Heat Fusion is the process in which Polyethylene Pipe materials are aligned, cleaned or trimmed, heated to their melting point, brought together, and allowed to cool to form homogeneous material. At Robert L. Cave Inc. we have the capability of all heat fusion techniques, socket, butt, sidewall, and electro-fusion up to eight inch capacity
For Reliability, all underground piping, especially for geothermal, joints must be thermally fused rather than mechanically coupled. The arguments for this are:
1. Heat fusion jointing results in a joint which is stronger than the pipe itself. The pipe wall at the fusion joint has a larger cross section which gives the joint the added strength.
2. The connection or joint is all polyethylene, eliminating corrosion problems.
3. Industry standards (ASTM, PPI) in their respective written guidelines recommend thermal fusion for proper fusion.
Heat Fusion Methods: The Industry has accepted several heat fusion techniques, methods will depend on the pipe manufacture’s recommendations and the ease with which the trained field personnel can reliably fabricate ground heat exchangers.
Socket Fusion Jointing: In the socket fusion method, two pipe ends are joined by fusing each pipe end to a socket fitting. This method requires two heat fusion procedures for each joint.
Butt Fusion: Is a type of heat fusion joining is the butt fusing procedure where two pipe ends are simultaneously heated to a plastic state by a heater plate and brought together to form the heat-fused joint. A single heat fusion process is required to form the joint between the two polyethylene pipe ends. The butt fusion process is preformed by using specially designed machines which provide for securely holding the two pieces to be fused, aligning them, trimming and squaring their ends, heating the surfaces to be joined with a heater plate, and butting them together while they are in a plastic state which produces a double rollback bead.
Sidewall Butt Fusion Joining: In addition to joining the flat ends of pipe or fittings, we at Robert L. Cave Inc., can also use the butt fusion process to join the concave surface of a service saddle to the convex surface on the sidewall of a pipe. This is done by heating these surfaces with appropriate convex and concaved-shaped heaters and then butting these surfaces together. This is known as sidewall fusing joining.
Electro-Fusion: This type for heat fusion is especially useful when pipes get damaged, usually by some excavation work. The electro-fusion process is preformed by using specially design facing and welding machines, and specially manufactured socket fitting.