pumps &pumping system

8/4/2019 Pumps &Pumping System

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Pumps and Pumping Systems


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Energy Balance for a Typical PumpingSystem

ELECTRICITY

100%

12% LOSS

2% LOSS

24% LOSS

9% LOSS

11% LOSS

MOTOR

COUPLING

PUMPS

VALVES

PIPES

WORK DONE ON WATER


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(Source:ASHRAE HVAC Systems and Equipment Handbook 2004)

Base plate-mounted centrifugal pump installation


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Centrifugal pump


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(Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)

A double-suction, horizontal split-case, single-stage centrifugal pump

Pump motor Centrifugal pump body


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CENTRIFUGAL PUMPS

DEFINITION: DEVICE THAT USES AN EXTERNAL POWERSOURCE TO APPLY FORCE TO A FLUID IN ORDER TOMOVE IT FROM ONE PLACE TO ANOTHER

USED TO DECREASE THE MECHANICAL ENERGY OFFLUID.

THE ENERGY DECREASES MAY BE USED TO DECREASETHE VELOCITY. THE PRESSURE OR THE ELEVATION OFTHE FLUID.


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CENTRIFUGAL PUMPS

PUMPS FIND APPLICATION IN VARIOUS TYPES OFINDUSTRIES SUCH AS

-CHEMICAL

-PETROCHEMICAL

-REFINERIES-FERTILISERS

-PAPER

-SUGAR ETC

THE PUBLIC WORKS, THERMAL POWER STATIONS, SEWAGETREATMENT PLANTS AGRICULTURAL SECTOR ALSO FINDMAJOR APPLICATION FOR PUMPS.


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*ADVANTAGES OF CENTRIFUGAL PUMPS

- SIMPLICITY

- LOW FIRST COST

- UNIFORM FLOW ( NON - PULSATING)

- SMALL FLOOR SPACE

- LOW OPERATION & MAINTENANCE EXPENSE

- QUICK OPERATION AND

- ADOPTABILITY TO USE WITH MOTOR OR

TURBINE DRIVE.

CENTRIFUGAL PUMPS


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INDUSTRY /SECTOR ANNUAL SAVING POTENTIAL

(in Rs. Million)* (in MW)

CHEMICAL &

PETROCHEMICAL PLANT 700 29.30

PULP AND PAPER PLANT 675 28.30

STEEL PLANT 400 16.70

FERTILIZER PLANT 300 12.60

THERMAL POWER PLANT 270 11.30

TEXTILE PLANT 100 4.20

CEMENT PLANT 45 1.90

COMMERCIAL BUILDINGS &

HOTELS 60 2.50

PUBLIC WATER WORKS 1500 62.80

OTHERS 200 8.40

TOTAL 4250 178.00

BREAK-UP OF ENERGY SAVINGS POTENTIAL

IN PUMPS

* BASED ON AVERAGE ELECTRICITY PRICE OF Rs 3.00 PER

UNIT AND OPERATING PERIOD OF 8000 HOURS PER YEAR


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HEAD

CAPACITY

CENTRIFUGAL PUMP CHARACTERISTICS


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HEAD

CAPACITY



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E

FFICIENCY

CAPACITY


BHP

CAPACITY


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HEAD

CAPACITY


OPERATING POINT


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ENERGY CONSERVATION IN PUMPS ATDESIGN STAGE

SELECT PUMPS IN THEIR RANGE OF GREATEST EFFICIENCY,WHICH IS USUALLY IN THE RANGE OF 50-70% OF THEIRMAXIMUM CAPACITY.

DO NOT ALLOW AN EXTRA PRESSURE LOSS IN THE PIPINGAS A SAFETY FACTOR

PROVISION FOR AIR VENTING FROM THE SYSTEM IN DESIGN,INSTALLATION AND MAINTENANCE.

DO NOT OVERSIZE THE PUMP.

ENSURE ALL THE JOINTS ARE LEAK PROOF TO AVOID AIR

IMPRESS DURING PUMPING OPERATION. ENSURE THAT (NPSH)A >(NPSH)R

KEEP SECTION LIFT OF 4.5 TO 5M.


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SPECIFIC SPEED

SPECIFIC SPEED IS A CORRELATION OF PUMP CAPACITY,HEAD AND SPEED AT OPTIMUM EFFICIENCY.

DEFINITIONTHE SPECIFIC SPEED OF AN IMPELLER, IS THE REVOLUTIONPER MINUTE AT WHICH A GEOMENTRICALLY SIMILARIMPELLER WOULD RUN, IF IT WERE SUCH A SIZE AS TODISCHARGE 1M3/S, AGAINST 1M HEAD.

THIS IS A NUMBER EXPRESSED AS .

NS = ( N*Q)/H3/4Ns = SPECIFIC SPEED

N = ROTATIVE SPEED IN rpmQ = CAPACITY,m3/s

H = TOTAL HEAD, m

( Head per stage for a multistage pump)


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PUMP SUCTION PRESSURE

* SYSTEM PRESSURE

* STATIC PRESSURE

* LIVE PRESSURE DROP

PUMP DISCHARGE PRESSURE

* SYSTEM PRESSURE* STATIC PRESSURE

* LINE PRESSURE DROP

* PRESSURE DROP ACROSS INSTRUMENTS

* PRESSURE DROP ACROSS EQUIPMENTS DIFFERENTIAL PRESSURE

= DISCHARGE PRESSURE - SUCTION PRESSURE

PUMP PROCESS DESIGN


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HEAD

CAPACITY


STATIC

HEAD

FRACTIONHEAD


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HEAD

CAPACITY


STATIC HEAD

EFFICIENCY

SYSTEM CHAR.


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PUMP - OVER DESIGN* MORE USUALLY ENCOUNTERED DUE TO

DESIGNERS OVER PROVISION OF SAFETY

MEASUREMENT

* RESULTS HIGH EQUIPMENTS COST

* THE SYSTEM COULD SUFFER DUE TO THE

FOLLOWING

- THROTTLING MAY OCCUR, LEADING TOWEAR ON VALVES NOT DESIGNED FOR

CONTROL AND INCREASED NOISE LEVELS

- CAVITATION

- OVER LOADED MOTOR

- REDUCED PUMP LIFE ( ESPECIALLY IF THE

FLOW RATES ARE MUCH ABOVE THE

OPTIMUM)

- PUMP INLET CONDITIONS WILL SUFFER

- HIGH ENERGY COST


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PUMP - UNDER DESIGN

* PUMPS OPERATING AWAY FROM THEIR

DESIGNED DUTY POINTS, AT HIGHER HEADSAND DECREASED FLOW , RESULTING IN THE

PLANT BEING UNABLE TO MEET ITS DESIGN

PERFORMANCE

* INCREASE IN NOISE LEVELS

* REDUCED PUMP LIFE


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DESING CONSIDERATIONS

* OVER DESIGN LEADS TO CONSIDERABLE LOSS OFEFFICIENCY & ENERGY IN PUMPS

* MINIMISE OVER DESIGN

* AN IDEAL SAFTY MARGIN FOR A PUMP WILL

BE 10 % EACH ON CAPACITY & HEAD

* THE IDEAL MARGIN FOR MPSH WHOUD BE

0.5 - 1.0 M ON THE NPSH REQUIRED

* THE NORMAL ALLOWABLE MARGINS IN

POWER ARE 5 - 15 % BETWEEN THE MAXIMUMPOWER IN OPERATING A PUMP & THE MOTOR

RATING


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VARIOUS TYPE PUMP EFFICIENCY

