Research On Sealing Performance Of Clamp Type High Pressure Self-tightening Flange

Bolt flange joints are widely used in petrochemical,nuclear energy and other industries.To improve the sealing performance of flange joints under high pressure conditions,clamp type high pressure self-tightening flanges are used,referred to as Karan.This paper studies Karan from three aspects:calculation method,applicable working condition and detection method.According to the design method of flange and clamp parts in ASME ?-3,combined with the self-tightening principle of T-shape gasket,the calculation method of Karan's bolt load and sealing pressure was determined.The sealing pressure and the internal pressure have a linear increasing relationship.The narrower the sealing surface,the larger the sealing surface spacing,the better the self-tightening effect.The larger the axial gap between the flange and the gasket support surface,the narrower the sealing surface,the larger the cross-sectional area of the gasket,the greater pre-tightened sealing pressure.The form of contact between the sealing surface will also affect the self-tightening effect.The self-tightening effect is best when the inclination of the flange cone is slightly larger than the inclination of the gasket.The ANSYS software was used to establish a 2-inch Karan joint model,and the specific pressure of the gasket sealing under different internal pressure conditions was analyzed.The simulated values were consistent with the theoretical calculation results.Based on this,the article studied the influence of internal pressure,temperature,and bending moment on the sealing performance of Karan.The results show that the maximum pressure value of Karan at normal temperature is 70MPa.The increased temperature will increase the sealing pressure at medium pressure,and will reduce the sealing pressure at high pressure.The bending moment increases the sealing pressure on the tension side of the Karan,and the sealing pressure on the pressure side decreases first and then increases.And bending moment makes the stress of the Karan pipeline increase rapidly.Through analysis,it is determined that the dangerous cross section of Karan is mainly located on the inner wall of the pipe and the flange shoulder and neck junction.The paper improves the stress distribution of the dangerous section through the optimized design of the Karan joint.In order to test the sealing performance of the Karan structure,a water pressure test device was built and tested.The results show that the Karan joint has no significant leakage under the internal pressure of 50MPa,and the pressure drop within 15 minutes is less than 5%of the loading pressure,which meets the sealing requirements of the API 6A standard.Under the service conditions of Karan joints,the change of bolt force determines the change of Karan sealing performance.In order to detect the bolt force on Karan,this paper studies the ultrasonic acoustic elasticity measurement method of bolt force at high temperature.This method uses a waveguide bar as the connection medium,which can be used for online detection of bolt force under high temperature conditions.The thesis completed the calibration test of the bolt force within 250?.The results show that the bolt stress has a linear relationship with the ultrasonic time difference.Karan joints are currently mainly used in the connection of high-pressure vessels in the fields of nuclear power and chemical industry,which improves the tightness of high-pressure vessels and provides technical support for the development of petrochemical and nuclear energy industries.However,Karan connectors currently rely on foreign imports,so research on Karan joints is necessary.