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P E R F O R M A N C E | Q U A L I T Y | S E R V I C E | T R U S T

PERFORMANCE | QUALITY | SERVICE | TRUST

A pump is the heart of any pumping system. The principles of pumping liquid have been known since the time of the early Egyptians. They have raised water for irrigation from the Nile River to the plains. A working definition of a pump for our time might be:

A PUMP IS A DEVICE THAT ADDS ENERGY TO A LIQUID IN ORDER TO

MOVE IT FROM ONE POINT TO ANOTHER

There are, of course, many kinds of pumps in use. Their horsepower may be as little as a friction of the horsepower or as large as several thousand horsepower. Pressure ranges from ounces per square inch to many thousand PSI. Pumps can be driven by electric motors, gas or diesel engines, steam engines or back on the farm, by hand.

There are many types of centrifugal pumps: volute, diffuser, regenerative-turbine, vertical-turbine, mixed-flow (propeller) and self-priming. Of the aforementioned types of centrifugal pumps, National Pump Company specializes in the manufacture of vertical turbine pumps and Packaged Pump Stations. This enables National Pump to offer its distributors and end-users a complete pumping solution.

Introduction


Theory of Operation

Liquid goes in…

Liquid comes out…

Or so we hope…

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Centrifugal Pump Basics

• The impeller is only part of the hydraulic design. Work is useful only when the product being pumped is controlled.

• The Volute/Bowl is the other part of the hydraulic design which transforms the velocity of the liquid into pressure and controls the product being pumped.

CENTRIFUGAL FORCE-RaceCarSequence 7-19-09.mov

CENTRIFUGAL FORCE-RaceCarSequence 7-19-09.mov


A - Impeller Suction

B – Impeller Vane

C – Bowl Diffusers

D – Bowl Discharge

Vertical Turbine Basics


Discharge Case

Liquid InletImpeller

Impeller Vane

Discharge Bowl w/ Diffuser Vanes

Bowl Bearing

Vertical Turbine Pump Basics


Vertical Turbine Basics

• The impeller vanes and Bowl Diffuser vanes are matched for optimum pump performance.

• The diffuser straightens the flow from the impeller into the next impeller to limit the amount of flow pre-rotation and to maximize pump efficiency.

PERFORMANCE | QUALITY | SERVICE | TRUSTSecond Edition 2/4/11

Performance Curve

HP= 18

NPSHr= 12’

FLOW= 1000

HEAD= 62’

Note: A pump

only knows to

follow its

curve


Proper Pump Selection

Optimum Range = 50 – 120% of BEP


Applying National Pumps to your System ?

1. Determining Pump Application and

System Requirements

2. Pump Selection and Sizing

3. Pump Repair or Replacement


Pump and System Requirements

MARKET OFTEN DETERMINES PUMP REQUIREMENTS

• Agricultural – Crops - flood, spray

• Municipal – Water supply & distribution, water treatment, wastewater

collection, desalination

• Municipal Well - Municipal, deep well > 40’ w/ service capability

(drillers/installers)

• Industrial - Mining, power, dewatering

• Power - Generating Power Plants

• Commercial / HVAC - Buildings and institutions for the occupancy of

people (HVAC)

• OEM’s - Process cooling/heating, pump packagers, etc.

• Golf / Turf - Commercial turf, golf

• Oil and Gas - Oil production, refining, pipeline, gas processing, fuel oil

• Water Systems - Residential, snow making, flood control, ground

water development


Pump System


Determining Needs (INPUTS)• Flow and Head

• Efficiency (Target or HI Standard)

• Well, Wet Well, or Suction Can?

• Water or Oil Lube (Water Inj.)

• Setting Depth ( Elevations )

• High and Low Water Levels

• Suction Pressure

• NPSHa (calculated)

• Application – Raw Water, Booster, High Service

• Motor Controls (ATL, PWS, RVSS, VFD)

• Motor Requirements (Encl., Amb. Temp.)



• Filled out pump Data Sheet

• Basic information needed to

quote – Standard Pump or

Bid & Spec. Project

• Proper information will:

speed-up quote Time

increase quote accuracy



• Pump Requirement Data

Form

• ISO 9001 Document



• Oil lubrication is recommended after 100 ft of setting (if not using a pre-lube system)

• Oil Lube/enclosed Lineshaft w/an electrical solenoid for automatic or manual valve for oil line lubrication

• Water Lube/ Open line shaft using the water as the lubrication for the bearings (also known as product lubricated)

Oil Lubrication vs. Water Lube


Determining Needs (OUTPUTS) Total Dynamic Head

• Elevation Differences (feet)

• Pressure Requirements (psig)

• Column Pipe Friction Loses

• Discharge Head Friction Losses

Pump Selection / # of stages

Pump Total BHP

• Pump (Bowl) Efficiency and BHP (calc.)

• Shaft HP



Determining Needs (OUTPUTS) Hydraulic Thrust

• Impeller Thrust – K factor

• Impeller Weight

• Shaft Weight

Shaft Stretch

Column Stretch

Net Stretch

Running Clearance

Impeller Lift

Available Lateral



Pump Selection - Web Version


Pump System Example

30’

50’150’

120 psig

• 1,000 GPM


Sizing Example

• Total Dynamic Head

= (50’ + 30’) + (120 psig. x 2.31) + (2.97 x 150’) + 0.47= 204.92 ( 205’ TDH )

100

Static W.L. Disch. El.

