Bearing Seals or Shields?—These 3 Qs Will Help You Make The Right Choice

By IBT Inc

October 17, 2018

Bearings

Determine The Right Bearings For YOUR Application & Environment

The basic function and design of a ball bearing have not changed drastically since it was invented in the 1700s. However, features, such as bearing seals and shields, have since been adapted to both protect ball bearings from contamination and retain their proper lubrication levels.

…But how do you know which one to choose?

According to Tim Zerger, IBT’s Bearings & PT Director, there are a few key questions you can ask yourself to help you determine whether a seal or a shield could better extend the life of your bearing:

1 – What is it that you need to protect your bearing from?

First, the environment in which your bearings operate in can help you identify potential contaminants so that you can then select your bearings accordingly.

For example, shielded bearings have a gap that can allow finer contaminants or water from washdown applications to enter the bearing and get into the raceways. This could wash out the grease or cause the roller or balls to skid, creating heat and infusing the metal surfaces together.

Selecting a sealed bearing could help prevent this kind of bearing failure. Unlike shields, standard seals can be trusted to keep out most contaminants. However, according to Zerger, it is important to note that, in harsher washdown applications, high water pressure between 1000-1800 psi could potentially fold the lip of the seal and allow water to get into the bearings. That is—if the bearing is not protected or covered.

2 – How fast will the bearing be going?

Speed also has a key role to play in the seals vs. shields debate. When it comes to standard bearing seals, although they are ideal for keeping out contaminants, they are fairly limited in terms of speed—As the size of a sealed bearing increase, it’s speed capacity decreases.

For example—A larger bearing (40mm bore / 80mm od) can handle up to 5,600 rpm sealed, while a smaller (10mm bore / 30 mm od) can handle up to 17,000 rpm sealed.

Shielded bearings, on the other hand, are not limited by speed.

3 – What temperature will the bearing be operating under?

Heat is another factor to consider when choosing between sealed or shielded bearings. Whether the heat source is internal or external, bearing seals, typically made of rubber or plastic, risk melting if the temperature reaches 212° F. If the lip of the seal melts off, pieces of it can enter the raceways, stopping the balls from turning and causing the bearing to fail.

Shielded bearings can withstand higher temperatures up to 250° F, which is the standard operating temperature maximum of bearing steel and grease.

 


 

Koyo-RD-TypeSealed-Ball-BearingKoyo Offers A Better Solution—The RD Type Sealed Ball Bearing

What if there was a third option that was the best of both worlds?—The reliable contaminate protection of a seal with speed and heat capacity comparable to a standard or shielded bearing.

Koyo introduced the RD Type (Light Contact) Sealed Ball bearings for exactly that purpose. Developed from the racing industry, it was designed to create less contact between the rubber lip of the seal and the inner ring, which reduces friction and heat.

The improved seal technology allows the Koyo RD bearing to operate at up to 90% of open bearing speeds, while reducing contamination linked to early bearing failure. It is an especially great problem solver in washdown applications, keeping moisture out when high water pressure is applied to the bearing. Learn more about it here.

 


 

Want More Insight On Bearing Seals & Shields?

Bearings have been the cornerstone of IBT Industrial Solutions since the company was founded in 1949. If you’re looking for the knowledge and expertise you need to select the best parts for your application and environment, contact Tim Zerger, IBT’s Bearing and Power Transmission Director, or give us a call at 913-677-3151 today!

 


 

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