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Do your bearings need shielding and sealing?
Ball bearings and roller bearings can be equipped with different types of metal shields and rubber seals. Metal shields and rubber seals are often called bearing closures. Bearing seals prevent contaminant particles from reaching critical surfaces inside the bearing, helping to retain lubricant in the bearing, thereby extending bearing life. There are several types of bearing closures, and different types of bearing shields can be supplied on the same bearing, as well as special designs. Aubearing is a leading bearing manufacturer in China and can provide bearing closures to meet your various needs.
Type ZZS – removable non-contact metal shield, fixed in the outer ring by clamping wire. This type of guard is made from 300 series stainless steel and is only suitable for miniature bearings and instrument series bearings. Maximum tolerable operating temperature is 600° F. Since there is no contact with the inner ring, there is no significant effect on torque or speed, and its performance is similar to that of an open bearing. Removable closure allows cleaning and relubrication. The code for single-sided non-contact metal shielding is ZS.
Type ZZ – Non-removable, non-contact metal shield retained in the outer ring by crimping or pressing. It is important to note that this type of metal guard cannot be removed once installed. Type ZZ metal guards are generally made of 300 series stainless steel. On larger bearings, the metal guards on Type ZZ are made from 1008 or 1010 strip steel. Maximum operating temperature tolerable is 450° F. Because there is no contact with the inner ring, there is no significant effect on torque or speed, and performance is similar to open bearings. The code for single-sided non-removable, non-contact metal shielding is Z.
Type 2RS – double-sided contact rubber seal. Double-sided rubber seals typically use nitrile rubber bonded to a steel insert. The rubber seal is held in a groove in the outer ring. This type of seal can be removed, but care must be taken not to bend or cut the sealing lip. Maximum operating temperature tolerable is 240° F. This type of seal contacts the inner ring and provides better protection than a metal shield in contaminated environments. However, type 2RS seals cause an increase in torque and reduce the maximum speed capability of the bearing. Certain lubricants and chemicals can react with rubber. The code for individual rubber seals is RS.
Type 2RU – Non-contact molded rubber seal. This type of seal typically uses nitrile rubber bonded to a steel insert. The seal is held in a groove in the outer ring. This type of seal can be removed, but care must be taken not to bend or cut the sealing lip. Maximum operating temperature tolerable is 240° F. This type of seal has a very thin lip that is adjacent to the inner ring but does not touch it. It provides better protection than the ZZ or ZZS models, but does not bear the torque it is supposed to perform. Certain lubricants and chemicals can react with rubber. The code for single-sided non-contact molded rubber seals is RU.
Type 2VS – Molded Viton seal. This type of seal is made of Viton bonded to a steel insert. The seal is held in a groove in the outer ring. This type of seal can be removed, but care must be taken not to bend or cut the sealing lip. Maximum operating temperature tolerable is 400° F. This type of seal contacts the inner ring and provides better protection than a metal shield in contaminated environments. However, this results in a reduction in the bearing’s maximum speed capability. The seal has excellent chemical resistance. The code for single side molded Viton seals is VS.
Type TTS – Glass-reinforced PTFE seal retained in outer ring by clip wire. This type of seal can be removed, but care must be taken not to bend or cut the sealing lip. Maximum operating temperature tolerable is 400° F. This type of seal contacts the inner ring and provides better protection than a metal shield in contaminated environments. However, this results in an increase in torque and a reduction in the bearing’s maximum speed capability. This type of seal has less torque than the 2RS type, but is fragile. The seal has excellent chemical resistance. The code for a single seal is TS. PTFE seals are not used with all series of bearings.
As mentioned before, bearings can obtain a combination of closures on one side. For example, a combination of sealing and shielding (such as RSZ) can provide greater protection from contaminants than double shielding (ZZ or ZZS). The RSZ combination will exhibit less torque than the 2RS configuration. The side of the bearing with the seal should be oriented so that it faces the contaminated environment.
Other types:
For larger bore diameter bearings (above 10 mm), labyrinth rubber seals are available. These bearings have a groove in the inner ring and where the sealing lip contacts. This allows for a effective seal without increasing torque. Double lip rubber seals are also available and/or are usually labyrinth seals. These are effective in extreme environments.
Felt Seal – A felt seal consists of two metal plates fixed to the outer ring of the bearing. There is a felt washer between the two boards. The felt washers are soaked in oil before assembly and contact the ground outer diameter of the inner ring. These seals exhibit minimal frictional resistance.
Shrouded Seals – These seals consist of a rubber seal held in place by two steel caps or shrouds secured to the outer ring. These types of seals can contain up to three seals (or lips) between two metal caps. They are used in the most extreme environments and exhibit great resistance.
Both felt and shrouded seals take up extra space and are generally only suitable for larger bore bearings.Due to their construction, tapered roller bearings or angular contact bearings are usually not provided with dust caps and seals. External seals are often incorporated into the original design for harsh or extreme environments.
For bearings used in special industries, such as the food and beverage or pharmaceutical industries, manufacturing equipment must comply with strict hygiene and safety standards. In these environments, contamination protection is crucial. Therefore, choosing a contact seal will help ensure that dust does not enter the bearing. For equipment that requires regular flushing, contact seals can also provide effective waterproofing. This will prevent grease from washing out of the bearing, the rollers or balls from slipping, or excessive heat being generated. Many steel bearings in this industry require the use of non-toxic lubricants approved to NSF (formerly USDA) H1 or H2 standards.
What speed do the bearings run?
For high-speed applications such as bicycles and skateboards, non-contact sealing is a better option. Non-contact seals provide better protection against contamination than shields and do not affect maximum speed or bearing torque.
Conclusion
How much do you know about the description of bearing closures? If you are unsure which type to choose for your application, please contact Aubearing. Aubearing will share the knowledge of bearing sealing based on years of bearing manufacturing experience for your reference.