* AUXIAL PUMP 80 %

* MIXED FLOW PUMP 70 %

* SINGLE STAGE CENTRIFUGAL PUMP 60 %

* MULTISTAGE CENTRIFUGAL PUMP 40 %

* TURBINE PUMP 50 %

* SUBMERCIBLE PUMP 35 %

* RECIPROCATING PUMP 30 %

* JET PUMP 15 %


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CASE STUDY 1

1.5 Kg/cm27.2m

0.4m

Globe valve

0.15Kg/cm2 0.8Kg/cm2

0.35Kg/cm2

21.2m

7. 5Kg/cm2


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Liquid pumped = hydrocarbon fluid

Flow rate =115m3/hr

Specific gravity at PT =1.20

Viscosity = 0.64

Vapour pressure =1.5Kg/Cm2

Geometric pipe length

Suction =10m

Discharge =100m

Fluid velocity

Suction =1m/s

Discharge =2m/s


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Equilibrium length in m

Pipe fitting suction Discharge

Gate valve 1.6 1.2Strainer 12 9

Elbow 6.1 4.6

Tee 4.8 3NRV 27.5 19.8

Entrance - 8

Exit 12 8Reducer 1.6 1.2


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Find out the following

A) suction & Discharge line sizes

B) Suction & Discharge pressure

C) Motor Hp required

D) (NPSH)a

Pump should be located at the storagearea so that the line pressure drop issmaller. Positive head developed is more.


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RECOMMENDED VELOCITIES FOR SIZING PUMP

SUCTION & DISCHARGE PIPE LINES

DESCRPTION SUCTION DISCHARGE

(m/s) (m/s)

VISCOUS LIQUIDS 0.50 0.80

LIGHT OILS 0.80 1.00

WATER 1.50 1.5 - 2.00

PIPE DIAMETER

PUMPIN

GCOST

CAPITA

LCOST

ECONOMIC PIPE DIAMETER


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Solution:

Suction side:Fluid flow rate = 115m3/hr

Q = Av

Q = /4Ds2*v

115/3600 = /4Ds2*1

Ds = 0.2016m

pf = 4fLv2/2gD


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Geometric length of the suction sideEquivalent length=10mL = (1.6*2)+4.8+(12*1)+(1.6*1)+3(6.1)+12

= 39.9+12=51.9.

L = Geometric length + equivalent pipe length for fitting.L = 10+51.9=61.9 m

NRe = [(D**v)/]= [(0.2016*1*1200)/0.6*10-3 ]

= 403200Since Turbulent flowF = 0.0035+0.264(403200)-0.42

F = 4.67*10-3

F = [(4*4.67*10-3*61.9*12)/2*9.81*0.2016]

= 0.2922m= 0.2922*10-4*1200= 0.0351Kg/Cm2


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Static head = (7.2-0.4)*1200*10-4 = 0.816Kg/Cm2

Suction pressure Kg/Cm2

System pressure 1.5

Static head 0.816

Line pressure drop -0.0351

Suction pressure 2.2809Kg/Cm2

Discharge side:

Q = AdVd

115/3600 = /4Dd2*2

Dd = 0.1426m


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Equivalent length calculation.

Gate value 6*1.2 7.2

Elbow 3*4.6 13.8

Tee 4*3 12.0Entrance 2*8 16.0

Exit 1*8 8

NRV 1*19.8 19.8

76.8 m

L = 100+76.8

= 176.8m

NRe = DVP/

= (0.1426*2*1200)/0.6*10-3

= 570400F = 0.0035+0.264(570400)-0.42

= 4.51*10-3


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pf =[(4*f*L*v2)/2gD]

pf = 4*4.51*10-3*176.8*22/2*9.81*0.1426= .56m

= 4.56*10-4*1200= 0.547Kg/Cm2

Static head = (21.2-0.4)*10-4*1200= 2.496Kg/Cm2

Discharge pressure Kg/Cm2

System pressure 7.5Pressure drop across cv 0.8Pressure drop across orifice 0.15Pressure drop across He 0.35Static head 2.496Line Pressure drop 0.547

Discharge pressure = 11.843Kg/Cm2


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Differential pressure = Discharge pressuresuction pressure= 11.843-2.2809

= 9.5621Kg/Cm2

= 95.621mWC

(NPSH)aSuction pressureVapour pressure

= 2.2809-1.5

= 0.7809 Kg/Cm2

=7.809 mWC

Safety margin = 0.600/7.209 mWC

=7.209/1.2 = 6.0075MLC

Horse power required

HHP = (115/3600)*[(1200*95.621)/75]= 48.87

BHP = HHP/Pump = 48.87/0.6 = 81.45Motor HP = BHP/Motor = 81.45/0.9 = 90


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CASE STUDY 2

CALCULATE NPSH AVAILABLE FOR THE PUMP SHOWN IN FIG.

LIQUID PUMPED CONDENSATE AT 850C AT 50m3/hr.

SPECIFIC GRAVITY AT 850C =0.9VISCOSITY AT 850C =0.32cpVAPOUR AT 850C =0.48kg/cm2

EQUIVALENT PIPE LENGTHFOOT VALVE =12mELBOW =3.2mGATE VALVE =1.4mSTRAINER =0.2mREDUCER =0.9m

0.5m

1m

0.5m

100pipe

4 x 3reducer


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SOLUTION:

Static head =10-4x900x1.5=0.135kg/cm2

System pressure =10.33mwc=1.033kg/cm2

Line pressure droppf =[(4*f*L*v2)/2gD]

L =(12*1)+(3.2*1)+(1.4*1)+(0.2*1)+(0.9*1)=17.7

L = 3+17.7=20.7

/4*D2*v = Q

/4*0.12*v = 50/3600

V= 50/3600*4/*1/0.01

V=1.77m/sec

NRe = [(D**v)/]=[(0.1*900*1.77)/0.32*10-3]=497812.5

F = 0.0035+0.264(497812.5)-0.42

F =4.57*10-3

pf =[(4*4.57*10-3*20.7*1.772)/(2*9.81*0.1)]=0.604m


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Kg/Cm2

System pressure 1.033

Static head -0.135

Line pressure drop(10-4*900*0.604)

-0.054=0.884Kg/Cm2

(NPSH) available

0.884

-0.480 (Vapour pressure)

