Pipes made of high density polyethylene (HDPE) and other thermoplastic materials do not corrode. However, this considerable advantage, because HDPE is limited to a line pressure of 125 psig, cannot be utilized for the replacement or rehabilitation of trunk lines in gas/liquid distribution systems and transmission lines where pressures range from 150 psig up to 1500 psig or more, without some form of reinforcement. This paper describes an advanced technology for accomplishing this by use of a composite of thermoplastic materials. This technology can be used for high pressure applications in either a stand-alone mode, or as a pipe within a pipe, by its insertion into an existing damaged/degraded high-pressure steel pipeline. In either mode, arbitrarily high pressures can be achieved, health can be monitored with a built-in fiber optic sensor system, and wall loss due to corrosion precluded. The focus of the paper is on addressing some of the ancillary issues that arise in the utilization of the technology that are not usually of concern in steel pipelines: nonlinear stress analysis of heterogeneous materials, time/temperature dependent mechanical properties, greenhouse gas permeation, and the diminution of flow area associated with internal reinforcement.
Failure analysis of thermoplastic composite pipe (TCP) under combined pressure, tension and thermal gradient for an offshore riser application