Leakage phenomenon and selection principle of sealing gasket

The function of the sealing gasket is produced by the blocking effect on the internal medium formed by the contact pressure of the sealing material on the joint surface and the elastic restoring force to the external tightening force. There are four types of leakage phenomenon in general gaskets: leakage at the interface of the sealing ring, leakage leakage, diffusion leakage, and damage leakage. Interface leakage: The interface will leak at the sealing interface due to insufficient gasket compression, improper flange joint surface finish, and flange deformation. For interfacial leakage, use soft gasket to clamp in flange face to prevent. Penetration and leakage: Since most of the soft materials are made of fibers, the sealing ring is easily corroded by the medium, especially the pressure. Due to capillary phenomenon, the medium will permeate to the low pressure side, forming permeation. Diffusion leakage: Driven by the concentration difference, the medium leaks through the material transfer generated by the sealing gap or the capillary of the sealing material. Diffusion is the result of molecular motion and is not unidirectional. When the sealing pressure difference is extremely small or in a vacuum state, or when sealing permeable substances such as nitrogen and sealing hydrogen, as well as highly toxic and radioactive substances, special attention should be paid to the leakage and diffusion. Destruction and leakage: The working conditions at the sealing part are relatively bad, the thermal deformation is large, it is often subjected to vibration and impact, improper installation, excessive tightening force, repeated use, compression deformation, internal stress concentration, damage beyond the fatigue strength, material aging , deterioration, etc. will cause damage and leakage. This kind of leakage has the greatest impact and great harm, so it is necessary to strengthen prevention. So what aspects should be paid attention to when choosing sealing gaskets? The selection principle of sealing gaskets: according to the working pressure of the sealing gasket, the working temperature, the corrosiveness of the sealing medium and the form of the sealing surface. Generally speaking, at normal temperature and low pressure, non-metallic soft gaskets are used; when medium pressure and high temperature are used, metal and non-metallic composite gaskets or metal gaskets are used; when there are large fluctuations in temperature and pressure, flexible or Self-tightening gaskets; in low temperature, corrosive media or vacuum conditions, gaskets with special properties should be considered. Different flange forms require different gaskets. Smooth-faced flanges are generally only used for low pressure, with soft thin gaskets; under high pressure, if the strength of the flange is sufficient, smooth-faced flanges can also be used, but thick soft gaskets should be used, or inner belt reinforcement should be used. Wound gasket for ring or reinforcement ring. In this case, metal gaskets are also not suitable, because the required pressing force is too large, resulting in large deformation of the bolts, making the flange difficult to seal. If a metal gasket is to be used, the smooth surface should be reduced to reduce the contact area with the gasket. In this way, under the condition of the same bolt tension, the compressive stress of the reduced narrow smooth surface will increase. Company website: https://www.orksealing.com/