The air control mechanism functions alternately to pressurize and exhaust the air side of the diaphragm. This principle may be incorporated in both simplex and duplex pump designs. Simplex designs, which require a mechanical device to reposition the diaphragm after the discharge stroke, have more complex control systems. The more common duplex design incorporates two diaphragm chambers working in tandem with a common shaft. As one chamber discharges, the shaft repositions the diaphragm in the second chamber creating a suction condition, and it also sends a signal to the air control mechanism to reverse the motion.
Duplex designs are generally more versatile and operate at higher efficiencies.
The structure of the pump housing has a number of operating advantages. All sealing surfaces are static with no relative motion between components in contact with other elements, and high displacement ratios are possible without precision fits or close tolerances between components. The absence of close-fitting parts and low internal fluid velocities make the AOD pump an excellent choice for abrasive fluids. The AOD pump's diaphragm is a separation medium isolating the compressed air that is doing the work from the fluid being pumped. The differential pressure across the diaphragm and corresponding internal stresses are low in comparison with similar stresses in mechanically driven diaphragm pumps that use the diaphragm to generate pressure.