TLP MOORING Ursa length adjustment spools machined to high accuracy

Engineering specialist Motala Verkstad has received an order from Shell for 16 length adjustment spools for the Ursa tension leg platform. The 11 meter long x 55cm diameter spools will be made from steel supplied by Tecphy in France and will be attached to the bottom anchors at a water depth of 1,200m in order to adjust the length of the tethers.

Engineering specialist Motala Verkstad has received an order from Shell for 16 length adjustment spools for the Ursa tension leg platform. The 11 meter long x 55cm diameter spools will be made from steel supplied by Tecphy in France and will be attached to the bottom anchors at a water depth of 1,200m in order to adjust the length of the tethers.

"We have done this kind of work before, but the specification is for length adjustment with grooves rather than threads, so we have already made a dummy spool to ensure accuracy of the finished product," says heavy equipment product manager Haakan Frisk. "Making grooves is slightly more complex but we have already achieved very accurate tolerances on a test piece well within the specification."

Motala is also doing the machining for the Ursa stress joints being manufactured by Scana Bjorneborg. Production of the length adjustment spools started in February and will be delivered to Houston in pairs up to December 1997, where they will be coated with Xylan anti-corrosive material. "We have made larger pieces than Ursa in the past," says Frisk. "But this is the first contract that we have received directly from Shell and we are hopeful of getting further orders for both Ursa and other developments of this type."

Plant upgrade

The long-hole boring equipment used by Motala is unique in the Nordic region in that it can bore long holes up to 25m long. The company also has very diversified machinery due to the wide variety of products it manufactures. According to Frisk, this allows it to handle almost anything up to around 120 tonnes.

Motala has been undergoing a period of investment in new equipment at its plant including a computer numerical control system to be fitted to an 8.5 meter lathe, complementing the capabilities of an existing 21m lathe. The company is also investing SKr25 million in its machine shop to provide two new multipurpose machining centres capable of handling large items such as valve blocks.

In addition to its heavy equipment division which specializes in propeller and turbine shafts, risers, stress joints, milling and flat machining, Motala also makes Nash pumps, rolling stock and non-intrusive brain surgery equipment.

For more information contact Haakan Frisk, Motala Verkstad: telephone +46 141 229900 or fax +46 141 54924.

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