Brevini delivers bespoke gearboxes for pipe-laying operations

In the world of offshore oil and gas everything is built big, and the Pieter Schelte is no exception. Owned by the Swiss-based Allseas Group, this vessel will surpass the current largest platform installation / decommissioning and pipe-laying vessel by 50 per cent. Measuring 382m long and 124m wide, the vessel is designed for the installation and removal of entire gas/oil rig topsides and their corresponding steel jacket-based platforms, as well as being able to lay pipe up to 68 inches in diameter. Once complete, the Pieter Schelte will be able to lift entire topsides weighing 48,000 tonnes and steel jackets weighing up to 25,000 tonnes in a single lift. Specialist pipe-laying equipment will allow the vessel to operate in ultra deep water and continue to push the boundaries of what was previously possible.

During pipe-laying operations, it is crucial to keep the pipe under tension to maintain the bending and axial stresses within an acceptable range. Through continually controlling the tension on the pipeline being laid, integrity of the pipeline is guaranteed without the necessity of extensive support structures. If poor sea conditions result in an unworkable situation, i.e. the pipeline integrity can no longer be guaranteed, then the abandon and recovery (A&R) winches are used to lower the pipeline to the seabed in a precautionary abandonment procedure. When the conditions have improved, the pipe is recovered and the pipe-laying operation can be continued.

The A&R winch manufacturer required a reliable and very compact design as well as fast production times, and for these reasons Brevini was selected to supply the gearboxes. The custom-made gearboxes were based on the Posired 2 High Power series, a combination of the Posired 2 product and the S series planetary reduction. This powerful and efficient gearbox is capable of an output torque of 135kNm at a speed of 23.1rpm with an installed power of 520kW.

Tough marine environment

These bespoke gearboxes were supplied with a custom-made bell housing and an integrated disc brake as well as temperature sensors for bearing and oil temperature. The specification also called for an offshore coating to be applied to ensure the package could withstand operating in the tough marine environment.

Part of the procurement process required a complete factory acceptance test (FAT), where eight units were tested under full load for 8 hours. As part of this process, four of the tests were witnessed by a surveyor from the owners of the vessel as well as the winch manufacturer. Having successfully completed assembly and testing, all 32 gearboxes were delivered, with eight being fitted to each winch assembly.

Jeff van Nobelen, Project Engineer at Brevini comments: "The scale and capacity of the Pieter Schelte demanded a high-powered, high-quality transmission with a proven track record. We were able to provide a flexible, adaptable product that could be designed around their requirements and still delivered at a competitive price and on realistic time scale.

"The High Power series basically combines the benefits of both the Posired 2 range and the S series gearboxes to produce a very compact gear drive with high thermal efficiency and high torque output. Our very compact design coupled with our ability to produce 32 units of a bespoke design within a tight timeframe was instrumental in being awarded this contract."

To find out more about high-power gearboxes from Brevini, please visit www.brevini.co.uk.