Seals 101: Why a Good Bearing Seal Matters
While unmounted bearings have the luxury of off the shelf oil seals with a much larger sealing area than a mounted bearing, the level of exposure to real world conditions that mounted bearings are exposed to make it crucial to have a good bearing seal. Essentially, the bearing seal in a mounted bearing has two important jobs to do.
Dual Purpose of a Mounted Bearing Seal
In a mounted bearing, the seal will keep foreign debris and contamination out of the bearing. This proves especially important in food processing plants, outdoor environments and dirty bulk handling applications where the risks of these unwanted intruders are high.
A good bearing seal will also ensure that grease and lubricant stay inside the bearing. This not only helps the bearing perform as expected, but also prevents maintenance workers from having to relubricate them constantly to make sure clean grease/oil is in the bearing rolling element path.
Types of Bearing Seals
There are two categories of bearing seals— labyrinth seals and contact seals. Each of these types of seal has their own pros and cons to consider when selecting for your particular application.
Labyrinth seals, also known as non-contact style seals, usually require lubricant or in some cases a piece of felt or low coefficient of friction barrier to minimize contamination working through the labyrinth, or arranged steps that create a sealing gap.
Labyrinth seals are good for high operating speeds and low rotational torque, with no application related contamination. They are also less prone to damage during relubrication. The cons to labyrinth seals are a less effective sealing performance. They just aren’t as good at keeping the bad out (debris or contamination) or keeping the good in (lubrication).
Contact seals have one or more rubber lips bonded to the steel insert that rub against the inner ring surface or another metal sealing element, allowing for a more positive sealing. They are also best suited for lower operating speeds and higher rotational torque. The benefits of a contact seal can include improved grease retention and contamination exclusion. Unlike labyrinth seals, contact seals are really good at keeping the good in and the bad out. However, contact seals can be prone to damage if over lubricated. Overfilling the seal with lubrication can cause blown seals and the potential for increased operating temperatures. In a heavily contaminated environment re-lubing until grease comes out of the seal is an acceptable practice if and only if, the shaft is rotating and the grease is being added slowly with a light grease line pressure.
The industry standard for mounted bearings is a seal designed with a single lip rubber contact seal (which may or may not have an additional flinger or shield for added protection) that has an extremely wide suitability for most applications. However, this seal might not be the most ideal for every application.
Additional considerations when selecting a bearing seal for extreme applications include:
- In applications with very high contamination conditions, such as food processing plants conducting regular washdowns, multiple lip seals will provide better performance. Extra barriers such as end caps are often used as well.
- For high speed, low torque, ease of turning the shaft, or energy savings, a labyrinth seal is a better option.
- In applications where there are a wide variety of chemicals present, such as food processing, chemical processing, or wastewater treatment, there is a benefit to using seals made of more corrosion resistant material, than a rubber such as Viton®*
- In applications with high-pressure sanitation washdown, the industry standard IP69K test validates that the sealing can withstand high-pressure spray.
Regal's IP69K Washdown Solutions
By ensuring that you select a proper bearing seal for your application, you can save time and money for your organization, as well as avoiding any unnecessary downtime.
Some applications have specific needs that require custom seal solutions, such as this asphalt paving application success story.
Want to learn more?
Check out these additional Success Stories
* Viton® is a registered trademark of The Chemours Company.