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Valve
What affects the sealing performance III
2019-11-11
(6) Effect of surface hydrophilicity on sealing property
The hydrophilicity of the surface affects the amount of leakage due to the characteristics of the capillary. When there is a thin film of oil on the sealing surface, it is necessary to increase the pressure of the water passing through the gap. Due to the good hydrophilicity of the metal surface, kerosene can easily penetrate the gap between the casting and the sealing joint. Therefore, in some of the most critical situations, kerosene is tested for sealing hydraulics. The sealing test was carried out by filling the kerosene in the cavity, which is equivalent to the water pressure tightness test under the pressure of 0.3 MPa to 0.4 MPa.
(7) Effect of the presence of sealing oil film on sealing performance
The presence of a sealing oil film between the sealing surfaces has a significant effect on the sealability. When there is a sealing oil film on the surface, the hydrophilicity between the contact surfaces is destroyed, so that a large pressure difference is required to pass the medium through the capillary. In addition, a thick sealing oil film on the surface can block the passage of the medium and improve the sealing of the connection. When using oil film seals, it should be noted that when the oil film is reduced during operation, the thickness of the oil film should be restored. The grease used in the valve is not allowed to dissolve in the medium and should not evaporate, harden or have other chemical reactions.
(8) The influence of the rigidity and structural characteristics of the closure on the sealing performance
The rigidity and structural effects of the closure are due to the elastic nature of the part. Since the closing member of the closed-circuit valve is not absolutely rigid but has a certain elasticity, the size is varied under the pressure associated with the medium, which also causes a change in the interaction of the sealing surface forces. In order to compensate for the effect of these changes on the sealability of the closure member, it is preferred to have a smaller rigidity of the sealing surface, i.e., the elastic deformation is as large as possible.

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