Causes Of Main Failure Of Flat Gasket And Preventive Measures

- Sep 25, 2017-

Causes of Main Failure of Flat Gasket and Preventive Measures
Flat Gasket design, improper use will accelerate the Flat Gasket damage, loss of sealing performance. Experiments show that, such as the design of various parts of the sealing device is reasonable, simply to improve the pressure, and will not cause Flat Gasket damage. In high pressure, high temperature working conditions, the Flat Gasket damage is mainly due to the permanent deformation of the Flat Gasket material and the Flat Gasket was squeezed into the gap caused by the gap bite a Flat Gasket in the movement of distorted phenomenon.
Permanent deformation of Flat Gasket material
Since the synthetic rubber material for Flat Gasket is a viscoelastic material, the initial set of compression and rebound clogging capabilities are used for a long time, resulting in permanent deformation and consequent loss. Permanent deformation and spring loss are the main reasons for the loss of sealing performance of Flat Gasket. The following are the main reasons for the permanent deformation of O-ring materials.
1) The relationship between the compression ratio and the amount of elongation and the permanent deformation of the Flat Gasket The rubber of the various formulations used in the Flat Gasket produces a compressive stress relaxation in the compressed state where the compressive stress decreases with time small. The longer the use of time, the greater the compression rate and the amount of elongation, the elastic stress relaxation caused by the greater the stress drop, so that Flat Gasket elasticity, loss of sealing capacity. Therefore, it is advisable to try to reduce the compression rate under permissible use conditions. Increasing the cross-section of the Flat Gasket is the easiest way to reduce the compression ratio, but this will lead to an increase in the size of the structure.
It should be noted that people in the calculation of compression rate, often overlooked Flat Gasket in the assembly by the tensile caused by the reduction of the cross-section height. The change in the cross-sectional area of the Flat Gasket is inversely proportional to the change in its circumference. At the same time, due to the role of tension, Flat Gasket cross-sectional shape will change, it shows the height of the reduction. In addition, under the surface tension, the outer surface of the Flat Gasket becomes more flat, that is, the height of the cross section is slightly reduced. This is also a Flat Gasket compression stress relaxation of a performance.
The degree of deformation of the Flat Gasket section also depends on the hardness of the Flat Gasket material. In the case of the same amount of elongation, the hardness of the Flat Gasket, the cross-section height is also reduced more, from this point of view, should be used in accordance with the conditions of use of low hardness of the material. In the role of liquid pressure and tension, the rubber material of the Flat Gasket will gradually plastic deformation, Flat Gasket cross-section height will be reduced accordingly, so that the final loss of sealing capacity.
2) the relationship between temperature and Flat Gasket relaxation process
The use of temperature is another important factor that affects the permanent deformation of the Flat Gasket. High temperature will accelerate the aging of rubber materials. The higher the operating temperature, the greater the compressive permanent deformation of the Flat Gasket. When the permanent deformation is greater than 40%, the Flat Gasket to lose the sealing capacity and leakage. The initial stress value formed in the rubber material of the Flat Gasket due to compression deformation will gradually decrease as the Flat Gasket's relaxation process and the temperature drop. The Flat Gasket, which is working at zero temperature, may be reduced or completely eliminated due to a sharp decrease in temperature. In the case of -50 ~ -60 ℃, low temperature rubber material will completely lose the initial stress; even low temperature rubber material, the initial stress at this time will not be greater than 20 ℃ when the initial stress of 25%. This is because the initial compression of the Flat Gasket depends on the coefficient of linear expansion. Therefore, when selecting the initial compression amount, it is necessary to ensure that there is sufficient sealing capacity after the stress drop due to the relaxation process and the temperature drop.

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