ram assemblies 13 14 with the mould end portions 15 17 at a predetermined position the piston and cylinder assemblies 21 22 and the hydraulic jacks 31 are operated to lower the central mould portion 12 from its first predetermined position see fig2 to its second predetermined position see fig3 such that it is co axial with the mould end portions 15 17 the extent of the movement is determined by the lowered position of jacks 31 against which the central mould portion 12 comes to rest when the central mould portion 12 is stationary in its second position the ram assemblies 13 14 are again actuated to close and locate the mould end portions 15 17 in the central mould portion 12 in this position the blank 28 is supported at both its ends by the mould ends 15 17 the end portions 15 17 continue to be urged against the central mould portion to provide sealing of the mould during the subsequent operation the ends of the blank 28 are held to the mandrel by gripping means hot water is now pumped into the mould through passages not shown in the mould end portions and the pvc pipe blank is allowed to heat up to the water temperature around 90 u00b0 c the blank 28 is then expanded radially by means of fluid pressure exerted from within the blank 28 thereby urging the blank 28 into engagement with the inner surfaces of both the central mould portion 12 and the mould end portions 15 17 following expansion the pipe length is cooled by cold water passed through the pipe and the expanded pipe with its socket portion is now ready for removal from the mould.