Patent ID: 8256089

Claim:
A method of covering the inside surface of a steel connection part having an empty inside volume defined by said inside surface, with a liner constituted by a layer of substantially uniform thickness of a thermoplastic material, said connection part having at least two open tubular ends suitable for connecting respectively to at least two steel pipe elements having the same internal liners, the method being characterized in that the following steps are performed: a) closing said open ends of said connection part with covers, at least one of said covers presenting a filler orifice with an isolation valve suitable for enabling granules of said thermoplastic material to be introduced into said inside volume, and preferably also a ventilation or purge orifice with an isolation valve, and all other openings, if any, in said part are plugged; b) introducing said granules of said thermoplastic material into said inside volume through said filler orifice, in an amount that is necessary and sufficient for obtaining a layer of said thermoplastic material over all of said inside surface with a substantially uniform desired thickness; c) heating the walls of said connection part defining said inside volume to a temperature enabling said granules to be melted; d) causing said connection part to turn simultaneously about at least two different axes of rotation for a length of time that is sufficient and at a speed that is sufficiently low to enable said thermoplastic material to melt on said inside surface and to be distributed in substantially uniform manner over all of said inside surface; and e) while maintaining said rotation, cooling said connection part or allowing said connection part to cool prior to removing said covers.