▶ A pump is a mechanical device used to move fluids, such as liquids, gases or slurries by pressure or suction
▶ Main purposes of Pumps
• Transfer of liquid from one place to another place (e.g. water from an underground aquifer into a water storage tank)
• Circulate liquid around a system (e.g. cooling water or lubricants through machines and equipment)
(Pumps of Desalination Plant)
Classified by operating principle
Types of Water pump
▶ Centrifugal pump
- A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a
fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid
enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially
outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system.
Centrifugal pumps are typically used for large discharge through smaller heads.
- Volute Pump, Turbine Pump
- Radial flow pumps, Axial flow pumps, Mixed flow pumps
- single stage pump & multi stage pump
• The volute of a centrifugal pump is the casing that receives the fluid being pumped by the impeller, slowing down
the fluid's rate of flow. A volute is a curved funnel that increases in area as it approaches the discharge port.
The volute converts kinetic energy into pressure by reducing speed while increasing pressure, helping to balance
the hydraulic pressure on the shaft of the pump.
• A turbine pump is a centrifugal pump that is mainly used to pump water from deep wells or other underground and
man-made bodes of water to water distribution systems. A centrifugal pump consists of a pump shaft, a rotating
device known as an impeller, and a motor or an engine. A turbine pump may consist of multiple semi-open or
enclosed impellers, also known as "stages." A metal plate called shroud supports the vanes of the impeller in an
open or semi-open impeller, whereas in an enclosed impeller, the shroud encloses the impeller vanes. The turbine
pump also consists of a water intake point and a water discharge point.
• Radial flow pumps Often simply referred to as centrifugal pumps. The fluid enters along the axial plane, is
accelerated by the impeller and exits at right angles to the shaft (radially). Radial flow pumps operate at higher
pressures and lower flow rates than axial and mixed flow pumps.
• Axial flow pumps differ from radial flow in that the fluid enters and exits along the same direction parallel to the
rotating shaft. The fluid is not accelerated but instead "lifted" by the action of the impeller. They may be likened to
a propeller spinning in a length of tube. Axial flow pumps operate at much lower pressures and higher flow rates
than radial flow pumps.
• Mixed flow pumps, as the name suggests, function as a compromise between radial and axial flow pumps, the
fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0?90 degrees from
the axial direction. As a consequence mixed flow pumps operate at higher pressures than axial flow pumps while
delivering higher discharges than radial flow pumps. The exit angle of the flow dictates the pressure
head-discharge characteristic in relation to radial and mixed flow.
▶ Reciprocating pump
- A reciprocating pump is a positive plunger pump. It is often used where relatively small quantity of liquid is to be
handled and where delivery pressure is quite large.
• A plunger pump is a type of positive displacement pump where the high-pressure seal is stationary and a smooth
cylindrical plunger slides through the seal. This makes them different from piston pumps and allows them to be
used at high pressures. This type of pump is often used to transfer municipal and industrial sewage.
• A piston pump is a type of positive displacement pump where the high-pressure seal reciprocates with the piston.
Piston pumps can be used to move liquids or compress gases.
(Plunger Pump and Piston Pump)
• A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial
vacuum. The first vacuum pump was invented in 1650 by Otto von Guericke, and was preceded by the suction
pump, which dates to antiquity.
• A diaphragm pump is a positive displacement pump that uses a combination of the reciprocating action of a rubber,
hermoplastic or teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of
pump is also called a membrane pump.
• Water hammer is a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction
suddenly (momentum change). Water hammer commonly occurs when a valve is closed suddenly at an end of a
pipeline system, and a pressure wave propagates in the pipe. It may also be known as hydraulic shock.
( Water Hammer Phenomenon in pipelines )
※ Consider a long pipe AB : Connected at one end to a reservoir containing water at a height H from the center of the pipe.
At the other end of the pipe, a valve to regulate the flow of water is provided.
- If the valve is suddenly closed, the flowing water will be obstructed and momentum will be destroyed and consequently a
wave of high pressure will be created which travels back and forth starting at the valve, traveling to the reservoir, and
returning back to the valve and so on.