Abstract Two pipes are joined together by fitting the ends into a thermoplastic sleeve contg. electrical resistances. When the pipes are correctly positioned with their ends abutting an electrical current is passed through the electrical resistances to heat the sleeve and shrink it around the ends of the pipes to join them together with a fluid tight seal. Insulation is provided between the sleeve and tubes. Used for joining pipes when positioned in factories. A continuous layer of insulation extends along the pipes and over the joint. Pref. the electrical resistances are a woven fabric of glass or asbestos fibres which is hot pressed into the inner face of the sleeve. The insulation may be glass fibre, mineral wool or polyurethane foam.