Plastic Pipes Conference Association # 1998 Gothenburg
Hinchcliff, Troughton
There are a number of different mechanical test methods available to assess the quality of butt fusion welded joints in polyethylene (PE) pipes. However, little published information exists on the correlations that may or may not exist between the results from these methods. This paper compares the results from five short-term mechanical test methods : three point bend, dumb-bell tensile, waisted tensile, low temperature (-60°C) tensile, and Charpy impact, on butt fusion joints in 355mm outside diameter (OD) PElOO pipes. In addition, the size of the weld beads was measured. Butt fusion joints were produced using one standard and two non-standard welding parameters, in order to produce joints of nominally different quality. Results from this study showed that, of the five short-term coupon tests examined, only one, the waisted tensile test, was able'to differentiate between welds made under the standard and non-standard welding conditions. Even in this test the failure mode and failure load could not distinguish between all three welding conditions; only the extension at break and energy to break values showed differences. The results also showed that the dimensions of the external weld bead could discriminate between the welds made under the standard and the hvo non-standard conditions. This suggests that measuring the bead height rather than the bead width should give a clearer discrimination between welds made under different conditions.
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