A diaphragm pump is a positive displacement pump that uses a flexible membrane to pump fluids. The pump uses a series of check valves to ensure that fluid can only travel in one direction through the chamber. The diaphragm itself can be expanded and contracted using pressurized air or fluids, or motors.
Generally speaking, a diaphragm pump moves fluids using a two-part cycle. In the first part, the diaphragm is pulled away from the input/output valves so that the volume of the chamber increases. This increase in volume results in a decrease in pressure within the chamber relative to the input and output, creating a vacuum effect that draws fluid in. Check valves on the input and output connections ensure that fluid can only enter the chamber through the input connection.
After the first phase completes, the membrane in the diaphragm pump is pushed back into the chamber. The volume within the chamber then decreases and the pressure increases. The fluid within the chamber is pushed through the output connection. As with the input cycle, the attached check valves allow fluid to exit the chamber only through the proper connection.
In most cases, the diaphragm itself is sealed to the sides of the pump, completely separating the chamber from the actuating mechanism. Because the mechanism doesn’t actually move the diaphragm, but rather stretches and contracts it, there is little friction within the pump itself. This feature of the diaphragm pump sets it apart from other types in that it allows the pump to run dry for extended periods of time without incurring damage. This, along with their flexible designs, allows diaphragm pumps to be used in anything from heavy industrial applications to artificial hearts.
There are two primary types of actuators for diaphragm pumps. The first utilizes pressured air or fluid to expand or contract the diaphragm. An increase in the pressure on the actuator side of the pump pushes the diaphragm into the chamber, increasing the pressure on the fluid within the chamber and forcing it through the output. Likewise, a decrease in pressure on the actuator side causes the diaphragm to flex away from the chamber.
The second type of actuator uses a mechanical device attached to the diaphragm to push and pull it into and out of the chamber. The effect within the chamber is identical regardless of the type of actuator used. Only the mechanism used to drive the pulsations of the diaphragm is different.