Engineering Standards for Reinforced Thermoplastic Pipe
Authors: Gibson A.G. , Cantrill J.L. , Groves S.J. 
Published: October 2008

This paper describes the activities of Phase 1 of the Joint Industry Project on Implementation of Reinforced Thermoplastic Pipe in the Oil and Gas Industries. The initial aim of the JIP was to promote applications of this new class ofproduct in the transport of oilfield fluids, in gas transmission and in subsea flowlines. The future aim is to consolidate the documentation already produced and to extend the principles to apply to a wider range of flexible non-metallic pipe systems.

Introduction

RTP is a three-component pipe, as shown in Figure 1, comprising a thermoplastic liner, reinforcing layers and a thermoplastic outer cover. The potential offered by this type of product for a wide range of applications in the oil and gas industries has been recognized for some time1–5.

Currently, RTPs employ MDPE (PE80 or PE100) for the liner and cover, along with aramid fibre reinforcement. Other thermoplastics such as PA11 and PVDF are envisaged for more specialized fluid service. The choice of reinforcement is influenced by the fact that aramid is resistant to attack by fluids and can be used without undue fibre/fibre damage in its non-impregnated state. It also shows very well defined, reproducible regression behavior under load, which is important for establishing a long-term design basis. For future use other reinforcements, including steel wire, carbon and Eglass, are also under consideration.

The JIP on Implementation of Reinforced Thermoplastic Pipes in the Oil and Gas Industries is funded by a consortium of manufacturers and end-users and was established in 1999. The sponsors are six potential end-users, three manufacturers of the product and the UK Health and Safety Executive. The aim of the JIP, which is jointly managed by the Advanced Research Partnership and the University of Newcastle upon Tyne, is the removal of barriers to the use of RTP in three key application areas:Onshore transport of oilfield fluidsOnshore transmission of gaseous fuels, andOffshore applications

It was recognized at the outset that onshore applications, such as the one shown in Fig. 2, were of greatest immediate interest and it was agreed that the first activities of the JIPshould address these.

Figure 1. RTP construction (schematic).(Available in full paper)

RTP products retain many of the advantages of conventional PE pipe, including flexibility and ease of deployment, as well as impact and corrosion resistance. The products under development and trial cover the working pressure range, 30-75 bar, and diameters in the range 3"-10". However, higher pressures and larger diameters are under consideration. It is also envisaged that the RTP documentation could be extended to cover related non-metallic systems such as the spoolable thermosets.

Figure 2. RTP field trial in the Oman (Courtesy, Pipelife Nederland bv.) (Available in full paper)

RTP joints are an essential part of the technology, and they must allow the load carried by the reinforcement to be transmitted into the body of the coupler without resulting in undue stress concentrations.