Plumbing Brass and Copper | Carbide Tool Tips | Stainless Steel and Copper Saucepans

A manufacturer of a simple plumbing fitting (brass fitting to 16mm copper pipe) was experiencing a 4% leak rate on newly brazed parts. The average production rate was 6000 parts per month and this was causing concern.

The brazing was carried out on a hand operated, fixed burner shuttle machine, brazing 6 components on about a 2 minute cycle. The brass fittings were placed onto jigs and the copper tube fitted. A 6% silver-copper-phosphorous ring was placed over the tube and flux paste applied using a paintbrush.

We suggested that inconsistent fluxing was causing the high leak rate. It was felt the fitting in position 1 had too much flux, whereas the fitting in position 6 had too little. The fittings were numbered and brazed in the normal way for one week. The results showed that of those fittings that leaked 80% were from the first position and 20% from the sixth position.

We carried out tests using braze paste with an alloy of copper-tin-phosphorous until we found a grade that gave good results. Due to the timed dispensing system and the fixed flux to metal ratio of the paste, the same amount of flux and braze alloy were applied to each fitting giving a more consistent joint and therefore significantly reducing the leak rate. Six years after we started to supply this customer the line foreman retired and we asked him what the leak rate had dropped to, as we had received no figures. He told us that there had only been 15 parts in that time.

Therefore we saved the company the costs involved in re-brazing, the cost of 6% silver and cleaned up the brazing area due to the controlled application of the flux.

If you have a metal joining problem we may well have the solution, contact us for more details.

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