Composites are extensively used to manufacture pipes with different diameters. Composite pipes made of glass fibers and thermoset polymer resins provide a strong, corrosion-resistant, and lightweight structure as a good alternative to metal, asbestos, concrete, and polyethylene pipes. Similar to most industries arising from the military industry, composite pipes are from the heart of composite pressure tank manufacturing technology.
The terms GRP, GRV, and GRE used in the composite pipe industry all refer to the various configurations of composite pipes made of a fiberglass-based structure with polyester, vinyl, or epoxy resin depending on their various applications. GRVE pipes, which refer to composite pipes made of glass fibers and epoxy resin-modified vinyl ester resin, are a subgroup of GRV pipes and can’t be considered in the GRE group
Polyesters are often used to manufacture pipes of different diameters and for public use in the working pressure range up to 40 bar (4 MPa). Vinyl esters are more resistant against corrosion by strong corrosive liquids (e.g., acids and bleaches) and can resist higher temperatures. Epoxy resins show better properties than polyester and vinyl esters and are additionally recommended for gas or oil transmission applications. GRP pipes have currently more applications in industries than other types of composite pipes due to their generality and wide range of applications.
GRP pipe was first introduced in 1948. As a cheap, corrosion-resistant material, GRP pipe performs better than coated steel or stainless steel pipes, and other types of metals. GRP pipes were used in the chemical industry in the late 1950s due to their resistance to chemically prone environments and the safety of composite materials against hazardous and damaging corrosion. From 1960 to 1990, GRP pipes were accepted for municipal water and sewage treatment. GRP pipe efficiency is known by useful life, strength, and resistance to corrosion. Thus, it eliminated the inner and outer coatings and/or cathodic protection
Composite pipes include gravitational and compressive pipes in terms of fluid transport.
In gravitational pipes, the fluid is conveyed by gravity or at low pressures to continue flowing. These pipes are suitable for enduring low pressures and are installed underground while bearing high soil and traffic pressure. Wastewater pipes are an example of gravitational pipes
In pressure pipes, fluids are conveyed at pressures higher than in gravity pipes. These pipes are more employed in water conveyance, and oil, gas, and marine industries, where various products are conveyed with pressures up to about 32 bar. In the oil and gas industry, products may be conveyed at pressure up to 70 or 250 bar
Classification of composite pipes
Composite pipes GRP, GRV, or GRE are often classified and introduced by diameter (DN), nominal pressure (PN), and stiffness (SN). In general, the composite pipe is introduced as DN-PN-SN, regardless of the resin utilized. For example, a 400-16-5000 pipe has a diameter of 400 mm, a working pressure of 16 bar, and a stiffness of 5000 Pascals. Composite pipes are available in small (e.g., 200 mm) to very large (e.g., 4000 mm) diameters.
The nominal pressure shows the maximum pressure at operation in bar or atmosphere and does not depend on the depth of the pipe burial. Each nominal pressure classification according to the installation depth of the pipe and the bed and trench conditions can be linked to a stiffness category. Composite pipes are generally manufactured and supplied in pressure classes of 6 to 32 bar
The stiffness of composite pipes indicates the resistance to deformation due to the load caused by vertical burial. The pipe’s capacity to resist deformation and deflection due to external forces and the vacuum pressure inside the pipe depends on its stiffness. Composite pipes are delivered with stiffness ranging from 1250 to 10,000 Pascals. Each new product has a distinct combination of diameter, pressure, and stiffness. Such a combination indicates the broad and varied range of composite pipes available