Sealing principle for static sealing

1. Sealing principle for static sealing

O-ring is widely used in static seal. If the design use are correct, the O-ring seal can achieve no leakage in the static seal.

After the O-ring is installed into the sealing groove, its cross-section bears the contact compression stress produces elastic deformation. The shock absorber bearing supplier produces a certain initial contact pressure Po on the contact surface. Even if there is no medium pressure the pressure is very small, the O-ring can achieve sealing by its own elastic force; when the chamber is filled with pressure medium, under the action of medium pressure, the O-ring will move to the low-pressure side, its elastic deformation will be further increased to fill close the gap δ. At this time, the contact pressure on the coupling surface of the sealing pair rises to PM:

Pm=Po+Pp

PP -- contact pressure transmitted to contact surface through O-ring (0.1MPa)

Pp=K•P

K -- pressure transmission coefficient, for rubber O-ring, k = 1;

P -- pressure of sealed liquid (0.1MPa).

Thus, the sealing effect is greatly increased. Because K ≥ 1, PM > P. Thus, as long as the O-ring has the initial pressure, it can realize the sealing without leakage. The contact state of O-ring is changed by the pressure of medium itself to realize the sealing property, which is called self sealing effect.

In theory, even if the compression deformation is zero, it can be sealed under oil pressure. However, in fact, the O-ring seal may be eccentric when installed. Therefore, after the O-ring is installed in the sealing groove, its cross-section is generally subject to 7% - 30% compression deformation. The static seal takes the bigger compression ratio value, the dynamic seal takes the smaller compression ratio value. This is the plane pressure bearing supplier. Since synthetic rubber needs to be compressed at low temperature, the pre compression shrinkage of static seal O-ring should be considered to compensate its low-temperature shrinkage.

2. Sealing principle for reciprocating sealing

Reciprocating seal is one of the most common sealing requirements in hydraulic pneumatic components systems. Reciprocating motion seals are used on power cylinder piston cylinder block, piston intervention cylinder head various kinds of slide valves. The gap is formed by a cylindrical rod a cylindrical hole, the rod moves axially in the cylindrical hole. The sealing action limits the axial leakage of the fluid. When used as reciprocating seal, the pre sealing effect self sealing effect of O-ring are the same as that of static seal. Because of the elastic force of O-ring, it has the ability of automatic compensation after wear. However, due to the liquid medium sealing, due to the action of rod movement speed, liquid pressure viscosity, the situation is more complex than static seal.