Reasons For The Failure Of The Rotary Shaft Lip Seal To The Ring Seal
Apr 04, 2022
After the rotating shaft lip seal is rotated, the gap will be automatically followed and compensated with the shaft under the action of the backlog of the oil film and the clamping force of the spring. The sealing effect is good, and the volume is small and easy to install. It is widely used, typically on the spindle of hollow drilling machines and on the application of thick and thin piston rods. Due to improper use, processing and maintenance, the lip seal ring of the rotating shaft is easy to cause the lip to wear and cause the seal to fail.
During installation, the sealing ring passes through the parts with sharp corners such as keyway and undercut, and it is easy to be scratched by the sharp corners of these parts. Inappropriate chamfering of the shaft end or excessive force during assembly will cause the lip of the sealing ring to turn over. And the spring falls off, and the sealing ability is lost. Improper assembly is the main cause of seal wear.
When replacing the sealing ring, use the sheath to guide the lip to slide forward to the sealing position to protect the lip from being scratched: use fine sandpaper for chamfering, etc., and push the sealing ring inward with even force and proper lubrication Oil, push gently so that the lips are not turned over.
The surface roughness value of the shaft is too large, and the shaft surface is easy to adhere to iron filings, dust and other particles, which invade the sealing lip and rub against the shaft, and wear the lip to cause leakage.
The surface roughness value of the shaft is too small, the surface of the shaft is too smooth, and the lubricating oil is difficult to form an oil film or maintain, which will cause dry friction between the lip and the shaft, resulting in damage to the sealing ring. Therefore, too large or too small roughness will cause the wear of the seal during operation, which is more obvious under heavy load.
When machining the rotating shaft, the surface roughness of the shaft is controlled at 0.4~1.6, the surface hardness is HRC32-42, and the chrome plating process of the rotating shaft is added. The rotating shaft is chrome-plated, which can make the surface have high hardness and surface roughness, and have better heat resistance. After use below 500 ℃, the gloss and hardness have no obvious change. The friction coefficient of the chromium plating layer is small, especially the dry friction coefficient, which is low among all metals, and has good wear resistance. The good cooperation between the lip and the plated hub can reduce wear and improve the service life of the lip seal.
The eccentricity of the shaft is an important indicator of the lip seal ring of the rotating shaft. When the eccentricity is greater than the specified value, the shaft will vibrate during movement. As the rotational speed of the shaft increases, the vibration increases correspondingly, which causes the lip seal to be impacted and abnormally backlogged, causing the lip to wear.
Maintenance found that the rotational speed of the shaft is inversely proportional to its eccentricity. The higher the rotational speed, the smaller the shaft eccentricity, and the lower the rotational speed, the larger the shaft eccentricity. Since the material of the rotary shaft lip seal is mainly NBR, it has good oil resistance, wear resistance and water resistance, but as the temperature of the working environment increases, the flexural resistance and tear resistance are significantly reduced. Therefore, with the increase of system pressure, oil temperature, impact, etc., the lip of the rotary shaft lip seal will be torn and rolled in the hydraulic cylinder until it fails.
Fluorine rubber with better comprehensive performance is selected as the material of the rotary lip seal, which has good high temperature resistance, low temperature resistance, resilience, breaking strength and enhanced elongation. The operating temperature range is -70 ~ 200 ° C, which can improve Service life of seals.
