O-rings exhibit abrasive wear

When there is relative motion in the sealing gap, dust and sand particles from the working environment adhere to the piston rod surface and are carried into the cylinder along with the oil film during the reciprocating motion of the piston rod. These particles become abrasive particles that penetrate the O-ring surface, accelerating O-ring wear and eventually causing it to lose its sealing performance. To avoid this, dust rings must be used at the extended shaft end of reciprocating sealing devices.

The roughness of the sliding surface is a direct factor affecting the friction and wear of the O-ring surface.

Generally speaking, a smooth surface results in less friction and wear, so the roughness value of the sliding surface is often very low (Ra 0.2-0.050 μm). However, tests show that excessively low surface roughness (Ra below 0.050 μm) can also negatively impact friction and wear. This is because minute surface irregularities help maintain a necessary lubricating oil film. Therefore, appropriate surface requirements must be selected. The material of the sliding surface also affects the lifespan of the O-ring. The greater the hardness, wear resistance, and ability to maintain a smooth surface of the sliding surface material, the longer the lifespan of the O-ring. This is also a key reason for chrome plating on the surface of hydraulic cylinder piston rods.

In dynamic sealing devices, friction and wear are significant factors affecting O-ring damage. The degree of wear primarily depends on the magnitude of the frictional force. When the liquid pressure is low, the magnitude of the frictional force on the O-ring depends on its pre-compression.

Increased frictional force generates a large amount of frictional heat between the rotating or reciprocating shaft and the O-ring. Since most O-rings are made of rubber, which has extremely poor thermal conductivity, this frictional heat causes rubber aging, leading to O-ring failure and compromising its sealing performance. Friction also causes surface damage to the O-ring, reducing its compression. Severe friction can quickly cause surface damage to the O-ring, resulting in loss of its sealing properties.