Working principle and structural characteristics of the gap seal

The gap seal is ensured by a small fit clearance between the relatively moving parts. There are several annular grooves (typically 0.5mm x 0.5mm) on the piston. Its function, on the one hand, can reduce the contact area between the piston and the cylinder wall; on the other hand, the uniform distribution of the oil pressure in the groove makes the piston in the center position and reduces the side caused by the low precision of the part. The friction between the piston and the cylinder wall caused by the pressure and can reduce the leakage.

The gap seal method has a small frictional resistance, but the sealing performance is poor, and the processing precision is high. Therefore, it is only suitable for occasions with small size, low pressure and high speed (working environment, medium). The gap between the piston and the cylinder wall is usually 0.02-0.05 mm.

The gap seal is characterized by simple structure, small frictional resistance and long service life, but the machining precision of the parts is high, it is difficult to completely eliminate the leakage, the sealing effect is poor, the sealing performance cannot be improved with the increase of the pressure, and the mating surface wears. Can not automatically compensate after. Therefore, the gap seal is only used for the sealing between the cylinder bore and the piston which is small in size, low in pressure and high in moving speed.


1. There is no friction between the seal and the moving parts in the gap seal, so there is no wear. This kind of seal structure can be used in high pressure medium and high speed.

On the device

2. The sealing structure is simple, durable, reliable in operation, low in heat generation and long in life, requiring almost no maintenance;


1. There is a gap in the sealing surface of the gap seal, so the leakage cannot be completely prevented, so leakage inside is allowed, and then the tank is returned to the tank through the drain port. Rude

This requirement does not allow leakage of any media or the use of different media in the connector.

2. The sealing effect of this structure mainly depends on the gap size of the sealing surface, the pressure difference of the medium and the processing precision of the sealing surface. Where the gap size and both

The uniformity has the greatest influence on the sealing performance, so the sealing structure has high requirements on the geometry and surface processing precision of the parts, and the processing cost is high.