=0.364 Kg/Cm2

=3.64 mwc

Safety margin =0.60mwc

=3.04mwc

(NPSH)a =3.04mwc

=3.04/0.9

=3.378MLC


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BOILER FEED PUMP WILL HAVE A CAPACITY

OF 1.2 TO 1.25 TIMES THE BOILER CAPACITY

COOLING TOWEER PUMPS IN A POWER PLANT

WILL HAVE A CAPACITY OF 60 TIMES THE

BOILER CAPACITY

PUMP CAPACITY


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PUMP EFFICIENCY = USEFUL OUTPUT POWER, kW

INPUT POWER, kW* 100

HHP

BHP* 100=

INPUT POWER, W =1 .73 VI COS V - SUPPLY VOLTAGE , 440 V

I - CURRENT CONSUMED BY THE PUMP, AMPS

COS - POWER FACTOR, NORMALLY > 0.8

W - POWER CONSUMED IN WATTS

OUTPUT POWER, BHP =

Q - FLOW RATE , m3/s

P - DIFFERENTIAL HEAD, kg/m2Q * P

102

PREDICTION OF PUMP EFFICIENCY


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FLOW RATE MEASURED, Q = 45 m3 /h

HEAD ,P = 30 kg/ cm2

= 30* 104 kg /m2

USEFUL OUTPUT POWER, kW

= (FLOW RATE, m3/ s) * (DIFFERENTIAL HEAD kg /m2) * 1/102

= 45 / 3600 * ( 30* 104) * 1/102

= 36.76 kW

VOLTAGE MEASSURED = 400 V

CURRENT MEASSURED = 85A

POWER FACTOR = 0.85

INPUT POWER, kW = 1 .73 VI COS / 1000

= 1 .73 * 400*85*0.85 / 1000

= 50 kW

36.76

EFFICIENCY = * 100

50

= 73.52 %

PREDICTION OF PUMP EFFICIENCYCASE STUDY 3


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EFFICIENCY OF CENTRIFUGAL PUMPS

Pump = (Output / Input)x100Pump = [Q*H*g*] / [3600 x motor x 1000 x P]

P = Input power in KW = [( 3 *V*I*COS) / 1000]

Q = Flow rate in m3/ h

G = Acceleration due to gravity, 9.807m/s

H = Head in m

= Fluid density, Kg / m3

Pump = Pump efficiency

Motor = Motor efficiencyV = Supply voltage, V

I = Current drawn by the motor, A

Cos = Power factor


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PUMP PERFORMANCE WITH IMPELLER

DIAMETER & OR SPEED CHANGE

Q1,H1,BHP1,D1 & N1 - INITIAL CAPACITY,

HEAD, BRAKE HORSE POWER, DIAMETER

& SPEED

Q2,H2,BHP2,D2 & N2 - NEW CAPACITY,

HEAD, BRAKE HORSE POWER, DIAMETER

& SPEED

DIAMATER CHANGE ONLY

Q2 = Q1( D2 /D1)

H2 = H1(D2/D1)2

BHP2 = BHP1(D2/D1)3


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CENTRIFUGAL PUMPS-CAPACITY

CONTROL

PARALLEL OPERATION

CONTROL VALUE WITH BY PASSREGULATION

SPEED REGULATION

THROTTLING AT CONSTANT SPEED


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ENERGY CONSERVATION OPTIONS IN

PUMPING SYSTEM

IMPELLER TRIMMING DOWN SIZING THE IMPELLER IMPELLER REPAIR AND REPLACEMENT REPLACEMENT WITH SMALLER PUMPS

SPEED VARIATION COMBINED THROTTLING & SPEED CONTROL DECENTRALIZATION OF PUMPING SYSTEM AVOID UNNECESSARY PUMPING

PROVIDE OVERHEAD TANK FOR GRAVITY FLOW


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FOR THE GIVEN PIPE SIZE

Normal Flow Rate = Q1 Normal Pressure Drop = P1 Max. Flow Rate = Q2 Max. Pressure Drop = P

2

What is the relation between P1& P2?

P2 = X2P1

Where X = (Q2/ Q1)

F l


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For example:

Q1 = 65 m3/ h , P1 = 0.45 kg / cm2

Q2 = 80 m3/ h , P2 = ?

P2 = (Q2/ Q1)2

*P1

=(80/65)2 * 0.45= 0.68 kg / cm2


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PUMP PERFORMANCE WITH IMPELLER

DIAMETER & OR SPEED CHANGE

SPEED CHANGE ONLY

Q2 = Q1(N2/N1)

H2 = H1(N2/N2)2

BHP2 = BHP1(N2/N1)3

DIAMETER AND SPEED CHANGE

Q2 = Q1(D2/D1 * N2/N1)

H2 = H1(D2/D1 * N2/N2)2

BHP2 = BHP1(D2/D1 * N2/N1)3


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* THE SUCTION LINE SHOULD NEVER BESMALLER THAN PUMP INLET & SHOULD BE

LARGER IF FEASIBLE

* WHEN TWO OR MORE PUMPS ARE CONNECTED

TO A COMMAN HEADER, A SUCTION LINE

SHOULD BE SELECTED LARGER ENOUGH SO

THAT THE FLUID DOESNOT TRAVEL FASTER

THAN 0.8 m/s THROUGH THE SUCTIONLINE AT

THE COMBINED CAPACITY.

* SLOPE UNIFORMLY TO PUMP FROM FLUID

SUPPLY TO AVOID AIR PACKETS

* BYPASS DESIGN SHOULD TAKE FLUID BACK

TO FLUID SOURCE & NOT INTO SUCTION LINE

* SUCTION LINE SHOULD BE FIRMLY ANCHORED

OR BURIED TO AVOID PUTTING A STRAIN ON

THE PUMP & TO HELP PREVENT SYSTEM

VIBRATIONS FROM ACTING DIRECTLY ON

THE PUMP

DESIGN OF PIPINGS


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DESIGN OF PIPINGS

FACTORS TO BE CONSIDERED IN THE DESIGN OF

SUCTION PIPING :

* PUMP SHOULD BE AS CLOSE TO THE FLUID

SUPPLY AS POSSIBLE

* USE FULL OPENING VALVES & AVOID

CONSTRICTING VALVES

* THE IDEAL PIPE ARRANGEMENT IS SHORT

AND DIRECT, USING NO ELLS. SHOULD ELLS

BE REQUIRED USE 45O LONG, RADIUS INSTEAD

OF 900

ELLS

* IF A REDUCER IS REQUIRED IN SUCTION LINE

BETWEEN MAIN LINE & PUMP, USE AN

ECCENTRIC REDUCER RATHER THAN

CONCENTRIC WITH STRAIGHT PORTION IN

TOP

CAVITATION:


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CAVITATION:

IT IS A PHENOMENON WHICH HAS BEEN KNOWN FOR ITSDESTRUCTIVE POWERS & GENERALLY ARISES BECAUSE OFTHE BOILING OF A LIQUID DUE TO LOW PRESSURE RATHER

THAN HIGH PRESSURE. CAVITATION CAN CREATE SEVERE EROSION ON PUMP

IMPELLERS WHICH IN TURN SETS UP VIBRATION AND NOISE,RUNNING WITH A RESULT AND LOSS IN PUMPINGEFFICIENCY.

