Alexander Kielland wreck

Alexander Kielland was a Norwegian semi-submersible rig in the Ekofisk oil field. In March 1980 the rig capsized creating the worst disaster in Norwegian waters since World War II killing 123 people. The rig, located approximately 320 km east from Dundee, Scotland, was owned by the Stavanger Drilling Company of Norway and was being hired by the U.S. company Phillips Petroleum at the time of the disaster. The rig was named after the Norwegian writer.

After 40 months of service, the floating drill rig was no longer used for drilling purposes but served as a semi-submersible ' flotel ',living quarters for the nearby "Edda" platform.

The accident

In driving rain and mist, early in the evening of 27 March 1980 more than 200 men were off duty in the accommodation on the Alexander Kielland. The wind was gusting to 40 knots with waves up to 12m high. The rig had just been winched away from the Edda production platform. Minutes before 18.30 those on board felt a 'sharp crack' followed by 'some kind of trembling'. Suddenly the rig heeled over 30° and then stabilised. Five of the six anchor cables had broken, the one remaining cable was preventing the rig from capsizing. The list continued to increase and at 18.53 the remaining anchor cable snapped and the rig turned upside down. 130 men were in the mess hall and the cinema. The rig had seven 50-man lifeboats and twenty 20-man rafts. Four lifeboats were launched, only one managed to release from the lowering cables. (A safety device did not allow release until the strain was removed from the cables.) A fifth lifeboat came adrift and surfaced upside down, its occupants righted it and gathered 19 men from the water. Two of Kiellands rafts were detached, 3 men were rescued from them. Two 12-man rafts were thrown from Edda and rescued 13 survivors. 7 men were taken from the sea by supply boats and 7 swam to Edda.

No-one was rescued by the standby vessel which took an hour to reach the scene.

Of the 212 people aboard 123 were killed, making it as of 2007 the worst disaster in Norwegian offshore history since WWII. Most of the workers were from Rogaland.

Investigation

One year later in March 1981, the investigative report concluded that the rig collapsed owing to a fatigue crack in one of its six bracings (bracing D-6), which connected the collapsed D-leg to the rest of the rig. This was traced to a small 6 mm fillet weld which joined a non load-bearing flange plate to this D-6 bracing. This flange plate was used to hold a sonar device used during drilling operations. The poor profile of the fillet weld contributed to a reduction in the fatigue strength of the weld. Furthermore, the investigation found considerable amounts of lamellar tearing in the flange plate and cold cracks in the butt weld. Cold cracks in the welds, increased stress concentrations due to the weakened flange plate, the poor weld profile, and cyclical stresses (which would be common in the North Sea), seemed to collectively play a role in the rig's collapse.

The rig was recovered in 1983 on the third attempt since the disaster. It was scuttled later that year after a search for missing bodies was completed, as well as several tests to determine the cause of the disaster. The fatigue crack had grown over time from a hydrophone port in the bracing tube. Judging by paint on part of the fractured surface the crack was probably due to improper labor at the plant in Dunkerque, France where the rig was built in 1976.

Other major structural elements then failed in sequence, destabilising the entire structure. The design of the rig was flawed owing to the absence of structural redundancy.

Consequences

A consequence of the Alexander Kielland disaster was the tightening of command organization on offshore installations in the North Sea so there was a clear source of authority for ordering abandonment in crises. The 14 minutes between initial failure of the leg and the rig's eventual capsize left a window in which most of the personnel on board could have escaped, given a more effective command structure. But it would seem that no one took charge on the night. These revised command structures (more akin to conventional shipping command structures) are now frequently put into use when vessels lose anchorage in storm conditions, or when fixed installations are threatened by out-of-control vessels.

imilar Incidents

Not long after the Alexander Kielland rig capsized its sister rig "Henrik Ibsen" tilted over, but was straightened up again.

Approximately 18 months later the Ocean Ranger rig "turned turtle" in similar weather conditions off the Newfoundland coast. A subsequent investigation into the causes of the Ocean Ranger disaster by the US Coastguard established that structural failure was not a factor.

Bibliography

*Bignell, V & Fortune, J (1984) "Understanding Systems Failures" Ch. 5 ISBN 0-7190-0973-1
*"The Alexander L. Kielland accident", report of a Norwegian public commission appointed by royal decree of March 28, 1980, presented to the Ministry of Justice and Police March, 1981 ISBN B0000ED27N

External links

* [http://www.exponent.com/multimedia/cases/kiel.html An animation by Failure Analysis Associates (now Exponent)]
* [http://www.multinet.no/~falk/ Website alleging the accident was an act of sabotage]
* [http://stavanger.clickwalk.no/cgi-bin/seq.cgi?id=133&by=stavanger&lang=1&ttype=3/ Petroleum Museum, Norway]
* [http://home.versatel.nl/the_sims/rig/alk.htm Oil rig disasters listing and descriptions]
* [http://www.twi.co.uk/professional/protected/band_13/oilgas_caseup34.html Welding Institute work on disaster]