Structure and sealing principle of skeleton oil seal and installation precautions

The skeleton oil seal is relatively simple and generally consists of three parts: the oil seal body, the reinforced skeleton and the self-tightening coil spring. The sealing body is divided into bottom, waist, cutting edge and sealing lip according to different parts. Generally, the inner diameter of the skeleton oil seal in the free state is smaller than the shaft diameter, that is, it has a certain "interference". Therefore, after the oil seal is installed on the oil seal seat and the shaft, the pressure of the oil seal edge and the contraction force of the self-tightening coil spring will generate a certain radial tightening force on the shaft. After a period of operation, the pressure will rapidly decrease or even disappear. , Therefore, adding a spring can compensate the self-tightening force of the oil seal at any time.

Sealing principle:

Due to the presence of an oil film controlled by the oil seal edge between the oil seal and the shaft, the oil film has fluid lubricating properties. Under the action of the surface tension of the liquid, the rigidity of the oil film just makes the oil film and the air contact end form a meniscus, which prevents the leakage of the working medium and thus realizes the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak; if the thickness is too small, dry friction may occur, causing the oil seal and shaft to wear; if there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. .

Therefore, when installing, it is necessary to apply some oil on the sealing ring, and at the same time ensure that the skeleton oil seal is perpendicular to the axis line. If it is not perpendicular, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also lead to excessive sealing of the lip. wear. During operation, the lubricant in the casing seeps out a little, so that it is ideal to form an oil film on the sealing surface.

Precautions when skeleton oil package is assembled:

1. Receive a fixed quantity of oil seals.

2. The oil seal must be kept clean from receipt to assembly.

3. Before assembling, check the oil seal well, and measure whether the size of each part of the oil seal is consistent with the size of the shaft and the cavity. Before installing the oil seal, firstly compare the size of the shaft diameter with the inner diameter of the oil seal, and make sure they are consistent. The size of the cavity should be compatible with the outer diameter and width of the oil seal. Check whether the lip of the oil seal is damaged or deformed, and whether the spring is detached or rusted. Prevent the oil seal from being placed flat during transportation, and being squeezed and impacted by external forces, which will destroy its roundness.

4. Do the machining inspection procedure before assembly. Measure whether the dimensions of the cavity and the shaft are correct. Especially the inner chamfer. There should be no slope. In the assembly part, there should be no burrs, sand, iron filings and other debris in the part where the shaft is installed (chamfering), which will cause irregular damage to the lip of the oil seal. It is recommended to use an r-angle for the chamfering part.

5. In terms of operation skills, you can feel it with your hands to see if it is smooth and round.

6. Before installing the oil seal, do not tear the wrapping paper too early to prevent debris from adhering to the surface of the oil seal and being brought into the work.

7. Before installation, the oil seal should be smeared with an appropriate amount of lithium-based ester added with molybdenum disulfide between the lips to prevent dry grinding of the lips when the shaft starts instantaneously, affecting the interference of the lips. As soon as possible, assemble. If the oil seal seat where the oil seal is installed is not installed immediately, it is recommended to cover it with a cloth to prevent foreign matter from adhering to the oil seal. Hands or tools coated with lithium grease must be clean.

8. The oil seal should be flat-packed and should not be inclined. It is recommended to use hydraulic equipment or socket tools for installation. The pressure should not be too high, the speed should be even and slow.

9. For the oil seal machine installed this time, mark it to facilitate tracking, and pay attention to the entire process.