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Regional technology project pops welded bubbles

Connect, no. 127, November/December 2003, p.7

Welding of fabricated 'T' to 20 inch diameter spiral welded aluminium tube
Welding of fabricated 'T' to 20 inch diameter spiral welded aluminium tube

When welders at Hiatco, the Annfield Plain-based welding company, hit unexpected technical problems, expert help from TWI via a North East regional project came up with the solution.

Hiatco specialises in welding aluminium and stainless steel. Its welders must regularly pass 'approval' tests to confirm their competence to carry out particular tasks.

Recently, when the welders took their approval test on joining aluminium alloy pipe in a butt joint, they failed because x-ray inspection revealed unacceptable porosity - bubbles caused by trapped gas in the welds which would weaken the joints. Exactly similar tests had previously been completed successfully, and so with no obvious reason for failure, Hiatco's welding supervisor Michael Errington called on TWI for advice.

One of TWI's team of welding engineers, Geoff Eames, took up the challenge and began a series of checks and trials to find the cause of the problem. The welders were using the tungsten inert gas (TIG) arc welding process, which involves a shield of argon to protect the molten weld metal from the air.

Geoff therefore thoroughly checked the equipment and the purity of the gas, before starting to make some trial welds. These demonstrated the importance of completing all weld passes without allowing the pipes to cool, and showed that it was crucial to select an appropriate water based degreasing agent.

As a result Geoff was able to advise Hiatco of the methods to adopt to produce welds of suitable quality. With the problem solved, the company's welders were once more appropriately qualified for a full range of welding tasks.

TWI's help was available to Hiatco under the Joining Forces North East technology transfer programme. The programme aims to boost growth, competitiveness and innovation in the regions small and medium sized companies.

For more information on the programme and how your company can benefit, contact TWI (Technology Centre) North East on 01642 210512.

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