A Novel Approach to the Qualification of Non-Metallic Pipe Systems

This paper discusses the possibilities offered by ramp pressure loading tests to generate data for determining the long term load-bearing characteristics of plastics pipe systems. In addition to ramp pressure loading, procedures are also considered where the pressure is held at a constant value for a period of time, after which the product is subjected to a ramped pressure burst test. The method discussed relies on the material in question obeying Miner’s law in its static fatigue behaviour. The pipe system to which the procedure has been applied is Reinforced Thermoplastic Pipe (RTP), in which the reinforcement is aramid fibre. However the results are expected to apply to any polymeric system where there is evidence of conformity to Miner’s law. A set of ramp loading tests, and constant pressure plus burst tests are reported and compared with the results of conventional ‘constant pressure’ stress rupture tests and a method is proposed for converting these results into ‘equivalent’ constant pressure values. The results obtained on RTP using this new approach lie close to those generated using constant pressure.