Pumps
By Rahul
What is a Pump??
A Pump is a machine that drives fluid from one location to another
location.
History &Origins of a Pump
• 2000 BC Egyptians invent the shadoof to raise water. It uses a long suspended rod
with a bucket at one end and a weight at the other. Even they were used in
Mohenjo-Daro and Harappa Civilization too.
• 200 BC Greek inventor and mathematician Ctesibius invents the water organ, an
air pump with valves on the bottom, a tank of water in between them and a row
of pipes on top. This is the principal design that is now known as the reciprocating
pump.
• 1851 John Gwynne files his first centrifugal pump patent.
• 1859 Jacob Edson invents the diaphragm pump and founds the Edson Corporation
in Boston.
• Origin of the word Pump: Pump is a Dutch word. Mostly it was used by Dutch
sailors.
Classification of Pumps
Dynamic Pump
1.Centrifugal pump.
2.Axial Pump
3.Radial Pump
Pumps
Positive Displacement
Pump
1 Reciprocating Pump
2.Rotary Pump
(Gear, vane, Screw pump
and peristaltic pump)
Positive displacement Pump
• Why they are called positive displacement pump?? Any Idea??
• They work on the principle of Positive displacement.
• Positive Displacement: No/Minimum back flow of liquid while pumping
the liquid out of pump. Their design is such that there is a minimum back
flow of liquid. There is minimum spacing b/w Stationary and rotary
parts.
• Examples: Piston/Plunger Pump, Diaphragm Pump.
• Is there any Technical term for this back flow??.
Piston/Plunger Pump Diaphragm Pump
Piston-pump GIF.gif
Diaphragm_pump_animated.gif
Rotary Pumps
Gear_pump_animation.gif
Peristalsis.gif
c)Peristaltic Pump
a) Gear Pump, b)Screw pump
Dynamic Pumps
• Why the name??
• These pumps impart Kinetic energy to the fluid and sends out the
liquid out of pump. During the transfer, some amount of energy is
converted to pressure energy and delivered as a Head.
• As the velocity and pressure changes from time to time, these pumps
are called dynamic pump( “dynamic” means change).
• Ex : Axial Pumps, Radial Pump and Centrifugal Pump.
Centrifugal Pumps
• The fluid from the inlet port enters at the center of the impeller. The
rotating impeller imparts centrifugal force to the fluid and causes it to
move radially outward. This results in the fluid being forced through
the outlet discharge port of the housing. The tips of the impeller
blades merely move through the fluid while the rotational speed
maintains the fluid pressure corresponding to the centrifugal force
established.
• Ex: Centrifugal Pump, Axial Pump, Rotary Pump
Parts of Centrifugal Pump
Types of impeller
Types of casing
Cavitation= Vaporisation inside pump casing
Condition of cavitation: Local pr. < Vapour pressure at local temperature
How to avoid cavitation?
Net Positive Suction Head (NPSH)
NPSH (in m) = [(Pressure@ suction flange – Vapour pressure at suction
temperature)]/(rg),
If NPSH is –ve, the liquid would release vapour at the suction flange.
NPSH required at different flow rates is specified by pump
manufacturer so that if in an installation the NPSH available is below
the NPSH required, it would lead to cavitation.
Hence, during operation the user must ensure the (available NPSH) >
(required NPSH) to avoid cavitation.
Centrifugal Pump Characteristics
Operating point of a pump system?
Power of a Pump
Affinity Laws: Centrifugal Pumps
Centrifugal pump affinity laws
Performance Changes in rotating speed (n) Changes in Impeller Diameter (DI)
Flow Rate Q2 n2 Q2 DI 2
(Q) Q1 n1 Q1 DI 1
2 2
Differential H 2 n2 H 2 D2
Head h
H1 n1 H1 D1
3 3
Brake Horse BHP2 n2 BHP2 D2
Power
BHP1 n1 BHP1 D1
Characteristics of other pumps ? Reciprocating / Gear etc
a): Reciprocating pump @ fixed strokes/min;
b): Screw Pump at constant RPM and viscosity
Pump installation
Spare pump and change over without shutting flow
Centrifugal pumps
Spare pump and change over without shutting flow
Positive displacement pumps: (a) reciprocating, (b) rotary
Pump Selection
Pump type
Parameters
considered Centrifugal Reciprocating Rotary
High discharge High head
Suitability
Low head Low discharge
High - flow
Low - flow varies with
Flow stability practically High
system resistance
constant
Flow Delivery Continuous Periodic
High liquid viscosity Not preferred above 10 cSt Suitable Suitable
Handling liquid with
Yes No No
suspended solid
Low (Cannot
High (Can run at high Low (Cannot run
Energy Consumption run at high
speed) at high speed)
speed)
Efficiency Low Highest Higher
Capital and Low (Simple
High Low
Maintenance Cost construction)
Floor area required Less
Wear and tear Less
21
Priming Required Not Required
What happens if we connect
a)Pumps In Series?
b)Pumps In Parallel?
THANK YOU
