Classification of Pumps

Pumps may be classified on the basis of the applications they serve, the materials from which they are constructed, the liquids they handle, and even their orientation in space. All such classifications, however, are limited in scope and tend to substantially overlap each other.A more basic system of classification,first defines the principle by which energy is added to the fluid, goes on to identify the means by which this principle is implemented, and finally delineates specific geometries commonly employed. This system is therefore related to the pump itself and is unrelated to any consideration external to the pump or even to the materials from which it may be constructed.

Under this system, all pumps may be divided into two major categories:

 (1) Kinetic/Rotodynamic,in which energy is continuously added to increase the fluid velocities within the machine to values greater than those occurring at the discharge so subsequent velocity reduction within or beyond the pump produces a pressure increase.

 (2)Positive Displacement, in which energy is periodically added by application of force to one or more movable boundaries of any desired number of enclosed, fluid-containing volumes, resulting in a direct increase in pressure up to the value required to move the fluid through valves or ports into the discharge line.

Kinetic pumps can be further classified as centrifugal,mixed flow and axial.Positive displacement pumps can be further classified as reciprocating,blow case and rotary.

Classification of Pumps

Kinetic pumps generate pressure hydrodynamically by using impellers which shift fluid by momentum,rather than positive mechanical travel.They are appropriate for high volume requirements of numerous industrial processes,especially the centrifugal type.
  • Single-stage,single-entry pumps are adequate for lower capacity applications,and for higher duties the single stage.double entry type of pump is favoured for higher efficiency.
In cases where the pressure is required at a higher degree than that of a single-stage centrifugal pump,a 2-stage pump using 2 impellers can be used.
  • Pumps with more than 2 stages are usually referred to as multi-stage pumps.
  • In some unique cases,where high pressure requirements are needed.pumps can have more than 8 stages.It is common for multi-stage machines to have radially by reciprocating or rotary action.

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 pump are 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 it 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 pump are typically used for large discharge through smaller heads. Centrifugal pump are often associated with the radial-flow type. However, the term "centrifugal pump" can be used to describe all impeller type rotodynamic pumps including the radial, axial and mixed-flow variations.

Centrifugal Pump


Axial-Flow Pump

Axial-flow pump differ from radial-flow pump 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. Axial-flow pump operate at lower pressure and higher flow rates than radial flow pump.

Mixed-Flow Pump

Mixed-flow pump function as a compromise between radial and axial-flow pump. The fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0 and 90 degrees from the axial direction. As a consequence mixed-flow pump operate at higher pressures than axial-flow pump while delivering higher discharge than radial-flow pump.

Radial-Flow Pump

The fluid that enters along the axial plane is accelerated by the impeller and exits at right angles to the shaft (radially). Radial-flow pump operate at higher pressures and lower flow rates than axial and mixed-flow pumps.

Positive-displacement pump can operate by forcing a fixed volume of fluid from inlet pressure section of the pump into the discharge zone of the pump. It can be classified into two types:

  • Rotary-type positive displacement pump:
  1. Internal gear pump
  2. Screw pump
  • Reciprocating-type positive displacement pump:
  1. Piston pump
  2. Diaphragm Pump

Rotary-Type Positive Displacement Pump

Positive displacement rotary pump can move the fluid by using rotating mechanism that creates a vacuum that captures and draws in the liquid. Rotary positive displacement pump can be classified into two main types:
  • Gear pumps - a simple type of rotary pump where the liquid is pushed between two gears.
  • Rotary vane pumps - similar to scroll compressors, these pump have a cylindrical rotor encased in a similar shaped housing. As the rotor orbits, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump.
Gear Pump


Reciprocating-Type Positive Displacement Pump

Reciprocating pump move the fluid using one or more oscillating pistons, plungers or membranes (diaphragms), while valves restrict fluid motion to the desired direction. Pump in this category are simple with one cylinder or more. They can be either single-acting with suction during one direction of the piston 36 motion and discharge on the other or double-acting with suction and discharge in both directions.Typical reciprocating pumps are:
  • Plunger pumps - a reciprocating plunger pushes the fluid through one or two open valves, closed by suction on the way bac
Plunger  Pump
  • Diaphragm pumps - 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.
Diaphragam Pump

  • Piston displacement pumps - usually simple devices for  pumping small amounts of liquid or gel manually.
Piston Displacement Pump

We discussed about the classification of pumps and its various types.This is just a small portion or root of the family of pumps more and more amazing new generation pumps are waiting for you.

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