pump basics

Centrifugal Pump Basics

Terms commonly used in the Terms commonly used in the pumping industrypumping industry


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, accelerated down the blades and thrown against pump casing that directs flow out of discharge


Centrifugal Pump

Liquid into impeller eye frompump suction

Impeller Rotation


Centrifugal Pump Curve


1 Gallon of water (U.S. @ 60DegF) weighs 8.33 lbs

1 cubic foot of water contains 7.48 gallons

Specific Gravity (Sp Gr) of a fluid is the relationship of the density (lbs/ft3) to that of water (62.3 lbs/ft3)

WATER COLUMN

1 psig

2.31 ft

1” 1”

Basic Fluid Facts


WATER1.0 sp gr

GASOLINE0.8 sp gr

BRINE1.2 sp gr

hp = gpm*hd*sp gr*100 3960*Pump Eff

Pump head (ft) = psig*2.31 sp gr

231 ft

120 psig80 psig100 psig

Pump Shut-off Head 231ft

Specific Gravity


1 inch square column of air, the height of the earth’s atmosphere (From Sea Level) weights 14.7 lbs

Air Column 14.7 psia

0 psig

1” 1”

BASIC FLUID FACTS


Basic Centrifugal Pump EquationsFor 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)


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

System Resistance


A “Closed” hydronic system is one that has only one interface with air or flexible membrane

An “Open” hydronic system is one that has more than one interface with air or a flexible membrane

Open & Closed Systems


LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDINGHEIGHT

BalancingValve

3-Way Control Valve

Isolating Valve

LOAD

“Closed” System


System Resistance Curve

CAPACITY

Friction Losses

“Closed” System Resistance Curve


Static Suction Head

CONDENSER

Static Head

“Open” System


HEA

D

System Head Curve

CAPACITY

Friction Losses

Total Static Head

“Open” System Resistance Curve


LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDINGHEIGHT

BALANCINGVALVE

2 WAY CONTROL VALVE

ISOLATINGVALVE

LOAD

“Closed” System with Minimum Maintained Pressure


HEA

D

System Head Curve

CAPACITY

Friction Losses

MinimumMaintainedPressure

“Closed” System Resistance Curve with Minimum Maintained Pressure


Terms commonly used in the Terms commonly used in the pumping industrypumping industry

pump basics

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