Centrifugal Pump Basics

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

Centrifugal Pump Basics

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 Basics

Centrifugal Pump

Liquid into impeller eye frompump suction

Impeller Rotation

Centrifugal Pump Basics

Centrifugal Pump Curve

Centrifugal Pump Basics

Centrifugal Pump Curve

Centrifugal Pump Basics

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

Centrifugal Pump Basics

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

Centrifugal Pump Basics

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

Centrifugal Pump Basics

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)

Centrifugal Pump Basics

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

System Resistance

Centrifugal Pump Basics

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

Centrifugal Pump Basics

LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDINGHEIGHT

BalancingValve

3-Way Control Valve

Isolating Valve

LOAD

“Closed” System

Centrifugal Pump Basics

System Resistance Curve

CAPACITY

Friction Losses

“Closed” System Resistance Curve

Centrifugal Pump Basics

Static Suction Head

CONDENSER

Static Head

“Open” System

Centrifugal Pump Basics

HEA

D

System Head Curve

CAPACITY

Friction Losses

Total Static Head

“Open” System Resistance Curve

Centrifugal Pump Basics

LOAD

LOAD

LOAD

SOURCE

EXPANSION

BUILDINGHEIGHT

BALANCINGVALVE

2 WAY CONTROL VALVE

ISOLATINGVALVE

LOAD

“Closed” System with Minimum Maintained Pressure

Centrifugal Pump Basics

HEA

D

System Head Curve

CAPACITY

Friction Losses

MinimumMaintainedPressure

“Closed” System Resistance Curve with Minimum Maintained Pressure

Centrifugal Pump Basics

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