To speed production of the small-bore hydraulic tubes used on its products designed for undersea oil and gas recovery, Siemens Subsea Products has begun using a Unison all-electric tube bender at its Kongsberg, Norway facility.
Siemens Subsea’s products are designed for long-term deployment and operate at depths greater than 3,000 meters (9,000+ feet). As a consequence, the tubes used to convey hydraulic fluid for power and control purposes are subject to extremely high internal and external pressures.
These tubes feature complex bends requiring high accuracy. Prior to the use of the Unison tube bender, Siemens either fabricated the tubes manually or bought them in pre-formed sub-assemblies. By implementing all-electric rather than hydraulic tube benders, Siemens Subsea says it has achieved more accurate and repeatable results, reduced energy consumption and generated less noise. Technical advisor for Siemens Subsea products, Terje Barth Andersen, says Unison’s machines allow faster tool changeover, which is important because the company produces the tubes in small batch sizes.
The tube bender Siemens Subsea is using is a 25-mm model based on Unison’s Breeze platform of all-electric machines and incorporates a rise-and-fall pressure die, which enables it to perform right- and left-handed bending. This capability increases flexibility and throughput by allowing parts production from a single length of tubing in one continuous cycle.
A key requirement in tube production is to minimize stressing of the tubes at their bend points to prevent in-service failure. This is achieved by avoiding use of small bend radii. Though many conventional tube-bending machines are incapable of handling large bend radii, the Unison machine features full-stroke programmable positioning of the pressure dies and clamps to enable bends with a center-line radius five times greater than the diameter of the tube.
All critical movement axes on the tube bender are controlled by precision servomotors, enabling fast and repeatable fabrication of parts with accuracies within fractions of a millimeter, according to Unison. The machine generates high torque for bending tubes fabricated from exotic alloys such as Inconel, Duplex and Super Duplex. These alloys are typically required for their subsea corrosion resistance.
Each tube designed by Siemens Subsea is first produced on an Inventor 3D CAD system. The company often produces prototypes to verify accuracy and feed corrections back into the production process to ensure the quality of subsequent parts. Automating the tube-bending process will accelerate this procedure because a production computer network links the CAD system and bending machine. This will help Siemens Subsea products maintain fully traceable manufacturing records.
“We calculate that the machine will pay for itself in less than two years, based solely on the number of tubes that we can now process in house instead of purchasing as ready-made parts,” says Andersen.