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8/3/2019 Fluid Transportation
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Types of Fluid
Liquids (Non compressible)
Gases (Compressible)
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Fluid Transportation
Work needed to increase themechanical energy of a fluid,which in turn can increase theflow rate (velocity), pressure
or elevation of fluid
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Fluid Transportation Equipment
• Pumps
• Fans
• Blowers
• Compressors
• Vacuum Ejectors
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What are Pumping System?
• 20% of world’s electrical energydemand
• 25-50% of energy usage in someindustries
• Used for
•Domestic, commercial, industrial andagricultural services
•Municipal water and wastewater
services
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Objective of Pumping
System
•
Transfer liquid from source todestination
• Circulate liquid around a system
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Components of Pumping System
•Main pump components•Pumps
•Prime movers: electric motors, diesel
engines, air system•Piping to carry fluid
•Valves to control flow in system
•Other fittings, control, instrumentation• End-use equipment
•Heat exchangers, tanks, hydraulic
machines
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•Head
•Resistance of the
system•Two types: staticand friction
•Static head•Difference inheight between
source anddestination
• Independent of
flow
destination
source
Statichead
Static
head
Flow
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• Static head consists of
•Static suction head (hS):Verticaldistance for lifting liquid relative topump center line
•Static discharge head (hD) : verticaldistance between centerline and liquidsurface in destination tank
• Static head at certain pressure
Head (in feet) = Pressure (psi) X 2.31
Specific gravity
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Friction head
• Resistance to flow in pipeand 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)
Frictionhead
Flow
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Pumping System Characteristics
In most cases:Total head = Static head + friction head
Systemhead
Flow
Static head
Frictionhead
Systemcurve
Systemhead
Flow
Static head
Frictionhead
Systemcurve
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Types of Pumps
• Classified by operating principle
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal
gear
External
gear LobeSlide
vane
Others (e.g.
Impulse, Buoyancy)
Pumps
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internal
gear
External
gear LobeSlide
vane
Others (e.g.
Impulse, Buoyancy)
Pumps
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Positive Displacement Pump
Reciprocating
• Piston
• Plunger
• Diaphragm
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Positive Displacement PumpReciprocating (Piston & Plunger)
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Positive Displacement PumpReciprocating (Axial Piston)
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Positive Displacement PumpReciprocating (Radial Piston)
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Positive Displacement PumpReciprocating (Diaphragm)
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Rotary
• Gear• Lobe
• Screw
• Cam
• Vane
Positive Displacement Pump
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Gear Pump
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Gear Pump
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Rotary Gear Pump
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Lobe Pump
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Screw Pump
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Vane Pump
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Centrifugal Pumps
• Axial Flow
• Radial Flow• Mixed Flow
• Peripheral
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Liquid Flow Path inside a Centrifugal Pump
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Casing
Casings are generally of two types:
volute and circular.
Volute casings: B uild a higher head;
Circular casings: Low head and high capacity.
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Volute Casing
A volute is a curved funnel
increasing in area to the
discharge port. As the area of thecross-section increases, thevolute reduces the speed of the
liquid and increases the pressureof the liquid.
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Circular Casing
Circular casing have stationary
diffusion vanes surrounding the
impeller periphery that convertvelocity energy to pressureenergy. Conventionally, the
diffusers are applied to multi-stage pumps.
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Casing
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Casing
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Impeller
The impeller is the main rotating
part that provides the centrifugalacceleration to the fluid.
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Impeller-Classification
Based on major direction of flow
in reference to the axis of rotation
Radial flow
Axial flow
Mixed flow
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Impeller-Classification
Based on suction type
Single-suction: Liquid inlet on oneside.
Double-suction: Liquid inlet to the
impeller symmetrically from bothsides.
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Impeller-Classification
Based on mechanical construction
Closed: Shrouds or sidewallenclosing the vanes.
Open: No shrouds or wall to enclose
the vanes. Semi-open or vortex type.
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Impeller Types
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Pump Application
Circuit Arrangement Once Through Arrangement
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Capacity of Pump
• Stuffing Boxes and packing
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Specific Speed Ns
• Specific speed is a measure of thegeometric similarity of pumps. Specificspeed (Ns) is a non-dimensional designindex that identifies the geometric
similarity of pumps.• It is used to classify pump impellers as to
their type and proportions.
• Pumps of the same Ns but of different sizeare considered to be geometrically similar,one pump being a size- factor of the other.
Specific speed Calculation
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Specific speed Calculation
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Specific Speed Ns
As per the formula, it is defined as
the speed in revolutions per
minute at which a geometricallysimilar impeller would operate if itwere of such a size as to deliver
one gallon per minute flowagainst one-foot head.
Pump input or brake horsepower (BHP) is
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Pump input or brake horsepower (BHP) is
the actual horsepower delivered to the pump
shaft
Pump output or hydraulic or water
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Pump output or hydraulic or water
horsepower (WHP) is the liquid horsepower
delivered by the pump
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Pump Flow vs Head
Centrifugal Pumps Positive DisplacementPumps
Resultant Characteristics of Two Identical
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Resultant Characteristics of Two IdenticalCentrifugal Pumps
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Leakage
• Stuffing Boxes and packing
A Typical Manufacturer`s Performance
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A Typical Manufacturer s PerformanceCurves
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CavitationsIf the pressure drops below the vapourpressure of the fluid being moved, theliquid may vaporize. The bubbles that formcause a volume increase and “chock” the
pump. Then as the pressure is increasedby the pumping action, the bubblesimplode, creating shock waves that can pitand erode the equipment.
• Serious Noise• Vibration
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Net Positive Suction Head
NPSH
The difference between the totalsuction head at the suction flangeand the vapour pressure of the
liquid
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Leakage
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Power
• Electric Motor
• Steam Turbine
• Gas Turbine
• Diesel Engine
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Leakage
• Stuffing Boxes and packing
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Leakage
• Stuffing Boxes and packing
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The Affinity Laws
The mathematical expressions thatdefine changes in pump
o Capacity,
o Head
o BHP
when a change is made to pumpspeed, impeller diameter, or both.
Th Affi i L
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The Affinity Laws
Capacity, Q changes in directproportion to
o Impeller diameter D ratio, or
oSpeed N ratio
Q2 = Q1 x [D2/D1]
Q2 = Q1 x [N2/N1]
Th Affi i L
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The Affinity Laws
Head, H changes in direct proportionto the
oSquare of impeller diameter D
ratio, oroSquare of speed N ratio
H2 = H1 x [D2/D1]2
H2 = H1 x [N2/N1]2
Th Affi i L
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The Affinity Laws
Brake Horse Power, BHP changes indirect proportion to the
oCube of impeller diameter D ratio,
oroCube of speed N ratio
BHP2 = BHP1 x [D2/D1]3
BHP2 = BHP1 x [N2/N1]3
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The Affinity Laws
If changes are made to bothimpeller diameter and pump speedthe equations can be combined to:
• Q2 = Q1 x [(D2xN2)/(D1xN1)]
• H2 = H1 x [(D2xN2)/(D1xN1)]2
• BHP2 = BHP1 x [(D2xN2)/(D1xN1)]3