FRP piping - Introduction

FRP piping is commonly employed in the chemical industry.

FRP is a composite material consisting of thermoset resin and a fiber reinforcement. There are many types of resins and reinforcements and each imparts specific properties to the final product. Some of the resins include Polyester, Epoxy or Phenolic resin. Glass Fiber "E-glass" is the most widely used reinforcement.

Pipes can be manufactured by contact moulding (hand lay-up) or hand lay-up in combination with filament winding.

Types of Glass Fibre Reinforcements

• Chopped Strand Mat
• Rovings
• Woven Glass Fabrics
• Surface Veil

They are manufactured from glass or synthetic fibres such as polyester. The surface veil is generally the innermost layer in contact with the process fluid.

Safety Factors

Piping designed for pressure service are generally designed to a safety factor of 10:1. This means that the allowable strength is 10% of minimum ultimate values. The safety factor takes into account the loss of strength of the laminate under continuous long term load and loss of strength due to corrosion effects of process fluid.

Corrosion Barrier

For corrosive process fluids, a resin rich layer is provided on the innermost layer. Typically a corrosion barrier may consist of the following

• Inner surface 10-20 mil of resin reinforced C veil, Nexus® or Synthetic veil.
• 2-5 layers of Type E glass fiber chopped strand mat.

Additives

Antimony Trioxide or brominated compounds are added to provide excellent fire resistant characteristics to FRP.

Joining Methods

• Butt and Strap Joints
• Bell and Spigot Joints
• Threaded Joints

Applicable Standards

• BS 6464 -   BS specifications for Reinforced plastic pipes, fittings and joints for process plants
• 41-GP-22 -   Canadian specifications for Reinforced Polyester Process Equipment
• ASTM D2996  -   Standard Specification for Filament-Wound "Fiberglass"(Glass-Fiber-Reinforced Thermosetting-Resin) Pipe
• ASTM D2997  -   Centrifugally Cast "Fiberglass" (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe
• ASTM D1599  -   Standard Test Method for Resistance to Short-Time Hydraulic Failure Pressure of Plastic Pipe, Tubing, and Fittings
• ASTM D5421  -   Standard Specification for Contact Molded "Fiberglass" (Glass-Fiber-Reinforced Thermosetting Resin) Flanges
• ASTM D3517  -   Standard Specification for "Fiberglass" (Glass-Fiber-Reinforced Thermosetting-Resin) Pressure Pipe
• ASTM D5685  -   Standard Specification for "Fiberglass" (Glass-Fiber-Reinforced Thermosetting-Resin) Pressure Pipe Fittings
• ASTM D4024  -   Standard Specification for Machine Made "Fiberglass" (Glass-Fiber-Reinforced Thermosetting Resin) Flanges

FRP vs Carbon Steel