Radial oil seal

Radial oil seals are designed for sealing shafts in bearing housings. Providing long-lasting sealing efficiency, they consist of a rubber sealing lip, metal case and a Stainless steel spiraled tensioning spring and with external dust lip.

Oil seals are designed with asymmetric lip angles. The angle between the shaft and lip on the air side is smaller than that the angle on the lubricant side to prevent lubricant from leaking out of the system. A stainless steel garter spring located on the main sealing lip provides the appropriate radial load against the shaft. In grease lubricated bearing units, it is not only the small gap between the seal lip and the shaft that provides sealing against contaminants. The grease in the vicinity of the seal lip and grease in between two sealing lips also provide a sealing action.

  • Misalignment for shaft diameter up to and including 100 mm is approximately 3°
  • Speeds of up to 10 m/s.
  • Made of NBR up to 90 deg C
  • Stainless steel spring
  • Blue detectable colour for the food industry

The NBR material of the Oil Seal is much softer than the shaft, but due to friction between the shaft and the seal, it is possible for wear to occur on the contact surface of the shaft. The degree of wear depends on the structure of the shaft material. In general, the metal from which the shaft is made should have a homogeneous fine granulous structure and must have a minimum surface hardness of HRc 45. If the lubrication is doubtful, or the medium is contaminated, dirt can enter from the outside and the speed of the shaft is more than 4 m/sec. The hardness of the shaft should be a minimum of HRc 55. In general, shafts of carbon steel or stainless steel are most suitable. Even more important than a correct interference fit of the Oil Seal is a perfectly smooth shaft in the region of the seal. The surface roughness of the shaft depends on the average profile depth Ra of the tool marks caused by the machining process.

For normal circumstances, the shaft in the region of the seal must have a surface roughness of approximately:

  • Ra = 0,4 – 0,8 mm
  • CLa = 8 tot 25 mm
  • Rz = 1,0 tot 4,0 mm and
  • Rmax ≤ 6,3 mm

AS Seal

The Radial AS seal type is pressure-tight, by the pressure of the grease the lip will pressed closer to the shaft as shown in the illustration. Therefore it can not be greased through the seal, the seal has to be used in combination with a CS or CC seals or as AS-AS / AS-VK assembly used on places with none abrasive surrounding just to close and become a maintenance free bearing unit.  It is necessary that if you do the initial greasing, to keep the cap a little bit open. to ensure that air can escape.

IMPORTANT INFORMATION FOR INITIAL GREASING OF THE BEARING UNITS FROM EXTREMEBEARING

In some configurations, the bearing units from EXTREMEBEARING are pressure-tight! It is necessary that if you do the initial greasing, to keep the cap a little bit open. Otherwise, problems like in the picture below can happen….

Even, when it should be necessary to add some grease, you always should take care that no overpressure will be in the housing! The EXTREMEBEARING units are pressure tight in following configurations: AS/AS – AS/VK – CL/CL – CL/VK

Please inform your maintenance crew about this special service operating instruction. It can be helpful to dismount the grease nipples and exchange them with a standard stainless screw, so it will be impossible to make mistakes.

SA  Seal

Oil seals are designed with asymmetric lip angles as shown the illustration. The angle α between the shaft and lip on the air side is smaller than that the angle β on the lubricant side to prevent lubricant from leaking out of the system. When grease is used, the difference in angles is less important and often reversed to provide better sealing against contaminants from outside. We call these seal version SA. Leakage is less of a concern here due to the consistency 15 of grease, which prevents excessive loss of lubricant. Therefore, the main purpose of the grease seal is to keep contaminants out.

In grease lubricated bearing units, it is not only the small gap between the seal lip and the shaft that provides sealing against contaminants. The grease in the vicinity of the seal lip and grease in between two sealing lips also provide a sealing action.
To improve bearing life for bearing shaft seals, it is recommended to use an automatic lubricator, or lubricate with some regularity. Only a small quantity is necessary when slowly flushed into the bearing cavity to force dust and moisture away from the seal lips.

 

Note:

This SA seal is not suitable for applications where high hygiene requirements are demanded, because the loaded lip makes a dirt chamber. For this type of application, use our CC design. The SA and, to a lesser extent the type SA are too not suitable, for abrasive contamination. For this type of application, use our CS design.

Grease 

Not only the small gap between the seal lip and the shaft that provides sealing against contaminants. The grease in the vicinity of the seal lip and grease in between two sealing lips also provide a sealing action.
The gaps between the lips and the stator of the seal must be greased to keep out dust and water. To improve bearing life for bearing shaft seals, recommended is to use an automatic lubricator or lubricate with some regularity. Only a small quantity is necessary when slowly flushed into the bearing cavity to force dust and moisture away from the elements.

Examples of grease diagram using  AS seals

If the contamination is only on one side of the bearing unit, a seal combination can be chosen so that by re-greasing the grease on this side will first leaving the bearing housing and the contamination with the grease shall flow away from the sealing lips. As example a AS-CS combination in this picture

AS-VK assembly

AS-AS  Seal assembly

AS-CS Seal assembly