Abstract: A centrifuge system for removing impurities from metal working coolant. The centrifuge of the system includes a liquid inlet, a first liquid outlet for high density liquid, a second liquid outlet for low density liquid, a discharge means for a shoot of particulate material, and a pressure port for receiving liquid under pressure to cause the shoot. A line receives high density liquid from the first liquid outlet. The line discharges into a tank. A branch line connects the line to the pressure port. A valve in the line can stop flow to the tank. When the valve is closed, pressure at the pressure port is increased to cause the shoot.