What factors should we consider when choosing an O-ring

The use of each O-ring is not the same, we choose O-ring, to consider its working environment and conditions, sealing requirements, physical properties and so on. Like life, we have to choose clothes for ourselves, which O-rings are suitable for machines, which are suitable for the automotive industry, which are suitable for electronic products, we have to consider the various physical properties of O-rings, so as to meet the real needs of customers. So, when we choose O-rings, what specific factors to consider:


(1) Working medium and working conditions


In the specific selection of O-ring material, we must first consider the compatibility with the working medium. Secondly, the working conditions such as pressure, temperature, continuous working time and operation cycle at the seal are considered comprehensively. If used in rotating situations, the temperature rise due to friction heat should be considered. Different sealing materials have different physical and chemical properties.


(2) Sealing form


According to the type of load can be divided into static seal and dynamic seal; According to the seal use can be divided into hole seal, shaft seal and rotary shaft seal; According to its installation form, it can be divided into radial installation and axial installation. When the shaft is sealed in radial installation, the deviation between the inner diameter of the O-ring and the diameter to be sealed should be as small as possible; For hole seals, the inner diameter should be equal to or slightly less than the diameter of the groove. Axial installation, to consider the direction of pressure. When the internal pressure, the outer diameter of the O-ring should be about 1% to 2% larger than the outer diameter of the groove; When the external pressure is applied, the inner diameter of the O-ring should be about 1% to 3% smaller than the inner diameter of the groove.


(3) Other factors affecting sealing performance


The hardness of the O-ring material is the most important indicator for evaluating the sealing performance. The hardness of the O-ring determines the compression amount of the O-ring and the maximum allowable extrusion clearance of the groove.


The maximum allowable extrusion clearance is related to the system pressure, O-ring section diameter and material hardness. Generally, the higher the working pressure, the smaller the maximum allowable extrusion clearance value. If the clearance exceeds the allowed range, it will lead to the extrusion or even damage of the 0 ring.


Another index to evaluate the sealing performance of the O-ring is the compression permanent intersection of the selected material. Under the action of pressure, the 0-shaped ring as an elastic element produces elastic deformation, and permanent plastic deformation will occur with the increase of pressure. Generally, in order to prevent permanent plastic deformation, the maximum compression allowed by the 0-ring is about 30% in the static seal and about 20% in the dynamic seal.


The O-ring is installed in the groove, in order to ensure its sealing performance, an initial compression should be reserved. For different applications, the amount of precompression relative to the section diameter W is also different. Usually, it is about 15% to 30% in the static seal, and about 9% to 25% in the dynamic seal.


Stretching and compression When the O-ring is installed in the groove, it should be stretched or compressed. If the tensile and compression values are too large, it will cause the O-ring section to increase or decrease excessively, because the tensile 1% correspondingly reduces the section diameter by about 0.5%. For the hole seal, the 0-shaped ring is best in a tensile state, and the maximum allowable tensile amount is 6%; For shaft seals, the O-ring is best compressed along its perimeter, with a maximum allowable perimeter compression of 3%.


When we do not know how to choose the right O-ring, we can consider these working media, working conditions, sealing forms and other factors, which can avoid a lot of detcorners. We Forever Seals will customize the O-ring according to the specific performance requirements of customers, and our Forever Seals has professional engineers to answer the professional questions for customers.


If you have other questions, please visit the Forever Seals official website for consultation www.freseals.com


Chat with us