Fitting and pipe joint using the fitting

A joint between two steel pipes arranged end to end, each of said pipes containing a thermoplastic liner, the two liners being shaped at their opposing ends so as to afford a recess which accommodates an electrofusion fitting, the opposed ends of the steel pipes being joined by an arc-welded joint, said electrofusion fitting comprising an open-ended tubular body having an outside surface, an inside surface and, end regions at axially opposed ends thereof, the outside surface of each of said end regions of said thermoplastic body being adjacent to a heating coil, said coil in one of said end regions being connected in series to said coil in the other of said end regions, and the outside surface of the body having a central, annular recess containing insulating material, said outside surface of each of said regions making an angle of less than 10.degree. with the longitudinal axis of the thermoplastic body, said, outside surface of each of said end regions including first and second annular zones between which zones lies a respective one of said heating coils, said zones not being melted when said respective heating coil is energized, and said thermoplastic body containing a hollow cylindrical support body which extends parallel to said axis adjacent the inside surface of said thermoplastic body at a location opposite to the locations of the heating coils and all of said zones.

A method of making an electrofusion fitting, said fitting comprising an open-ended tubular body having an outside surface, an inside surface, the outside surface, and end regions at axially opposed ends thereof, of each of said end regions of said thermoplastic body being adjacent to a heating coil, said coil in one of said end regions being connected in series to said coil in the other of said end regions, and the outside surface of the body having a central, annular recess containing insulating material, said outside surface of each of said end regions making an angle of less than 10.degree. with the longitudinal axis of the thermoplastic body, said outside surface of each of said end regions including first and second annular zones between which zones lies a respective one of said heating coils, said zones not being melted when said respective heating coil is energized, and said thermoplastic body containing a hollow cylindrical support body which extends parallel to said axis adjacent the inside surface of said thermoplastic body adjacent a location opposite to the locations of the heating coils and all of said zones;

• the method comprising:
• (a) arranging the support body within the thermoplastic body;
• (b) machining the outside surface of the thermoplastic body to form the central, annular recess;
• (c) machining the outside end surfaces of the thermoplastic body so that a machined outside surface of each of said end regions makes an angle of less than 10.degree. with the longitudinal axis of the fitting;
• (d) winding wire to form said coils each of the coils being wound on one of said machined outside end region surfaces, the windings of each coil being placed in a recess or groove in a respective machined outside end region surface, and winding the wire while it is hot onto said respective machined outside end region surface;
• (e) connecting said coils in series;
• (f) connecting said coils to leads which are formed of wire compatible with the material which is to form the welded joint between the ends of the steel pipes;
• (g) positioning the leads so that they protrude from the fitting at two points spaced apart on a diameter midway between the ends of the fitting;
• (h) fitting insulating sleeves to the leads;
• and
• (i) positioning a body of insulating material in said central, annular recess of said body.

A method of making an electrofusion fitting, said fitting comprising an open-ended tubular body having an outside surface, an inside surface, and end regions at axially opposed ends thereof, the outside surface of each of said end regions of said thermoplastic body being adjacent to a heating coil, said coil in one of said end regions being connected in series to said coil in the other of said end regions, and the outside surface of the body having a central, annular recess containing insulating material, said outside surface of each of said end regions making an angle of less than 10.degree. with the longitudinal axis of the thermoplastic body, said outside surface of each of said end regions including first and second annular zones between which zones lies a respective one of said heating coils, said zones not being melted when said respective heating coil is energized, and said thermoplastic body containing a hollow cylindrical support body which extends parallel to said axis adjacent the inside surface of said thermoplastic body adjacent a location opposite to the locations of the heating coils and all of said zones;

• the method comprising:
• (a) arranging the support body within the thermoplastic body;
• (b) machining the outside surface of the thermoplastic body to form the central, annular recess;
• (c) machining the outside end surfaces of the thermoplastic body so that a machined outside surface of each of said end regions makes an angle of less than 10.degree. with the longitudinal axis of the fitting;
• (d) winding wire to form said coils, each of the coils being wound on one of said machined outside end region surfaces, the windings of each coil being placed in a recess or groove in a respective machined outside end region surface, and winding the wire while it is hot onto said respective machined outside end surface;
• (e) connecting said coils in series;
• (f) positioning a tapped electrical connector on said body for each coil,
• (g) connecting each of the coils to its respective tapped electrical connector;
• and
• (h) positioning said insulating material in said central, annular recess of said body.

A method of making a joint between two steel pipes arranged end to end each containing a thermoplastic liner, the two liners being shaped at their opposing ends so as to afford a recess which accommodates an electrofusion fitting, the method comprising:

• providing an electrofusion fitting comprising an open-ended tubular thermoplastic body having an outside surface, an inside surface, and end regions at axially opposed ends thereof, the outside surface of each of said end regions of said thermoplastic body being adjacent to a heating coil, said coil in one of said end regions being connected in series to said coil in the other of said end regions, and the outside surface of the body having a central, annular recess containing insulating material, said outside surface of each of said end regions making an angle of less than 10.degree. with the longitudinal axis of the thermoplastic body, said outside surface of each of said end regions including first and second annular zones between which zones lies a respective one of said heating coils, said zones not being melted when said respective heating coil is energized, and said thermoplastic body containing a hollow cylindrical support body which extends parallel to said axis adjacent the inside surface of said thermoplastic body at a location opposite to the locations of the heating coils and all of said zones;
• positioning the electrofusion fitting in the recesses afforded by the liners;
• connecting an electrical supply to said heating coil to weld the fitting to the linings;
• and
• joining the ends of the steel pipes by arc welding to produce a welded joint between the steel pipes.