Study On Structural Strength And Sealing Performance Of Rectangular Middle Flange Of Gate Valve

Bolted flange connection structure is a detachable connection form which is widely used in petrochemical and engineering machinery industries.With the diversification of industry process design and manufacturing requirements,flanges with noncircular sections are also widely used in engineering practice,such as the rectangular middle flange gate valves.Since the current design specifications for non-circular section flanges are immature.,the structural strength design of non-circular section flanges has important research value.In this paper,the rectangular flange of the gate valve is taken as the research object,the structure conversion of the equivalent round flange is carried out,combined with the finite element numerical simulation,the structural strength and sealing performance of the rectangular flange of the gate valve are studied.The main content and methods are as follows:(1)The geometric structure conversion of the rectangular flange of the gate valve was carried out,and the following four schemes were selected: The first scheme is to select the equivalent circular gasket by the gasket pressing area;the second scheme,the equivalent circular flange is selected based on the average perimeter of the gasket;the third scheme is to use the long axis plus the short axis length of the rectangular flange of the gate valve as the equivalent circle diameter;the fourth scheme is based on the standard " Steel Chemical Container Strength Calculation Regulations"(HG/T 20582-2011 The equivalent coefficient provided in)to find the diameter of the equivalent round flange.And calculated the bolt pre-tightening force under the pre-tightening conditions and operating conditions of each scheme,which provides a basis for the subsequent finite element simulation of load application.(2)The three-dimensional finite model of the rectangular middle flange of the gate valve was established,and the appropriate stress intensity evaluation and sealing performance evaluation methods were selected.(3)Apply the bolt pre-tightening force calculated from the four schemes to the gate valve rectangular flange model,perform finite element simulation of the rectangular flange under pre-tightening conditions,analyze the stress and strain distribution of each element,and evaluate the stress intensity.Through analysis,the third scheme is the one with the best sealing performance under the condition of meeting the strength requirements.(4)Perform finite element simulation of operating conditions under different medium pressures for Scheme 3,and observe the influence of medium pressure on the stress and strain distribution of rectangular flanges and the sealing performance.At the same time,the flange strength and rigidity check under the operating conditions,and the gasket sealing ability evaluation,the results show that this scheme can meet the strength and sealing requirements under the operating conditions.(5)Conduct thermal-structure coupled field analysis to simulate the stress and strain distribution and sealing performance of Scheme 3 under different temperature conditions.The results show that the scheme meets the requirements of strength and sealing performance under high temperature conditions.It is concluded that the third option can meet the requirements of pre-tightening and the strength and sealing performance under various working conditions,and the settlement is simple.For gate valve rectangular flanges,this method can be used for structural strength design and sealing performance calculations.