What is "diaphragm pump"

Diaphragm \Di"a*phragm\, n. [L. diaphragma, Gr. ?, fr. ? to fence by a partition wall; dia` through + ?, ?, to fence, inclose; prob. akin to L. fareire to stuff: cf. F. diaphragme. See Farce.]

1. A dividing membrane or thin partition, commonly with an opening through it.

2. (Anat.) The muscular and tendinous partition separating the cavity of the chest from that of the abdomen; the midriff.

3. (Zo["o]l.) A calcareous plate which divides the cavity of certain shells into two parts.

4. (Opt.) A plate with an opening, which is generally circular, used in instruments to cut off marginal portions of a beam of light, as at the focus of a telescope.

5. (Mach.) A partition in any compartment, for various purposes.

   Diaphragm pump, one in which a flexible diaphragm takes the place of a piston.

A diaphragm pump (also known as a Membrane pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or teflon diaphragm and suitable valves on either side of the diaphragm ( check valve, butterfly valves, flap valves, or any other form of shut-off valves) to pump a fluid.

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.
• Those employing volumetric positive displacement where the prime mover of the diaphragm is electro-mechanical, working through a crank or geared motor drive, or purely mechanical, such as with a lever or handle. This method flexes the diaphragm through simple mechanical action, and one side of the diaphragm is open to air.
• 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. Diaphragm Pumps deliver a hermetic seal between the drive mechanism and the compression chamber, allowing the pump to transfer, compress, and evacuate the medium without a lubricant.

An elastomeric diaphragm can be used as a versatile dynamic seal that removes many of the limitations found with other sealing methods. They do not leak, offer little friction, and can be constructed for low pressure sensitivity. With the right material consideration, diaphragms can seal over a wide range of pressures and temperatures without needing lubrication or maintenance.