The test can be used to determine whether cold slug or unfused areas are present, to determine the amount of moulded-in stress produced by the moulding process, reveal contamination and to show the quality of the weld. Complete fittings are subjected to a temperature of 150° centigrade in an air-circulating oven for a given time depending on the wall thickness of the fitting. The surfaces of the fitting are examined before and after heating. Cracks, blisters,*delamination or weld opening is measured, expressed as a percentage of the wall thickness.
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