Although laying conditions vary from site to site, the following information will cover eventualities encountered in the normal installation of FRC™ pipes.
Care should be taken to ensure that trenching conforms to any local regulations or other statutory requirements, particularly in regard to shoring. The following methods of jointing pipe will result in efficient and speedy installation.
Trench Sizes
The width and depth of trenches to be excavated will depend on the following factors:
- Pipe size
- Type of soil
- Location (under roadway, pathway or in countryside)
- Pipe invert
- Pipeline direction (whether straight or deflecting around a curve).
Trenches should be excavated in accordance with drainage plans and specifications. The pipe designer has specified the pipe strength class based on a maximum trench width at the level of the top of the pipe and the trench depth and/or pipe invert level. The width and depth of the trench nominated should not be exceeded without first checking with the pipeline designer.
Preparing the Trench
The trench bottom provides the foundation for the pipeline and therefore should be stable and uniform along the pipeline. In good working conditions, sandy or loamy soil, the trench bottom can be made sufficiently even with stones and rocks removed, to provide continuous support for the pipes without the need for underbedding. Depressions left in the trench bottom below the pipe can result in damage to the pipe. When the trench bottom is flat, localised holes or pockets that are 50mm deep should be dug to accommodate any pipe couplings, so that the pipe is supported over the whole length of the barrel and not on the couplings only.
An uneven trench bottom, which can be encountered in hard or rocky ground, necessitates the placement of granular bedding to support the pipeline. The thickness of bedding required depends on the irregularity of the trench bottom and the installation conditions. As a guide, the bed material should be spread across the full trench width to a depth of 100mm to 150mm above the highest projection in the trench bottom and compacted to prevent settlement of the pipeline.
Pipe Jointing
Rubber Ring Joint
Ensure that both the pipe spigot and the socket are clean before applying HardiJoin™ lubricant to the socketed end. Fit the ring into the groove of the spigot, ensuring that the small side of the ring is facing the end of the pipe. Lower the pipe to just above the bedding level, on a minimal angle and push the pipe home.
Note: Rubber ring jointed pipe can be laid by jointing either the male spigot into the female socket or the female socket onto the male spigot with no effect on the joint integrity. However typical installation involves inserting the spigot into the already laid socket.
Supertite™ Joint
Supertite™ jointed pipes are supplied spigotted at both ends with a loose Supertite™ 'V' ring coupling for jointing on-site. It is recommended for the convenience of pipe laying that Supertite™ pipes be pre-socketed prior to installation as this leaves only one operation for the installation crew to complete. Pipes should be left plain ended where fittings are to be located.
To joint the pipes, first check that the coupling is free from dirt and place the 'V' rubber rings into the coupling with the pointed side of the rings pointing outwards. Lift the end of the pipe clear of the ground to allow positioning of the coupling and apply Hardijoin™ lubricant to the pipe spigot back to the witness groove. Draw on the Supertite™ coupling with a slight twisting motion, until the coupling is pushed back to the witness groove.
Allow the coupling to set in position for a minimum of 4 hours, and then proceed to joint the pipe, remembering to coat the end of the previously laid pipe end with Hardijoin™ lubricant.
HardiJoin™ Lubricant
HardiJoin™ lubricant is a special compound that consists of a soft soap solution, which facilitates jointing of rubber ring FRC™ pipe systems. It is essential that HardiJoin™ lubricant be used and not oil or grease as these will cause deterioration of the rubber rings. In an emergency, a solution of soap or soap powder and water can be used as a jointing compound.
The following table identifies the number of pipes which can be jointed per litre of HardiJoin™ lubricant:
Note: All dimensions are nominal.
Deflecting Pipes on a Curve
Where a pipeline is required to follow a curve, it is essential that the pipe be joined while directly in line with the previous pipe and the deflection made after jointing. It may be necessary to widen the outside edge of the trench so that the pipes can be jointed in a straight line and then deflected to follow the curve.
The following tables show the maximum recommended rotation at a joint for each pipe size, together with each resulting minimum radius curvature and the corresponding deflection for each 4m length of pipe.
Note: All dimensions are nominal.
Note: All dimensions are nominal.
Cutting Pipes
Refer to our Working Safe information before installation.
From time to time it will be necessary to cut pipes and install fittings. The preferred method of cutting is by an abrasive disc or diamond blade power saw. All power cutting operations should be carried out in an open air situation or in well ventilated spaces. Power cutting tools should be equipped with either a dust suppressant or dust collection system.
When power cutting is not available, pipes may be cut using a hammer or hammer and chisel. Cut ends should be trimmed back about 6mm to virgin material using a coarse rasp. As there is no steel reinforcement to corrode, no further protection of the cut end is required.
Jointing Cut Pipe
James Hardie provide a selection of methods to join cut pipe. Please contact James Hardie FRC Pipes Customer Service for more information.
Bedding Pipes
AS3725 'Loads on Buried Concrete Pipes' defines the types of bedding and the minimum requirements for the soil materials around the pipes and the compaction of these materials. For a typical H2 support type, it is recommended that FRC™ pipes be supported with compact select fill up to a depth of 30% of the diameter. This should be placed and compacted around the haunches of the pipe using suitable tamping bars.
The remainder of the pipe can be surrounded by ordinary compacted fill (if suitable) to 300mm above the pipe crown.
When bedding and backfilling around FRC™ pipes, avoid damaging pipes by excessive impact from heavy compaction equipment. Keep large stones and rocks and other hard objects out of the fill adjacent to the pipe.
Backfill should be placed and compacted in layers, bringing up the haunch and side zones on both sides of the pipe evenly. The difference between the level of material on each side of the pipe should never exceed two compaction layer thicknesses to ensure that the pipes are not eased slightly out of alignment.
Avoid running heavy construction equipment over the pipes until a sufficient cushion of material has been placed.
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