Epoxy Resin

Epoxy resins are used to a wide range of moderately strong acids and alkalis, conveying water, condensates, hydrocarbons and caustics Fiberglass epoxy piping is used in oil fields at pressures up to several thousand per square inch (kilopascals). Epoxy resins cannot be categorized by resin type as easily as polyesters. The type of curing agent or hardener, is critical with epoxy resins because the agent influences the composite properties and performance.
For optimum chemical resistance, these mixtures usually require a heat cure and/or post cure. The cured resin has good chemical resistance, particularly in alkaline environments, and can have good temperature resistance. There are several types of base epoxy resins and associated curing agents Curing agents typically used for epoxy resin are:
• Cyclo aliphatic amine
• Aliphatic amine
• Aromatic amine
• Anhydride

Polyester Resin

Polyester resins are commonly used to produce large-diameter water and sewage piping. Polyesters have excellent water and chemical resistance and are noted for acid resistance. Polyester resins are cured by organic peroxide catalysts. The type and amount of catalyst will influence gel time, cure time, curing temperature and the degree of cure. Isophthalic polyester resin is typically used. Isophthalic polyester is a relatively low cost resin with limited chemical resistance.

Vinyl ester Resin

Compared to polyester, vinyl ester resin has very good chemical resistance, especially against acids, high temperature and chemical resistant vinyl ester based resins, e.g. Novolac vinyl ester, are also available.



Pipeline and piping systems shall be designed so that mechanical integrity is maintained under all coincident loading conditions and process temperatures to which these systems can be exposed, and shall represent the most severe anticipated conditions experienced during installation and within the service life of the system.
GRE pipe systems are more sensitive to mechanical overloading, surge and water hammer effects than steel systems. This requires special care when designing GRP pipe systems.
CPI designer are actively involved throughout the entire project from start to finish, including late installation changes, system hydro testing and up to commissioning.

Jointing System

CPI is offering various types of bonded and mechanical joints for GRE piping system. These tend to be proprietary in nature but can generally be categorized into the following types:
a) Adhesive-bonded joints, (conical bell & spigot)
b) Laminated joints (butt & wrap joint)
c) Mechanical O-ring bell-and-spigot elastomeric seal joints (key – lock joint)
d) Flanged joints
e) Threaded joints
f) Metallic/GRP interfaces.

Adhesive-bonded joints

The adhesive-bonded joint is a rigid type of joint, which consists of a slightly conical (tapered) bell end and a machined tapered spigot end. Adhesive joints have the lowest material cost of all joints and are structurally efficient when made up correctly. Make-up of the adhesive joint tends to become more difficult for larger sizes, particularly for pipe above 600 mm diameter. CPI recommend to use adhesive bonded joint up to 600 diameter and up to 65 bar design pressure.


1. pipe with integral socket end
2. adhesive
3. finishing fillet
4. pipe with spigot end

Laminated joints

The laminated joint consists of plain-ended pipe and fittings, prepared, aligned and laminated with reinforcing fibers and resin/hardener mixture as shown in Figure.


1. laminate overlay
2. pipe laminate
3. laminate length
4. tapers not steeper than 1 in 6
5. pipe centre line

Mechanical O-ring elastomeric bell-and-spigot seal lock joints (Key-lock joint)

Elastomeric bell-and-spigot seal lock joints are made up of a spigot end and a socket end with O sealing rings. The socket will be an integrated part of the pipe. If a tensile-resistant joint is required, a locking strip can be incorporated as shown in Figure.
These are the simplest joints to assemble and they can be designed to enable a small amount of axial and angular movement within the joint. They are cheaper and generally structurally more efficiently than flanged joints, but more expensive than adhesive joints. They are bulkier than adhesive joints, but have the advantage that they can be quickly assembled in poor working conditions and are the preferred joint for concrete gravity-base system piping and ballast transfer piping in ships.


1. pipe with integral socket end
2. elastomeric ring
3. locking strip
4. pipe with spigot end
5. insert hole for locking strip

Flanged joints

Flanged joints facilitate connections with steel piping and allow easy assembly and disassembly of piping systems. The outside diameter and hole spacing of flanges should meet the requirements of ASME B16.5/ASME B16.47. GRP flanges are always flat-faced and, accordingly, matching flanges should also be flat-faced in order to avoid the crack.

Threaded connections

Thread joints are normally use for high pressure piping systems. Threaded end connections which conform to API standards should meet the requirements of API 15HR. Threaded end connections which are the design of the manufacturer should meet the specification. CPI recommend to use threaded joints for high design pressure (more than 70 bars).


1. 1 standard API threads
2. pipe body – male end
3. pipe body – female end
4. pipe center line

Temperature Limitations for GRP

Chemical Resistance of GRP Material


CPI is accredited by
• TUV Nord - ISO 9001 & ISO 14001
• FM 1614

Client Approvals


GRP pipe is used in many industries, including

Typical applications services for the use of GRP pipe include