Rubber Rings Manufacturers introduced that when selecting the compression rate of O-rings, the following three aspects should be considered:
1. There must be enough sealing contact area;
2. Friction as small as possible;
3. Try to avoid deformation.
From the above factors, it is not difficult to find that they are contradictory to each other. A large compression ratio can obtain a large contact pressure, but an excessive compression ratio will undoubtedly increase the sliding friction and shape. If the compression ratio is too small, it may cause leakage due to the coaxiality error of the sealing groove and the O-ring error that does not meet the requirements and disappears part of the compression amount. Therefore, when choosing the compression ratio of the O-ring, there are various factors to be weighed. Generally, the compression ratio of static seals is greater than that of dynamic seals, but the extreme value should be less than 25%, otherwise, the compressive stress will be significantly relaxed, resulting in excessive deformation, especially in high-temperature conditions.
The selection of the compression rate W of the O-ring seal should consider the conditions of use, static seal or dynamic seal; static seals can be divided into radial seals and axial seals; the leakage gap of radial seals (or cylindrical static seals) is radial Gap, the leakage gap of axial seal (or plane static seal) is an axial gap. According to the pressure medium acting on the inner diameter or outer diameter of the O-ring, the axial seal is divided into two situations: internal pressure and external pressure. The internal pressure increases and the external pressure reduces the initial stretching of the O-ring. For the above-mentioned different forms of static seal, the action direction of the sealing medium on the O-ring is different, so the pre-pressure design is also different. For dynamic seals, it is necessary to distinguish whether it is a reciprocating seal or a rotary seal.
1. Static seal: The cylindrical static seal is the same as the reciprocating seal, and generally takes W=10% to 15%; the plane static seal takes W=15% to 30%.
2. For dynamic seals, it can be divided into three cases; reciprocating motion generally takes W=10% to 15%. The Joule heating effect must be considered when selecting the compression rate of the rotary motion seal. Generally speaking, the inner diameter of the O-ring for rotary motion is 3%-5% larger than the shaft diameter, and the compression rate of the outer diameter is W=3%-8%. In order to reduce frictional resistance, O-rings for low-friction motion generally choose a smaller compression rate, that is, W=5%-8%. In addition, the expansion of rubber materials caused by medium and temperature must be considered. Usually, outside the given compression deformation, the maximum allowable expansion rate is 15%. Exceeding this range indicates that the material selection is not suitable, and O-rings of other materials should be used, or the given compression deformation rate should be corrected.