VARIOUS FACTORS, EITHER COLLECTIVE OR INDIVIDUALLYCONTRIBUTE TO THIS PHINOMENON IN THE PUMPING FIELD.

ABNORMALLY HIGH SUCTION LIFTS OR IN CORRECT PIPELAYOUTS ARE TWO PROMINENT FAULTS.

GENERALLY SPEAKING, CENTRIFUGAL PUMPS ARE LIMITEDTO SUCTION LIFT OF A APPROXIMATES 4.5M HIGHER VALUECAN BE ACHIEVED UNDER CERTAIN CIRCUMSTANCE .


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THEORETICAL SUCTION LIFT 10.35M FOR WATER AT 40CSUCTION LIFT IS REDUCED BY

ATTITUDE

FRICTIONAL LOSSES IN THE SUCTION BY INCLUDINGVELOCITY HEAD AND ENTERY LOSSES.

THE EFFECT AND VAPOUR PRESSURE OF THE FLUID AT P.T.

REQUIRED NPSH.


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THE EFFICIENCYOF PUMP CAN BE IMPROVED BY THE ADOPTION OF THE FOLLOWING MEASURES

* RIGHT SELECTION OF PUMP FOR A PARTICULAR

APPLICATION

* SELECTION AND INSTALLATION OF CORRECT SIZE PUMPS

* ENERGY EFFICIENT OPERATING PRACTICES

* UNITIZATION OF PUMPS

* INSTALLATION OF VARIABLE SPEED DRIVERS

* SEREGATION OF HIGH-HEAD AND LOW-HEAD USERS

* UTILIZATION OF GRAVITY HEAD

CONCLUSON


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* INSTALLATION OF HIGH EFFICIENCY PUMPS

* RELOCATION OF PROCESS CODENSERS

* ADOPTION OF THE PROPER DESIGN PARAMETERS

FOR PUMPS AND PIPING

* PROPER INSTRUMENTATION AND CONTROL FOR EFFICIENT

OPERATION, MONITORING AND CONTROL

THE ENERGY EFFICIENCY IN PUMPING SYSTEMS IS BEST

ACHIEVED BY ADOPTION OF ENERGY CONSERVATION AND

RATED DESIGN CONSIDERATIONS AT THE IMPLEMENTATION

/ PROJECT STAGE.

CONCLUSON


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VALVES


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Types of Valves

Two basic groups: Stop valves - used to shut off or partially shutoff the flow of fluid ( ex: globe, gate, plug,needle, butterfly)

Check Valves - used to permit flow in onlyone direction (ex: ball-check, swing-check, lift-check)

Special types: Relief valves Pressure-reducing valves Remote-operated valves


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Globe Valve Most common valvein a propulsion plant Body may be straight,

angle, or cross type

Valve inlet and outletopenings aredesigned to suit

varying requirementsof flow

Valve may beoperated in thepartially open position

(throttled) Commonly used in

steam, air, oil andwater lines


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GateValve

Used for a straight line of flow where minimumrestriction is desired

Not suitable for throttling

May be rising stem or nonrising stem


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Ball Valve Most ball valves are

quick acting - only require90o turn to completelyopen or shut valve

Some ball valves mayhave gearing for ease ofuse (also increasesoperating time)

Used in seawater,sanitary, trim and drain,air, hydraulic, and oiltransfer systems


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Butterfly Valve

Lightweight, relatively small, and quick acting

May be used for throttling Used in freshwater, saltwater, lube oil, JP-5,

F-76, and chill water systems


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Check Valve

Allows fluid toflow in a systemin only onedirection

May be swing, lift,or ball type

Check valves

may be built intoglobe valves orball valves


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Relief Valve

Installed in piping systems toprotect them from excessivepressure

The relieving pressure is setby the force exerted on thedisk by the spring

Relief valves may have alever which allows manualopening of the valve for testpurposes


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Valve Operating Devices

Manual Handwheel or lever is directly connected to the stem and

is operated by hand

Hydraulic Hydraulic pressure is applied to one side of a pistonwhich is connected to the stem of the valve

Motor A hydraulic, electric, or air driven motor is used to turn the

stem of the valve

Solenoid Uses an electromagnet to open or close a valve against

spring pressure


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IMPROVING PUMPSPERFORMANCE & REDUCING

ENERGY CONSUMPTION


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Questions

How do pumps perform?

How can I select an efficient pump?

What causes a pump to become inefficient?

How can I determine my pumpsperformance?

How can I improve my pumps performance?

Will improving my pumps performance

reduce my energy bill?


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Basic Concepts

DefinitionEnergy = kilowatt-hours

o One kilowatt is 1.34 horsepower

o Hours = operating time

Energy cost is based on kwhr consumed andunit energy cost ($/kwhr)

Reducing energy costs

Reduce Input Horsepower

Reduce Operating HoursReduce Unit Energy Cost


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Improving Pumping Plant Efficiency

Adjust pump impeller

Repair worn pumpReplace mismatched pump

Convert to an energy-efficientelectric motor

Centrifugal or Booster Pump


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Shaft Frame Impeller Discharge Inlet

StuffingBox

BalanceLine

Volute WearingRings

entrifugal or Booster ump

Deep Well Turbine


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Deep Well Turbine


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SubmersiblePump


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Improving Pumping Plant

Performance


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Impeller Adjustment


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Effect of Impeller Adjustment


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Effect of Impeller AdjustmentCapacity

(gpm)

Total

Head(feet)

Overall

Efficiency(%)

Input

Horsepower

Pump 1 Before 605 148 54 42

After 910 152 71 49

Pump 2 Before 708 181 59 55

After 789 206 63 65

Pump 3 Before 432 302 54 61

After 539 323 65 67

Pump 4 Before 616 488 57 133

After 796 489 68 144


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Same Operating

Time

Same Volume

of Water

Pump 1 +16.7% -22.8%

Pump 2 +18.2% +5.0%

Pump 3 +9.8% -12.3%

Pump 4 +8.3% -16.8%

Effect of Impeller

Adjustment on Energy Use


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Repair Worn Pump


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Effect of Pump Repair


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Effect of Pump Repair

Before Pumping lift = 95 feet

Capacity = 1552 gpm

IHP = 83

Efficiency = 45%

After Pumping lift = 118

feet

Capacity = 2008 gpm

IHP = 89

Efficiency = 67%

Summary of the Effect of Repairing Pumps


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Summary of the Effect of Repairing Pumps

63 pump tests comparing pump performance before-and-after repair

Average percent increase in pump capacity 41% Average percent increase in total head 0.5%

(pumping lift only) Average percent increase in pumping plant

efficiency 33% IHP increased for 58% of the pumping plants.

