Solving a Common Filter Coolant Problem

All grinders have a bit of oil or grease in the sump.  Sometimes this oil or light grease is agitated with air and can get whipped into a butter-like consistency.  Once the oil or grease is in this butter-like consistency, it does not re-dissolve.  There are some things you can do to try and prevent this from happening.coolant_test_instruments-11.jpg

I would check the pH of the machine coolant first. Neutral pH is 7.5.  Most coolants for filter units are slightly basic and have a  pH 8 -9 partly to prevent this sort of thing.  By having a machine coolant with a more basic pH, the solution changes oils and greases into soap (saponification.)  If your coolant turns acidic (below 7.5 and maybe 6 – 6.5) then you risk having the oils and grease turn into a whipped or butter-like consistency.  See our section on Machine Coolant and Machine Coolant filters for information on how to test coolant.

Follow the filter coolant manufacturers’ recommendation for pH adjustment. 

If your coolant supplier doesn’t give you any directions then you can add sodium carbonate (washing soda, maybe water treatment chemical) or sodium hydroxide (caustic lye).    Sodium bicarbonate or any other antacid will also work.   Even Alka Seltzer.  

Be careful when adding the sodium carbonate or sodium hydroxide, and add it slowly.  It will generate gas (probably largely CO2) so do it in an open area with a fan on.   

Check for a leak on a fitting.  A little is normal as with weeping hydraulic cylinders. 

filter_units-3.jpgCheck for air in the filter system or in the coolant dispensing system.  Typically just draining the system and refilling will prevent this if it is just an air bubble.  If it is a loose fitting it may be sucking in air. 

You should be able let the coolant sit and skim the “butter” off the top. 

You can also use scrap cloth or similar as a crude filter until you can remove all the “butter”.

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