There are many causes of distortion damage, the most important of which is due to the piston, piston rod and cylinder tube gap is not uniform, eccentric too large, O-ring section diameter is not uniform, due to the cause of the O-ring in more than a week by the uneven friction, some parts of the O-ring friction is too large, distortion. Usually, the small section size of the O-ring, easy to produce friction uneven. This is the reason for the distortion (the large section diameter of the O-ring used for motion with the O-ring is fixed). In addition, due to the coaxial deviation of the sealing groove, the unequal sealing height and the uneven diameter of the O-Ring section, the part of the O-ring may be compressed too much, and the other part is too small or uncompressed. When the groove is eccentric, that is, the coaxial deviation is greater than the amount of the O-ring compression, the seal will be completely invalidated.