Average percent increase in input horsepower 17%

Adjusting/Repairing Pumps


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Adjusting/Repairing Pumps

Adjustment/repair will increasepump capacity and total head

Adjustment/repair will increaseinput horsepower

Reduction in operating time isneeded to realize any energysavingsMore acres irrigated per set

Less time per set

Energy costs will increase ifoperating time is not reduced


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Replace Mismatched Pump

A mismatched pump is one that isoperating properly, but is not operatingnear its point of maximum efficiency


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Capacity (gpm)

Efficie

ncy

(%)

00

ImproperlyMatchedPump

Matched Pump


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Mismatched PumpPumping Plant Test Data

Pumping Lift (feet) 113

Discharge Pressure (psi) 50

Total Head (feet) 228

Capacity (gpm) 940

Input Horsepower 112

Overall Efficiency (%) 48


99/348

Test 1

(Normal)

Test 2 Test 3

Capacity (gpm) 940 870 1060Pressure (psi) 50 79 15

Pumping Lift (feet) 113 112 112

Total Head (feet) 228 295 147

IHP 112 112 104Overall Efficiency (%) 48 57 38

Multiple Pump Tests


100/348

Replacing this pump with one operating at anoverall efficiency of 60% would: Reduce the input horsepower by 19% Reduce the annual energy consumptionby 34,000 Kwhr Reduce the annual energy costs by$3,400 (annual operating time of 2000

hours and an energy cost of $0.10/kwhr)

Replacing a Mismatched Pump


101/348

Replacing a Mismatched Pump

Pumping plant efficiency willincrease

Input horsepower demand

will decrease

Energy savings will occurbecause of the reduced

horsepower demand

How do I determine the


102/348

condition of my pump?

Answer: Conduct a pumping plant testand evaluate the results using the

manufacturers pump performance data


103/348

Pumping

Lift


104/348

Pump

Capacity

DischargePressure


105/348

FLOW METER

8 PIPE DIAMETERS DIAMETERS

2 PIPE

FLOW


106/348

Input

Horsepower


107/348

Is a pump worn or mismatched?

Multiple pump tests

Compare pump test datawith manufacturers pumpperformance curves

200TOTAL HEAD (fe et)


108/348

0 100 200 300 400 500 600 700 800 900 1000 1100

PUMP CAPACITY (gpm )

0

50

100

150

200

REPAIRED PUMPPumping Lift = 102 ft

Capacity = 537 gpmInput Horsepower = 28

Overall Efficiency = 50%Kwhr/af = 211

WORN PUMPPumping Lift = 45 ftCapacity = 624 gpm

Input Horsepower = 19

Overall Efficiency = 39%Kwhr/af = 123

LargeDifference

SmallDifference

100TOTAL HEAD (feet)


109/348

2000 2400 2800 3200 3600


0

20

40

60

80

1983 (64%)1984(54%)

1985 (62%)

100TOTAL HEAD (feet)


110/348

2000 2400 2800 3200 3600


0

20

40

60

80

1983 (64%)

1984 (66%)

1985 (55%)

Recommended Corrective Action


111/348

Recommended Corrective Action

Eo greater than 60% - no corrective action55% to 60% - consider adjusting impeller

50% to 55% - consider adjusting impeller;

consider repairing or replacing pump ifadjustment has no effect

Less than 50% - consider repairing orreplacing pump


112/348

Energy-efficient Electric Motors


113/348

Horsepower Standard Energy

Efficient10 86.5 91.7

20 86.5 93.0

50 90.2 94.5

75 90.2 95.0

100 91.7 95.8

125 91.7 96.2

Efficiencies of Standardand Energy-efficientElectric Motors


114/348

Variable Frequency Drives

What is a Variable Frequency


115/348

q yDrive?

Electronic device that changes thefrequency of the power to an electricmotor

Reducing the power frequency reduces

the motor rpmReducing the motor rpm, and thus the

pump rpm, decreases the pumphorsepower demando A small reduction in pump rpm results in a

large reduction in the horsepower demand


116/348

When are Variable Freq enc


117/348

When are Variable Frequency

Drives Appropriate?One pump is used to irrigate differently-

sized fields. Pump capacity must be

reduced for the smaller fieldsNumber of laterals changes during the

field irrigation (odd shaped fields)

Fluctuating ground water levels

Fluctuating canal or ditch water levels


118/348

Unthrottled Throttled VFD

Acres 80 50 50Pressure (psi) 80 64 60

Capacity (gpm) 1,100 600 700

Input Horsepower 128 90 55

RPM 1770 1770 1345

Overall Efficiency (%) 40 24 44

Centrifugal pump used to irrigate

Both 80-and 50-acre fields


119/348

Note: Pumping plants should beoperated at the reduced frequency

for at least 1,000 hours per yearto be economical


120/348

Convert To Diesel Engines

Options for Converting From Electric Motors toEngines


121/348

Engines

Direct drive (gear head)

Engine shaft to pump shaftefficiency = 98%

Diesel-generator

Engine shaft to pump shaft

efficiency less than about 80%

Considerations


122/348

Brake Horsepower = Shaft HorsepowerEngines and motors are rated based on

brake horsepower ( 100 HP electric motorprovides the same horsepower as a 100 HPengine

Input horsepower of an engine is greaterthan that of an electric motor for the same

brake horsepower


123/348

Engine HorsepowerMaximum horsepower

Continuous horsepower

About s of the maximum horsepower

Derated for altitude, temperature,accessories, etc.

200


124/348

110

128

144

157167

173

1200 1400 1600 1800 2000 2200

ENGINE RPM

0

50

100

150

BRAKEH

ORSEPOWE

R


125/348

0.390.38

0.37 0.37 0.370.38

1200 1400 1600 1800 2000 2200ENGINE RPM

0.30

0.32

0.34

0.36

0.38

0.40

FUELCONSUM

PTION

(lb/bhp-h

r)

40


126/348

33.2

34.2

35.1 35.134.7

33.9

1200 1400 1600 1800 2000 2200

ENGINE RPM

30

32

34

36

38

EN

GINEEFFIC

IENCY(%)

160

PUMP HP CONTINUOUS ENGINE HP


127/348

1400 1500 1600 1700 1800 1900 2000 2100 2200

RPM

0

20

40

60

80

100

120

140

HORS

EPOWE

R

PUMP HP CONTINUOUS ENGINE HP


128/348

Fuel Use Versus RPM

RPM Pump FlowRate (gpm)

Gallons of Dieselper Hour

Gallons of Waterper Gallon of

Diesel

1500 1228 9 81871600 1731 11 96171700 2161 15 86441800 2486 19 8019

Electric Motors vs Diesel Engines:Which is the Best?


129/348

Which is the Best?

