Editing Pump (section)

===== '''Reciprocating positive-displacement pumps''' =====
[[Image:Hand pump-en.svg|thumb|Simple hand pump]]
[[File:Old hand water pump.jpg|thumb|Antique "pitcher" pump (c. 1924) at the Colored School in Alapaha, Georgia, US]]
{{See also|Reciprocating pump}}
Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to the desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the chamber pressure and the inward pressure of the plunger will then open the discharge valve and release the fluid into the delivery pipe at constant flow rate and increased pressure.

Pumps in this category range from ''simplex'', with one cylinder, to in some cases ''quad'' (four) cylinders, or more. Many reciprocating-type pumps are ''duplex'' (two) or ''triplex'' (three) cylinder. They can be either ''single-acting'' with suction during one direction of piston motion and discharge on the other, or ''double-acting'' with suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th century—in the early days of steam propulsion—as boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating [[hand pump]]s were widely used to pump water from wells. Common [[bicycle pump]]s and foot pumps for [[Inflatable|inflation]] use reciprocating action.

These positive-displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation and the pump's volumetric efficiency can be achieved through routine maintenance and inspection of its valves.<ref>{{Cite news|url=https://info.triangle-pump.com/blog/what-is-volumetric-efficiency|title=What Is Volumetric Efficiency?|last=Inc.|first=Triangle Pump Components|access-date=2018-01-03}}</ref>

Typical reciprocating pumps are:
* ''[[Plunger pump]]'' – a reciprocating plunger pushes the fluid through one or two open valves, closed by suction on the way back.
* ''[[Diaphragm pump]]'' – similar to plunger pumps, where the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids.
* ''[[Piston pump]]'' displacement pumps'' – usually simple devices for pumping small amounts of liquid or gel manually. The common hand soap dispenser is such a pump.
* ''[[Radial piston pump]]''{{dash}}a form of hydraulic pump where pistons extend in a radial direction.
* Vibratory pump or vibration pump{{dash}}a particularly low-cost form of plunger pump, popular in low-cost [[espresso machine]]s.<ref>{{Cite web|url=https://www.home-barista.com/espresso-machines/faqs-and-favorites-t1541.html|title=FAQs and Favorites{{dash}}Espresso Machines|website=www.home-barista.com|date=21 November 2014 }}</ref><ref>{{Cite web|url=https://clivecoffee.com/blogs/learn/the-pump-the-heart-of-your-espresso-machine|title=The Pump: The Heart of Your Espresso Machine|website=Clive Coffee}}</ref>  The only moving part is a spring-loaded piston, the armature of a [[Solenoid (engineering)|solenoid]].  Driven by [[Rectified sine wave#Half-wave rectification|half-wave rectified]] [[alternating current]], the piston is forced forward while energized, and is retracted by the spring during the other half cycle.  Due to their inefficiency, vibratory pumps typically cannot be operated for more than one minute without overheating, so are limited to intermittent duty.