GRP Pipes

The GRP pipes and fittings are constructed from resin and glass fiber reinforcement combined with additives to form a composite structure to satisfy the performance requirements of these specifications. The pipes and fittings are designed to achieve a minimum working life of 50 years under all applicable loading, environmental and installation conditions. Pipes can be produced using an unrestrained joint or using a restrained joint where no thrust blocks are used at the change of directions.
The construction of the pipe and the joints is different for both loading conditions.

All pipes and fittings have a minimum initial specific stiffness – determined in accordance with ASTM D 2412 – or ISO 7685 of 5000 N/m2 for burial depths up to 10 m and 10000 N/m2 for greater depths. A stiffness of 2500 N/m2 could be used for burial depth up to 4 m depending on the native soil and the backfill.
In all cases, the pipe stiffness selection criteria is verified by design calculations in accordance with AWWA M 45 design manual.

All pipes and fittings are capable of withstanding the working pressures, test pressures and loading mentioned in the specifications.

The pipes and fittings are designed to withstand up to 5% long term deflection in their installed conditions.

Pipes will have a 50 year strain corrosion design value as per ASTM D3262 section 6.3.1 latest edition for sewer pipes. Representative samples from production will pass the strain corrosion control requirements of ASTM D3262 section 6.3.2 for the 100 and 1000 hour test.

1. Applicable Standards

2. Manufacture

All pipes are manufactured by the continuous filament winding process utilizing an advancing mandrel. Or by the Dual filament winding method.
The internal surface of the pipes and fittings is smooth and resin rich.
The internal and external surfaces are clean and free from defects such as protruding fibers, voids, bubbles, cracks, blisters, tackiness and foreign matters. Cut laminate surfaces are coated with liner resin and have a smooth finish.

3. Resin

The resin used for the internal liner of the pipes and fittings is of an unsaturated resin that can provide the corrosive resistance required. The resin in the structural wall of the pipes and fittings is of the unsaturated Polyester type incorporating styrene as the polymer monomer, but other resins may be used depending on the application.

No pigments are added.

All resins used have been tested in accordance with the resin manufacturer’s specification for viscosity and reactivity performance. All resin systems are at least equal to the requirements of BS 3532 - type B.

4. Glass

In general the Fiberglas reinforcement of the ‘E’ type may be used in the laminate. The sewer pipe meets the requirement of ASTM strain level (ASTM D 3262).

The reinforcements comply with the standards listed below as appropriate.

                       
Glass Roving used in the structural wall does not exceed 2400 Tex.

5. Pipe Liner

All pipes and fittings have a resin rich liner of an average thickness 1.0 mm comprising an innermost resin rich layer (i.e. that in contact with the liquid) suitably reinforced with “C” glass veil or ECR veil (for sewer applications). The remainder of the liner consists of a layer of Glass Chopped strand roving and has a minimum glass content between 25% and 35 % by weight.
For the Dual filament pipe systems continuous glass fibers are used in the structural wall.
The pipe and fittings are provided with a resin rich external surface of approximately 3 mm.

6. Pipe Structure

The pipe is a corrosion resistant composite laminate consisting of polyester resin, Fiberglas filament winding, Fiberglas chopped roving (if applicable), surfacing veil and finely graded sand (applicable for the larger diameters). The laminate has a central core with high content of sand to give the pipe its rigidity and stiffness.

7. Dimensions and Tolerances

Dimensions and Tolerance conform to the recommendations of the ISO 10467 and ISO 10639.

8. Fittings

All fittings such as bends, tees, junctions, reducers and the like conform to ISO 10467. The construction or bends are swept or mitered as designed. Laminated joints used in the fabrication of fittings are equal or superior in strength to the sections they join.

9. Flanges

GRP flanges are flat faced and drilled to BS. 4504 PN 10 or PN16 drilling pattern. Flanges are filament wound or contact molded. GRP Flange gasket are of a design, material and thickness as recommended by the GRP fitting manufacturer.

10. Joints (for buried pipes)

Except where otherwise detailed on the drawings, all pipes and fittings have  joints. Joints of GRP coupling , Butt and Wrap type or Key-Lock.
All couplings should have the same composition as the pipe. All joints are capable of withstanding the various tests specified for the appropriate class of pipe. Rubber gaskets meet the requirements of the appropriate parts of BS 2494 and be of the EPDM (for water applications) formulation. Other material type depending on medium.  
It is ensured that joint gaskets are suitable for use in the prevailing climatic, soil, ground water and working conditions.

11. Aggregates and Fillers

            Additives if used are from 98% pure silica sand as defined in BS-5480 1990 and AWWA C-950 and do not contain impurities.  The aggregates are used in the stiffening layer of the pipe wall. GRP pipe specifications are based on the performance requirements specified in the relevant ASTM and AWWA standards. The piping systems do not necessarily conform to the pressure classes and dimensions given in these standards.

The applicable standards are:

The general pipe wall structure is depicted in Figure 2