Diaphragm Pump
A diaphragm pump is a hydraulically or mechanically actuated positive displacement pump that uses a combination of reciprocating action and either a flapper valve or a ball valve to transfer liquids. Diaphragm pumps are self-priming and are ideal for viscous liquids. Virtually all major industries utilize diaphragm pumps. They are commonly used to move abrasive fluids, including concrete, or acids and chemicals. They are also common in automobiles and aircraft. A diaphragm pump is also known as a membrane pump, air operated double diaphragm pump (AODD) or pneumatic diaphragm pump.
A diaphragm pump is a type of a type of positive displacement pump that uses the reciprocating action of a flexing diaphragm to move fluid into and out of the pumping chamber.
They work when the flexing diaphragm creates a vacuum at the inlet of the chamber that draws the fluid into the chamber. When the diaphragm moves in the opposite direction, it causes the volume of the pumping chamber to decrease, forcing the fluid out the discharge port of the pump.
Diaphragm pumps use check valves at the inlet and outlet of the pumping chamber to ensure that the fluid flows in one direction and out the other without leaking backwards.
An Air Operated Diaphragm (AOD, or Air Operated Double Diaphragm (AOOD)) Pump is a type of reciprocating positive displacement pump. The AOD Pump is operated by compressed air allowing the pump to transfer and compress the medium without a lubricant and can be used without an electrical power.
A diaphragm pump (also known as a Membrane pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic diaphragm and suitable valves on either side of the diaphragm to pump a fluid. AODD pumps (also known as Air operated diaphragms pumps, pneumatic diaphragm pumps, AODD pumps, AOD pumps) are used for endless applications in mining, industrial and general plant service. Powered only by compressed air, they are especially used where electricity isn’t available, or in explosive or flammable areas.
AODD Pumps are a type of reciprocating diaphragm pump which contains two diaphragms driven by compressed air. Air section with shuttle valve applies air alternately to the two diaphragms; each diaphragm has a set of check/ball valves.
The working principle of AODD pumps is as follows.
Figure 1
· The air valve directs pressurized air to the backside of Diaphragm A, pushing it away from the centre of the pump. Acting as a separation membrane between the compressed air and liquid, the elastomeric diaphragm applies pressure to the liquid column, while also balancing the load in order to remove mechanical stress from the diaphragm.
· As the compressed air moves Diaphragm A away from the centre of the pump into its discharge stroke, the pressure created within Chamber a pushes out the liquid through its discharge valve.
· At the same time, the common shaft pulls the opposite diaphragm (Diaphragm B) inward on its suction stroke with the air behind it having been forced out to the atmosphere through the exhaust port of the pump.
· The movement of Diaphragm B toward the centre of the pump creates a vacuum within Chamber B. Atmospheric pressure forces fluid into the inlet manifold forcing the inlet valve ball in Chamber B off its seat. The liquid is then free to move past the inlet valve ball and fill liquid Chamber B (see shaded area).
Figure 2
· When the pressurized diaphragm, Diaphragm A, reaches the limit of its discharge stroke, the air valve redirects pressurized air to the backside of Diaphragm B.
· The pressurized air forces Diaphragm B away from the centre while pulling Diaphragm A toward the centre via the common shaft.
· Diaphragm B is now on its discharge stroke, which forces the inlet valve ball in Chamber B onto its seat due to the hydraulic forces developed in Chamber B and the manifold of the pump. These same hydraulic forces lift the discharge valve ball off its seat in Chamber B; while the opposite discharge valve ball in Chamber A is forced onto its seat, forcing fluid to flow through the pump discharge.
· The movement of Diaphragm A toward the centre of the pump creates a vacuum within Chamber a and the atmospheric pressure forces fluid into the inlet manifold of the pump.
· The inlet valve ball in Chamber A is forced off its seat, allowing the fluid being pumped to fill Chamber A from the inlet manifold.
Figure 3
· At the completion of the stroke, the air valve again redirects air to the backside of Diaphragm A, which starts Diaphragm B on its exhaust stroke.
· As the pump reaches its original starting point, each diaphragm has gone through one exhaust and one discharge stroke. This constitutes one complete pumping cycle.
· The pump may take several cycles to completely prime depending on the conditions of the application.
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