Liquid to be pumped (i.e., condensate, Dowtherm, hydrocarbons, liquid food products, etc.) enters the pump tank via inlet check valve, vent valve is opened and stem/air valve is closed. The pump mechanism float rises with increasing level until "high level" when the compression spring simultaneously forces closed the vent valve and opens the steam/air (pressure) valve. The pressure forces the liquid through the exit check valve (the volume pumped per cycle is dependent upon pump tank size). During the pumping period, ball float drops as the liquid level recedes to "low level." The action of the compression spring then simultaneously forces open the vent valve and closes steam/air valve. Pressure in the pump tank dissipates through the vent, and liquid to be pumped enters through the inlet check valve beginning a repeat cycle.
The table below indicates pounds per hour for liquids with specific gravity = 0.9 to 1.0 with a filling head of 12 inches above the pump top, and using steam as the motivating force. For other specific gravity fluids, filling heads and motivating force mediums, check with your representative.
(Approximate utility usage is 3 lbs. of steam per 1,000 lbs. of liquid pumped, 100 std. cubic feet of compressed air per 1,000 lbs. of liquid pumped)