Reinforced thermoplastic pipe (RTP) is a generic term referring to a reliable high strength synthetic fiber (such as glass, aramid or carbon) or high strength steel wire reinforced pipe system.
Typically, the materials used in the construction of the pipe might be polyethylene (PE), PA11 or PVDF and may be reinforced with aramid or polyester fiber or high strength steel wire, although other combinations are used. It is available in coils up to 400 m (1,312 ft) in length. The pipes are available in pressure ratings from 30 to 450 bar (3 to 45 MPa; 435 to 6,527 psi). Recent innovations include gas tight RTP and RTP for high operating temperatures.
Some RTP systems are fully certified according to certification bodies like the American Petroleum Institute. Over the last few years this type of pipe has been acknowledged as a standard alternative solution to steel for oilfield flow-line applications by major oil companies and operators. Reinforced thermoplastic pipes are used for a variety of on- and off-shore applications, including: high pressure water injection pipelines, water transport solutions, effluent water disposal, oil and gas flow-lines, oil and gas gathering lines and gas pipeline.
An advantage of RTP pipes is its very fast installation time compared to steel pipe, as average speeds up to 1,000 m (3,281 ft)/day have been reached installing RTP in ground surface (which is not possible with steel pipes when considering the welding time). Primarily, the pipe provides benefits to applications where steel may rupture due to corrosion (RTP is corrosion free) and installation time is an issue.
Reinforced thermoplastic pipe consists of a thermoplastic liner overwrapped with unbounded aramid or glass fiber composites, then coated with thermoplastic. It is used in lower pressure and less demanding temperature applications compared to the fully bonded TCP (thermoplastic composite pipe). Although TCP pipes also consist of reinforced thermoplastic composites, quite similar as RTP pipes, they are suited to higher pressures and a greater temperature range for two reasons. First, some TCP uses higher performing thermoplastic resins, such as PEEK, and/or higher strength reinforcement like carbon fiber. Second, TCP layers are bonded to each other through melt-fusion, which yields higher performance properties than RTP made from the same materials.
As is often the case with composites, the first such property is light weight — TCP weighs as little as one-tenth the weight of steel pipe — but the combination of light weight and flexibility of the pipe makes for a critical advantage: the pipe can be spooled on relatively small drums and subsea pallets. Because of this, smaller vessels can transport and install long spans of TCP — a logistical and economic boon in more remote offshore locations (for example, off the West African coast), where deployment of conventional heavy-lift vessels is a costly proposition. Another cost-saving advantage created by the melt-fusing capacity of TCP is that the pipe can be terminated and end fittings installed onsite.
TCP offers a combination of high strength, flexibility and ease of termination, giving it the best qualities of conventional metal pipe (strong but rigid) and flexible pipe made from unbounded layers of helically applied metal wires and extruded thermoplastics (flexible but heavy, and very costly to terminate onsite). TCP is fully capable of efficiently handling the demanding pressures and temperatures of subsea applications — both from external conditions and from the internal conditions created by the fluids moving through them. TCP’s thermoplastic liner also offers high flow-rates due to its low coefficient of friction. Finally, two other key TCP properties — corrosion and fatigue resistance — make TCP highly durable, even as energy companies are more frequently pumping sour (that is, acidic) crude oil found deeper underground.