Unit energy cost

Capital costs, maintenance costs, etc

Hours of operation

Horsepower

Cost of pollution control devices for

engines


130/348

ElectricMotor

Diesel Engine

Capital Cost $5,500 $11,500 $16,500 $16,500

Unit Energy Cost $0.14/kwhr $0.95/gal $0.95/gal $1.25/galTotal Cost ($/af) 60.5 37.8 39.9 48.5

Comparison of electric motor and

diesel engine100 HP1,100 gpm2,000 hours per year


131/348

Optimizing PumpSystems for Energy

Efficiency

What Is A Pump System?


132/348

p y

A Pump System comprises of all piping,fittings and valves before and after a pumpas well as the motor and motor driver.

There can be multiple pumps, motors anddrives, and they can be arranged tooperate in parallel or in series.

Pump Systems can have static head(pressure), or be circulating systems(friction only systems)

First, Let's Get A Big PicturePerspective


133/348

133

pOf Energy Flow in Pumping

SystemsElectric utilityfeeder

Transformer

Motor breaker/starter

Motor

Adjustable

speed drive(electrical)

Coupling PumpFluid

system

Ultimategoal

At each interface, there areinefficiencies. The goal should

be to maximize the overall costeffectiveness of the pumping, orhow much flow is delivered perunit of input energy.

Specific Energy Es


134/348

p gy s

= Motor efficiency

= Pump efficiency

m

h

Es =fHS

g

mh

HS

= Fluid density

= Gravitationalconstant

= Static head

= Hydraulic System

factor

fHS

HS

g

=Pel x Time

Pumped Volumeph

ph

Understand The Ultimate Goal


135/348

136

Understand The Ultimate Goal

Electric utilityfeeder

Transformer


Motor

Adjustable


Coupling PumpFluid

system

Ultimategoal

Maximize the overall effectiveness.

It Is Essential To Understand The


136/348

137

Ultimate Goal Of The Fluid System To

Optimize It Understand why the system exists

Have clearly defined criteria for what isreally needed

Understand what's negotiable and what'snot

RequirementsFor Designing A System


137/348

For Designing A System

Duration Curve (Flow) System Curve (Pressure vs. Flow)

Pump & Component selection

Annualized Flow Duration Curve


138/348

0

1000

2000

3000

0 2000 4000 6000 8000 10000

Time [hours]

Inflow

[GPM]

Annualized Flow Duration Curve

Understand The Fluid System


139/348

140

Understand The Fluid System

Electric utilityfeeder

Transformer


Motor

Adjustable


Coupling Pump Fluidsystem

Ultimategoal

Maximize the overall effectiveness.

System Curves Are Made Up Of TwoFundamental


140/348

141

Components - The Static Head And The

Frictional Head120

80

40

0

Head,ft

500040003000200010000Flow rate, gpm

Static/Fixed

Friction

Total

Hydraulic System f


141/348

Hydraulic System

Factor The Hydraulic System factor is

defined as The ratio of a hydraulic

systems static head to total head.

Head

Flow

Total

head Loss Head

Static Head

SYSTEM CURVE

HSf

HSf

fHSHS

HS +

HF

=

What Are Some Sources OfFriction In Pumping Systems?


142/348

143

Friction In Pumping Systems?

Pipe walls

Valves

Elbows

Tees

Reducers/expanders

Expansion jointsTank inlets/outlets

(In other words, almost everything that the pumpedfluid passes through, as well as the fluid itself)


143/348

Operational Costs Are InfluencedBy The Selection Of Components

And Their Size

al Frictional Cost Per 100 ft Of Pipe


144/348

al Frictional Cost Per 100 ft Of Pipe

Assumptions: 80% combined pump and motor efficiency,electricity cost = 10 /kWh

5000

4000

3000

2000

1000

0

Annualcost($)

500040003000200010000

flow rate (gpm)

12"

14"

16"

Frictional Losses Can Be


145/348

Frictional Losses Can Be

ranslated Into Operating Costs

12-inch line, 100 ft length, 10/kWh, full open valves,

80% combined pump & motor efficiency

Assumptions:

1000

800

600

400

200

0

AnnualC

ost($)

25002000150010005000flow rate (gpm)

Check valveButterfly valveSch. 40 pipe (new)


146/348

Nameplate Data Applies ToOne Particular Operating


147/348

148

One Particular Operating

Point200

150

100

50

0

Head,f

t

500040003000200010000Flow rate, gpm

Rated:3190 gpm, 97 ft

How Do We Know Where We'll Be


148/348

100

90

80

70

60

50

40

30

head(ft)

500040003000200010000

flow rate (gpm)

Operating On The Pump Curve?

Pump and systemcurve intersection(operating point)

System head curve

Pump head curve

Nameplate

Efficiency And Brake Horsepower Are


149/348

Commonly Plotted vs. Pump Flow

100

90

80

70

60

50

40

30

20

10

0head(ft)

,power(bhp),efficiency(%)

500040003000200010000

flow rate (gpm)

System

Pump headbrake hpefficiency

Operating

point

BEP

Using A Larger Pipe Changes The


150/348

g g p gFrictional Part Of The System Curve

100

90

8070

60

50

40

30

head(ft)

500040003000200010000

flow rate (gpm)

System head,12" pipe

System head,

16" pipe

CENTRIFUGAL PUMP PERFORMANCE


151/348

CENTRIFUGAL PUMP PERFORMANCE

WITH VSD REGULATION

FLYGT C 3531

30-60 HZ (295-590 RPM)

Specific Energy in Three DifferentSingle Pump Systems


152/348

Single Pump Systems

Throttling

VSD Regulation

Speed / Flow

No static head 85% static head50% static head

Speed / FlowSpeed / Flow

On-Off Regulation

Now Let's Look At The


153/348

154

Electrical End Of The ShaftElectric utilityfeeder

Transformer


Motor

Adjustable


Coupling PumpFluid

system

Maximize the overall effectiveness

Ultimategoal

Motor Efficiency CurvesA D d U Si A d


154/348

Are Dependent Upon Size AndType

100

90

80

70

60

50

Efficiency(%)

1.21.00.80.60.40.20.0

Power (fraction of rated)

Rated horsepower3 57.5 1025 50100 125200fit 7.5 fit 100

Understanding DriveP f


155/348

156

PerformanceElectric utility

feeder

Transformer


Motor

Adjustable


Coupling PumpFluid

systemUltimate

goal

Maximize the overall effectiveness

The Efficiency Of Inverters


156/348

y

Is Affected By Operating Speed100

90

80

70

60

efficiency(%

)

1251007550speed (% of rated)

Typical inverter efficienciesas a function of motor speed

Evaluate System Design


157/348

Is the system effectivenessacceptable?

If the system has static head,Compare with frictionlessperformance!

Re-Evaluate System ChoicesRelative To Needs


158/348

Relative To Needs

Number of pumps

Pump sizes

VFD operation?

