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Introduction to the rubber O-ring specification material "point devouring" phenomenon


Time:

2022-03-11

Since rubber is substantially incompressible, the volume of the o-ring seal is less than the volume of the groove preventing the seal, otherwise the excess rubber would be squeezed out within the gap between adjacent metal components. For a typical seal in hydraulic machinery applications, the groove is generally filled with 65%-70% of the space by the seal specification. However, experiments have shown that o-ring seals work better in high-pressure gas applications, with more grooves filled and a higher degree of extrusion.

I. What is the "extrusion" effect? What are the problems caused by the lack of extrusion and groove filling process?

Insufficient extrusion and groove filling of the seal structure can produce explosive decompression damage, which means that the frequency of explosive decompression increases, while excessive extrusion and groove filling can also make the operating temperature higher and the o-ring intended for rubber expansion when exposed to certain media.

Anti-extrusion seals, as mentioned earlier, the rubber seal material properties are generally similar to the very viscous fluid, in the role of operating pressure, the rubber seal material will be squeezed into the low pressure side of the shell gap, this effect is called "extrusion".

Second, what is the "point devouring"? Does the operating pressure affect the damage of the sealing material of the rubber seal?

In applications where the pressure is relatively gradual, the rubber will recover and will not cause any damage to the surface. However, with rapidly changing pressure cycles, the rubber extrusion does not have sufficient time to recover before the gap closes and is extruded into the groove. Each subsequent pressure cycle will result in more extrusion of the rubber seal material, causing the seal to fail. This process, however, is called "point erosion".

In dynamic applications where gaps are more common, although seal extrusion is inevitable between adjacent metal sealing elements, the extruded gaps formed by the assembly of ambulances are just as likely to occur in static flange type seal applications.