Sealed or serviceable bearing: your choice?

[jgmo]

"Purged bearings" are fast becoming a thing of the past because the technology of sealed bearings has evolved so well.
I personally know a guy that destroyed over a million dollars of conveyor equipment his first day on the job as an "oiler" by overgreasing the purged bearing systems.
That can't happen with sealed bearings.

 

[Lee1051]

Lube question. so i've replaced a number of idler pulleys on my zero turn, a few on my pickup. never seen a grease serviceable idler pulley, all sealed.
asked an engineer friend who designed pulleys, and a good small engine guy why so...they both said sealed bearings are superior & will outlast grease serviceable, due to contaminants, etc.

your take? do you agree w/engineers & mechanics above based your own experience? btw, i'm glad to have grease serviceable mower spindles & front end zerks on my old pick up. thx in advance

Any time you can add grease as a option it's a good option to have. We've all had non grease bearings make noise that quiet down with a little wd40.

 

[ArlyA]

Any time you can add grease as a option it's a good option to have. We've all had non grease bearings make noise that quiet down with a little wd40.

wd-40 is a parts cleaner which I occasionally use to get grease off of something. Real poor, short term lubricant.

 

[adolphbell]

I have a Deere 54" mower deck and over the last 22 years (bought it new) I have replaced four idler pulleys and never have had replace the pulleys that have zerks.

 

[ScottGilfordNH]

Great topic…I’ve been a ball bearing engineer for over 36 yrs. Here’s a bearing guys perspective and sorry for the long post, but ask an engineer what time it is and they tell you how to build the clock….,
Basically, all greases are not compatible. I avoid EP Moly based grease in a rolling element bearing. I have seen many bearings ordered from the factory only to see the OEM call out an incompatible grease , different grease for maintenance. Lithium complex greases tolerate water intrusion better than clay based greases. Not all synthetic oil base greases are compatible with mineral oil base.
If it’s sealed, the bearing was designed with a specific clearance, load-speed capacity, installation fit, grease fill percentage of the internal cavity void, for the very reason many have referenced on the seals blowing out, but percent fill of lube is really controlled to maintain the film thickness between the rolling elements permitting minimal heating of the grease in shear flow…..a ball or roller bearing is only suppose to run on a film or lube and it acts lube an oil pump internally, never touching metal on metal…..I’ll stop here.
A sealed maintenance free bearing really shouldn’t use a clay based grease. A relube bearing is more costly, and has special seals and lube passages, but these are mainly on the sliding bearings, spherical plain bearings (ball joints, tie rods, journals).
Injecting grease in a failing rolling element bearing with a needle could work, but it probably is failing by that point. If it made noise, it’s failing.
Spindle bearings are specially designed for relube and are damaged if done incorrectly, wrong grease, over pressured, etc.
if a bearing is designed for relube, it will always outlast a sealed maintenance free, if maintained. Those special holes and lube grooves are not expensive to machine, but all the cost is in the debur operation in manufacture and OEMs don’t like the added cost. Depending on the bearing, load and speed, rubber seals may not survive and hence the steel shields/slingers, which don’t work well in wet-muddy areas. The designer had to make a trade off, load capacity for long life.
Bearings are designed to wear out, keeps me employed, but I hate nothing than a bearing failure on my personal equipment and the needle injection is my last ditch effort to buy time, waiting for the replacement.

 

[5030]

wd-40 is a parts cleaner which I occasionally use to get grease off of something. Real poor, short term lubricant.

Try non existent lubricant. WD40 is a moisture dispersant not a lubricant. The WD in WD40 denotes 'water dispersant', nothing more.

 

[big bubba]

ScottG: most definitive info i've run across on the subject. i think the belt generated heat on a mower only shortens the sealed idler pulley as well.
i need to find a good pulley supplier online now that my old one seems to be out of business. Fortunately have a good source for Kevlar belts
i never did pay attn to compatible grease types for general purpose, guess i should, regards

 

[WinterDeere]

Try non existent lubricant. WD40 is a moisture dispersant not a lubricant. The WD in WD40 denotes 'water dispersant', nothing more.

Product names are chosen by marketing types, and rarely indicate their entire range of potential uses. Just read the back of the can, which states it is also a lubricant. It's based on mineral oil, one of the most common lubricants on earth.

That said, it is a pretty poor lubricant for most applications, on its own. Where there may be some merit in its use us reinvigorating old grease. Depending on grease type and compatibility, the addition of the small amount of mineral oil in the WD-40 base may replace what has been lost from the grease. Grease is a mixture of lubricant (usually mineral oil) with binders (soaps), and addition of any mineral oil may help to re-invigorate dried grease and buy some extra life. Old dried out grease is usually the remaining soaps/binders, after the mineral oil has wicked away from it.

Because there are other solvents used in WD-40, it'd likely be safer to use plain mineral oil, if this is your goal. But it's going way too far to claim WD-40 is "non existent lubricant" or "only for water displacement", both of which are completely untrue.

 

[5030]

Whatever floats your boat.

 

[MHarryE]

Some applications are designed for relube ball bearings. Disk harrows are the first thing that come to mind. My 27' disk has 16 relube flanged bearings. Due to their application - working buried in dirt much of the time, they are triple sealed (lots of friction - the designs are not to be used on high speed shafts) with relube flanges. They still wear out quickly. Filling a regular sealed bearing with grease is also a friction generator/life shortener.