Mechanical tests, performed at TWI, to confirm the quality of polypropylene and PVDF welds made by infrared (IR) fusion have proved the process to be an effective alternative to conventional butt fusion.
Industrial Member, George Fischer Piping Systems Ltd, Invented the IR system (which is commercially available) for the jointing of piping systems. The technology differs in a number of ways from butt fusion in that it utilises radiant heat, bringing the risk of contamination in the jointing surfaces down to the absolute minimum. Heat transfer by means of infrared radiation requires no equalisation process and this significantly improves bead geometry and reproducibility. A further difference is in the control of the jointing pressure: on the IR machine the jointing distance, which defines the jointing pressure, is set before fusion takes place.
TWI's Engineering Department carried out short term mechanical tests on two specimen geometries and at temperatures of 20◦C and 40◦C.
The low temperature tests were achieved by testing in a climatic box or by containing the test specimen in a specially designed insulating box after it had been cooled to temperature.
In all cases, results proved that parent material strengths can be achieved with IR welding. Also, the novel specimen geometry and insulating box offer a practical means of testing butt fusion welds.
George Fischer is using the welding data produced in the study for predicting the long term behaviour of welded joints.
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