How does a diaphragm pump work? Step 1
An air-driven diaphragm pump is an oscillating positive displacement pump. The pump moves fluid from the fluid chambers until the end of a stroke is reached. The drawings and explanations below will give you some insight into the operation of the pump.
There are a number of moving parts that come into contact with the pumped fluid: these are the two diaphragms connected by a shaft, the two intake valve balls and the two exhaust valve balls.
The diaphragms separate the compressed air from the pumped liquid; in doing so, the mechanical stress on both sides of the diaphragm is equal, resulting in a long diaphragm life. The valve balls open and close on the valve seats and control the fluid flow.
How does a diaphragm pump work? Step 2
The air distribution system sends compressed air through the right air chamber to the back of diaphragm A. The compressed air pushes the diaphragm away from the center block toward the fluid chamber. The opposite membrane (membrane B), which is connected to membrane A through the shaft, moves inward toward the center block.
Diaphragm B is now in the "suction" position; the air behind the diaphragm is exhausted through the air outlet duct. Membrane A is now compressing against atmospheric pressure. The movement of membrane B toward the center block creates a vacuum in fluid chamber B.
Due to the pressure difference created, fluid will push the valve ball off the valve seat through the inlet piece. The resulting space between the valve ball and valve seat allows fluid to flow into the fluid chamber. (bottom left).
How does a diaphragm pump work? Step 3
When the pressurized diaphragm A reaches the end of its stroke, the air slide sends compressed air to the back of diaphragm B. The compressed air pushes diaphragm B away from the center block while the shaft pulls diaphragm A toward the center block. The air behind membrane A is exhausted through the air outlet channel. Diaphragm B is now in the "press" position while diaphragm A is in the "suction" position. Diaphragm B pushes the inlet valve ball (lower left) onto the valve seat due to hydraulic pressure in the fluid chamber.
The hydraulic pressure pushes the exhaust valve ball out of the seat and the inlet valve ball into the seat. The fluid in the fluid chamber will now enter the outlet through the resulting gap between valve ball and seat and exit the pump. The "suction" motion of diaphragm A toward the center block creates a vacuum in fluid chamber A. Due to the pressure differential created, fluid will push the valve ball off the valve seat through the inlet piece. The space created between the valve ball and valve seat allows fluid to flow into the fluid chamber. (bottom right).
When the pump returns to its original starting position, each diaphragm has completed both a "suction stroke" and a "delivery stroke. We call this a pumping cycle. Depending on the application, the pump needs several cycles to completely fill with the liquid to be pumped.