Load characteristics of cold water pipe based on fibreglass-filled HDPE composites

Abstract

Cold water pipe (CWP) which is used in ocean thermal energy conversion stationary surface platform should be able to keep water at a temperature of ~5°C, with the result that cold water could be used to liquefy ammonia vapor from a turbine generator to generate electricity. CWP has an inner diameter of about 3m to 4m that reach to 500m water depth. CWP on the stationary platform will experience stresses due to current and wave loads and the weight of the pipe itself. This paper will explain the loading that occurs. Seawater currents generate movement of CWP in the horizontal direction which causes the pipe to be subjected to bending stress. Bending loading fluctuates with different wavelengths and angles each time. In addition, seawater currents lead vortex-induced vibration. The properties of pipe material used should be lightweight, flexible and strength that subjected to wave and current loads. HDPE material is suitable for CWP than other polymeric materials. Because of lightweight and flexible. For the strength, it is filled with short fiberglass in order to withstand low temperature and corrosion. The CWP bending due to seawater current causes the structure of the pipe material to experience repetitive tensile and compressive loading. And due to waves occurs axial tensile load. So that the main load on the CWP is the tension and pull loading that occurs repeatedly or fluctuating in sinusoidal shape and the resistance of the CWP will be more accurately known by fatigue testing alternating load.