Pump - Part 1

 Contents : 

    1.0 Introduction to Pump

    2.0 Classification of Pumps

    3.0 Construction and working Principal of Pumps 

Introduction to pump
The pump is one of the most important accessories of prime mover; Pumps are used for increasing pressure of a liquid, feeding the water, forcing the lubricating oil into machine parts and other various industrial and domestic applications.

Rising of water from wells is the earliest form of pumping. Modern applications are much broader. Modern pumps function on one of two principles. By far the majority of pump installations are of the velocity head type (Kinetic Energy). In these devices, the pressure rise is achieved by giving the fluid a movement. At the exit of the machine, this movement is translated into a pressure increase.

The other major type of pump is called positive displacement. These devices are designed to increase the pressure of the liquid while essentially trying to compress the volume.

Many varieties of pumps are available. The selection of the pump class and type for a certain application is influenced by head required, layout, fluid characteristics, intended life, energy, cost and materials of construction. Very important parameters for design of pumps are pressure and liquid flow rate.

Classification of Pumps :
There are many ways of classification of pumps based on their type of construction, application, function, Principal of energy addition etc,

    1. Kinetic Energy or Velocity head pumps

         1.1 Centrifugal pumps

               1.1.1 Volute pump

               1.1.2 Diffuser pump

               1.1.3 Vertex pump

          Sub Classification based on type of flow

               1. Axial flow pump (single or multistage)

               2. Radial flow pump (single or double suction)

               3. Mixed flow pump (single or double suction)

               4. Peripheral pump (single or multistage)

         1.2. Special Effect

               1.2.1 Gas lift pump

               1.2.2 Jet pump

               1.2.3. Hydraulic ram pump

               1.2.4. Electromagnetic pump

  2. Positive displacement pumps

         2.1. Reciprocating pump

               2.1.1 Piston, plunger

                    2.1.1.1. Direct acting pump (simplex or duplex)

                    2.1.1.2. Power pump (single / double acting,

                             simplex, duplex, triplex, multiplex)

               2.1.2. Diaphragm pump (mechanically or hydraulic driven,

                      simplex or multiplex)

         2.2. Rotary pump

               2.2.1. Single rotor pump

                    2.2.1.1 Vane Pump

                    2.2.1.2 Piston pump

                    2.2.1.3 Screw pump

                    2.2.1.4 Diaphragm or flexible member

               2.2.2. Multiple rotor pumps

                    2.2.2.1 Gear pump

                    2.2.2.2 Lobe pump

                    2.2.2.3 Screw pump

                    2.2.2.4 Circumferential piston pump

3. Construction and working principal of major pumps

Centrifugal Pumps :
A pump which employs centrifugal force for conveying liquids from one place to other is called centrifugal pump. It is similar to a reversed water turbine. Centrifugal pumps are used in more industrial applications than other type of pump because these pumps offer low initial and maintenance costs. Centrifugal pumps are smooth, non-pulsating in operation and has ability to tolerate non-flow conditions.

The most important parts of the centrifugal pump are the rotating impeller and a stationary casing. The centrifugal pumps are sub classified based on design of the casing as Volute type, vertex type and diffuser type.

In centrifugal pumps kinetic energy of the leaving water from the impeller is converted into potential energy which is utilized to increase the delivery head of the pump.
When the impeller rotates, the liquid is discharged by centrifugal force from its centre, by this action vacuum is created at suction eye which is connected with suction pipe and the liquid from reservoir flows in to the impeller.

Volute pump :
In volute pumps area of flow gradually increases from throat towards the delivery pipe. The increase in area of flow decreases the exit velocity and hence pressure increases in the casing.

Diffuser pump :

In diffuser pump , the fluid passes through a ring of fixed vanes or diffuser after the fluid has left the impeller, that diffuse the liquid, this provids a more controlled flow and a more efficient conversion of velocity head into pressure head. Providing fixed diffuser increases the efficiency of the pump up to 90 percent.

Vortex pump :
Vortex casing is a casing in which circular chamber is provided between the casing and the impeller. Vortex casing will increase pump efficiency by reducing eddies formation to a considerable extent.