Diaphragm pump

Diaphragm pump schematic.

A diaphragm pump is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of pump is also called a membrane pump.

There are three main types of diaphragm pumps:

• Those in which the diaphragm is sealed with one side in the fluid to be pumped, and the other in air or hydraulic fluid. The diaphragm is flexed, causing the volume of the pump chamber to increase and decrease. A pair of non-return check valves prevent reverse flow of the fluid.^[1]
• Those employing volumetric positive displacement where the prime mover of the diaphragm is electro-mechanical, working through a crank or geared motor drive. This method flexes the diaphragm through simple mechanical action, and one side of the diaphragm is open to air.^[2]
• Those employing one or more unsealed diaphragms with the fluid to be pumped on both sides. The diaphragm(s) again are flexed, causing the volume to change.

When the volume of a chamber of either type of pump is increased (the diaphragm moving up), the pressure decreases, and fluid is drawn into the chamber. When the chamber pressure later increases from decreased 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 cylinder in an internal combustion engine.

Characteristics

Diaphragm pumps:

• have good suction lift characteristics, some are low pressure pumps with low flow rates; others are capable of higher flows rates, dependent on the effective working diameter of the diaphragm and its stroke length. They can handle sludges and slurries with a relatively high amount of grit and solid content.
• suitable for discharge pressure up to 1,200 bar
• have good dry running characteristics.
• are low-shear pumps.
• can be used to make artificial hearts.
• are used to make air pumps for the filters on small fish tanks.
• can be up to 97% efficient.
• have good self priming capabilities.
• can handle highly viscous liquids.
• are available for industrial, chemical and hygienic applications
• cause a pulsating flow that may cause water hammer

Mini diaphragm pump

• mini diaphragm pumps operate using two opposing floating discs with seats that respond to the diaphragm motion. This process results in a quiet and reliable pumping action. Higher efficiency of the pump is evident in the longer lifer of the motor pump unit.
• These DC motor diaphragm pumps have excellent self-priming capability and can be run dry without damage, Rated to 160 Deg. F (70 Deg. C).
• No metal parts come in contact with materials being pumped; diaphragms and check valves are available in Viton, Santoprene or Buna-N construction. So these mini diaphragm pumps are great chemically resistant.
• mini diaphragm pumps prime within seconds of turning the pump on; prime is maintained by two check valves (one on either side).Separated from the motor, the pump body contains no machinery parts, so pump can be in dry running condition for a short while.
• A built-in pressure switch insides the pump can automatically stop the pump, when the pressure reach a setting data.

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  CFD animation of a diaphragm pump

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  Double acting membrane pump on oil tanker deck

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  Membrane pump animation

References

1. ^ Mechanical diaphragm pump
2. ^ Electric diaphragm pump