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 Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

thermoplastic A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains as ...

teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...

diaphragm and suitable valves on either side of the diaphragm (

check valve A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have ...

, butterfly valves, flap valves, or any other form of shut-off valves) to pump a

fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

. 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 An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

hydraulic fluid A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backho ...

. 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 An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

. 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.

Characteristics

Diaphragm pump characteristics are: * Self-regulated: The flow rate of an air-powered diaphragm pump can be easily set from zero to maximum just by adjusting the air inlet or the fluid outlet valve. No need to stop running the pump before closing the fluid outlet valve. The pump will just stop by itself and will not consume energy or overheat. Reopening the valve will make the pump restart to resume operation. * Self priming and have good suction lift characteristics. * Can be designed to handle abrasive sludges and slurries with a relatively high amount of grit and solid content. * Have good dry running characteristics. * Handle fluids smoothly and carefully, the diaphragm pump design avoids mechanical or chemical damages to the fluid during the transfer: No shear, no foam and no heating. * Pump design separates pump fluids from potentially sensitive internal pump parts. * A multitude of different diaphragm

elastomers An elastomer is a polymer with viscoelasticity (i.e. both viscosity and Elasticity (physics), elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a ...

can be selected, allowing compatibility with very corrosive solutions. * Can handle low to medium viscous liquids. A viscosity correction chart can be used as a tool to help prevent under-sizing AOD pumps. * Can be effectively driven by compressed air or by electricity. Air driven versions typically achieve the safety requirements to operate in flammable or explosive atmospheres. * Hydraulically driven versions are suitable for discharge pressure up to 1,200 bar. * Internal pump parts can be suspended and isolated within oil, to promote pump longevity. * Can be up to 97% efficient. File:DiaphragmPump.gif, CFD animation of a diaphragm pump File:Membrane pump on oil tanker deck.jpg, Double acting membrane pump on oil tanker deck File:Membraanpomp.svg, Membrane pump animation

Air compressors

Small mechanically activated diaphragm pumps are also used as

air compressor An air compressor is a machine that takes ambient air from the surroundings and discharges it at a higher pressure. It is an application of a gas compressor and a Pneumatics, pneumatic device that energy conversion, converts mechanical power (from ...

s and as a source of low-grade vacuum. Compared to other designs, diaphragm compressors are quiet, cheap, and have no moving parts in the air stream. This allows them to be used without added lubrication in contact with the air, so the compressed air produced can be guaranteed clean. An example is a typical aquarium air pump.

Main Diaphragm Pump Manufacturers

ARO
founded in 1930. * Verder * Graco
GODO
founded in 1990.

References

{{reflist Pumps