TUBE NEWS TN December 2017 - Page 10

» Currently available advanced flexible enclosures exploit the opportunities offered by advanced engineering polymers. These innovative products offer many attractions over metal glove box alternatives; significant reduction in cost, very small floor footprint and availability of a range of sizes. The products supplied for use on the Ti22 car were developed by Huntingdon Fusion Techniques Ltd in the UK and have rapidly becoming the globally preferred welding enclosures 2. Technical Specification The vertical sides are made from translucent material and the top is constructed using optically clear sheet. Ultra violet stabilized engineering polymers are used throughout during manufacture. Material thickness is nominally 0.5 mm (480 microns). A principle access zip is fitted and this has a total length typically 60% greater than the enclosure diameter i.e. a 900 mm enclosure will have a 1400 mm long main zip. Additional entry points provide for operators gloves. A service panel incorporates access ports for welding torches and for electrical leads and cooling water supplies. A purge gas entry port and an exhaust valve to vent displaced gas to atmosphere are incorporated into each enclosure. Cost and Weld Success Size for size the cost of a flexible enclosure is less than 10% that of a metal glove box. The welds are free of discolouration and the mechanical properties are unaffected. Flexibility Size and shape can be made to meet customer requirements. Weight is very low and the enclosures occupy little space – the collapsed volume of a 1.25 metre diameter system is less than 0.2 cubic metres and weighs only 8 kg. They can thus be moved easily and stored efficiently so floor footprint is minimised. 10 TUBE NEWS December 2017 Large viewing area The entire upper section is manufactured from optically transparent ultra-violet stabilized engineering polymer. This offers the opportunity for use by several operators at the same time – ideal for training purposes. Multiple access points. Systems can be manufactured with numerous access locations for personnel gloves and gas/electrical entries. Large leak-tight zips afford easy access for components. Measurement and control of oxygen content in the purge gas was assured though the use of a PurgEye Nano weld purge monitor. These instruments extract purge gas from the vicinity of the weld and employ a zirconium based sensor to measure oxygen levels. For high quality and repeatable welding of titanium alloys there is a requirement for the purge gas to contain less than 0.005% oxygen or 50 parts per million (ppm) 3. The currently available weld purge monitors are the result of several years’ research and development. They satisfy the workshop and site requirements for sensitivity and accuracy whilst at the same time offering reliability and ruggedness. Some offer programmable facilities coupled with data recording for quality control purposes. Conclusions The completed Ti22 MkII car has already featured prominently in a Long Beach Grand Prix race. All the titanium welds performed successfully including the critical suspension components. It finished 4th in the race.