Device for protecting threadings and butt-type joint bearing surfaces of metallic tubes

A device for protecting male or female threadings and butt-type annular joint bearings of metallic tubes comprising:

• a metallic tube provided with a joining region at one end thereof, said joining region including screw threadings which terminate in a butt-type joint having a butt-type bearing surface and inside and outside surfaces where said bearing surface and said inside surface meet to form an annular inner edge, a plastic ring provided with screwthreads for engaging said threadings of said metallic tube, said ring further having an annular abutment region provided with a front face which is dimensioned so as to face the butt-type bearing surface of the metallic tube when the ring is tightly screwed onto said tube, said front face having an inner surface which comprises a first annular tight sealing means which cooperates with the butt-type joint bearing surface near said annular inner edge to insure sealing, said front face being further dimensioned such that a closed annular volume is created between the entire butt-type joint bearing surface and said front face.