Diaphragm pumps are the answer for some of the toughest challenges in pumping-- especially when the liquid being pumped is highly viscous, such as molasses, food or heavy oil; contains bio-media such as in fermentation; contains a high percentage of solids, such as with sewage and slurries; contains abrasives such as sand or activated carbon; or has highly corrosive solutions such as strong caustics. Diaphragm pumps can be manufactured in any size, from smaller than a quarter to larger than a car--and from virtually any material that can be machined or fabricated.

Construction

Simple diaphragm pumps consist of a flexible diaphragm that can be made from any rubber, plastic or elastomeric compound that's compatible with the material being pumped. They also have a displacement chamber with a volume slightly greater than the volume the diaphragm can displace. The entire perimeter of the diaphragm is tightly held and sealed in place between the side of the displacement chamber and a flange, which is tightly bolted or clamped to the chamber. Each displacement chamber also has two valves, usually spring-loaded ball valves or flapper valves made from the same material as the diaphragm. One of the valves admits the media being pumped to the diaphragm chamber, and the other allows the material to exit the diaphragm chamber. Finally, there's a motor or driving mechanism that flexes the diaphragm in and out of the chamber to suction in and force out the media.

Operation

Diaphragm pumps work by flexing the diaphragm out of the displacement chamber to draw in a defined volume of the pumped media through the inlet valve, then flexing into the chamber to push the media back out of the exhaust valve. Their operation is very similar to the draw in, push out, concept of human breathing. First they draw in through an inlet pipe, then they push out through an outlet pipe.

Pump Motors

Diaphragm pumps can be driven by almost any kind of rotational motor--including electric, internal combustion such as gasoline or diesel, air or hydraulic. Or they can be driven from the opposite side of the diaphragm by air pressure, vacuum, hydraulics or water pressure.

Other Features

Diaphragm pumps are useful for industrial situations in which contaminants may present issues. They're easy to disassemble, clean and sterilize for bio-applications, and are relatively inexpensive to manufacture, use, and maintain compared to other specialty pumps.

Disadvantages

Diaphragm pumps, with their cyclical operation, move fluids through pipes in pulses, cannot be run at high speed, and require more maintenance than other types of pumps. They can be noisy and are not particularly energy efficient.