Why are O-rings permanently deformed?

Why are O-rings permanently deformed?


O-ring is the most widely used in all sealing products, the production process is relatively simple, the application of more materials. The O-ring is a typical sealing effect caused by extrusion deformation, and the installation and sealing surface contact pressure, when the pressure is greater than the pressure of the sealing medium, the sealing effect will occur when the pressure is less than the leakage.


In many tests, it was found that most of the reasons for the damage of the O-ring, not from the O-ring design or pressure, good design if only unilaterally increase the pressure, will not cause damage to the O-ring, the fundamental reason is due to the working environment of high temperature and high pressure under the O-ring permanent deformation and squeezed into the gap caused by bite.


There are several reasons for the permanent deformation of the O-ring:


(1) O-ring compression and tensile factors


Due to the different formulations of O-rings, the compression and stretching amounts of O-rings produced by different companies are also different. The product in the long-term compression state will produce compressive stress relaxation imagination, this phenomenon will gradually expand with time, the longer the time the amount of compression and stretching will be smaller, so that its lack of elasticity leads to leakage phenomenon, the most direct way to change is to increase the cross-section size of the product, but it will also lead to the increase of the product in the structure.


(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 is, it will accelerate its aging speed at high temperature. The higher the temperature in the environment, the greater the deformation of gas compression will be. When the O-ring is installed, there will be initial stress, which will sleep the sealing ring for a long time relaxation and gradual reduction in temperature and slowly disappear, in some cases may disappear with a 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%. Therefore, when installing O-rings, set the initial stress, and fully consider the temperature factor in the working environment.


(3) The influence of medium working pressure on O-ring deformation


Compared with the above two factors, the pressure of the medium has a greater impact on O-ring deformation, which is the most common situation that causes O-ring deformation in all working conditions. With the development of modern hydraulic equipment, the pressure of the hydraulic medium is increasing, and O-ring working in this high-pressure environment for a long time will lead to permanent deformation of the O-ring, which is irreversible. Therefore, different materials should be selected for different working pressures, and relatively pressure-resistant rubber materials should be selected. Accordingly, in response to higher working pressures, the hardness of the sealing ring of pressure-resistant materials will also rise.


The pressure of the working medium is the main factor that causes the permanent deformation of the O-ring. The working pressure of modern hydraulic equipment is increasing day by day. A long time of high pressure will cause permanent deformation of the O-ring. Therefore, the design should choose the appropriate pressure resistant rubber material according to the working pressure. The higher the working pressure, the higher the hardness and high pressure resistance of the material used.


Therefore, before selecting materials, we must clearly understand what kind of working environment the customer puts the rubber O-ring in, so that we comprehensively consider the wear resistance, high pressure resistance and other factors of the required materials to provide customers with rubber materials and customize products suitable for customers.


If you have other questions, please visit the eternal seal official website for consultation www.frseals.com


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