Pipe diameters

Component selection


159/348

When the System isCommissioned the Theoretical

Calculations Should be

Compared to Actual OperationalData to Ensure that it is

Operating as Intended

Summary


160/348

y

Most avoidable losses are in the pump andfluid system, not in the electrical front end

However, the electrical front end can helpreduce the fluid system losses

Be careful with local optimization

Determine the specific energy and comparewith the ideal


161/348

MEASUREMENTS

Pressure measurement


162/348

Together with temperature and flow,

pressure is the most important parameters inindustrial process control

The unit of pressure is the Pascal (Pa) with1Pa being 1N/m2

At the surface of the earth, the atmosphericpressure is generally about 100KPa. This issometimes referred to as a pressure of 1bar.

1.Manometers

U-tube manometer


163/348

The cistern manometer

The inclined tube manometer

2.Diaphragms

Reluctance diaphragm gauge Capacitance diaphragm gauge

Bourdon tubes


164/348

3

Force-balanceDead-weight tester

Spring

4Electrical pressure gauge

Strain gauge

Piezoelectric

piezoresistance

P

The basic manometer consistsof a U-tube containing a liquid.A

diff b t

Manometers


165/348

P2

P1

1 2P P gh

pressure difference between

the gases above the liquid inthe two limbs produces adifference h in vertical heights

of the liquid in the two limbs.If one of the limbs is open tothe atmosphere then the

pressure difference is thegauge pressure.

Water, alcohol and mercury are commonlyused manometric liquids. U-tubemanometers are simple and cheap and can


166/348

manometers are simple and cheap and can

be used for pressure differences in therange 20 Pa to 140KPa. The accuracy istypically about 1%.

Temperature affect---------liquid expansion

0 0

0

0 0 0

---real temperature

(1 ) exp

1

m V V

V V r r coefficient of cubical ansion of the liquid

V

V

Thus the pressure when measured by a


167/348

U-tube manometer at a temperature ,when the manometer liquid density at

0C is known, is given by:

0

1h gP gh

Cistern manometer

An industrial form of the U-tube manometer is


168/348

An industrial form of the U tube manometer is

cistern manometer. It has one of the limbswith a much greater cross-sectional area thanthe other.A difference in pressure betweenthe two limbs causes a difference in liquid

level with liquid flowing from one limb to theother.

1 2

1 2

2 2

1 2

1 1

( )

( ) ( 1)

P P gH h d g

A h A d

A d AP P d g d g

A A

c d g

Hhd

P1

P2

A2

A1


169/348

This form of manometer thus onlyrequire the level of liquid in one

limb to be measured from a fixedpoint.


170/348

The inclined tube manometerThe inclined tube manometer is a U-tube

manometer with one limb having a largercross-section than the other and the narrowerlimb being inclined at some angle to thehorizontal. It is generally used for themeasurement of small pressure differences

and g ives greater accuracy than thec o n v e n t i o n a l U - t u b e m a n o m e t e r .

dP1

P2


171/348

H d

h

2 21 2 ( 1) ( 1) sin

1 1

A AP P d g gx

A A

x

Since A2 is much greater than A1, theequation approximates to:

1 2 sinP P gx

Initial zero levelwith no pressuredifference

Diaphragms


172/348

With diaphragm pressure gauges, a differencein pressure between two sides of a diaphragmresults in it blowing out to one side or the other.If the fluid for which the pressure is required is

admitted to one side of the diaphragm and theother side is open to the atmosphere, thediaphragm gauge gives the gauge pressure. Iffluids at different pressures are admitted to thetwo sides of the diaphragm, the gauge givesthe pressure difference.


173/348

1.Bourdon tubes


174/348

The bourdon tube may be in the form of aC fl t i l h li l i l I ll f


175/348

C, a flat spiral, a helical spiral. In all forms,

an increase in the pressure in the tubecauses the tube to straighten out to anextent which depends on the pressure.

This displacement may be monitored in avariety of ways, for example, to directlymove a pointer across a scale, to move aslider of a potentiometer, to move the core

of an LVDT.

2 Reluctance diaphragm gaugeThe displacement of thecentral part of the


176/348

p

diaphragm increases thereluctance of the coil on oneside of the diaphragm anddecreases it on the other.

With the two coils connectedin opposite arms of an a.c.bridge, the out of balance

voltage is related to thepressure difference causingthe diaphragm displacement

2

0 0

2

N sL


177/348

AC

d

d


178/348

Capacitance pressure transducers were originally

developed for use in low vacuum research. Thiscapacitance change results from the movement of adiaphragm element. The diaphragm is usually metalor metal-coated quartz and is exposed to the process

pressure on one side and to the reference pressureon the other. Depending on the type of pressure, thecapacitive transducer can be either an absolute,gauge, or differential pressure transducer.

02

d

C d


179/348

The capacitor can also form part of the tuning

circuit of a frequency modulated oscillator and sogive an electrical output related to the pressuredifference across the diaphragm.


180/348

Calibration of thepressure gauges in the

i f 20P t

force balance gauge


181/348

Dead-Weight Tester

Schematic

region of 20Pa to

2000kPa is generallyby means of the Dead-weight tester. Pressure

is produced by windingin a piston. Thepressure is determinedby adding weights to

the platform so that itremains at a constantheight.

MgP

A

Potentiometric Pressure Transducer


182/348

Measurement of lowpressures (vacuum)


183/348

Vacuum tends to be used for pressures lessthan the atmospheric pressure, namely

1.013105 Pa. A unit that is often used forsuch pressure is the torr, this being the

pressure equivalent to that given by a columnof mercury of height 1 mm.

1mmHg=133.322Pa=1 torr

The lower the absolute pressure is, the higherthe degree of vacuum is.

Pressure measurement


184/348

Pressure driven equipment (IC engines, turbines, etc.) Pneumatic or Hydraulic mechanical elements

Biomedical applications (Blood Pressure, BarometricChambers)

Losses in pipes and ducts energy efficiency Atmospheric conditions (weather forecast, altitude)

Indirect measurement of flow rate or velocity

Scuba diving

Many, many more ...

Pressure


185/348

Pressure in a fluid acts equally in all directions

Pressure in a static liquid increases linearly with depth

p=increase indepth (m)

pressureincrease

g h

The pressure at a given depth in a continuous, static body of

liquid is constant.

p1p2

p3 p1 =p2 =p3

Measuring pressure (1)Manometers


186/348

h

p1p2=pa

liquid

density

x y

z

p1 = px

px = py

pz= p2 = pa

(negligible pressure

change in a gas)

(since they are at

the same height)

py - pz =gh

p1 - pa =gh

So a manometer measures gauge pressure.

Measuring Pressure (2)Barometers


187/348

A barometer is used to measure

the pressure of the atmosphere.

