BOX PROTECTOR FOR A THREADED JOINT FOR PIPES

摘要

A box protector 21 for protecting the inner surface of a box 11 of a threaded joint for pipes having a female threaded portion and a shoulder surface 14 with the shoulder surface being sloped by an angle theta with respect to the direction perpendicular to the pipe axis has a male threaded portion 22 which threadingly engages with at least a portion of the complete threads of the female threaded portion of the box and a shoulder surface 21b which sealingly contacts the shoulder surface 14 of the box to form a first seal portion, and the shoulder surface 21b is sloped by an angle thetaRho (thetaRho > theta) with respect to the direction perpendicular to the pipe axis. The protector has a circumferential groove 30 in its outer peripheral surface in the vicinity of the shoulder surface 21b and an elastic seal ring 28 which contacts the shoulder surface 14 of the box 11 and forms a second seal portion.