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Refurbishing a bearing Answered

I have the problem at work that we have less than perfect oil pumps - for vegetable oil of the really hot kind.
If you ever had to deal with hot vegatable oil you know getting proper sealing is only one problem.
The other and much bigger is esterfication - when the oil turns into a resin like goo.
Depending on the ongoing temperature and blend of oil this goo is anything from rubber like to really rock hard, like amber without the trapped insects.

Recently the manufacturer changed the pump design, so instead of getting my expected spare parts I got a new pump.
With that one they fixed the problem of a leaking housing by providing a leaking ceramic seal on the drive shaft LOL
Now, instead of having to replace pump/motor shaft seals every 3 months or so I also have failing motors.
The hot oil has no issues getting into the front bearing....
Can't really get fully sealed bearings that tolerate the heat and justify their price around here, so I needed som ideas.

If you need a spanner to turn a motor of just 1/2hp and know the bearing isn't worn out it is time for drastic measures.
This trick also works for stainless steel cookware but most won't have a big enough container to submerge them.
The "resin" is oil based but with the esterfication it is more a polymer or plastic.
Most solvents struggle to even soften the stuff, let alone remove it.
The bearing in quesion is a common and in the caged form cheap 6203ZZ - standard on many bikes, alternators and well motors.
After scraping off what came off from the outside I pulled it off the shaft.
Needless to say I was unable to make it spin or move it by hand - but I had to check once it was off LOL

The cleaning involves dangerous chemicals, so be advised that proper PPE with face shield, gloves and apron is highly recommended!
Same for doing it outside for ventilation purposes!

I used a magnetic stirrer/hotplate cobo and a stainless steel jug.
Filled enough water to allow the bearing to stand upright and fully submerged on the inner wall.
For the about 150ml of water I added 3 tablespoons of sodium hydroxide (drain cleaner without the aluminium shavings).
Last but not least I set the temp to a cosy 100°C - just under the boiling temp for this mix.
After about an hour the water was brownish from the dissolved gunk.
All up 3 hours and I decided to clean the bearing, netralise the mix and dispose it in into my collection container.
I was able to move the bearing but could feel the rubbery bits moving along on the inside.
Another round of 3 hours fixed this and the bearing was spinning freely.
Just in case I did one more round with a fresh mix but it showed no visible discoloartion anymore.
Wrapped in some paper towel I shook the remaining hydroxide solution out and let it sit for a few minutes in alcohol-.
This step was repeated several times to ensure all the corrosive mix is out and that the bearing will dry quickly.

How to re-grease a caged or even sealed bearing??
I don't have a suitable adapter for a high pressure grease gun...
But I do have a hotplate and a vacuum pump....
Long story short the grease was heated in a small tuna can (I ate the tuna, sorry)´, the bearing added and fully covered.
Into the vaccum chamber, pump on...
First round quite some air came out and formed bobbles that left some open channels.
Could not heat the grease to go fully liquid as it started to smell at just over 200°C :(
Two round later however I could not see anythng happening anymore when the vacuum was at max.
I hate the cleaning but at least after that was done the bearing was back to its old glory.

If you have bearings that are really hard to get and that are just dry and a bit dirty inside then this trick might help you.
So why does the sodium hydroxide work so well?
In a concentrated solution and hot it is a potent agent - do not let any aluminium get near it!
Nothing in a bearing however is affected by it and it transform most oils and greases into a soap like thing that helps with the removal of the remaining stuff.
The "cooking" also makes sure there is little to no oxygen left in the water, so no rust will form unless you forget the alcohol cleaning.
Once you see how easy you can shake the hydroxide solution out of the bearing to get it dry and even better with the alcohol you realise why caged bearings are no good in a wet or dirty environment.


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