'Smart' fittings

Citation

(2000), "'Smart' fittings", Aircraft Engineering and Aerospace Technology, Vol. 72 No. 5. https://doi.org/10.1108/aeat.2000.12772eab.007

'Smart' fittings

"Smart" fittings

Keywords TW Metals, Couplers

Shape memory alloy couplings supplied by aerospace metals distributor TW Metals have been used on external pipework of a propellant tank for the European Space Agency's XMM spacecraft, launched in December.

Supplied to Dowty Aerospace, Wolverhampton, CryoFit1 couplings were used to alleviate a technical problem, helping to maintain the launch schedule. The specific application was to repair critical plumbing sections where welding would not have been possible.

Designed for use with aluminium, titanium, copper nickel and stainless steel tubing, CryoFit fittings are manufactured from Tinel, a nickel-titanium alloy with shape memory characteristics. They are manufactured by Aerofit Products Inc. of California and distributed world-wide through TW Metals Ltd.

Fittings are machined with an inside diameter smaller than the outside diameter of the tube on which they will be used and then expanded at cryogenic temperatures, so that the inside diameter is larger than the outside diameter of the tube. The fittings are stored in liquid nitrogen. On-site installation can reportedly be achieved in seconds. The fittings are positioned over a tube end or joint and, as they warm from their cryogenic storage temperature, they shrink down on to the tube with a high radial force and form a permanent metal-to-metal seal. The shape memory capability of Tinel is said to ensure that they always exert a permanent swaging force on the tube.

CryoFit couplings have been used extensively in aircraft programmes and on US satellites. XMM marks its first European space industry application. As pressure grows to build satellites with ever shorter delivery times, TW Metals believes that "smart" materials such as CryoFit will be used increasingly to speed production because they require neither the purging nor the X-ray verification of welded joints. The use of shape memory alloy couplings is said to also avoid any risk of interference with sensitive components nearby.

XMM is the European Space Agency's high throughput X-ray spectroscopy mission. It will function as an observatory for an anticipated ten years, obtaining data on cosmic X-rays ranging from stellar objects to distant galaxies. XMM will carry three advanced X-ray telescopes, each with high-precision nested mirrors. The large collecting area offered by the three telescopes will allow observations of millions of X-ray sources.

The spacecraft was successfully launched by an Ariane 5 rocket on 10 December 1999 from Korou in French Guiana.

Details available from TW Metals Ltd. Tel: +44 (0) 23 8073 9333; Fax: +44 (0) 23 8073 9601.