Manufacturing Process of FRP Pipes

FRP pipes can be divided into three layers: liner layer, structural layer and outer anti-aging layer. The liner layer featuring excellent corrosion resistance, can effectively prevent seepage; while, the structural layer can reinforce the FRP pipe by improving its rigidity and strength. And the outer anti-aging layer is characterized by excellent resistance to aging, corrosion as well as UV.

Filament winding, as the most extensively method, is generally used to manufacture FRP pipes such as pressure pipes, drainage pipe and chimney pipes. Here is a simple introduction of FRP pipe manufacturing process.

Mandrel preparation.
The mandrel of FRP pipe is installed waiting for cleaning and polishing.

Clean and polish the mandrel to ensure a smooth surface without any potholes, dust, debris or other fixtures affecting the quality of FRP pipes. Then wrap a thin mylar parting film around the mandrel to make the pipe extraction much easier.

Machine & material preparation.

Check up on the equipment and make sure it is operating properly, especially resin and curing agent are in correct composition and the dual pump performs well without any clogging. All of this is to ensure high precision and stable operation of your equipment.

Liner production.
  • Compound the resin for liner layer according to the requirements of local regulations, working environments and temperature conditions.
  • Prepare the reinforce materials of liner layers. Cut reinforce materials into certain width and mounted them to specific position for easy winding.
  • Manufacture the liner layers based on the design requirements. Impose reasonable tension during the winding process for excellent lapping. Meanwhile, use compression rollers to press bubbles out and ensure the reinforce materials are fully steeped with resin.
  • Check the liner layer to ensure required thickness is achieved without white patch, bubbles, poor adhesive and adhesive hanging phenomena.
Liner curing.

The liner layers are cured through far infrared depth curing process to enhance solidification degree and improve anti-corrosion properties.

Liner inspection.

Check the pipe again to ensure liner layers in manufactured without bubbles, impurity, white patch, part curing phenomena. Most all, ensure the liner layer is qualified with reasonable resin ratio.

Filament winding.
The filament winding process of FRP pipes

The filament is automatically impregnated in the resin tank, and then reciprocating winded around the rotating mandrel at a specific angle. Normally, different helical angles impart different strength in the hoop or axial direction as required.

Pipe curing.
Wound FRP pipe is cured by far infrared curing station

After the filament winding process, FRP pipes are far infrared cured about 1 hour to 2 hours based on weather condition. Meanwhile, the mandrel rotates at an even speed to ensure the pipe is cured evenly.

Trimming & extraction.
A FRP pipe is separated from the mandrel by extraction machine.

When the Barcol hardness of the FRP pipe is more than 30, then trim the pipe and separate it from the mandrel.

Pipe testing.

Test the pipe through following aspects:

  • Visual inspect: Ensure the surface of FRP pipes is smooth without cracking, delamination, holes, debris, burrs, bubbles and obvious defects that affect pipe performance. In addition, the pipe end should be flush.
  • Dimensional inspection: check the length, thickness, Barcol hardness and socket size of FRP pipes.
  • Hydraulic pressure leakage test: Fill the pipe with water until the pressure reach about 1.5 times of pipeline design pressure and then retain the water no less than 2 minutes. Check the surface of FRP pipe and piezometer carefully. The pipes without leakage are qualified.
  • Mechanical property testing.

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