Plastic Pipes Conference Association # 1992 Eindhoven
Vanspeybroeck
This paper describes the test methods to study rapid crack propagation (RCP) behaviour of polyethylene (PE) pipes, including the evaluation of the correlations between different test methods. The test methods concerned are the Full Scale test, the Small Scale Steady State (S4) test, the Small Scale Steady State Scum (S5) test and the Robertson test. The Full Scale test provides the most widely trusted assessment of the Critical Pressure (p,), but is expensive and laborious in execution. The Critical Pressure p, is the critical value of the operating pressure at which a fast crack runs through the entire length of the pipeline. This p, is shown to be a function of material properties, pipe dimensions and properties of the pressurizing fluid. The Small Scale Steady State tests (S4 and 55) are developed in order to achieve steady state RCP in small specimen, by restraining the decompression which normally accompanies the propagation of the crack. The effects of important parameters such as pipe wall thickness, pipe diameter, test temperature, pipe material grade etc., which strongly influence the RCP behaviour, are determined. The Robertson test was proposed during the 70's to obtain a cheap and reliable characterization of RCP susceptibility. This test has shown its reliability in 20 years of practice.
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