There are circumstances where the application of electrofusion or butt-welding of Polyethylene is simply not possible due to emergency repair situations, environmental conditions, location or the inability to provide a dry & clean environment to conduct welding in.
In these circumstances mechanical connectors can be utilised. A wide range of mechanical products for Polyethylene pipe are available, these include;
- Connections between pipes – such as inserting a replacement pipe section
- Providing a flanged end to attach equipment such as valves & pumps
- Connections to provide off takes for air valves or angled intakes
- Repair clamps to repair & support damaged pipe.
In accordance with WIS 4-24-01 there are several types of mechanical restraint joints for PE, each carries a different designation depending on its ability to maintain transfer of lineal forces along the pipeline
- Type 1 fittings: where the end-load resistance of the joint is greater than the longitudinal strength of the pipe. Meaning that in tension, the pipe will always fail before the joint, regardless of the pipes operating condition – equivalent of a welded joint.
- Type 2 fittings: where the end-load resistance of the joint is greater than the maximum axial forces assumed to be acting on the joint (see IGN 4-01-02). Meaning the joint will provide restraint to the operating pressure under normal conditions.
- Type 3 fittings: where the end-load resistance of the joint is less than that required for Type 2 fittings. Meaning all other joints typically rubber ring socketed joints, which do not provide any restraint.
If restraint is not available within the fitting itself, external restraint flanges anchoring each side of the unrestrained joint can provide equivalent restraint.