Thanks for your help!
Final comment on coolant. The brown skim is way oil and other contaminants. What will happen over time to coolant concentration depends on actual chemicals in the coolant and outside conditions present. My experience says that with heavy use, water is expelled from the mixture causing concentration of coolant to increase. Thus plain water must be added to maintain proper concentration. It might be possible with synthetic or semi-synthetic coolants and light use to have the coolant "flashing off" and leaving water behind, causing concentration to decrease. Synthetic and semi-synthetic coolants usually contain glycol, similar to alcohol.
Just cycle your coolant pump while adding a cup of raw coolant at a time and rechecking %.
Thanks for your help!
If it's a case of the coolant separating, can you set the coolant pump up so it cycles over, only put the nossle into a return hose, or could you add a small agitator to the tank. Connect it to a timer so it cycles over for 10min every second day.
@Gary - That would be acceptable. But it is also good to run the spindle through its speed range, and move the axis around too. Do whatever you have time to do to take care of your tools and they are more likely to be ready to take care of you.
You might have large amount of bacteria/fungi growing in your coolant also causing the rust issues. To combat that problem, keep oil skimmed off and I plumbed a 0-30 psi regulator (had on hand) into my existing air system with a flow control and ran a few lines into my reservoir with diffusers on the ends to keep the coolant oxygenated. You can get test strips that you dip in coolant and incubate a few days to see if you have excessive growth, then a sump side bactericide might be needed like Triadine.
One of the biggest problems I see with coolant is how it's mixed. You have 2 choices, jet mix, or add coolant to the water. NEVER put concentrate in a bucket then fill with water. The biocides in the coolant react with water, without enough water on mixing, the coolant gets too "hot" and will not bind well with the water. The lead chemist from GC Chemical was the one that explained this too me, not my opinion.
on advice from the tech guy i spoke to, i have added neat oil to the sump near the coolant pump to get the concentration up. I added 3ltr of neat oil and ran the machine with the coolant on this morning but it still remains at about 3%. I dont understand how. The sump holds approx 100ltr so 3ltr of neat oil should have brought it up at least a small amount. Strange!
I do not understand "neat" oil. Here, "neat" oil or "neatsfoot" oil is a light yellow oil obtained from the feet and shinbones of cattle, used chiefly to dress leather. I should have questioned you on this before.
If by "neat" oil you are meaning a water-soluble oil used in machining for lubrication and cooling, then I am with you. If you are actually adding oil, as in a petroleum product, NOT water-soluble, then please stop.
You should be adding the the same liquid that you normally mix with water in its undiluted condition to your sump. For a 100 liter sump, 1 liter of undiluted coolant should boost your refractometer reading 1%.
When I say neat oil I mean the coolant without adding water. It's a soluble coolant which is mixed to 5%. Im not putting a random oil in there