When choosing an O-ring, it is generally necessary to consider the sealing of the O-ring. Common O-ring sealing methods include rotary seal, back-and-forth seal, transverse (shaft) seal, vertical (diameter) seal, dynamic seal and other seals state. For example, when the back and forth seal is under pressure, the section of the O-ring will be deformed by force. At this time, it is appropriate to choose a slightly larger size than the standard size. Generally, there is a principle that the inner diameter of the O-ring should be reserved for the diameter of the groove and the length of the gap in the direction of the force point when the force is deformed and flattened.
If a transverse (shaft) seal is used, an O-ring that is 1%-3% smaller than the diameter of the shaft should be selected, so as to ensure that the O-ring can be tightly connected to the shaft and not easy to fall off. For vertical sealing, choose an O-ring with a larger inner diameter of 1%-3%, so that it is not easy to fall off and be crushed. According to the actual needs to choose the material, do the above points, the principles that need to be followed when choosing an O-ring generally do not have to worry about choosing the wrong O-ring.
In addition to the general requirements for the material of the sealing ring, the O-ring should also pay attention to the following conditions: elasticity and resilience. Stable performance, not easy to swell in the medium, small thermal shrinkage effect (Joule effect). Does not corrode the contact surface, does not pollute the medium, etc. Appropriate mechanical strength, including expansion strength, elongation and tear strength, etc. Easy to process and form, and can maintain precise dimensions. The most suitable and commonly used material to meet the above requirements is rubber, so O-rings are mostly made of rubber materials. There are many varieties of rubber, and new varieties of rubber are constantly emerging. When designing and selecting, you should understand the characteristics of various rubbers and choose them reasonably.