Qualitek fine mill drain valve adjustment

Our Qualitek fine mill has a metal trap at the bottom where gold nuggets collect to prevent them from being pulverized unnecessarily.
This trap has a drain hole that can be opened during operation to release partially milled ore.
Total mill output is the sum of the ore passing through the top outlet via the cyclone (-75 micron) plus the ore dropping from the drain valve at the bottom. By opening this valve, the milling rate can increase dramatically (300% to 500%).
As the valve is opened gradually the maximum particle size starts to increase. This adjustment is ore dependent and optimum milling rate / particle size will depend on the exact function for the mill.
Ore passing through the top outlet into the cyclone will always be -75 micron.
This video illustrates the effect of opening the drain valve for gold dump and gold reef ore.