Quality Assurance of GFRP Pipes for Seawater Cooling of Power Plants

Many electrical power plants are located along coastlines and use seawater for cooling purposes. The traditional material for the pipes was, until not so long ago, steel that posed severe maintenance problems due to corrosion and accumulation of sediment on its surface. In the last three decades glass fiber reinforced polyester (GFRP)-pipes of various compositions replaced some steel pipes, mainly for being corrosion free and easy to maintain. This advantage of the GFRP pipes is offset by their low stiffness, complicated design and testing procedure before and during production, and higher cost. A joint project with the Agricultural Engineering Department to design and test large-diameter GFRP pipes began at the Composite Mechanics Laboratory, Technion–Israel Institute of Technology, in 1978. The present paper addresses some of the problems and the experience accumulated over the years. Based on the long-term service experience, it is suggested that four tests are sufficient for the full assessment and certification of the respective main composite pipe characteristics, namely, hoop stiffness, hoop strength, longitudinal strength, and interlaminar shear strength. The first three are required for the proper performance of the pipe and its resistance to fracture and buckling. The last (interlaminar) property is an important indicator of interlaminar integrity of the pipe, to ensure proper fabrication procedure.