A British-made weld purge monitor, said to be technically more advanced than its predecessors and more cost-effective, provides precise indication of the oxygen content of weld purge gas.

The Argweld MKV weld purge monitor, from Huntingdon Fusion Techniques Limited, allows welding to begin as soon as the correct oxygen level is reached, without the need for any estimation or guesswork. It can be used by any industry welding stainless, duplex or chrome steels, as well as nickel alloys. Industries using such materials, and needing to be in absolute control of their “back of weld” quality, include: aerospace, beverage, food, semiconductor, nuclear, automotive, processing, pipeline and petrochemical.
“By showing the operator exactly when the oxygen content is low enough to commence welding, the purge monitor eliminates premature starts, as well as avoiding the waste of time and excessive use of inert gas resulting from any unnecessary delay in starting,” says Darren Sewell for Huntingdon Fusion Techniques.
The Argweld MKV has a 13-mm-high liquid crystal display, providing a continuous accurate reading of oxygen levels down to 0.1 per cent (1,000 ppm), and indication of oxygen down to 0.01 per cent (100 ppm).
It can be connected to the exhaust port on the purge device or enclosure so that the gas flows over the sensor to provide continuous monitoring and indicate any purge problems that could affect weld quality.
Alternatively, the monitor can be used in sampling mode by attaching a stainless steel probe  – which is inserted either through the weld joint gap into the volume being purged, or into the exhaust port of the purge device – and drawing a sample across the sensor with a rubber bulb.
With a measuring range of 0.01 per cent to 20.9 per cent oxygen (100 ppm to atmosphere), the monitor has an accuracy of +0.2 per cent at 20 per cent and +0.02 per cent at 2 per cent. It measures 155 mm x 81 mm x 38 mm; weighs 210 gm; has a working temperature range of +40C to –40C; and is powered by a 9V PP3 battery.
Each monitor is supplied complete with a kit to measure the purge gas exhaust from inflatable purge dams, or from an open root weld configuration and a carrying strap, together with operating instructions and calibration and test certificates.