FRP/GRP Plastic Pipes How to Strengthen Plastic Pipes with Polyester/Epoxy Resins Reinforcement

Editor: Dominik Stephan

Owing to their cost and several other advantages, many water industries are fast picking up FRP or GRP pipes replacing traditional metal pipes. As they need no protection against corrosion, they offer apparently maintenance free long service.

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With its high hoop tensile strength and ability to resist corrosion, fiberglass reinforced plastic is one of the best piping material today. (Picture: CPPI)
With its high hoop tensile strength and ability to resist corrosion, fiberglass reinforced plastic is one of the best piping material today. (Picture: CPPI)

Nowadays a great deal of interest is being taken in water reuse (reclaimed water or recycled water). Normally, wastewater (sewage) is treated to remove impurities and discharge water into rivers or seas. The purpose of the water reuse is sustainability and water conservation, rather than discharging the treated wastewater to surface waters such as rivers and oceans. The wastewater is converted into potable water by means of reverse osmosis. Using this technology, Sembcorp, Singapore, has converted wastewater of the Changi Waste Water Treatment Plant into potable water.

We, at Chemical Process Piping (CPP), believe that water reuse projects – such as above mentioned Changi Waste Water Treatment Plant – will grow necessitating FRP (Fiberglass Reinforced Plastic) or GRP (Glassfiber Reinforced Plastic) piping as well.

Advantages in Water Applications

When it comes to water treatment, FRP or GRP piping plays an important role in such plants as they offer some remarkable advantages, such as:

  • 1. Wide range of material properties
  • 2. Highly corrosion resistance
  • 3. Smooth inner surface and hence low friction
  • 4. Long life
  • 5. Negligible maintenance cost in comparison with
  • metallic piping
  • 6. No external protective cover required for
  • buried application

Technical Specialties of FRP and GRP Plastic Pipes

We are accustomed to see ordinary thermoplastic piping like PVC and polyethylene around us, thus, for non-technical decision makers it may be a bit difficult to conceive the efficacy of the FRP or GRP pipes. Most of the thermoplastic-based pipes are non-reinforced extruded products. To the contrary, FRP or GRP pipes are manufactured by winding processes that use thermosetting polyester/ epoxy resins reinforced with continuous fibre or glass filaments. Once the thermosetting resins undergo a chemical change, it is irreversible after curing, which ensures good temperature withstanding capability of these pipes. The filament reinforcement makes the piping components mechanically strong. Taken both together, the pipes become long lasting with light weight.

It is important to note that in FRP or GRP piping, the material of construction and product are manufactured simultaneously. Thus, from the manufacturing angle, it is less complicated and obviously economic. The Continuous Filament Winding (CFW) Plant produces FRP or/and GRP pipes at very competitive prices and at high volumes.

FRPs have wide range of material properties, which can be changed by altering the layup sequence of the laminate. Hence, properties such as modulus of elasticity, tensile strength are not fixed but have a range. For example: their modulus of elasticity varies from 12000 to 24000 N/mm2 and tensile strength (in axial) ranges between 80 to 180 N/mm2.

High chemical resistance is another property that makes FRP or GRP pipes useful to a wide range of industries. They also can be made fire retardant and electrically conductive, which is useful in mining industries.