Joint sealing system of flat welding flange
The joint sealing system of flat welding flange is mainly composed of a pair of flanges, a gasket and several bolts and nuts. The sealing process is also a process of deformation and harmony among various components under the working conditions of pre tightening, pressure rise, temperature rise, normal operation, strike and starting from scratch.
The primary planning drawback of flat welding flange is that it cannot guarantee no leakage. This is the lack of planning: the connection is dynamic, and such as thermal expansion and fluctuating periodic load will cause the movement between flange faces, affect the function of the flange, thus damage the integrity of the flange, and eventually lead to leakage. It is impossible for any product to have no defects, just try to control the lack of products as much as possible, so Cangzhou Ruitai pipe fitting manufacturing Co., Ltd. tries to improve the performance of products when producing flat welding flange, so as to make it play a big effect.
Sealing principle of flat welding flange
Two sealing surfaces of bolt knead flange gasket and form sealing, but this also leads to sealing damage. In order to keep the seal, it is necessary to maintain a huge bolt effect force, so the bolt should be made large. The large bolt must match the large nut, which means that the bolt with large diameter is needed to create conditions for tightening the nut. But the larger the bolt diameter, the more tortuous the applicable flange will be by increasing the wall thickness of the flange part. The whole equipment will need huge size and component, which becomes a special problem in the offshore environment, because in this case, the component is always the first problem that people must pay attention to. And, fundamentally, the flat welding flange is an ineffective seal, which requires 50% of the bolt load to knead the gasket, and only 50% of the load to maintain the pressure.
Features of flat welding flange: flat welding flange not only saves space and reduces weight, but also ensures that the joint will not leak and has good sealing performance. The compact flange size is reduced by reducing the seal diameter, which will reduce the seal face section. Secondly, the flange gasket has been replaced by the sealing ring to ensure the matching of the sealing face. In this way, only a small amount of pressure is required to compress the sealing surface. With the decrease of the required pressure, the size and quantity of the bolts can be reduced accordingly, so the final gauge marks a new product with small volume and light weight (70% – 80% less than the traditional flange). Therefore, the flat welding flange is a kind of comparative flange product, which reduces the quality and space, and plays an important role in industrial use.
Analysis of deformation and harmony of sealing system
The flat welding flange joint sealing system is mainly composed of a pair of flanges, a gasket and several bolts and nuts. The sealing process is also a process of deformation and harmony among various components under the working conditions of pre tightening, pressure rise, temperature rise, normal operation, strike and starting from scratch. In this paper, the flange joint system is considered as a whole, considering the flange stress, gasket stress, bolt stress, flange deformation, gasket deformation and bolt deformation under high temperature and high pressure, and the specific load deformation analysis is carried out to establish the flange moment balance equation and deformation harmony equation, and the high temperature creep flange deformation harmony equation.
Analysis of residual stress on gasket surface
It is enough to study the general strength of the national standard flange, but the rigidity of the flange is not infinite. Under the effect of bolt pre tightening force and medium pressure, the flange produces certain warpage deformation, which makes the flange plate deflect. When the deflection angle reaches a certain value, the seal will fail, and leakage will occur. In this paper, the flange of the ring joint is studied, and the gasket is octagonal gasket. Because there are many kinds of nonlinearity in the flange joint, such as structure, contact, material and so on, considering the mutual effect of each component of the joint, the national standard marine flange joint can be analyzed as a system. The finite element ANSYS software is used to study the stress and strain of the flange and the residual stress distribution on the surface of the gasket under the pre tightening and operating conditions, and to qualitatively analyze the relationship between the flange stiffness and the seal.
Rigidity calculation of flange
The high temperature and high pressure of the stainless steel flange of the equipment bring many technical problems to the sealing. With the increase of equipment temperature and medium pressure, the compression force on the gasket will decrease, so the required bolt force will increase, and the bending moment of bolt force to the center will increase, so that the rigidity of the flange will decrease. The increase of bolt moment and the decrease of flange stiffness will lead to flange warping and deflection, and the residual stress on gasket surface will be severely distributed unevenly in radial direction. Through the structural simplification and deformation analysis of the flange, the stiffness calculation method of the equipment flange is obtained, the dispersion rules of the flange stiffness are summarized, and the failure mechanism of the flange seal under high temperature is reminded theoretically.
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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