Patent ID: 7469721
Filing Date: 2008-12-30
Classification: E21B,F16L

Abstract:
1. A thread protector for protecting a threaded end portion of a metal pipe comprising: a body having threads for threaded engagement with threads formed on a threaded end portion of a pipe; and a valve-type elastically flexible annular sealing projection with opposing faces, each opposing face radially extending from the body such that the sealing projection elastically flexes when one of the opposing faces is line contacted by an end surface of the pipe when the threads of the protector are engaged with the threads of the pipe, wherein a minimum height of the valve-type elastically flexible annular sealing projection in a radial direction of the pipe necessary for the sealing projection to remain in contact with the pipe when loosening of the thread protector occurs is H, and H is defined as follows: H=(N×TL×cos β)/[sin β-sin(20°-α)], wherein N is the maximum number of loosening turns of the thread protector from a position of maximum tightening on the pipe, TL is the thread lead of the pipe, β is an angle of a sealing surface of the sealing projection with respect to the radial direction of the thread protector prior to tightening on the pipe, and α is a slope with respect to the radial direction of the surface of the pipe which the sealing projection contacts.