Pumps are mechanical devices used to move liquids by increasing pressure or velocity. They are essential in engineering systems such as water supply, hydraulic systems, chemical processing and power generation.
The main types of pumps are centrifugal (kinetic) and positive displacement pumps, each suited to different flow and pressure applications.
This page provides an overview of the main pump types, their operating principles and key performance characteristics used in engineering design.
Pumps are generally classified into two main categories based on how they move fluid:
Note: Links to more detailed information are included in the rows below.
| Pumps | |||||
| Kinetic | Positive Displacement | ||||
| Peripheral Pumps | Rotodynamic Pumps | Reciprocating Pumps | Rotary Positive Displacement Pumps | ||
| Radial Flow | Diaphragm | Plunger | Single Rotor | Multiple Rotor | |
| Axial Flow | Sliding Vane | Gear | |||
| Mixed Flow | Flexible Vane | Screw | |||
| Mono | Lobe | ||||
| Peristaltic | |||||
| Piston | |||||
The system head generally consists of two parts:
The difference between the suction and discharge levels in an open system. This is usually independent of flow.
This is the friction head loss in the piping and is related to flow. Under turbulent flow conditions, the friction loss is proportional to velocity2, producing a parabolic system curve.
A pump delivers head relative to flow rate. Maximum head occurs at zero flow (dead head) and minimum head at maximum flow. Both extremes are undesirable.
The operating point is where the pump curve intersects the system curve, ideally near the best efficiency point (BEP).
Pumps in series increase head, while pumps in parallel increase flow. Multi-stage pumps use multiple impellers to achieve high head.
The energy imparted to a fluid by a pump is measured as head (in metres) per unit weight of fluid.
dH = (Z2 - Z1) + (P2 - P1)/(ρg) - (v22 - v12)/(2g)
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Where: dH = Fluid head developed across pump (m) Z1 = Fluid supply level (m) Z2 = Fluid discharge level (m) P1 = Pressure at pump inlet (N/m2) P2 = Pressure at pump outlet (N/m2) ρ = Fluid density (kg/m3) g = Acceleration due to gravity (9.81 m/s2) v1 = Fluid velocity at inlet (m/s) v2 = Fluid velocity at outlet (m/s) |
NPSH (Net Positive Suction Head) is the pressure required at the pump inlet to prevent cavitation.
Cavitation occurs when liquid vaporises due to low pressure, causing noise, damage and reduced efficiency.
NPSHA = ( Pi + Pb - Pv ) / ( g ρ ) + Ve2 / ( 2g ) + Ze - Fe
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Where: Pi = Surface pressure of fluid (N/m2) Pb = Barometric pressure (N/m2) Pv = Vapour pressure of fluid (N/m2) ρ = Fluid density (kg/m3) g = Acceleration due to gravity (9.81 m/s2) Ve = Fluid velocity at pump inlet (m/s) Ze = Height of fluid above pump inlet (m) Fe = Friction loss in suction pipe (m) |
A pump is a mechanical device used to move fluids by increasing pressure or velocity.
The main types are centrifugal (kinetic) pumps and positive displacement pumps.
Pump head is the energy imparted to a fluid, expressed as height in metres.
NPSH is the minimum pressure required at the pump inlet to prevent cavitation.
Cavitation is the formation of vapour bubbles due to low pressure, causing damage and reduced performance.