Mel Kanninen, Kyle Bethel and Aron Ekelund
Papers # 2010 Vancouver
It is well known that gas permeation in thermoplastic pipe is proportional to pressure. Accordingly, quantitative consideration must be given to this phenomenon to properly design and operate reinforced thermoplastic composite pipe (RTCP) in high pressure applications. In this paper a permeation predictive model based on classical diffusion theory has been developed for multilayer RTCP carrying greenhouse gases. The methodology uniquely includes the potential for both an internal pressure build-up that has the potential to burst the outer layer of the composite, and for the back pressure from permeation build-up in the annulus between the inner surface of a rigid steel host pipe and the outer surface of the composite pipe to collapse the inner layer. The focus of this paper is on the prototypical RTCP known as the Smart Pipe® although other types of RTCP are also analyzed along with conventional low pressure plastic pipe. The analysis work presented herein is a first step towards a complete and validated approach for coping with gas permeation. While not yet supported by experimentation, this work shows that all types of RTCP must be vented during high pressure service, albeit for different reasons, and there is a sound basis for determining the rate and mode of permeation that must be vented.