Flexible shafts utilise copper-beryllium Brush Alloy 25

Flexible shafts utilise copper-beryllium Brush Alloy 25

Keywords Alloys,Brush Wellman, Offshore, Shafts

Used in the offshore oil and gas industry, mud motor flex shafts must be able to operate even when they are being forced around a radius. To be reliable they must therefore be made of a material with exceptional properties and BrushWellman claims to have come up with a solution with its copper beryllium Brush Alloy 25.

A combination of low stiffness and high strength allows the shafts to be bent by approximately 2.0°per foot yet still return to their original shape. Because the shafts are also rotating, the material is cycling between compression and tension so must have good fatigue resistance too. In order that the shafts can be dismantled it is essential that the threads on either end can be unscrewed. Many materials would start to "pick up" in applications such as this unless an anti-seize compound was used (a not entirely satisfactory solution to the problem), but Brush Alloy 25 reportedly has a low coefficient of friction and the components can, we are informed, be readily dismantled.

Brush Alloy 25 is also stated to be easily machined and has excellent resistance to corrosion and stress corrosion cracking. Another useful property claimed, is that the alloy can be precipitation hardened by heat treatment to adjust the strength. The mud motor flex shafts are machined from Brush Alloy 25 with a typical yield strength of 120,000psi. To suit other applications, the yield strength can be adjusted from around 20,000-200,000psi.

In addition to supplying the Brush Alloy 25, Brush Wellman can also provide advice to designers from its team of materials experts and engineers. For those companies which do not have their own facility in-house, Brush Wellman can provide a finite element analysis service.

Details from: Brush Wellman Limited. Tel: +44 (0)118 930 3733; Fax: +44 (0)118 930 3635.