For a hydro-sizer (fluid bed classifier) the overflow velocity must have sufficient traction to remove the size and density of the particles you want gone. The easy way is to use a settling velocity chart such as is found on the USGS Wentworth grain size chart.

Settling velocity of Quartz spheres

1.00 mm . . . 15 cm/sec

0.25 mm . . . 3 cm/sec

0.06 mm . . . 0.3 cm/sec

The T1200 at max voltage, 13.6 at zero head produces 1200 GPH under field conditions about 900GPH or 15GPM or 0.25GPS

There are 3785.412 cubic centimeters in a US gallon so our flow is 946.353 CCPS

Divide the pump output by the settling velocity to get the volume area size at the pumps flow rate.

The convert that to area using the circle area formula, Pi r

^{2} or divide by Pi then take the square root

1.00 mm . . . 15 cm/sec = 63.09 cc = 9 cm diameter

0.25 mm . . . 3 cm/sec = 315.45 cc = 20 cm diameter

0.06 mm . . . 0.3 cm/sec = 3154.51 cc = 62 cm diameter

I would think that the overflow would be in the -0.06 mm (230 mesh) or 0.3 cm/sec or less.

If you use a device about a foot square that is 30 x 30 or 900 square cm. at a flow of 0.3 cm/sec or 27 cubic centimeters per second

27 x 60 x60 = 97,200 cc per hour / 3785.412 = 25 GPH

If my numbers are good.