Hello guys, I have a query regarding which method of inline mixing of a coolant with water would yield a homogeneous mixture. Application is to mix a coolant with water at a particular concentration possibly without using an agitator or a separate tank.

Coolant is fed from a drum using a pump and water is fed under gravity. Both liquids are mixed in-line in a dispenser (static mixer.. or just in a pipe) and fed to the machine sump.

Case 1 : Both liquids turn on at the same time. Since coolant quantity is very less compared to the quantity of water (1:20 approx), required coolant flows out of the dispenser before the required water. The two liquids might mix in the sump.

Case 2: I 'pulse' the coolant.. for eg. if I have to feed 5 litres of coolant concentrate with 95 litres of water, i divide the flow time of coolant into 10 equal pulses.. i.e 500 ml per 9.5 litres of water. The coolant pump turns off after every 500ml of coolant passes through, and turns ON after 9.5 litres of water has flown. And so on...

Case 3: I use proportional valves & variable flow-rate pumps to match the flow-rate of chemical and water so they start and stop at the same time. This increases the capital cost multi-folds due to the use of the proportional valves and the special pump.

Which one would you recommend?

I have taken a small lab-scale trial but could not really find too much of a difference in the concentration of the mixed solution in each case. I am interested in achieving a homogeneous mixture before the solution reaches the sump, and not rely on agitation in the sump to cause the mixing.

I am not convinced by Venturi mixers as they require a constant flowrate and pressure of the 'motive' fluid (water). Dosatron units don't allow automatic changing of mixing ratios, otherwise they would have been ideal.

Also, would you guys happen to know of the Auto Refill option on Haas machines? I know it uses a Venturi mixer, but would like to know if it is effective like it claims.

Any help will be appreciated. Thanks.