GRP pipes joints and fittings for use in sewerage, industrial waste and water (other than potable)
1996 Edition

The standard defines dimensional tolerances for GRP pipes and fittings as follows: For large sizes such as DN 1300 and DN 1500, inside diameter tolerances are ±5 mm, with inside diameter ranges from 1295 to 1320 mm for DN 1300 and 1495 to 1520 mm for DN 1500. Outside diameter tolerances for the same sizes are also ±5 mm, with nominal outside diameters of 1330 mm and 1534 mm respectively. Fittings tolerances, while not explicitly detailed, generally align closely with pipe tolerances to ensure proper joint compatibility. These tolerances maintain dimensional consistency critical for effective assembly and system performance.

IS 14402 permits the use of glass fibre reinforcements such as woven roving fabrics of 'E' glass fibre conforming to IS 11273:1992, glass fibre rovings as per IS 11320:1985, and chopped strand mats following IS 11551:1986. The resin systems specified include thermosetting unsaturated polyester resins compliant with IS 6746:1993. These materials combine to provide the necessary mechanical strength, chemical resistance, and durability for GRP pipes used in sewerage, industrial waste, and non-potable water systems. Fillers may be included as required by manufacturing processes.

The chemical resistance evaluation is conducted according to the method outlined in Annex F of IS 14402, which corresponds with ASTM D 3681-1989 standards. Testing involves subjecting pipe specimens to chemical exposure while under controlled mechanical deflection to simulate actual service conditions. Specimens, typically at least one nominal pipe diameter or 300 mm in length, are placed between steel plates with an elastomeric pad to ensure uniform strain. The test monitors mechanical property degradation and visual defects over time at ambient temperatures. Results are analyzed via log-log regression to extrapolate long-term performance, ensuring the pipe’s durability in chemically aggressive environments.

Acceptable workmanship defects under IS 14402 include chips up to 6.5 mm in size, surface cracks no longer than 6.5 mm, crazing limited to 25 mm, resin-rich edges with maximum thickness of 0.8 mm from the edge, shrink marks with diameters up to 14 mm and depths not exceeding 25% of wall thickness, and wormholes with diameters up to 6.5 mm. Defects such as through-thickness cracks, internal delamination, burn damage, and incomplete filling are not permitted. Other imperfections like blisters, fish-eyes, dry spots, orange-peel texture, and porosity have defined maximum dimensional limits to ensure structural integrity and hydraulic performance.

IS 14402 encompasses joints and fittings including bends, tees, junctions, and reducers designed for GRP pipes. Fabrication methods include using sections or portions of straight pipes with mitre cuts that are externally overwrapped and, where feasible, internally reinforced with woven roving or chopped strand mat to ensure longitudinal and circumferential tensile strengths equal to or exceeding that of the pipe. Moulded fittings can be produced using hand lay-up, contact moulding, hot or cold press moulding, and tape winding techniques. Smooth internal finishes are mandatory, and external restraints during installation are critical to maintain joint integrity.