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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.