Milk is drawn into an air separator tank by a vacuum pump which is then shut off by a controller actuated by a level gauge in the tank. - The controller then opens a valve in the supply line and maximum flow is pumped through the supply line and through the flow meter at its output. - At a given low level in the tank, the supply valve is cut off, but minimum flow through the flow meter is maintained by a stop valve and throttle controlled by the controller. - Alternatively, the stop valve and throttle can be replaced by a hydrometer controlling the pump
