How do the seal manufacturers solve the problem when the seal is twisted?

Rubber O-rings are often used in some places that need to be sealed. One of the characteristics of these places is that the gaps are matched, and they are often matched by yin and yang. The O-ring is placed between the two to strengthen the seal between the two. It also acts as a shock absorber. However, many people found that the O-ring was squeezed apart, some were squeezed between the gaps and cracked, and some were gradually twisted and deformed due to use! So how did these phenomena arise? How should we solve it?

1. Gap bite
The sealed parts have poor geometric accuracy (including roundness, ovality, cylindricity, coaxiality, etc.), misalignment between parts, and expansion of the inner diameter under high pressure, which will cause the expansion of the sealing gap and the gap squeeze. intensification of the phenomenon.
In order to prevent the gap bite, the seal factory strictly controls the hardness of the O-ring seal and the seal gap. Select a sealing material with suitable hardness to control the gap. The hardness range of commonly used O-rings is HS60~90. Those with low hardness are used for low pressure, and those with high hardness are used for high pressure. It is an effective method to prevent the O-ring from being squeezed into the gap by using the appropriate sealing ring to protect the retaining ring.
The twisting of the rubber O-ring refers to the phenomenon that the O-ring twists in the circumferential direction, and the twisting phenomenon generally occurs in the dynamic sealing state.
There are many reasons for twisting damage, among which the main ones are due to uneven clearance of piston, piston rod and cylinder barrel, excessive eccentricity, uneven diameter of O-ring section, etc., due to the frictional force that the O-ring is subjected to more than one week Uneven, some parts of the o-ring rub too much and twist. Generally, O-rings with smaller cross-sectional dimensions are prone to uneven friction. Causes distortion (The O-ring for motion is larger than the diameter of the cross-section of the O-ring for fixing.)
In order to prevent the O-ring from being twisted and damaged, the seal factory should pay attention to the following points when designing
1) The concentricity of the installation groove of the O-ring should be considered from two aspects: ease of processing and no distortion.
2) The section size of the O-ring should be uniform, and lubricating oil or grease should be fully applied to the sealing part during each installation. Occasionally, a felt-ring refueling device saturated with lubricating oil can also be used.
3) Increase the cross-sectional diameter of the O-ring. The cross-sectional diameter of the O-ring for dynamic sealing should generally be larger than that for static sealing. In addition, the O-ring should be avoided as a seal for large-diameter pistons.
4) When twisting damage occurs under low pressure, a sealing ring can be used to protect the retaining ring.
5) Reduce the surface roughness of the cylinder barrel and piston rod.
6) Use materials with low friction coefficient to make O-rings.
7) The seal factory can replace the O-ring with a seal ring that is not prone to distortion.