Difference between revisions of "Positive Displacement Pumps"

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Positive Displacement Pumps (view source)

Revision as of 03:39, 15 March 2012

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* [[peristaltic pumps]]
* [[peristaltic pumps]]
* [[rope pumps]]
* [[rope pumps]]
===[[Impulse pumps]]===
[[File:pulser pump.jpg|thumb|The pulser pump]]
Impulse pumps use pressure created by gas (usually air). In some impulse pumps the gas trapped in the liquid (usually water), is released and accumulated somewhere in the pump, creating a pressure which can push part of the liquid upwards. Impulse pumps include:
* [[Hydraulic ram pumps]] - uses pressure built up internally from released gas in liquid flow. (see below)
* [[Pulser pump]]s - run with natural resources, by kinetic energy only.
* [[Airlift pump]]s - run on air inserted into pipe, pushing up the water, when bubbles move upward, or on pressure inside pipe pushing water up.
===[[Velocity pumps]]===
[[Image:Centrifugal 2.png|thumb|right|A centrifugal pump uses a spinning "impeller" which has backward-swept arms]]
[[Rotodynamic pumps]] (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe. This conversion of kinetic energy to pressure can be explained by the First law of thermodynamics or more specifically by Bernoulli's principle.
Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.
These types of pumps have a number of characteristics:
# Continuous energy
# Conversion of added energy to increase in kinetic energy (increase in velocity)
# Conversion of increased velocity (kinetic energy) to an increase in pressure head
One practical difference between dynamic and positive displacement pumps is their ability to operate under closed valve conditions. Positive displacement pumps physically displace the fluid; hence closing a valve downstream of a positive displacement pump will result in a continual build up in pressure resulting in mechanical failure of either pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time).
===[[Gravity pumps]]===
===[[Steam pumps]]===
===[[Valveless pumps]]===
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