What are the types of pumps | Classification of pumps - interview questions

Pump introduction

What is a pump ?

• Rotating machine which transfer liquid from one place to another or from lower level to higher level.
• It convert mechanical energy into hydraulic energy.
• Adds engery to the liquid so as transfer liquid.

Adds engery to the liquid so as to transfer liquid :

• From one elevation to desired elevation by increasing potential energy.
• Against rsistance at reciver end against resistance in piping system
• With a desired flow velocity

Functions of pump

Mechanical energy to Hydraulic energy

• Kinetic energy
• Pressure energy
• Potential energy

A pump does not create pressure, it only provides flow.

Pressure is a just an indication of the amount of resistance to flow.

Types of pump

1.Positive displacement pump

2.Non positive displacement pump

Non positive displacement pump

1.jet pump

2.centrifugal pump

Positive displacement pump

1.Rotary pump

2.Reciprocating pump

Rotary pump

1.Gear pump

2.Lobe pump

3.Screw pump

4.Vane pump

Reciprocating pump

1.Piston pump

2.Diaphargam pump

Centrifugal pump

• As pressure increases, flow rate of pump decrease, though pump rpm remains constant
• Speed of an actuators never remains constant at variable pressure
• No positive seal is present between suction and delivery
• Some part of water flow back from delivery to suction under pressure
• Decreased net flow rate of the pump

Classification of Centrifugal pump

1.Axial flow pump

2.Mixed flow , Radial flow

3.Peripheral pump

Axial flow pump

• An axial flow pump essentially consist of an axial impeller.
•  Axial flow pump are in - line pumps that works on a vertical plane in relation to the water.

Single stage

1.Closed impeller

2.Open impeller

Multistage

1.Closed impeller

2.Open impeller

Mixed flow , Radial flow

Radial flow pumps are in - line centrifugal pump that operate on a horizental plane in relation to the flow direction of the water.

Mixed flow pump mixes features of radial flow and axial flow pump

Single suction

1.Non priming

2.Self priming

3.Single stage

4. Multi stage

Double suction

1.Non priming

2.Self priming

3.Single stage

4.Multi stage

Non priming

1.Closed impeller

2.Open impeller

3.Semi - Open impeller

Self priming

1.Closed impeller

2.Open impeller

3.Semi - Open impeller

Single stage

1.Closed impeller

2.Open impeller

3.Semi - Open impeller

Multi stage

1.Closed impeller

2.Open impeller

3.Semi - Open impeller

Peripheral pump

1.Single stage

2.Multi stage

Peripheral pumps operate by means of an impeller characterised by a large number of small dual flow radial blades arranged along its peripheral area.

Centrifugal pumps can further be classified as : 

1.End suction pump

2.In - line pump

3.Double suction pump

4.Vertical/Horizontal multistage pump

5.Submersible pump

6.Self priming pump

7.Axial flow pump

8.Split-case pump

Advantages and disadvantages of the following type of pump

Split case pump

Advantages

• Easy inspection without distrubing suction & delivery piping and electric motor.
• Simpler maintenace - lower maintenace down time.
• Lower shaft deflection-between-bearings design
• Lower NPSH - each eye handles half the flow.
• No/little axial thrust
• Higher efficiency - power is not lost in balancing hydraulic thrust.

Disadvantages

• Heavier than end suction due to large split flange.
• Shaft through eye require larger eye area and tighter turn for liquid entering the impeller.
• More sensitive to orientation and geometry of elbows infront of pump suction.
• Two shaft seal
• Chances of volute mismatch - upper & lower.

Inline pump

Advantages

• Pipe mounted
• Smallest footprint-utilizes the least amount floor spaces.
• Ease of maintenace 
• Factory aligned for life - no misalignment of pump and driver.
• Easy to install - no base plate, coupling or guard.
• Take less floor space
• Simpler piping-suction and discharge flange are in with each other.This eliminates the need for piping to change direction.Also eliminates elbows & fittings.
• Require no field alignment between pump & motor.

Disadvantages

• Motor is supported by the pump rather than by a base plate.so larger size may require external support.
• Inherently less stable compaired to base plate mounted end suction pump.This limit the size of unit to less than 150kw.
• Leakages from the packing or seals don't always drip down to a collection cup for disposal.This may cause corrosion damage to the pump/motor support.

Disadvantages : vertical mounted split case pump

• Requires thrust bearing
• "Top" casing, rotating assembly is not easy to take out using overhead crane special froklift or dismantling gear is required.