O-ring is the most widely used of all sealing products, the production process is relatively simple, and many materials are used. O-ring is a typical sealing effect produced by extrusion and deformation. When installing, it produces contact pressure with the sealing surface. When the pressure is greater than the pressure of the sealing medium, the sealing effect is generated, and when it is less than the pressure of the sealing medium, leakage occurs.
It has been found in many tests that most of the damage to the O-ring is not due to the design or pressure of the O-ring. If a good design only increases the pressure unilaterally, it will not cause the O-ring. The fundamental reason for the damage of the sealing ring is the permanent deformation of the O-ring sealing ring under the high temperature and high pressure of the working environment and the bite caused by being squeezed into the gap.
The reasons for the permanent deformation of the O-ring seal are as follows:
(1) Factors of o-ring compression and tension
Due to the different formulations of O-ring sealants, the compression and tension of O-rings produced by different companies are also different. In the long-term compression state, the product will produce the imagination of compressive stress relaxation. This phenomenon will gradually expand with time. The longer the time is, the smaller the amount of compression and tension will be, resulting in insufficient elasticity and leakage. The most direct way to change is to increase the cross-sectional size of the product, but it will also lead to an increase in the structure of the product.
(2) The relationship between temperature and O-ring relaxation process
Temperature is very important for the relaxation of O-ring. No matter what kind of rubber material, it will accelerate its aging speed at high temperature. When the temperature in the environment is higher, the deformation of air compression will be greater. When the product is deformed When it exceeds 40%, the O-ring will slowly lose its elasticity, causing leakage. When the O-ring is installed, there will be initial stress, which will gradually disappear due to the long-term relaxation of the sealing ring and the gradual decrease in temperature, and in some cases may disappear with the sharp drop in temperature , even if the rubber material is resistant to low temperature, compared with the stress generated at 20 degrees, it will not be greater than 25%, so when installing the o-ring seal, set the initial stress, and fully consider the temperature in the working environment. .
(3) Influence of medium working pressure on deformation of O-ring seal
Compared with the above two factors, the pressure of the medium has a greater influence on the deformation of the O-ring seal, which is the most common situation that causes the deformation of the O-ring seal in all working conditions. With the development of modern hydraulic equipment, The pressure of the hydraulic medium is getting bigger and bigger, and the O-rings work in this high-pressure environment for a long time, which will lead to permanent deformation of the O-rings. This deformation is irreversible, so for different working pressures. Choose different materials and choose a relatively pressure-resistant rubber material. Correspondingly, in order to cope with higher working pressure, the hardness of the sealing ring of the pressure-resistant material will also increase with the increase.
The pressure of the working medium is the main factor causing the permanent deformation of the O-ring. The working pressure of modern hydraulic equipment is increasing day by day. Prolonged high pressure can cause permanent deformation of the O-ring. Therefore, the appropriate pressure-resistant rubber material should be selected according to the working pressure in the design. The higher the working pressure, the higher the hardness and high pressure resistance of the materials used should be.
Therefore, before selecting materials, we must clearly understand what kind of working environment the rubber O-ring is placed by the customer, so that we comprehensively consider the wear resistance, high pressure resistance and other factors of the required materials, to give customers the glue materials, and customize products suitable for customers.