‘Right First Time’ Reduces Scrap Material

The subsea equipment manufactured at the plant is designed for long term deployment – many of the systems have a design life of 30 years and are intended for operation at depths up to and beyond 3,000 m. As a consequence, the tubes used within the equipment that convey hydraulic fluid for power and control purposes are subject to extremely high internal and external pressures and must be manufactured to exceptionally high standards.

A critical requirement is to minimize stressing of the tubes at their bend points by avoiding the use of small bend radii – which could lead to in-service failure. Whereas many conventional tube bending machines are incapable of handling large bend radii, the custom tube bender features ‘full stroke’ programmable positioning of the pressure dies and clamps, enabling it to create bends with a CLR (center-line radius) up to five times the diameter of the tube, with a fully automatic set up.

All critical movement axes on this tube bender are controlled by precision servomotors, enabling fast and repeatable fabrication of parts with accuracies to within fractions of a millimeter. The machine is also capable of generating the high torque needed for bending tubes fabricated from exotic alloys such as Inconel, Duplex and Super Duplex, which are used extensively for subsea applications to improve corrosion resistance.

The first Subsea project involving this tube bender is the South Belut Project production of 800 tubes, all made from 316 stainless steel and requiring complex bends and orbital welding in both ends, for use on the MQC umbilical termination units. These are used on various subsea structures, including Christmas trees, and Subsea versions can accommodate up to 13 hydraulic lines that demand extremely tight manufacturing tolerances.

Each tube is designed on an Inventor 3D CAD system and typically the shop then produces a prototype to verify its accuracy and feed any necessary corrections back into the production process to ensure the quality of subsequent parts. Automating the tube bending process accelerates this procedure – the CAD system and bending machine are linked by a production computer network – and helps Subsea maintain the fully traceable manufacturing records needed for this industry.

Andersen points out that the accuracy and throughput capabilities of this tube bender offer major economic benefits to shops working with expensive materials. “We calculate that this custom machine will pay for itself in less than two years based solely upon the number of tubes we can now process in-house instead of purchasing as ready-made parts. Furthermore, its automated set-up capabilities and control software flexibility help us significantly reduce scrap material by ‘right first time’ manufacturing. We also envisage selling excess tube bending capacity to the market, making this an even more cost-effective investment.”

Steve Haddrell of Unison adds, “This project from Subsea demonstrates a growing awareness of the benefits of all-electric tube bending. The traditional market for high-performance machines of this type is in the aerospace industry, where precision bending of exotic alloy materials is a common requirement. But shops serving the offshore oil and gas industries also face similar demands, as their products are used in ever more hostile environments.”

Siemens AG Energy Sector, Freyeslebenstrasse 1, Erlangen, Germany 91058, +49 180 524 70 00, Fax: +49 180 524 24 71, www.siemens.com/oilgas.

Unison North America/Horn Machine Tools, 40455 Brickyard Drive, Madera, CA 93638, 559-431-4131, sales@hornmachinetools.com, www.hornmachinetools.com.

Unison, Ltd., Olympian Trading Estate, Cayton Low Road, Eastfield, Scarborough, North Yorkshire, UK YO11 3BT, +44 (0) 1723 582868, Fax: +44 (0) 1723 582379, www.unisonltd.com.