Calculation Method of Tightening Torque on Threaded Connections

Tightening torque is one of the main factors that affect the connection quality in threaded connections. On the basis of elastic mechanics and by use of the thick-walled-cylindrical theory, an analytical model was established according with the geometric parameters of thread tooth, and then the calculation method of tightening torque on threaded connections was obtained by calculating the frictional torque on each threaded surface. Moreover, the friction coefficient on the contact threaded surface was also measured by experimental test. Taking P-110S threaded connection as a calculating example and comparing the tightening torque obtained by analytical model with the make-up torque in application, the analytical model and calculation method proposed in this paper are reasonable and it offers an accurate method to calculate the make-up torque in threaded connections.