Pipe and fittings
The riser is made of welded heavy-class ERW galvanised iron pipe to IS 1239 Part 1, with wrought steel fittings to IS 1239 Part 2. Joints are made by welding. Stainless steel tube needs approval from the PNGRB.
Pressure
The maximum operating pressure in the riser is 110 mbar. Where a regulator is fitted at the riser, the pressure upstream of it can be up to 4 bar. Pressure testing follows the PNGRB T4S regulations.
Valves and transition at the base
The riser isolation valve is placed 1.0 to 1.5 m above ground. The change from polyethylene to steel pipe is about 0.3 m above ground. An equal tee is fitted above the isolation valve so that the riser can be pressure tested.
Crossing a podium
Over a podium or roof, the pipe is either exposed and clipped to the structure or buried in polyethylene at least 375 mm deep.
Laterals
The branches to each flat are laterals. Riser tees are socket welded. Lateral joints can be threaded, with a welded connection at the riser end, and malleable cast iron fittings to IS 1879 are permitted.
Colour and drawings
Riser and lateral pipes are painted yellow. A design sketch is needed before installation, and an as-built drawing must go to the gas distribution company before commissioning.
Check the current edition
Guidelines and company requirements are updated from time to time. Confirm the current edition and the gas company's own requirements at the start of the project.
For help with riser design for a high-rise project, send us the building details. See our PNG riser stress analysis service.