O-ring compression rate calculation method
The compression ratio W is generally expressed by the following formula:
W=(d0-h)/d0×100%
The cross-sectional diameter (mm) of the d0-----o-ring in the random case;
h------o-ring groove bottom and the surface of the sealed surface (deep groove), that is, the cross-sectional aspect ratio (mm) after the o-ring is reduced
When choosing the compression ratio of the O-ring, it is necessary to consider from the given 3 level:
1. Have sufficient sealing to touch the total area;
2. The sliding friction is as small as possible;
3. Minimize permanent deformation.
It is not difficult to find out from the left and right elements that they have differences with each other. Large compression pressures result in large contact pressures, but excessive compression rates undoubtedly increase sliding friction and permanent shape. If the compression ratio is too small, the parallelism deviation of the sealing groove and the O-ring deviation will not meet the requirements, and a part of the reduction amount will be eliminated to cause leakage. Therefore, when selecting the compression ratio of the O-ring, it is necessary to measure the elements of each level. Generally, the packing sealing compression ratio exceeds the dynamic sealing property, but its extreme value should be less than 25%. Otherwise, the reduction of the ground stress is significantly relaxed, which will cause excessive permanent deformation, especially in high temperature load.
The selection of the compression ratio W of the o-ring should take into account the application standard, packing sealing or dynamic sealing; the packing sealing can be divided into axial sealing and radial sealing; axial sealing (or cylindrical packing sealing) The leakage gap is an axial gap, and the leakage gap of the radial seal (or plan packing seal) is a radial gap. The radial sealing property is based on the nominal diameter or the diameter of the O-ring in accordance with the working pressure. The gas pressure is also affected by the gas pressure and the pressure. The pressure is reduced by the pressure of the O-ring. The packing of the different ways is sealed, and the sealing material has different orientations for the O-ring, so the pre-working pressure design is different. For the dynamic sealing, it is necessary to distinguish between repeated motion sealing or rotary fitness sealing.
1. Packing seal: The cylindrical packing sealing equipment is the same as the repeated moving sealing equipment, usually taking W=10%~15%; the plan packing sealing equipment takes W=15%~30%.
2. For dynamic sealing, it can be divided into several situations; repeated movement usually takes W=10%~15%. Rotating fitness sealability When selecting the compression ratio, it is necessary to consider the Joule thermoelectric effect. Under normal circumstances, the nominal diameter of the O-ring for rotary fitness is 3%-5% larger than the shaft diameter, and the compression ratio of the diameter is W=3%. -8%. Low-friction fitness o-rings are used to reduce friction. Usually, a small compression ratio is selected, that is, W=5%-8%. In addition, the elastomeric material caused by the substance and temperature should be fully considered. rise. In general, in addition to the reduced deformation given, the maximum water content allowed is 15%. Exceeding this category indicates that the raw material is used in a problem, and should be changed to an O-ring of another raw material, or the reduction of the given deformation rate can be given.
