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Centrifugal Pump Basics

Terms commonly used in theTerms commonly used in the

pumping industrypumping industry

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Centrifugal, (Sen-trif-u-gal)

Tending to fly from a center

Thrown from a center

Centrifugal pump impeller does just that

Water drawn into impeller eye, accelerateddown the blades and thrown against pump

casing that directs flow out of discharge

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Centrifugal Pump

Liquid into

impeller eye from

pump suction

Impeller Rotation

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Centrifugal Pump Curve

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Centrifugal Pump Curve

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1 Gallon of water(U.S. @ 60DegF) weighs8.33 lbs

1 cubic foot of watercontains 7.48 gallons

Specific Gravity(Sp Gr) of a fluid is

the relationship of thedensity (lbs/ft3) to that ofwater (62.3 lbs/ft3)

WATER COLUMN

1 psig

2.31 ft

1 1

Basic Fluid Facts

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WATER

1.0 sp gr

GASOLINE

0.8 sp gr

BRINE

1.2 sp gr

hp =gpm*hd*sp

gr*100

Pump head (ft) = psig*2.31sp gr

231 ft

120 psig80 psig100 psig

Pump Shut-off Head 231ft

Specific Gravity

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1 inch square

column of air, the

height of the

earths atmosphere

(From Sea Level)

weights 14.7 lbs

Air Column 14.7 psia

0 psig

11

BASIC FLUID FACTS

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Basic Centrifugal Pump Equations

For variations in impeller diameter, at constant speed:

D1 = Q1 = H1 BHP1 = D13

D2 Q2 H2 BHP2 D23

For variations in speed, with constant impeller diameter:

S1 = Q1 = H1 BHP1 = S13

S2 = Q2 H2 BHP2 S23

Where: D = Impeller Diameter (Ins / mm)

H = Pump Head (Ft / m)

Q = Pump Capacity (gpm / lps)

S = Speed (rpm / rps)

BHP = Brake Horsepower (Shaft Power - hp / kW)

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Friction Loss for Water in Commercial Steel Pipe (Schedule 40)

System Resistance

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A Closed hydronic system is one

that has only one interface with airor flexible membrane

An Open hydronic system is one

that has more than one interfacewith air or a flexible membrane

Open & Closed Systems

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LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDING

HEIGHT

BalancingValve

3-WayControlValve

IsolatingValve

LOAD

Closed System

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System Resistance Curve

CAPACITY

FrictionLosses

Closed System Resistance Curve

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StaticSuction Head

CONDENSER

Static Head

Open System

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HEAD

System Head Curve

CAPACITY

FrictionLosses

TotalStaticHead

Open System Resistance Curve

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LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDING

HEIGHT

BALANCING

VALVE

2 WAY CONTROL

VALVE

ISOLATING

VALVE

LOAD

Closed System with

Minimum Maintained Pressure

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HEAD

System Head Curve

CAPACITY

FrictionLosses

MinimumMaintainedPressure

Closed System Resistance Curve with

Minimum Maintained Pressure

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Terms commonly used in theTerms commonly used in the

pumping industrypumping industry