The service life of seals is generally divided into long life, medium life and short life. For example, if the life of lip seal ring of rotating shaft is longer than 1000h, it can be called long life; if it starts to leak at 400 ~ 600H, it is called medium life; if it leaks within 100h, it is called short life. The service life of radial lip seal ring is longer than 1000h, medium life is 400 ~ 800H, and short life is less than 100h.

The service life of the rubber seal can reach medium and long life. At this time, the failure of the seal is mainly due to aging of rubber material or wear of seal lip. The failure of seals whose service life is less than 100h is usually due to improper selection of sealing structure, elastomer or shaft surface roughness. The pressure surface of radial lip seal ring is lip like, which makes the lip fully contact with the sealing surface to produce sealing effect. It is widely used in the dynamic sealing of reciprocating hydraulic cylinder. Rotary shaft lip seal ring, also known as oil seal, is mainly used as a low-pressure fluid medium for rotary shaft seals, its role is to prevent media leakage along the shaft and external dust, impurities invasion.

Main factors affecting rubber seal failure

Selection and assembly quality

Improper selection and selection of unqualified seals (such as bad lip, local deformation, hardening, self tightening spring corrosion and unqualified size, etc.) often lead to the phenomenon of replacing one with another. In addition, during assembly, local deformation of the seal caused by forced pressing and the seal surface scratched by the burr at the sharp edges such as spline and thread will cause seal failure. The shape, type and material of sealing ring should be selected reasonably according to the type of seal, the type of working medium, pressure, temperature and the relative velocity between two pairs of sealed parts. Before assembly, carefully check whether the selected seals are out of date, aging, deformation, etc.; at the same time, all sealing surfaces shall be thoroughly cleaned, and the assembly site shall be free from pollution and wind sand; During assembly, special tools should be used to press in to ensure the concentricity between the seal and the shaft. Especially when there are threads, keyways and splines on the shaft, the guide sleeve must be used to install it. It is strictly forbidden to force in or directly knock with a hammer and sharp tool.

Improper selection and contamination of oil

Improper selection of oil is mainly manifested in the compatibility with rubber seals. If the compatibility of the oil used is poor, it will accelerate the rubber deterioration, seal swelling and aging, and produce unsinkable sludge, etc., which will accelerate the wear of seals and cause seal failure. Therefore, we must pay attention to the compatibility with rubber materials when selecting oil

Improper management of seals

The chemical composition of rubber seal determines that the storage and management must meet the requirements. It is found that the unreasonable management of the rubber seal due to its placement, storage and transportation is the main factor causing the early failure of the seal. So we must pay attention to the management of rubber seals.

Other factors

(1) Operating temperature and environmental conditions

The working temperature of the oil in the system and the temperature around the sealing parts are too high, which can easily cause the rubber to soften, expand, harden and crack; in addition, the bad external environment and a lot of dust will cause different degrees of wear and tear on the seal lip.

(2) Dissolved air in the system

If there is air in the system, a large number of bubbles will be generated in the oil. When the bubbles reach the inner pressure surface of the seal, a large amount of energy will be released quickly, which will cause serious damage to the seal lip; In addition, if there is too much oil vapor in the system, and the pressure and temperature reach a certain value, it will cause the oil "spontaneous combustion", causing the seal support ring, anti extrusion ring ablation or melting, local carbonization of rubber seal, etc