Working principle of oil seal and countermeasures for leakage

1. Working principle of oil seal

1) In the free state, the inner diameter of the oil seal lip is smaller than that of the journal and has a certain amount of interference;

2) After installation, the interference pressure of the cutting edge of the oil seal and the contraction force of the self-tightening spring should produce a certain radial pressure on the rotating shaft;

3) When working, the lip of the oil seal forms a 0.25 ~ 0.5mm wide sealing contact band under the action of radial pressure. Under the action of lubricating oil pressure, the oil penetrates into the edge of the oil seal and forms an extremely thin oil film between the rotating shaft. The oil film is acted by the surface tension of the oil and forms a "crescent" surface along the outer edge of the oil seal edge to prevent the oil from spilling out.

2, the main factors causing oil seal leakage

The main factor of leakage is that the oil seal is not tight. When the shaft is worn and grooves are formed, even if the new oil seal is replaced, the contact pressure between the oil seal lip and the shaft drops, resulting in too small interference between the oil seal lip diameter and the journal after installation.

3, the oil seal is not tightly sealed and leakage measures

1) Master and identify the basic knowledge of shoddy products to choose high quality, standard oil seals.

2) Before installation, if the external surface roughness of the journal is low or there are rust spots, rust, burr and other defects, use a fine abrasive cloth or oil stone to smooth; Apply cleaning oil or lubricating grease to the lip of the oil seal or the corresponding position of the journal. The outer ring of the oil seal is coated with sealant and the key slot on the shaft is wrapped with stiff paper to avoid scratching the lip of the oil seal. The oil seal is rotated inward and pressed into it with special tools. Do not smash hard to prevent the oil seal from deforming or breaking the spring and failing; If there is lip flanging, spring off and oil seal skew, it must be removed and reloaded. It should be noted that when the journal is not worn and the oil seal spring is sufficiently elastic, do not tighten the inner spring without permission.

3) Applied to the mechanical oil seal general working conditions harsh environment temperature difference large dust more frequent vibration of the machine parts of the stress situation is constantly changing, so frequent inspection, frequent maintenance and frequent maintenance.

4) If the journal and bearing wear seriously, oil seal rubber aging or spring failure should be repaired and replaced in time.

5) The abnormal heating parts or assemblies should be removed in time to avoid mechanical overspeed and overload operation to prevent the oil seal lip temperature rise rubber aging lip early wear.

6) Always check the oil level if there are too many impurities in the oil alloy powder, metal iron filings to completely replace the new oil to change the oil brand and quality to meet the requirements of the season.

7) The oil seal that is not used for the time being should be kept properly to prevent oil, dust or sun exposure.

8) When the journal is worn into a "V" shape groove so that the contact pressure between the new oil seal lip and the shaft drops and cannot seal the oil, AR-5 two-component adhesive can be used for bonding, which is simple, reliable and wear-resistant.

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