Abstract: A coupling comprises a tubular insert (20), having an external shoulder (22) and external circumferential projections (26) separated by circumferential grooves (28, 30), and a tubular sleeve (14) having a largest internal diameter less than the external diameter of a pipe (10). The sleeve is advanced over the end (12) of the pipe and along the pipe away from the end. The pipe is constricted as the sleeve passes over it and then subsequently recovers to establish an end portion (18) which is unconstricted. The outside diameter of the insert is preferably not greater than the inner diameter of the pipe and the insert is inserted into the end portion of the pipe, the end of the pipe engaging the shoulder. The sleeve is then subjected to relative movement between said sleeve and said end until the end portion is gripped between the projections and the sleeve. The end of the sleeve preferably engages the shoulder (22). The coupling enables the pipe to be connected to other pipework.

Abstract: A pipe of polyethylene is reinforced by two layers of polyethylene tape wound around the pipe in opposite directions under tension. The pipe contains carbon black and the layers are unpigmented and free from fillers and are transparent to infra-red radiation to which the first major surface is exposed. The radiation is in the near infra-red region and has a substantial part of the radiant energy of a wavelength of less than 2.5 micrometers. Very little radiation is absorbed by the layers but a very high absorption occurs in the outer surface of the pipe. This causes the interface between the second major surface of the layer and the first major surface of the pipe and between the second major surface of the layer and the first major surface of the layer to reach temperatures at which fusion welding in the layers welds them together and welds the layer and the pipe together.

Abstract: An electrofusion coupler is slid over one of two thermoplastic pipes, each having a layer or layers of reinforcing fibers between the center of the wall of the pipe and the outside surface of the pipe. The end surfaces are trimmed in a butt fusion machine and the resulting end surfaces are forced against a heater plate. The plate is removed and the end surfaces are forced together. Internal and external beads involving inward and outward flow of material result, the outward flow ensures that there is at the welded joint an inner layer which is free from reinforcement fibers. The external bead is removed and the coupler is slid over the butt fused welded joint and energized to cause it to become fusion welded to the outside of the pipe.