Statfjord B GBS out of the dry dock

By Trude Meland, Norwegian Petroleum Museum

The bottom section of the GBS was towed out of the dry dock on 11 June 1979 and moored in the Gands Fjord off Stavanger while preparations were made to slipform the cells. This tow-out was a critical phase. The section had to be pulled out of the inner dock for 100 metres, before being turned 23 degrees and then towed out of the opening.

— The bottom section of the Statfjord B GBS is floating and on its way out of the construction dock in Hinnavågen. It is now being towed into the Gandsfjord where the rest of the concrete work and the concrete shafts will be completed in deeper waters. Photo: Aker/Norwegian Petroleum Museum

Very little wind could be tolerated, and the job had to be postponed twice. The first attempt was aborted after it transpired that bottom conditions at the dock gate had not been properly prepared, so that the draught was too shallow. A 70 000-cubic-metre supporting bank had to be removed.

Excessive wind prevented a second try. It was blowing no more than 10 metres per second, but that was potentially enough to drive the concrete structure off course.

But everything went according to plan the third time, and the bottom section was pulled out of the dock by winches with just 70 centimetres of clearance over the bottom.[REMOVE]Fotnote: Stavanger Aftenblad, 28 June 1979. Once the structure was clear of the dock, the winch cables were severed and the tugs took over. Compressed air, buoyancy and 20 000 horsepower divided between five tugs made it possible to move Statfjord B to the mooring site at a speed of two-three knots.

Attaching and tightening the moorings took two days.[REMOVE]Fotnote: Rogalands Avis, 11 July 1979. The chains intended to hold the structure in place were fixed to new attachment points. Four lengths measuring a total of six-seven kilometres were used.

The chains were of better quality than those used earlier, since the GBS would be significantly larger. With a breaking strength of 1 500 tonnes, compared with 1 300 tonnes before, they were attached to Lihalsen and Einerneset on the eastern shore of the Gands Fjord, and Vaulen and Kvalaberg on the western side. The attachments were simpler in design than their predecessors. No winches were placed on land, only steel plates set into the bedrock.[REMOVE]Fotnote: Stavanger Aftenblad, 5 January 1979.

To learn more, see: Building the concrete GBS for Statfjord B.