The bad news about inboard bearing assemblies

Posted by ACS Valves on August 24, 2016
The bad news about inboard bearing assemblies

Inboard bearings are a great option if you love throwing money into your valve and watching it get shredded before your eyes.

For such a small piece of your equipment, it might not seem important to keep your bearings outside of your housing endplates. But the difference between inboard and outboard bearings could actually make or break your machinery.

Here’s why:

Just avoid inboard bearings

The primary function of your bearings is to facilitate the rotation of your rotor. They can either sit on the inside of your housing endplates (inboard) or on the outside (outboard), separated from your shaft seal.

They are primarily used in machinery that conveys products that are easier to handle—nothing sticky or abrasive.

With inboard bearings, if your seals ever fail, you run the risk of contaminating your bearings or having them break down much sooner. Eventually, with this lack of protection, you may be facing more costly repairs or valve replacements.

With outboard design, bearings are separated by the housing endplate. There is a gap between the seal and the bearings.

Keep it compliant

If you’re looking to stay compliant (you should be), outboard bearings are a must.

NFPA 650: Standard for Pneumatic Conveying Systems for Handling Combustible Particulate Solids mandates that bearings should be “located outside the combustible dust stream where they are less exposed to dust and more accessible for inspection in service.”

Because bearings are rotating, they have the potential to act as an ignition source for combustible dust if they were to ever overheat. 

Having bearings more accessible for inspection will not only make it easier to maintain them and keep them clean, but also ensure that there is no build-up of dangerous and potentially explosive dusts.  

Protect. Your. Product.

Because an outboard bearing is separated by the housing endplate, if the seal ever fails, your bearings will be protected from any material contamination or build-up.

With a gap separating the seal and the bearing assembly, material has a path to escape without damaging the bearing components. It costs much less to replace a seal than it does to replace your valves or your end product. 

More valve variety

Outboard bearings generally give your valves more support, and also allow for a higher pressure differential when it comes to conveying your products. They can accommodate more alternative shaft seal arrangements than inboard bearings, as well as varying sizes in rotor shaft diameters due to a more adaptable design.

Categories: Safety , NFPA , ACS Updates