Saturday, 30 July 2016

HFT’s heat covers protect purging temperature rises

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Damaging your pipe purging systems due to high temperatures can be a thing of the past now that accessory Argweld® Heat Covers are available to protect them.

Although Huntingdon Fusion Techniques HFT®’s HotPurge™ Systems are very popular for heat-treated pipework, it is not possible for the company to manufacture this design for diameters below 6”.

To fill the gap for smaller diameter pipework and for larger diameter pipework that doesn’t justify the use of HotPurge™ Systems, HFT® has designed and manufactured Heat Covers for both PurgElite® and PurgExtra™ Tube and Pipe Weld Purging Systems with a temperature endurance of up to 300ºc.

The Heat Covers are held on with ties and there are holes provided for the PurgElite® and PurgExtra™ fittings, such as inlet, exhaust and crimped end.

The heat covers are usually provided as pairs, although they can be purchased individually in case of damage or loss.

For pipes that need to have the joints and the heat affected zones heat treated to higher temperatures, HFT® supplies extra long purge tubing that holds the two end dams together, so that the dams can sit just outside of the heated zone, where the temperature has fallen away, below 300ºc.

The welding of many metals such as titanium zirconium, chrome steels, duplex steels and stainless steel requires the oxygen at the back or underside of the weld, to be removed, to prevent oxidation.

In the case of tube and pipe welding, HFT® manufactures QuickPurge®, HotPurge™, PurgElite® and PurgExtra™ Systems that are designed to purge the contaminating gases such as oxygen, nitrogen, water vapour etc, from the rear of the weld, eliminating possible reject at worst and at best the post weld cleaning of the weld root, saving significant amounts of money in labour and material costs as well as the disposal costs where acids are concerned.

Many companies are still fabricating their own home made purging systems made of foam, cardboard, adhesive tape, wood and so on. Like paper, these materials contain a high percentage of water and water is very undesirable to have in the presence of a weld.

As these poor materials are warmed by the welding operation, they start to outgas their contaminating gases, which combine with the weld pool to cause porosity and oxidation.

Home made devices using foam and adhesive tape can also pick up metal contamination for other areas and introduce that into highly expensive metal joints of another material, which will cause a reject during quality control processes or failure of welds later on, once the joints have come into service.

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