pump

Pumping station is a redirect to this article. See also: Berzbuir pumping station , pumping station (Bremthal) and Kaiserswerth pumping station .

This article covers the machine. See Pump (disambiguation) for other meanings .

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Piston pump and plunger pump

Bucket & piston pump

Plunger pump set of a former waterworks

Pump of a former water station

Circuit symbol : pump

Handle pump for pumping groundwater

Historic water pump in Kaster

Oil pipeline : one of four pressure pumps in a pumping station

Horsehead pump for oil production near Landau

Dosing pump for fuel

Pumps convey liquids (incompressible fluids ), which also include liquid-solid mixtures ( suspensions ), pastes and liquids with a low gas content. As fluid energy machines convert pump as a working machine , a drive operating in kinetic energy of the fluid (pressure times volume).

In technical jargon, pumps are exclusively referred to as machines for the transport of incompressible fluids: The common term "air pump" is not correct in this language: In the case of compressible gases, one speaks either of a blower if volume is conveyed without significant pressure (e.g. for inflating an air mattress) or by a compressor , when gas is compressed under pressure: So " bicycle air pumps " are technically not pumps, but piston compressors .

Demarcation

Fluid flow machines for compressible media such as gases or vapors are compressors or fans :

• If compressible media are conveyed without there being a significant increase in pressure and the main objective is accordingly to increase the dynamic energy, the correct term is fan (colloquially, fan ).
• If gases and vapors as well as gas-liquid mixtures are conveyed and if their pressure increase through compression is an essential goal, the device is called a compressor .
• Machines that are used to generate a vacuum in a container are called vacuum pumps , but their function is also a compressor.

Devices that give a fluid an increase in energy by applying mechanical work, but in which the medium can flow in and out without additional guidance, are technically not pumps. Which includes:

• Pedestal and ceiling fans
• Propeller (aircraft and ship)
• Agitators

Classification of pumps

According to their functional principle, pumps are divided into two main groups: In the following, for the sake of simplicity, both groups are referred to as pumps.

Flow pumps

In fluid flow machines , the energy transfer is effected exclusively by fluid mechanical processes. The medium flows freely through the machine without flaps and valves. At a standstill, the medium could flow backwards through the pump. Therefore, depending on the application, slides , valves or non-return valves must be used. Flow pumps are not self-priming, so the suction lines must always be filled with liquid or there must be a sufficiently large volume of liquid in front of the actual impeller inlet. The maximum suction height is also limited here by the local air pressure and any flow resistance. Flow pumps should not be throttled during operation on the suction side, since there is a risk of the blades being destroyed by cavitation .

Flow pumps are also known as centrifugal pumps . They can be divided into the following types:

• Axial pump
• Diagonal pump
• Radial pump

Positive displacement pumps

With positive displacement pumps, the medium is conveyed through self-contained volumes; backflow is prevented by valves or flaps, other media or their shape by gravity . Except for design-related leaks, the medium cannot flow through the pump in the opposite direction even when it is not running. Positive displacement pumps are usually self-priming, which means that pumps designed for liquids can also convey gases for a mostly limited period of time and thus build up a vacuum that is sufficient for suction.

The maximum suction height ( geodetic suction height ) is limited by the vacuum that can be achieved, the local air pressure , the density of the medium and the flow resistance to be overcome. Displacement machines should not be shut off on the pressure side unless suitable measures have been taken using slip clutches , pressure relief and bypass valves and the like to prevent damage to the pump, the drive or the lines up to the shut-off point.

A distinction is also made between fixed displacement pumps and variable displacement pumps. Fixed displacement pumps always displace the same volume with each revolution. With variable displacement pumps, however, the displacement can be adjusted. In addition, the pumps can be divided into rotating and oscillating displacement pumps according to their delivery principle.

These include:

• Bellows ( bellows pumps or bellows pumps)
• Diaphragm pumps
• Scroll compressor
• Rotary piston pumps
  • Rotary lobe pumps
  • Rotary vane pumps
  • Rotary piston pumps
  • Gear pumps
• Eccentric screw pumps
• Screw conveyors ( Archimedean screw )
• Hydraulic ram
• Impeller pump
• Chain pumps
• Piston pumps
  • Axial piston pumps (e.g. "swash plate" or "inclined axis" version)
  • Reciprocating pumps (e.g. slurry pumps , fuel metering pumps , injection pumps )
  • pneumohydraulic pressure intensifier (also called pressure multiplier )
  • Radial piston pumps
• Rotary piston pumps
• Peristaltic pumps (including peristaltic pumps called)
• Pumping stations , in the simplest case a bucket in the well.
• Screw pumps (also screw pumps , helical piston pump or screw compressor called)
• Shaking pumps
• Sinus pumps
• Timing belt pumps

and many special constructions, as well as the heart in animals and humans .

Other constructions

Jet pumps occupy a special position . With them, the medium to be conveyed is accelerated by a jet of gas, steam or liquid. Although they use flow dynamic processes, they are still mostly counted as positive displacement pumps.

