The selection of rubber O-ring compression rate W should consider the use conditions, static sealing or dynamic sealing; Static seal can be divided into axial seal and axial seal; The leakage gap of the axial seal (or cylindrical static seal) is the axial gap, and the leakage gap of the axial seal (or flat static seal) is the axial gap. According to the pressure material acting on the inner diameter or diameter of the O-ring, the axial seal is divided into internal pressure and external pressure two cases. The internal pressure increases the stretch and the external pressure decreases the original stretch of the o-ring
. For the above different static sealing methods, the sealing material affects the O-ring in different directions, so the prepressure design is also different. For dynamic seals, repeat motion seals or rotary motion seals should be distinguished.
1. Static seal: cylindrical static seal equipment and repetitive motion seal device are the same, generally take W=10%~15%; Take plane static sealing equipment; W=15% ~ 30%.
2. For dynamic sealing, it can be divided into three cases; Repetitive motion is usually collected; W=10%~15%. Joule thermal utility must be taken into account when selecting the compression rate. In general, the inner diameter of the O-ring for rotating motion is 3%-5% larger than the shaft diameter, and the compression rate of the diameter W=3%-8%. O-rings are used for low friction motion. In order to reduce the friction resistance, generally choose a smaller compression rate, that is, W=5%-8%, in addition, should also consider the material and temperature caused by plastic material expansion. In general, in addition to the given compression deformation, the maximum allowable expansion rate is 15%. If it exceeds this range, it indicates that the use of the material is inappropriate and should be replaced with O-rings of other materials, or the given compression deformation rate should be adjusted.
After the rubber O-ring is loaded into the sealed pipe, there is generally a certain amount of tension. Like the compression rate, the amount of tension will also have a great impact on the sealing characteristics and service life of the O-ring. A large amount of stretching will not only make the O-ring difficult to install, but also lead to a reduction in compression due to a change in the cross section diameter d0, resulting in leakage.