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Do you know the design and use of O-rings

Update:05-01-2022
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Do you know the design and use of O-rings? Twist damage […]

Do you know the design and use of O-rings?

Twist damage

There are many reasons for twisting damage, the most important of which is the uneven clearance of the piston, piston rod and cylinder, excessive eccentricity, uneven cross-sectional diameter of the O-ring, etc., due to the friction that the O-ring receives more than one week. The force is not uniform, and some parts of the O-ring are too frictional and twisted. Generally, O-rings with small cross-sectional dimensions are prone to uneven friction. Distortion (this reason is that the cross-sectional diameter of the O-ring for movement is larger than that for the fixed O-ring.) In addition, due to the concentricity deviation of the sealing groove, the sealing height is not equal, and the cross-sectional diameter of the O-ring is uneven. , May make a part of the O-ring too compressed, the other part is too small or not compressed. When the groove is eccentric, that is, the coaxial deviation is greater than the compression of the O-ring, the seal will completely fail. Another disadvantage of the large deviation of the concentricity of the sealing groove is that the O-ring is compressed unevenly along the circumference. In addition, due to the uneven cross-sectional diameter of the O-ring, material hardness, lubricating oil film thickness and other factors, as well as the surface roughness of the seal shaft, one part of the O-ring slides along the surface of the workpiece, while the other part rolls. Distortion of O-rings. Movement makes the ring easily damaged due to twisting, which is an important reason for damage and leakage of the sealing device. Therefore, improving the processing precision of the sealing groove and reducing the eccentricity are important factors to ensure the reliable sealing and life of the O-ring. The sealing ring should not be installed in a twisted state. If it is twisted during installation, the twisting damage will happen quickly. During work, the twisting phenomenon will cut off the O-rings, resulting in a large amount of oil leakage, and the cut off O-rings will be mixed with other parts of the hydraulic system, causing major accidents.

In order to prevent the O-ring from twisting and damage, the following points should be paid attention to when designing

1) The concentricity of the O-ring installation groove should be considered from the two aspects of ease of processing and no distortion.
2) The cross-sectional dimension of the O-ring should be uniform, and the sealing part should be fully coated with lubricating oil or grease every time it is installed. Sometimes a felt ring type lubricating device impregnated with lubricating oil can also be used.
3) Increase the cross-sectional diameter of the O-ring. Generally, the cross-sectional diameter of the O-ring for dynamic sealing should 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) O-ring seals are made of materials with low friction coefficient.
7) The O-ring can be replaced by a sealing ring that is not prone to distortion.

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