The fitting consists of two components, a coated mild steel outer shell with coaxial internal copper sleeve, brazed around the circumference at each end and a steel insert. Polymeric electrostatic powder coating provides corrosion protection. The insert fits into the bore of the adjoining pipes and the outer shell covers this union.
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Preparation is minimal with the operator only being required to ensure that the pipe ends have been cut reasonably square, any large burrs removed and that the outer shell is located centrally over the joint.
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Biodegradable oil from a specially designed hand pump is introduced under pressure through a nipple on the shell filling the void between steel and copper. The copper increasingly deforms with increasing hydraulic pressure and in turn provides annular compression to the external wall of the pipe forcing the polymer into the slots machined in the insert. The insert now acts as a mould. Although there are large stress concentrations in the wall of the pipe over time or at elevated temperatures, these will relax out and the pipe will permanently take up the profile of the insert as in a cold moulding process. The properties of the copper have also changed. The deformation work hardens the copper ensuring a permanent joint after the pressure has been released.
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The width and depth of the slots machined on the insert together with the distance between them are very important. The slots provide two functions. Firstly they penetrate the thermoplastic pipe to a minimum set depth in order to carry the axial loads after the joint has been made. Secondly, they ensure that buckling under the large hoop stress does not take place when the joint is being made
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Very little preparation is necessary with this jointing system significantly reducing many of the potential sources of failure. There are no requirements for scraping, degreasing, accurate cutting of pipe ends or protection from weather conditions. Pipes can be joined when wet or even submerged. In addition there are no bolts eliminating the possibility of incorrect torque settings being used.