John Armitage, Product Engineer, Price, Pump Company
The general principle behind AOD, pumps is to transfer fluid through the pump by means of a user supplied source of compressed air. The AOD, pump consists of suction and discharge manifolds, suction and discharge ball valves, liquid and air chambers. The air chambers are separated by diaphragms, which are in turn, connected by a common shaft. The final and most important component is the air distribution system. The compressed air is directed into the air valve. Through a series of passages, the air is directed into one of the air chambers. As one air chamber fills with air, the diaphragm in that chamber will begin to expand into the pump chamber, displacing the fluid in that pump chamber past the discharge valve into the discharge manifold. Conversely, the shaft that is connected to the opposing diaphragm pulls it into its own air chamber. This creates a vacuum in the pump chamber, which "pulls" the fluid past the suction valve and into the pump chamber. As the pump chamber reaches its maximum capacity, the diaphragm will trigger a switch, which reverses the air-flow to the opposite chamber and the process is repeated. The two pump chambers are always simultaneously in opposing cycles of the stroke: one is always discharging fluid while the other is in the suction cycle. This continuous redirecting of the compressed air causes the reciprocating motion of the diaphragms, which results in pumping of the process fluid.
The basic design of AOD, pumps, offers many advantages over other pumping alternatives. Because the driving force of the pumps is compressed air, the pumps do not require complex electrical and/or electronic controls to install and operate. The pumps handle a wide variety of fluids ranging from very high to low viscosity, to those that are corrosive and/or abrasive. They also have the ability to pump low-density powders and can pass fairly large solids. AOD, pumps do not "shear" the fluid during transfer, so they are ideal for handling shear-sensitive media such as foods, paints and inks where fluid consistency needs to be maintained. Due to the diaphragms being fixed at the outer diameter bead, the pumps have static sealing surfaces and do not require mechanical seals. They are self-priming with lifts greater than 20 feet, and can run dry or against a closed discharge without damage. In some cases, they can even be run while completely submerged in the process fluid. For applications where performance needs to be varied, the pumps offer an infinitely variable flow rate without the need of a variable speed motor. Just by varying air inlet pressure the performance of the pump can be adjusted to suit the application. AOD, pumps are portable and because of their quick and easy installation, they are easily transferable from site to site. Couple all of this with their ease of repair and maintenance, and you begin to see why AOD, pumps have remained an industry favorite.
PFC Equipment can answer all of your AOD questions, contact our application engineers!