A brief discussion on the "biting" phenomenon of rubber O-ring sealing ring specifications and materials

Since rubber is essentially incompressible, the volume of the O-ring is smaller than the volume of the groove that prevents the seal, otherwise, excess rubber would be squeezed out of the gaps between adjacent metal components. For typical hydraulic mechanical application seals, the space filled in the groove by the seal ring specification is generally 65%-70%. However, experiments have proven that O-rings are more effective in high-pressure gas applications, with more groove filling and a higher degree of extrusion.

1. What is the "extrusion" effect? What problems can arise from deficiencies in the extrusion and trench-filling process?

Insufficient extrusion of the sealing ring structure and insufficient groove filling may cause explosive decompression damage, which means that the frequency of explosive decompression will increase, while excessive extrusion and groove filling will also cause the operating temperature to be higher, The rubber expansion phenomenon occurs when the type seal comes into contact with certain media.

For the anti-extrusion seal, as mentioned before, the performance of the rubber sealing ring material is generally similar to that of a very viscous fluid. Under the action of operating pressure, the rubber sealing material will be squeezed into the gap on the low-pressure side of the housing. This effect It's called "extrusion".

2. What is “snip”? Will working pressure damage the sealing material of the rubber sealing ring?

In applications where the pressure is relatively gradually reduced, the rubber will recover without causing any surface damage. However, during rapidly changing pressure cycles, the rubber extrusion volume does not have sufficient time to recover before the gap is closed, and it will be squeezed out of the groove. Each subsequent pressure cycle will cause more of the rubber sealing ring material to be extruded, causing the sealing ring to lose its sealing effect. However, this process is called "spot eating".

Although seal extrusion is unavoidable between adjacent metal sealing elements in dynamic applications where gaps are more common, extrusion gaps formed by assembly screws can also occur in static flange-type sealing applications.

In the context of rubber sealing, extrusion is a critical factor that needs careful consideration. As mentioned, extrusion occurs when the rubber material is forced into the gap on the low-pressure side of the housing under operating pressure. This is particularly relevant in applications with thick rubber O rings, where the material's elasticity and resistance to deformation play significant roles in maintaining an effective seal. The thicker the O-ring, the more it is subjected to these extrusion forces, which can compromise the integrity of the seal if not properly managed.

One significant issue is the potential for explosive decompression damage. This occurs when the pressure within the system decreases rapidly, causing trapped gas within the rubber material to expand and create internal stress. If the O-ring is not sufficiently extruded or if the groove is not adequately filled, the material may not be able to withstand these forces, advance to cracks, blisters, or even complete failure of the seal. This situation is exacerbated in high-pressure environments, where the risk of such damage is more pronounced.

Conversely, excessive extrusion and overfilling of the groove can also be problematic. When the rubber is excessively squeezed, it may advance to higher operating temperatures due to increased friction and deformation. Additionally, contact with certain media may cause the rubber to expand, further stressing the seal and potentially advancing to leakage. This is particularly important when using materials like neoprene gasket seals, which are designed to offer good resistance to various environmental factors but still require proper installation to avoid premature wear and tear.

Working pressure also plays a crucial role in the overall performance of rubber sealing rings. In dynamic applications where pressure fluctuates rapidly, insufficient recovery time for the rubber can result in "snip" damage, where portions of the material are gradually extruded from the groove and sheared off. Over time, this can severely degrade the sealing capability of the O-ring, necessitating frequent maintenance or replacement. Managing the balance between extrusion, groove filling, and pressure is thus essential to ensure the longevity and effectiveness of seals, whether they involve thick rubber O rings or neoprene gasket seals.