Rubber O-ring seal

Rubber O-ring is a kind of annular seal with a circular cross-section. It has the largest output, the highest degree of standardization and serialization among all sealing products, and the most mature type of sealing products.

In fluid sealing, rubber O-rings can be divided into static seals and dynamic seals according to their working states.

When the rubber O-ring is used for reciprocating sealing, its sealing mechanism is also self-sealing.

But since the rubber O-ring is in motion and fluid pressure is applied alternately from both sides of the O-ring, the process is extremely complicated. Through the experiments of piston rod seals, the mechanism of sealing and leakage of reciprocating O-rings is basically familiar. If the surface of the O-ring and the shaft is enlarged, the surface will be uneven, especially the contact surface of the rubber O-ring is in contact with the shaft by its protrusion. When the shaft starts to move to the right, the liquid pressure in this part will be greater than the working fluid pressure because the shaft will bring the liquid adhered to it into the wedge-shaped narrow area between the O-ring and the shaft. If this pressure is greater than the contact pressure of the O-ring, the rubber O-ring will be lifted up, and the liquid will invade into the recess, causing leakage. When the shaft moves in the opposite direction, because the movement direction of the shaft is opposite to the pressure direction, the leakage along the movement direction of the shaft is reduced, and the difference between the two forms the leakage to the outside during the reciprocating motion. Generally speaking, the greater the viscosity of the liquid and the greater the shaft speed, the greater the sliding effect and the greater the leakage.

The rubber O-ring is placed in the sealing groove, and one or both sides are the fluid medium required to be sealed. Whether by the mechanical pressure of the surrounding mechanical structure or by the pressure transmitted by the hydraulic fluid, the elastic body compensates for the gap by deformation (elastic or inelastic), forming a "zero gap", or preventing it from being sealed by it. fluid flow. The elasticity of the rubber compensates for manufacturing and fit tolerances, and the elastic memory inside the material is an important condition for maintaining a seal.

From a macromolecular point of view, the sealing behavior of rubber O-ring materials is similar to that of a very viscous fluid, which has the property of transmitting pressure to the surface in contact with it. When the rubber O-ring is installed in the groove and its section is compressed to a certain extent (usually 8 percent -25 percent ), an initial contact stress is generated. In the case of extremely low or zero pressure of the fluid being sealed (air, water, oil, etc.), under high fluid pressure, the rubber O-ring is pressed to the corner of the groove on the opposite side of the pressure, and It produces a stress distribution that blocks the fluid leakage channel and acts as a seal. That is, under large fluid pressure, the contact pressure of the seal is the sum of the initial contact stress of the rubber O-ring and the contact stress generated by the fluid pressure. The contact pressure is always slightly greater than the working pressure of the liquid, so the sealing effect is greatly improved.

Rubber is a hot-melt thermosetting elastomer, while plastic is hot-melting and cold-setting. Due to the different types of sulfides, the temperature range for molding and curing of rubber is also quite different, and it may even be affected by climate change and indoor temperature and humidity. Therefore, the production conditions of rubber products need to be adjusted appropriately at any time. If not, there may be differences in product quality.