First, Germany imported rubber O-ring, anti deformation causes the permanent deformation of the small o ring
Design and improper use will accelerate damage, resulting in the loss of sealing efficiency. Under high pressure and high temperature working conditions, the main cause of damage is the permanent deformation and the O type ring being squeezed into the sealing gap caused by gap bite and distortion phenomenon during the movement.       
Due to the use of synthetic rubber material is viscoelastic material, so the initial setting of the amount of compaction and rebound blocking capacity after a long time use, will produce permanent deformation and gradually lose function, eventually leakage. Permanent deformation and loss of elasticity are the main reasons for the loss of sealing performance. The following are the main causes of permanent deformation.
A) the relationship between compression ratio and tensile elongation and permanent deformation of the O-ring is imported from Germany
The rubber of various formulations used in small size O rings can produce compressive stress relaxation in compression state, and the compressive stress decreases with the increase of time. The longer the use time, the greater the compression ratio and the amount of tension, the greater the stress drop caused by the stress relaxation of the rubber, resulting in insufficient elasticity and loss of sealing capacity. Therefore, the compression ratio should be reduced as much as possible.
B) the relationship between temperature and permanent deformation
The use of temperature is another important factor affecting permanent deformation. High temperature accelerates the aging of rubber materials. The higher the working temperature, the greater the compression permanent deformation. When the permanent deformation is greater than 40%, the O ring loses its sealing capacity and leaks.
Working pressure and permanent deformation of C medium
The pressure of working medium is the main factor to cause permanent deformation. The working pressure of modern hydraulic equipment is increasing day by day. Long duration of high pressure will cause permanent deformation. Therefore, proper pressure resistant rubber materials should be chosen according to the working pressure. The higher the working pressure, the higher the hardness and the high pressure resistance of the material. Typically, the default import NBR rubber O-rings hardness is 70 degrees, if the pressure can choose 80 or 90 degrees.
Two, Germany imported rubber O-ring seal design, anti deformation groove depth small O-ring
The depth of the groove depends mainly on the required compression ratio. The depth of the groove and the clearance must be at least smaller than the cross section diameter in the free state, so as to ensure the amount of compression deformation required for sealing. Compression deformation by compression deformation at the inner diameter and outer diameter 8 'compressive deformation of the Delta', namely delta delta delta = '+''. When the Delta '= Delta', the center of the cross section coincides with the cross section center of the groove, and the circumference of the two center circle is equal, indicating that the O type ring is not stretched when it is installed. If the Delta '> Delta', then the circumference of the center circle of the section is smaller than the circumference of the center circle of the groove, which shows that the tension state is installed in the groove