A pneumatic diaphragm pump, also known as an air-operated double diaphragm (AODD) pump, is a type of positive displacement pump that uses compressed air to move a diaphragm back and forth, which in turn creates suction and discharge cycles to move a fluid. These pumps are known for their versatility and their ability to handle a wide range of fluids, including abrasive, viscous, and chemically aggressive materials. Here's how a pneumatic diaphragm pump works:
Diaphragms: Pneumatic diaphragm pumps consist of two flexible diaphragms, typically made of materials such as rubber, thermoplastic, or PTFE. These diaphragms separate the pump into two chambers: the liquid chamber and the air chamber.
Air Inlet and Outlet Valves: The air chamber has inlet and outlet valves connected to a compressed air source. These valves control the flow of air into and out of the air chamber.
Fluid Inlet and Outlet Ports: The liquid chamber has inlet and outlet ports for the fluid to be pumped. Check valves are often located at these ports to control the flow of liquid in and out of the pump.
Here's a step-by-step explanation of the operation of a pneumatic diaphragm pump:
Suction Stroke:
Compressed Air Inlet: During the suction stroke, compressed air is introduced into one side of the air chamber, causing the diaphragm on that side to flex and move away from the liquid chamber.
Liquid Inlet Valve Opens: As the diaphragm moves, it creates a vacuum in the liquid chamber, causing the liquid inlet valve to open due to the pressure differential.
Fluid Inlet: The vacuum in the liquid chamber allows the fluid to be drawn into the pump from the fluid inlet port.
Liquid Outlet Valve Closes: Simultaneously, the pressure from the incoming fluid pushes the liquid outlet valve closed to prevent backflow.
Discharge Stroke:
Compressed Air Inlet: In the next phase, compressed air is introduced into the opposite side of the air chamber, causing the diaphragm to flex in the opposite direction, pushing the diaphragm on the first side back to its original position.
Liquid Outlet Valve Opens: As the diaphragm moves, it pressurizes the liquid in the chamber, causing the liquid outlet valve to open due to the pressure increase.
Fluid Discharge: The pressurized liquid is expelled from the pump through the fluid outlet port, continuing the flow of fluid.
Liquid Inlet Valve Closes: Simultaneously, the pressure from the liquid discharge pushes the liquid inlet valve closed to prevent backflow.
This alternating process of diaphragm movement creates a reciprocating motion that draws in and expels the fluid, generating a pulsating flow. The ability to handle varying viscosities, solids, and chemicals makes pneumatic diaphragm pumps suitable for a wide range of applications, including chemical processing, wastewater treatment, paint and coatings, and many others. The use of compressed air allows for self-priming and the capability to handle shear-sensitive materials without damaging them.
