pumps and pumping systems part-1

Pumps & Pumping Systems

(Part-1)

M.M.Palitha Mahinda Munasinghe

Farm Mechanical Instructor

palithamahinda@yahoo.com

2

INTRODUCTIONINTRODUCTION

• Domestic, commercial, industrial and agricultural services

• Municipal water and wastewater services

Use of Pumping System

11/08/2007 mmpmm

3

Objective of pumping system

What are Pumping SystemsWhat are Pumping Systems

• Transfer liquid from source to destination

• Circulate liquid around a system

11/08/2007 mmpmm

4

• Components• Pumps

• Prime movers: electric motors, diesel engines, Wind mill

• Piping to carry fluid

• Valves to control flow in system

• Other fittings, control, instrumentation

• End-use equipment• Heat exchangers, tanks, hydraulic machines

What are Pumping SystemsWhat are Pumping Systems

11/08/2007 mmpmm

5

• Head• Resistance of the system

• Two types: static and friction

• Static head• Difference in height between

source and destination

• Independent of flow

Pumping System CharacteristicsPumping System Characteristics

11/08/2007 mmpmm

6

• Static head consists of• Static suction head (hs): lifting liquid relative to pump

center line

• Static discharge head (hd) vertical distance between centerline and liquid surface in destination tank

• Static head at certain pressure

Head (in feet) = Pressure (psi) X 2.31 Specific gravity

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

7

• Friction head• Resistance to flow in pipe and fittings

• Depends on size, pipes, pipe fittings, flow rate, nature of liquid

• Proportional to square of flow rate

• Closed loop system only has friction head(no static head) Friction

head

Flow

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

8

Total head = Static head + friction head

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

9

Pump performance curve

• Relationship between head and flow• Flow increase

• System resistance increases

• Head increases

• Flow decreases to zero

• Zero flow rate• risk of pump burnout

Head

Flow

Performance curve for centrifugal pump

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

10

Pump operating point

• Duty point

Rate of flow at

certain head

• Pump operating point

Intersection of

pump curve and

system curve Flow

Head

Static head

Pump performance curve

System curve

Pump operating point

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

11

Pump suction performance (NPSH)• Cavitations or vaporization: bubbles inside pump

• If vapor bubbles collapse• Erosion of vane surfaces• Increased noise and vibration• Choking of impeller passages

• Net Positive Suction Head• NPSH Available: how much pump suction exceeds liquid

vapor pressure• NPSH Required: pump suction needed to avoid cavitations

11/08/2007 mmpmm

Pumping System CharacteristicsPumping System Characteristics

12

Type of PumpsType of Pumps

Classified by operating principle

11/08/2007 mmpmm

Pumps

Dynamic

Centrifugal Special Effect

Others

(Impulse, Buoyancy)Positive

Displacement

Rotary

Internal Gear External Gear

Lube Slide Vane

Reciprocating

13

Type of PumpsType of PumpsPositive Displacement Pumps

• For each pump revolution• Fixed amount of liquid taken from one end

• Positively discharged at other end

• If pipe blocked• Pressure rises

• Can damage pump

• Used for pumping fluids other than water

11/08/2007 mmpmm

14

Positive Displacement PumpsPositive Displacement Pumps

• Reciprocating pump• Displacement by reciprocation of piston plunger

• Used only for viscous fluids and oil wells

• Rotary pump• Displacement by rotary action of gear, cam or

vanes

• Several sub-types

• Used for special services in industry

11/08/2007 mmpmm

15

Dynamic pumpsDynamic pumps

• Mode of operation• Rotating impeller converts kinetic energy

into pressure or velocity to pump the fluid

• Two types• Centrifugal pumps: pumping water in industry –

75% of pumps installed

• Special effect pumps: specialized conditions

11/08/2007 mmpmm