These are for example:

• Water jet pump (uses water to convey air or water)
• Steam jet pump (uses gas to convey air or water)

Further funding principles are:

• Mammoth pump or bubble pump (delivery by ascending gas bubble as a piston)
• Ram (hydraulic ram) (uses water to pump water)
• Horse head pump (deep pump)

In addition, there are other, sometimes exotic constructions that use electromagnetic or other physical properties of the conveying medium for energy transfer.

Examples of this:

• Ion getter pump (see also sorption pump in the article vacuum pump )
• Titanium sublimation pump
• Turbo molecular pump
• Electrochemical gas pump

Applications

Suction pump Sewage pump Barostat in neurogastroenterology Blood pump (in addition to the heart there are also artificial versions ) Drilling machine pump (for small delivery rates) Dosing pump Injection pump (petrol, diesel) Barrel pump Fire pump Slurry pump

Hand pump Reciprocating pump hydraulic pump Boiler feed water pump Fuel pump Piston pump Cooling water pump Bilge pump Air pump Micropump

Oil pump Pipeline pump Acid pump Dirty water pump Syringe pump Irrigation pump Tandem pump Submersible pump Circulation pump (circulation pumps in general: pumps in circuits) water pump

NPSH value

NPSH (holding pressure height) is a term from the USA ( Net Positive Suction Head ) and means - loosely translated - about the minimum intake height above saturation pressure . According to DIN EN ISO 17769, the corresponding German expression is holding pressure height . NPSH is given in meters (m).

Holding pressure height and NPSH value are not equivalent due to different reference points.

With NPSH, for example, the pressure difference between the vapor pressure and the pressure at the suction port inlet of the pump, and at the holding pressure level, the vapor pressure is compared with the pressure at the impeller inlet.

It is between net positive suction head of the pump (NPSH _R [required] or NPSH _req. ) And holding pressure level in the system (NPSH _A [available] or NPSH _prev. ) Distinguished.

Required NPSH (holding head of the pump)

The net positive suction head NPSH of the pump or _Inv. Corresponds to the total pressure drop from the suction nozzle (limit of supply) of the pump to the impeller inlet (pressure increase in the impeller zone) and indicates the absorbency of the pump.

Example: NPSH _req. = 2 m means that the pressure losses from the pump intake to the impeller inlet (including acceleration losses) correspond to a pressure head of 2 m water column. ${\displaystyle p/(\rho \cdot g)}$

If the holding pressure level of the pump (NPSH _req. ) Is not reached during operation, the evaporation pressure of the pumped liquid falls below the local level and thus cavitation (vapor formation with subsequent sudden condensation in the pressure increase zone of the pump). Cavitation can cause a drop in the delivery rate and the degree of efficiency, uneven running and damage to the internal parts of the pump through material removal (so-called abrasion).

The holding pressure level of the pump depends on the temperature via the saturation vapor pressure of the pumped liquid. However, it changes with each pump with the flow rate and speed. NPSH _required is usually given by the pump manufacturer either as a numerical value for a specific operating point of the pump or shown in connection with a performance curve in the form of a curve.

Existing NPSH (holding pressure head of the system)

The existing NPSH value includes all the individual data of the pump system that have an influence on the pressure at the suction port of the pump, such as density, temperature and vapor pressure of the pumped medium, pressure losses in the suction line, pressure in the suction tank and geodetic suction or inlet head for a specific flow rate in one single numerical value together.

Example: NPSH _existing = 4 m indicates that the liquid to be pumped at the suction port of the pump is still a positive 4 m water column away from the evaporation pressure . ${\displaystyle p_{D}}$

The following applies to the pressure at the suction port (only the suction side is considered):

${\displaystyle {\frac {p_{\mathrm {Stutzen} }}{\rho \cdot g}}={\frac {p_{\mathrm {D} }}{\rho \cdot g}}+\mathrm {NPSH} _{\mathrm {vorh.} }\,}$

Steam is generated and thus cavitation occurs when the steam pressure equals the pressure p at the suction nozzle, i.e. that is, if NPSH _exists 0 goes. ${\displaystyle p_{D}}$ ${\displaystyle \to }$

Since the holding pressure level of the pump (NPSH _req .) Must not be undershot, the value for NPSH _present must be at least the same, or better, slightly greater than that of the pump.

${\displaystyle \mathrm {NPSH} _{\mathrm {vorh.} }\geq \mathrm {NPSH} _{\mathrm {erf} }}$

If necessary, the suction tank must be placed higher or the pump lower, the nominal size of the suction line larger or the pressure in the suction tank increased.

literature

• Hellmuth Schulz: The pumps: working method, calculation, construction. 13., rework. Ed., Springer, Berlin 1977, ISBN 3-540-08098-8 .
• G. Vetter (Ed.): Pumps. 2nd edition, Vulkan-Verlag, Essen 1992, ISBN 3-8027-2696-0 .

Web links

Wiktionary: Pump  - Explanations of meanings, word origins, synonyms, translations

Commons : Pumps  - collection of images, videos and audio files

• Technical comparison of different pump types (including rotary lobe pumps, eccentric screw pumps, centrifugal pumps, gear pumps) with their advantages and disadvantages

Individual evidence

1. ↑ herold-gefrees.de