Study On Seal Characteristic And Makeup Torque Controlling Of Premium Connection

The failure of premium connection is almost caused by improper torque and severe environment during service. Overtonging will make the shoulder or sealing severe plastic deformation and undertonging will result in insufficient contact stress,which caused strength or seal failure. 2D axisymmetric model of premium connection often neglect screw-liter angle, which can not accurately reflect the correspondence between interference fit and torque in the makeup. For the reason, a 3D finite element model is built for VAM premium connection by using Abaqus software in consideration of screw-liter angle influences, which is used for simulation analysis on makeup torque, analysis sealing ability and connection strength on different makeup torques, axial forces, internal pressures and bending loads.Analysis results show that, under different axial tension and 80 MPa internal pressure, if the axial tension is greater than 800 KN, there exist a space in the shoulder, forming a leak path, internal pressure will leak into the path affecting the sealing ability. Under different axial compression and 80 MPa internal pressure, the small end of each ring bear a larger axial load, if the axial compression is greater than 600 KN, the possibility of galling is on the rise. Under bending and axial compression the contact stress of stretched shoulder is zero due to a space, the sealing ability decrease. Established premium connection model loading torque curve is basically matched with makeup torque curve obtained by experiment, makeup process of the premium connection under minimum, optimum and maximum makeup torque is simulated completely by 3D finite element, Circumferential contact stress of sealing and shoulder under the action of torques is larger and more uniform in the distribution, the maximum Mises stress of the thread are far lower than material yield strength.