Ernst van der Stok, Frans Scholten
Papers # 2014 Chicago
The Strain Hardening (SH) test and the Point Load Test (PLT) are two complementary tests designed to determine the quality of PE 100-RC. The SH test is a resin test, whereas the PLT is a pipe test. The SH test is a tensile test performed at 80 °C. Extensive research on the SH test has been conducted and published in the proceedings of previous International Plastic Pipe Conferences. The latest Round Robin, performed by seven different laboratories, resulted in similar outcomes with a very low variation coefficient. Experiments have shown that, due to the preparation by compression moulding of the test specimens, the SH test is a resin test and gives no information about pipe quality. Experiments in which specimens are prepared directly from pipes should give insight into whether the SH test can also be used to test the remaining pipe material quality. Future research will focus on checking the robustness of the SH test method. The minimum SH values for PE 100-RC resins must be agreed upon for the purposes of standardisation.
In the PLT, a pipe is placed under static internal pressure in a water bath at 80°C. A detergent is circulated inside the pipe while a point load is applied to the outer pipe surface. By changing the detergent from Dehyton to Arkopal results in reduced testing times. Multiple cracking is observed in the PLT. This is due to the high stresses necessary in order to speed up the failure process. Lowering the internal pressure of pipes in practice makes them less prone to failure due to point loading. This has practical implications for old pipelines. Further research will focus on standardising the test parameters and obtaining the same results between three international labs. A threshold failure time for PE 100-RC pipes should eventually be found.
