Gaiatsu of the excellent oil well pipe thread fittings

摘要

PROBLEM TO BE SOLVED: To improve external pressure resistance by forming a seal forming surface of a pin tip outer peripheral surface or a box inmost inner peripheral surface as a conical surface, making an effective diameter of a reference position of a pin tip seal forming surface larger than that of the box inmost part, and specifying a factor to decide a shape of the pin tip and the box inmost part. ;SOLUTION: A seal forming surface 13 of a conical surface shape is arranged on an outer peripheral surface on the tip more than a male screw 12 of a pin part 11 of a pipe 10 end part, and a seal forming surface 23 of a conical surface shape whose effective diameter is smaller than an effective diameter of the seal forming surface 13, is arranged on an inner peripheral surface on the inmost side more than a female screw 22 of a box part 21 inside of a coupling 20. A shoulder angle θ, the lip thickness ratio R, a lip length L, a seal length S and a seal taper T are set to [0≤θ≤20°, 0.25≤R≤0.75, 6≤L≤30mm, 3≤S≤10mm, 1/16≤T≤1 and f1.2 (f=-3.26×10^-1+3.19×10^-2×θ+1.43×R-4.67×10^-4×L+8.39×10^-2×S-6.2×10^-1×T)]. By the constitution, external pressure resistant performance of 1.2 times pipe collapse pressure can be satisfied.;COPYRIGHT: (C)1998,JPO