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Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Article Type: Equipment and software From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 4
When Huntingdon Fusion Techniques Limited (HFT) was developing tube welding machines in 1978 it became apparent that there was no reliable method for measuring the gas quality below the weld. Since the presence of residual oxygen in the weld was most undesirable – it leads to contamination and loss of strength – it was important that this aspect be addressed.
The practical method of removing oxygen from the vicinity of the joint is to flush out any air with inert gas – known as gas purging. Whilst this is acceptable and indeed still used for small tubes and pipes it is not cost-effective for larger sizes and certainly not for long lengths of pipe.
Emerging from these observations came two significant developments.
Responding to the challenge of oxygen monitoring, Ron Sewell, now chairman of a very much larger HFT, used his extensive gas physics background to design a dedicated oxygen measuring and monitoring device which subsequently became the industry standard across the world.
Concurrently with this development came a second innovation from HFT; the production of effective inflatable pipe purging systems to seal off discrete sections of tube so that only a small volume of oxygen local to the joint needed to be removed.
Over the last 30 years, the HFT purge monitor and a range of HFT pipe purge systems have been progressively improved to accommodate an increasingly wider range of applications.
The HFT Argweld® monitor is said to have become the world standard. Specially calibrated electronics claims an oxygen measurement accuracy down to 0.1 per cent and the instrument can be used for occasional sampling or as a continuously measuring instrument.
Used in conjunction with pipe purge systems, these monitors have been responsible for the development of the highest quality welds which are essential in the aerospace industry.