Mixing Soluble Oil Coolants

Dear MWF Magazine, Hi, we have a discussion in our shop, about pouring coolant in the bucket first then water, or first fill up the bucket with water and then poor the coolant in the bucket, and you seem to be the guy who can help us out, by sense I would agree with my colleagues that it doesn't matter which way since the ratio of coolant to water is the same, yet I have heard by the responsible people in different companies (and countries) and coolant comp. sales people, that you never put the coolant and then the water on top of it, since it will not mix properly, can you clarify this situation for us? Thanks, P.S. our our coolant is "Ashburn 9500" which is a petroleum based water soluble cutting oil

Dear Subscriber, I have used Ashburn products before myself, with very good results.  Mostly because they service their products very well, at least the group out of Houston did.   As far as mixing coolant and water, were not talking about acid and water here, so safety is not an issue.  Some metalworking fluids mix readily with water, and others need more encouragement, such as vegetable oil based fluids.  We want mixing, which means we want the highest possible Reynold's Number for the system, i.e., you want turbulence.  Turbulence results in better mixing every time.  Using a commercially available mixing nozzle is best.  If you don't have one, streaming water at city pressure, (higher velocity factor), for a longer period of time (since you will be adding more water than coolant) into a vessel containing the smaller quantity of coolant would be best.  This is true unless the source of the water flow is allowed to be blocked by the rising water level, thereby reducing the turbulence.  Prevent this if you can.  Another way is to pour the coolant in at the point you are blasting the water into the tank.  But you said you are using a bucket to mix a petroleum based product, so I assume this is make up concentrate to increase the concentration in the tank.  Get a paint stick, no big deal.  Ashburn 9500 mixes easily with water anyway.

One of the tests I would run with any Soluble Oil formulation is the inversion test.  This is where one adds water to the Soluble oil and measures how much water it takes to flip the emulsion from a water into oil emulsion (Invert), to an oil into water emulsion (Coolant).  My reasoning is if my customer tells me his coolant is thickening, I can do a % Water and see if he added enough water.  This normally happens in the small shop.  In this case either way is fine since they are using a bucket.  However, in making a master mix if the tank has a good mixer add water first then soluble oil mix until emulsified. If agitation is a problem add the Soluble oil first then the water that will provide decent agitation. However if the mixture has a thick stringy layer on the surface and no emulsion then you have a formulation problem, the coolant inverted and did not flip.  Contact your coolant supplier they will know how to handle that problem. 

Dom Dom