A diaphragm pump uses a combination of the reciprocating action of a rubber diaphragm and suitable non-return valves to pump a fluid.

There are two main types of diaphragm pump:

• In the first type, the diaphragm is sealed with one side in the fluid to be pumped, and the other in air. The diaphragm is moved up and down, causing the volume of the pump chamber to increase and decrease. A pair of non-return valves prevent reverse flow of the fluid.
• The second type of diaphragm pump has one or more unsealed diaphragms with the fluid to be pumped on both sides. The diaphragm(s) again are moved up and down, causing the volume to change.

When the volume of a chamber of either type is decreased (the diaphragm moving up), the pressure decreases, and fluid is drawn into the chamber. When the chamber pressure later increases from increased volume (the diaphragm moving down), the fluid previously drawn in is forced out. Finally, the diaphragm moving up once again draws fluid into the chamber, completing the cycle. This action is similar to that of the internal combustion engine.

Applications

Diaphragm pumps are low lift, low head pumps with low flow rates. They can handle sludges and slurries with a moderate amount of grit and solid content. Excessive solids cause blockages.

Diaphragm pumps can be used to make artificial hearts