Disch. Press.

Col. Friction

Col. Length

Disch. Head Frict. Losses


Sizing Example

• 1,000 @ 209’

• 8.34” Impeller

• 83.6% Eff.

• 62.9 BHP Design

• 69.9 BHP Max.


Sizing Example

• J11HC….4 stages trimmed to 8.34”

• Eff. = 83.6%

• HP = (1000 x 209) = 63.1 HP

(3960 x 0.836)

• SHAFT HP of 1.5” shaft = (1.14 x 150) = 1.71 HP (page 36)

100

• BHP = 63.1 (BHP) + 1.17 (SHAFT HP) = 64.3 at design point

• BHP = 69.9 + 1.17 = 71.07 at run-out

• Select a 75 HP motor for NON-OVERLOADING or VFD OPERATION


Sizing Examples

Down-Thrust Calculations

• Imp./Bowl Thrust = 7.9 (K factor) x 209 = 1650 lbs. (page 34) (K factor is Thrust per foot of TDH)

• Total Down Thrust = 1650 + (18.5x4) + (6.01 x 150) = 2625 #Imp. Thrust + Imp. Wt. x # Imp + 1-1/2” Shaft Wt x Setting

(page 34) (Page 37)


Sizing Examples

Shaft / Column Stretch & Bowl Lateral

• Shaft Elongation = .062 / 100 x 150 (Setting) =.093” (page 42…2600 # with 1-1/2” shaft)

• Column Elongation = .007 / 100 x 1.3 x 150 (Setting) = .01365” (page 43…1600#...8” column)

• Net Stretch = .093” (Shaft Stretch) - .01365” (Column Stretch) = .07935”

• Bowl Lateral – J11 Standard Lateral is 1” / 1-1/4” max. (page 34)

• Running Clearance – Est. = .19” (3/16”)

• Impeller Lift = .07935” (Net Stretch) + .19 (Running Clearance) = .26935”

• Available Lateral = 1.0” (Standard Bowl lateral) – 0.26935” (Impeller Lift) = .7306”


Q & A


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REPAIR OR REPLACE ?


Maintaining Pump Efficiency

“It is considered good practice to replace or repair wearing rings when the nominal clearance has doubled. The presence of abrasive solids in the liquid pumped may be expected to increase wearing-ring clearance rapidly.”

“Pump Handbook,” Karassik et al, 1986, Second Edition, p. 2.204


Level 1 – Basic Repair

Level 2 – Extended Repair

Level 3 – Complete Overhaul

Repair or Replace


Level 1 – Basic Repair

• Slight Wear in and on the Wear Surfaces

- Bearings

- Shafting

- Bowl or Impeller Wear Rings

- Packing Boxes

- Seals

• Impeller Vein Wear and Deformities due to Solids

• Bowl Wear due to Solids

Repair or Replace


Level 1 – Basic Repair ( Continued )

• Damaged or Old Packing

• Rust or Corrosion on Machined Surfaces

• Motor Overhaul

• Shaft Straightening

Repair or Replace


Level 2 – Extended Repair

• Replacing Bowl Assembly ( Re-Bowl )

• Replacing Shafts

• Replacing Packing Boxes or Seals

• Replacement Minor Components that cannot be Repaired

Repair or Replace


Level 3 – Complete Overhaul

• Replacement of Major Components

• Complete Pump Replacement

Repair or Replace


When re-bowling a pump NPC can fit our bowl assembly to any existing application

With this form found in our engineering catalog, the existing dimensions can be documented and used for to design the new bowl fit.

Repair or Replace


Repair or Replace


Q & A

Repair or Replace


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CENTRIFUGAL PUMP

PRINCIPALS


A few important pump principals to

understand:

1. Affinity Laws

2. Bernoulli’s Theorem

3. N.P.S.H. - Otherwise known as “Net Positive

Suction Head”


Affinity Laws


Performance depends on 4 items:

1. Pump Hydraulic Design (impeller type & design)

2. Impeller Diameter 3. Impeller Speed (RPM)

4. Pump Efficiency

En

clo

se

dS

oli

ds H

an

dli

ng

Op

en

The Affinity Laws

The affinity laws accurately predict the

effect of changing the speed and

impeller diameter of a centrifugal pump


• Change in Speed is directly proportional to change in Flow.

• 2 x RPM …..2 x FLOW

• 2 x RPM…...4 x HEAD

• 2 x RPM……8 x BHP

RPM 1 = Flow 1 3600 = Flow 1 Flow 1 = 2000 GPM

RPM 2 Flow 2 1800 1000 Double the Speed…Flow x 2

RPM 1 = Head 1 3600 = Head 1 Head 1 = 400 Feet

RPM 2 Head 2 1800 100 Double the Speed…..Head x 4

RPM 1 = BHP 1 3600 = BHP 1 BHP 1 = 252 HP

RPM 2 BHP 2 1800 31.5 Double the Speed…..BHP x 8

The Affinity Laws

2

3

2

3


• Change in Impeller Diameter is directly proportional to

change in Flow.

