For: Wikipedia:Village pump
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For: Wikipedia:Village pump
A pump is a device used to move fluids, such as gases, liquids or slurries. A pump displaces a volume by physical or mechanical action. One common misconception about pumps is the thought that they create pressure. Pumps alone do not create pressure; they only displace fluid, causing a flow. Adding resistance to flow causes pressure.
Types
Pumps fall into two major groups: positive displacement pumps and rotodynamic pumps . Their names describe the method for moving a fluid.
Positive displacement pumps
A positive displacement pump causes a fluid to move by trapping a fixed amount of it then forcing (displacing) that trapped volume into the discharge pipe. A positive displacement pump can be further classified as either
- a rotary-type, for example, the lobe, external gear, internal gear, screw, shuttle block, flexible vane or sliding vane pumps,
- the Wendelkolben pump or the helical twisted Roots pump.
- the liquid ring vacuum pump
Gear pump
main: Gear pump This uses two meshed gears rotating in a closely fitted casing. Fluid is pumped around the outer periphery by being trapped in the tooth spaces. It does not travel back on the meshed part, since the teach mesh closely in the centre. Widely used on car engine oil pumps.
Progressing cavity pump
Widely used for pumping difficult materials such as sewage sludges, contaminated with large particles, this pumps consists of a spiral shaped rotor, about 10 times as long as its width. This can be visualised as a central core of diameter x, with typical a curved spiral wound around of thickness half x, although of course in reality it is made from one casting. This shaft fits inside a heavy duty rubber sleeve, of wall thickness typically x also. As the shaft rotates, fluid is gradually forced up the rubber sleeve. Such pumps can develop very high pressure at quite low volumes.
Roots-type pumps
The low pulsation rate and gentle performance of this Roots-type positive displacement pump is achieved due to a combination of its two 90° helical twisted rotors, and a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous and non-vorticuless flow with equal volume. High capacity industrial "air compressors" have been designed to employ this principle as well as most "superchargers" used on internal combustion engines.
