Measures to prevent oil leakage from skeleton oil seals

In the hydraulic sealing system, due to various reasons, it will lead to the skeleton oil seal oil leakage, according to experience, summarize the following points to prevent the skeleton oil seal oil leakage measures.

1. Improve the surface quality of the parts: the contact situation between the sealing lip and the mating surface is the key to the sealing effect. If the surface of the journal is too rough, the projecting part of the seal lip is easy to dry contact through the very thin oil film, which leads to the wear of the seal, so the surface roughness of the journal should be controlled at Ra0.2~0.8μm, the surface hardness should be HRC55 and the quenching depth should be at least 0.3 mm. The surface of the journal to which the oil seal is fitted should be a non-spiral surface. The reason for the spiral lines on the journal surface is that when finishing the grinding wheel, the movement of the diamond on the dresser is spiral and therefore forms spiral lines on the surface of the grinding wheel. In this way, the grinding wheel will form a spiral line on the surface of the journal when processing the journal. This spiral line will scratch the sealing surface when the shaft is rotating and affect the sealing effect of the oil seal, so it is recommended to use the processing method of plunge grinding journal.

2. Check the quality of the oil seal before assembly: Before installing the oil seal, the quality of the oil seal must be checked first, such as finding gaps and cracks in the lip, aging rubber, rusting or failure of the spring, etc., can not be used. At the same time, the tolerance of oil seal installation hole must be strictly controlled, if the aperture is too large, there will be gap between oil seal and hole, causing oil leakage; on the contrary, if the aperture is too small, the oil seal will be deformed and cannot be used.

3. Improve the assembly process: special station apparatus and special tooling should be designed to ensure that the surface of the journal at the oil seal seal is not scratched, the oil seal lip is not damaged and the oil seal lip is installed in the correct direction; in the installation process, if the oil seal lip needs to pass through the thread, keyway, spline, etc., corresponding measures should be taken (such as using thick paper, tape, etc. to cover the thread surface) to prevent damage to the lip; if the lip side locking spring is loose, it can be cut off If the lip is loose, cut off 10~15mm and connect the locking spring firmly with the head and tail; when assembling, use a special pressure sleeve and press it gently into the oil seal hole seat, do not knock, and do not use a hammer to hit the oil seal directly; in different cases, the installation requirements are different. In the case of straight hole and processed end face, the installation tool shall press the oil seal to the processed face; in the case of installation hole with step, the installation tool shall press the oil seal to the end face of the step; in the case of straight hole and unprocessed end face, the installation tool shall press the oil seal to the end face of the shaft.

4. Timely replacement of lubricating oil: As the lubricating oil is subjected to mechanical friction in the process of use, coupled with stirring shear and air intrusion, it is easy to oxidize and deteriorate, forming a large number of abrasive particles, which will cause the oil seal to leak once it enters the mating surface of the oil seal. It is recommended that new equipment should be changed in the second trial, so that the initial particles generated by the intense wear and tear are discharged in a timely manner, and later the machine is replaced every 3 months of operation.

5. Other: When using oil seal mainly to prevent lubricant loss, the sealing lip of oil seal should be installed inward; if mainly to prevent pollutants from entering, the sealing lip should be installed outward. When used in an environment with more dust or rain, etc., oil seals with a secondary lip should be used. When the shaft diameter is large and the speed is high, the skeleton oil seal made of silicone rubber should be preferred, followed by the oil seal made of fluorine rubber, acrylic vinyl rubber and nitrile rubber. In addition, attention should be paid to controlling the vibration of the machine and the eccentricity of the spindle to reduce the probability of oil leakage.

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