• 2 x IMP DIA. …..2 x FLOW

• 2 x IMP DIA. …...4 x HEAD

• 2 x IMP DIA. ……8 x BHP

DIA 1 = Flow 1 20” = Flow 1 Flow 1 = 2000 GPM

DIA 2 Flow 2 10” 1000 Flow varies proportionally with Imp Dia.

DIA 1 = Head 1 20” = Head 1 Head 1 = 400 Feet

DIA 2 Head 2 10” 100 Double the Imp. Dia.…..Head x 4

DIA 1 = BHP 1 20” = BHP 1 BHP 1 = 252 HP

DIA 2 BHP 2 10” 31.5 Double the Imp. Dia. …..BHP x 8

The Affinity Laws

2

3

2

3

DIA 1

DIA 2


AFFINITY LAWS

RPM1 = Q1 = H1 = BHP1RPM2 = Q2 = H2 = BHP2

Therefore, IF….

RPM increases x 2Flow increases x 2Head increases SquaredBHP increases Cubed

2 3


AFFINITY LAWS

1800 rpm900 rpm

1800 rpm = x 2 for Flow….. X 4 for Head….x 8 for BHP900 rpm

2.2 BHP18.0 BHP


Bernoulli’s Theory


Ole Mr. Bernoulli’s Theorem

• Total energy in a fluid is the sum of its VELOCITY energy

and its PRESSURE energy.

Total Energy = VELOCITY + PRESSURE

• Centrifugal pumps increase Total Energy by first adding

VELOCITY Energy and then transforming it to

PRESSURE Energy.


Ole Mr. Bernoulli’s Theorem

1 2

• Total Energy at point 1 is equal to Total Energy at point 2

PERFORMANCE | QUALITY | SERVICE | TRUSTSecond Edition 2/4/11

Bernoulli’s EquationEnergy at Point 2 = Point 1 + Energy added by Pump

1

2


Bernoulli’s Equation

P + V + Z + Pump (feet) = P + V + Z + F

2g 2g

2 21 2211 2

P = Pressure in psig x 2.31 = feet

V = Velocity in feet/sec.

G = 32.2 ft./sec (gravitational constant)

Z = Elevation in ‘feet’

F = Friction

2

p

p


Bernoulli’s Equation - Quiz

Pick a flow and calculate!

400 GPM(page 41)

5.12 28.22 feet

28.22 feet

28.22 feet23.15.12

Vel.=18.16 ft/sec

Vel.=18.16 ft/sec

Vel.=10.21 ft/sec 1.62 26.6

26.60 ft / 2.31 = 11.5 PSI

10 PSI 10 PSI


Does Bernoulli’s equation apply here?




• Liquid leaves Impeller (A) and is collected in the area just before the diffuser Vanes (B)

• Diffuser Vanes (C) are designed to slowly increase in area and convert the high velocity to pressure energy

• The vanes also turn the flow to an axial direction providing a smooth flow into the next stage impeller.


Bernoulli’s Equation

Note: As liquid

enters the

impeller…velocity

increases….and

therefore the

pressure drops


NPSH


NPSH

Cavitation - a common problem in pumps and control valves -

causing serious wear and tear and damage. Under the wrong

condition, cavitation will reduce the components life time

dramatically.

What is Cavitation?

Cavitation may occur when the local static pressure in a fluid reach

a level below the vapor pressure of the liquid at the actual

temperature.

According to the Bernoulli Equation this may happen when the

fluid accelerates in a control valve or around a pump impeller.

The vaporization itself does not cause the damage - the damage

happens when the vapor almost immediately collapses after

evaporation when the velocity is decreased and pressure increased.

http://www.engineeringtoolbox.com/caviation-d_407.html

http://www.engineeringtoolbox.com/bernouilli-equation-d_183.html


The Dreaded NPSH

Velocity Increases

…Pressure Drops


The Dreaded NPSH

Area of Vapor Bubble

Collapse


Cavitation Damage


N.P.S.H. required

• NPSHr is derived from pump testing and is shown on

the performance curve

• NPSHr increases and become unpredictable on right

side of curve….which causes loss of performance


N.P.S.H. required

NPSHa > NPSHr

“NPSH available” must be a

minimum of 3 feet greater than

“NPSH required” to insure trouble-

free pump service.


To Calculate NPSHa …3 values are needed

atmP

HP

v


N.P.S.H. available

NPSHa is calculated as:

NPSHa = P + H - P

NPSHa – feet

P (vapor pressure) - psia x 2.31 = feet

H (height of fluid above impeller) - feet

P (vapor pressure of fluid) - psia x 2.31 = feet

atm v

v

atm


Pushes Water Into The Pump

Keeps a Liquid in a Liquid State

AtmosphericPressure

Atmospheric Pressure


Atmospheric Pressure


Vapor Pressure


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QUESTIONS ?

precast concrete never looked so good! · of the aforementioned types of centrifugal pumps,...

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