THREADED OIL-FIELD PIPE JOINT WITH INCREASED AIR-TIGHTNESS (VARIANTS) AND PRODUCTION METHOD THEREOF (VARIANTS) Russian patent published in 2005 - IPC

FIELD: oil and gas well forming.

SUBSTANCE: joint includes male and female tubular members with conical or cylindrical threads and thrust ends, outer and inner sealing surfaces. Inner surface of female member has conical part made as a chamfer and is terminal thread section. The end is of conical shape and tilts towards outer surface of female member relative vertical plane extending across female member axis. The conical surface mate to that of male member end and has area of transition from complete thread area to inner conical sealing surface having apex on female member axis. Transition part connected to complete thread area is cylindrical and has diameter exceeding that of thread or as a groove with triangular cross-section. One groove wall is terminal thread section. Another embodiment of the joint is also disclosed. Method for forming threaded joint adapted to connect hydraulic pressure tested oil field pipes having union nipple ends involves machining union nipple ends by cutting sealing end, turning outer conical sealing surface and outer tube surface for thread forming; cutting the thread; boring pipe to obtain fixed inner pipe diameter. One pipe end is heated by induction heating device up to t=950-980°C and upsetting tools are heated up to t≈250°C. Before upsetting the tools are lubricated with mixture containing graphite and axle oil taken with ratio of 1:8. Then heated swage and matrix perform combined upsetting of above end from inner and outer pipe surfaces. After the upsetting end plug is inserted in pipe from end to be further processed and upset surfaces are grinded for following machining. The machining process additionally includes turning thrust ledge and outer chamfer. Depression made in the form of groove with diameter less than thread diameter is formed at thrust end of union nipple. Another variant of threaded joint forming method is also disclosed.

EFFECT: increased reliability and air-tightness, improved testability and joint strength during assembling-disassembling and operation thereof.

4 cl, 16 dwg