What causes O-ring permanent deformation?

O-ring is one of the most widely used sealing products, the production process is also very simple, and the materials used are also many. The O-ring is a typical sealing effect caused by extrusion bending. Contact stress is generated with the protruding surface during installation. When the pressure is greater than the pressure of the sealing medium, it will produce a sealing effect, and when it is lower, it will leak.

In several commercial tests, it was found that most of the causes of O-ring damage were not caused by the design or pressure of the O-ring. Good design only unilaterally increases the pressure, will not cause damage to the O-ring. The root cause is that the O-ring is permanently deformed under high temperature and pressure in the working environment, and is bitten when squeezed into the gap.

O-ring permanent deformation causes are as follows:

1. Compression and tensile factors of O-ring.

Due to the different formula of the O-ring, the compression and stretching amount of the O-ring produced by different companies are also different. Commodities in the long-term compression state will produce compressive stress relaxation imagination. This situation will gradually expand over time. The longer the time, the smaller the amount of compression and stretching, resulting in insufficient elasticity leading to leakage. The most intuitive way to change is to improve the cross-section size of the product, but it will also lead to an increase in the type of commodity structure.

2, the relationship between temperature and O-ring tensioning process

Temperature is very important for the relaxation of the O-ring. No matter what kind of rubber material, it will accelerate its aging rate at high temperatures. When the ambient temperature is higher, the gas compression deformation is larger. When the product is deformed by more than 40%, the O-ring will gradually lose its elasticity, resulting in leakage.

For example, when the O-ring is installed, there will be initial stresses, which will relax for a long time, and the temperature will gradually drop and slowly fade. Under certain conditions, they may disappear with a sharp drop in humidity. Even if the plastic material is resistant to low temperature, it will not exceed 25% compared with the stress generated at 20 degrees. Therefore, when using O-ring seals, the humidity factor in the working environment should be fully considered.

3, the working pressure of the medium has an effect on the deformation of the O-ring.

Compared with the above two factors, the medium pressure has a greater impact on the deformation of O-ring, which is the most common situation of O-ring deformation under all working conditions. With the development of modern hydraulic equipment, the pressure of hydraulic medium is increasing. O-ring in this high-pressure environment for a long time, will lead to O-ring permanent deformation. This deformation is irreversible. Therefore, different materials and plastic materials against pressure should be selected according to different working pressures.

The medium pressure is an important factor that causes the permanent deformation of O-ring. The working pressure of modern hydraulic machinery is increasing. Long-term pressure can permanently deform the O-ring. Therefore, the design should use moderate compressive plastic materials according to the working pressure. The greater the working pressure, the greater the hardness and high pressure resistance of the material used.

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