Seal mechanism and seal failure

The function of the seal is mainly dependent on the deformation and tension of the seal between the two coupling parts,to prevent the leakage of working media and foreign matter such as air, dust and water into the hydraulic components and hydraulic system.The quality of the sealing device directly affects the working advantages of the Hydraulic drive system.Therefore, we must correctly select the form of seal and the shape and type of seal ring, design the structure size and precision of seal device, and select the material of seal ring.When the Assembly uses the seal, must choose the seal according to the use request and the seal working condition, carries on the assembly according to the assembly method so as not to cause the seal to be invalid.Seal failure is mainly due to seal damage caused by oil leakage, and due to improper seal crawling.

The main reason of low pressure leakage is that the initial interference of seals is not enough.This may be the result of a large seal groove or a small radial section size of the seal, in which case the fluid is forced through the seal face before the seal is applied, and too low a temperature can also reduce the interference, this is the seal contraction and loss of elasticity of the seal surface deformation, in addition to the sealing groove on the micro-crack will also cause the low-pressure leak seal.The cause of high-pressure leakage in addition to seal groove and seal the axial gap between the results of insufficient.The main causes of seal damage are fluid contamination, overload and unqualified, and the damage is mainly due to excessive wear and extrusion fracture.

*The causes of crawling due to failure of seals are:

(1)Under the influence of sealing material and oil temperature, the difference between static and dynamic friction coefficient is large;

(2)Metal parts have large sealing Surface roughness;

(3)The lubricating oil film can not be fully formed on the sealing contact surface;

(4)The size of the sealing groove is not right, or because the installation and the direction of operation are not the same center, the sealing parts twist and turn inside the groove, resulting in changes in friction resistance;

(5)Because of poor sealing and into the air or because of increased internal and external leakage are likely to produce crawling.