The principle behind heat fusion is to heat two surfaces to a designated temperature, and then fuse them together by application of the required force. This applied force joins the melted surfaces resulting in a permanent, monolithic fusion joint. PolyPipe® fusion procedures require specific tools and equipment for the fusion type and for the sizes of pipe and fittings to be joined.
Butt Fusion – This technique consists of heating the squared ends of two pipes, a pipe and fitting, or two fittings by holding them against a heated plate, removing the plate when the proper melt is obtained, promptly bringing the ends together and allowing the joint to cool while maintaining the appropriate applied force.
Saddle Fusion – This technique involves melting the concave surface of the base of a saddle fitting, while simultaneously melting a matching pattern on the surface of the pipe, bringing the two melted surfaces together and allowing the joint to cool while maintaining the appropriate applied force.
Socket Fusion – This technique involves simultaneously heating the outside surface of a pipe end and the inside surface of a fitting socket, which is sized to be smaller than the smallest outside diameter of the pipe. After the proper melt has been generated at each face to be mated, the two components are joined by inserting the pipe into the fitting. The fusion is formed at the interface resulting from the interference fit. The melts from the two components flow together and fuse as the joint cools.
Properly fused PE joints do not leak. If a leak is detected during pneumatic or hydrostatic testing, it is possible for a system failure to occur. Caution should be exercised in approaching a pressurized pipeline and any attempts to correct the leak should not be made until the system has been depressurized.
Note: PE cannot be joined by solvent bonding or threading. Extrusion welding or hot air welding is not recommended for pressure applications.