Diaphragm pump

The diaphragm pump is a machine for conveying liquids or gases, which is particularly insensitive to continuous stress and impurities in the material to be conveyed.

Its operating principle is a modification of the piston pump, but with the medium to be conveyed is separated by a membrane from the drive. It is also similar to the heart, but the used instead of a mechanical moving diaphragm twitch muscles.

The advantage of this pump is that is shielded by the separator of the drive from harmful influences of the delivery medium, such as sludge or debris in the pharmaceutical or food industry. One of the biggest drawbacks of the conventional piston pump, the problem of sealing of the piston is solved.

The deflection of the membrane is either hydraulically, pneumatically, mechanically or electromagnetically.

Areas of application

Diaphragm pumps are used where a leak-free pump design is especially important. For example, they are used where hazardous sludges are to pump or a dry run is to be feared. They are useful for transport of abrasive fluids, because they have no contact seals and due to the low maintenance requirements generally in sludges.

For higher pressures, they are not well suited, earlier they were often used in cars as fuel pump.

Mechanically

Mechanical diaphragm pumps have a slightly better efficiency than air operated diaphragm pumps, especially if you include the energy loss due to the generation of compressed air, but still can not come close to the efficiency of a hydraulic diaphragm pump.

Hand diaphragm pump

These are driven in most cases, a pump lever by hand. They are used for example for generating a vacuum for centrifugal pumps for pumping or smaller amounts of liquid. They are also a common working tool of firefighters in dangerous applications. Another example of an early form of the diaphragm pump, the bellows.

Mechanical transmission

These are driven in most cases, via a connecting rod and an eccentric by an electric motor. They are used for example in leak detection equipment to maintain the negative pressure.

Pumps of this type have been used for decades as a fuel feed pump in motor vehicles. Here they are actuated by the camshaft of the engine. In single-cylinder and two-stroke engines, the membrane was isolated from the vacuum of the intake tract directly actuated.

One application for this pump is about the membrane - priming pump at the fire department.

Hydraulic: Piston diaphragm pump

Hydraulic pumps are required for higher pressures. The back pressure of the hydraulic fluid relieved the membrane, thereby increasing its service life.

In a reciprocating diaphragm pump, the reciprocating movement of the piston via a working fluid is transferred to the membrane. As a working fluid, water is used with a water- soluble mineral supplement or a hydraulic oil. The operation of the reciprocating diaphragm pump can be considered in a manner similar to that of a pure piston pump, as it is directly caused by a constant head of liquid between the piston and the diaphragm, the movement of the piston, and thus a deflection of the diaphragm produces suction and pressure pulses. By the use of a liquid, the membrane is loaded, however, the whole surface and there is no point loading of the membrane as a clean membrane pump.

Pneumatic

They consist of a double casing comprising two interconnected via a connecting rod membranes. These are applied on the outer side of the conveying medium on its inner side by the compressed air. When the diaphragm has reached its end position, a valve is actuated by the connecting rod, which reverses the pressure air to the other membrane. An air-operated diaphragm pump transfers the air pressure without losses to the fluid. The only positive displacement pump, the delivery is set by stalling on the pressure side and can be adjusted very precisely, therefore. However Umsteuermoment occur in relatively large fluctuations in the delivery pressure ( no pressure surges, as the pressure drops, but can not rise above the atmospheric pressure ), which can interfere with some applications.

Another disadvantage is the relatively high energy requirement, because as much pressure compressed air is required, as is the subject of the pump.

Electromagnetic ( vibration pump )

This type of diaphragm pumps use a vibrating diaphragm which is moved by a magnetic alternating field.

The electromagnetic pumps are significantly more efficient than the pneumatic pumps ..

Swell

• Gerhard Vetter: Leak-free pumps, compressors and vacuum pumps. Vulkan-Verlag GmbH, 1998, ISBN Vulkan-Verlag GmbH, 1998, pages 251-260