Only Semi-Appropriate To The Story

I stumbled across this story while browsing Reddit. I’m surprised I’ve never heard of this terrible accident at a Norwegian underwater oil rig in 1988.

At 4:00 AM on November 5, 1983, four divers were in a Decompression chamber system attached 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 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 injured.

The situation just before this accident occurred 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 (T1 and T2), 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 as follows: (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 atm, and (e) open the clamp to separate the bell from the chamber system.

Operations (a) and (b) had been completed and D4 was about to carry out operation (c) when, for some reason, one of the tenders opened the clamp. This resulted in the high pressure within the system being released into the external atmosphere, causing 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.

The kind’ve trauma involved in an accident like this is pretty tragic.