A Performance-Based Design Methodology for Glass-Reinforced Plastic Pipework and Fittings

This paper is concerned with the development of a design methodology for glass-reinforced plastic (GRP) pipework and fittings. As the use of GRP material becomes more widespread procurement is being increasingly carried out on a performance basis against specified pressure ratings. This is analogous to schedules in metallic piping systems. However, there are, as yet, no design methods available that are able to relate the test data obtained in the measurement of long-term performance under simple internal pressure conditions to the wider requirements of pipe components in service. The most significant outstanding issue is the effect of material anisotropy and the need to cater for the wide variety of possible loading situations present in a typical piping layout. In this paper a rationale is presented based on a simple analysis which employs a limited range of measured data to derive an allowable design envelope. This is then used to develop a qualification procedure which can be used to establish pressure ratings and takes into account the behaviour of GRP materials under likely imposed loads.