Compression Rate And Extension Of Rubber O-ring
The selection of the compression rate W of the rubber O-ring should consider the conditions of use, static seal or dynamic seal; static seal can be divided into radial seal and axial seal; the leakage gap of radial seal (or cylindrical static seal) is radial The gap, the leakage gap of the axial seal (or flat static seal) is the axial gap. According to the pressure medium acting on the inner diameter or outer diameter of the O-ring, the axial seal can be divided into internal pressure and external pressure. The internal pressure increases and the external pressure decreases the initial tension of the O-ring.
. In the above-mentioned different forms of static seals, the direction of action 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 between reciprocating motion seals and rotary motion seals.
1. Static sealing: the cylindrical static sealing device is the same as the reciprocating sealing device, generally W=10%～15%; the plane static sealing device is W=15%～30%.
2. For dynamic sealing, it can be divided into three situations; reciprocating motion generally takes W=10%～15%. Rotary motion seals must consider the Joule heating effect when selecting the compression ratio. 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 W=3%-8%. O-rings used for low-friction movement generally choose a smaller compression rate, that is, W=5%-8%, in order to reduce frictional resistance. In addition, the expansion of the rubber material caused by the medium and temperature must also be considered. Usually outside the given compression deformation, the maximum allowable expansion rate is 15%. Exceeding this range indicates that the material selection is inappropriate, and O-rings of other materials should be used, or the given compression deformation rate should be corrected.
After the rubber O-ring is installed in the sealing groove, it generally has a certain amount of stretching. Like the compression rate, the amount of stretch has a great impact on the sealing performance and service life of the O-ring. A large amount of stretching will not only make it difficult to install the O-ring, but also reduce the compression rate due to the change in the cross-sectional diameter d0, which will cause leakage.