The simplest type of barometer

consists of a column of fluid.

p1 = 0vacuum

h

p2 = pa

p2 - p1 =gh

pa =gh

examples

water: h = pa/g =105/(103*9.8) ~10m

mercury: h = pa/g =105/(13.4*103*9.8)

~800mm

PRESSUREMEASUREMENT


188/348

Absolut, Differential

Barometer

Manometer

Absolute pressure


189/348

Presiune

referinta

Pabs = 0

TRPabs

Barometer


190/348

hgP

AhgA0AP

hgabs

hgabs

P=0

Patm

h

h

A

Patm A

0

Well-type manometer

Differentialpressure


191/348

12 PPP

P1P2

Types of pressures


192/348

Static And Dynamic Pressure


193/348

Dynamic pressure = Stagnation pressure (A) - Static pressure (B)

Static And Dynamic Pressure


194/348

Dynamic pressure = Stagnation pressure (A) - Static pressure (B)

Types of pressure transducers:


195/348

Liquid Column manometers Elastic tubes, diaphragms, membranes

(equipped with displacement or strain

sensors) Semiconductor elements (with implanted

stress elements)

Piezoelectic elements (directly convertcrystal lattice stress into voltage)

Liquid Column Manometers

PP


196/348

hgPP

AhgAPAP

12

12

P2

h h

A

P2 A

P1

P1 A

U tube manometer

Liquid Column Manometers

P


197/348

hgPP

AhgAPAP

12

12

P2h h

A

P2 A

P1

P1 A

12 AhgAPAP

InclinedManometer


198/348

r12

r

r

12

h)sin(gPP)sin(hh

h

h)sin(

hgPP

P2h

hr

AP2 A

P1

P1 A

Pressuretransducers


199/348

atm2 PPP

P2Patm

Pressure transducers

Elastic elements Tub


200/348

Changing pressurechange the shape ofthe elastic element

Shape changing isdetected by a resistiveor position transducer

Tip C Spirala Tubrasucit ElicoidalTuburiBourdon

CapsulaDiafragme

P Absoluta

PDiferentialaPlata

Ondulata

evacuat

Diferential sau absolut



201/348

Elastic elements Changing pressurechange the shape ofthe elastic element

Shape changing isdetected by aresistive or position

transducer

Pressure Sensor range


202/348

Elastic Type Manometers


203/348

More Elastic types...


204/348

Two dummy gages

mounted elsewhere

Why do we not put 4 active gages?

Dial-type Manometer


205/348

Dial-type Manometer as a mini measurement system

Diaphragm type manometers


206/348

To be able to detect pressure, we need to detect the

diaphragm deflection

Strain gauges used with Diaphragm


207/348

Strain gage based pressure cell

When a strain gage, is used to


208/348

When a strain gage, is used to

measure the deflection of an elasticdiphragme or Bourdon tube it becomesa comonent in apressure transducer

Strain-gage transducers are used fornarrow-span pressure and fordifferential pressure measurements.

Essentially, the strain gage is used tomeasure the displacement of an

elastic diaphragm due to a differencein pressure across the diaphragme If the low pressure side is a sealed

vacuum reference, the transmitter willact as an absolute pressuretransmitter.

Strain gage transducers areavailablefor pressure ranges as low as

1300 MPa

Capacitance based pressurecell

Capacitance pressure


209/348

Capacitance pressure

transducerswere originally developedfor use in low vacuum research. Thiscapacitance change results from themovement of a diaphragm element

(The diaphragm is usually metal ormetal-coated quartz and is exposed tothe process pressure on one side andto the reference pressure on the other.

Depending on the type Differential pressure transducers in avariety of ranges and outputs ofpressure, the capacitive transducercan be either an absolute, gauge, ordifferential pressure transducer.

Capacitance pressure transducershave a wide rangeability, from high

vacuums in the micron range to 70MPa.

The potentiometric pressure


210/348

The potentiometric pressure

sensor provides a simple methodfor obtaining an electronic outputfrom a mechanical pressuregauge.

The device consists of a precisionpotentiometer, whose wiper arm ismechanically linked to a Bourdon

or bellows element. This type of transducer can beused for low differential pressureapplications as well as to detectabsolute and gauge pressures.

The resonant wire pressuretransducer

The resonant-wire pressure transducer


211/348

p was introduced in the late 1970s. a wire is gripped by a static member at one

end, and by the sensing diaphragm at theother. An oscillator circuit causes the wire tooscillate at its resonant frequency.

A change in process pressure changes thewire tension, which in turn changes theresonant frequency of the wire. A digitalcounter circuit detects the shift. Because this

change in frequency can be detected quiteprecisely, This type of transducer can be used for low

differential pressure applications as well asto detect absolute and gauge pressures.

Resonant wire transducers can detectabsolute pressures from 10 mm Hg,differential pressures and gauge pressuresup to 42 MPa. Typical accuracy is 0.1% of

calibrated span, with six-month drift of 0.1%

Piezoelectric sensors

Piezoresistive pressure sensors are sensitive toh i t t d t b t t


212/348

changes in temperature and must be temperature

compensated. Piezoresistive pressure sensors can be used from

about 21 KPa to 100 MPa. Resonant piezoelectric pressure sensors measure

the variation in resonant frequency of quartz crystals under an

applied force. The sensor can consist of a suspended beam that

oscillates while isolated from all other forces. The

beam is maintained in oscillation at its resonantfrequency. Changes in the applied force result inresonant frequency changes. The relationshipbetween the applied pressure P and the oscillationfrequency is:

P = A(1-TO/T) - B(1-TO/T2) where TO is the period of oscillation when the

applied pressure is zero, T is the period ofoscillation when the applied pressure is P, and Aand B are calibration constants for the transducer.

These transducers can be used for absolutepressure measurements with spans from 0-100kPa to 0-6 MPa or for differential pressuremeasurements with spans from 0-40 kPa to 0-275kPa .

Magnetic pressure transducers

These included the use of inductance, reluctance, and eddy currents.


213/348

, , y

Inductance is that property of an electric circuit that expresses the amountof electromotive force (emf) induced by a given rate of change of currentflow in the circuit.

Reluctance is resistance to magnetic flow, the opposition offered bymagnetic substance to magnetic flux.

In these sensors, a change in pressure produces a movement, which in turnchanges the inductance or reluctance of an electric circuit.

Optical pressure transducers

Optical pressure transducers detect theff t f i t ti d t h


214/348

effects of minute motions due to changesin process pressure and generate acorresponding electronic output signal.

A light emitting diode (LED) is used as thelight source, and a vane blocks some ofthe light as it is moved by the diaphragm.As the process pressure moves the vanebetween the source diode and themeasuring diode, the amount of infraredlight received changes.

Optical pressure transducers do notrequire much maintenance.

They have excellent stability and aredesigned for long-durationmeasurements.

They are available with ranges from 35

kPa to 413 MPa and with 0.1% full scaleaccuracy.

Sensor/Cavity System Response(Helmholz Resonator)

4


215/348

0

0.5

1

1.5

2

2.5

3

3.5

Pressure

Pressure signal at the source

Pressure signal at the sensor face

2 / 2C a

fV L a

where Cis the sound velocity,L and a are the

length and area of the connecting tube and V

is the cavity volume.In this second order system air acts as mass,

the pressure acts as a spring and the

connecting tube as a damping element.

Thefundamental natural

frequency of the tube/cavity

system may be expressed as

Bourdon tube over pressureprotection

Most pressure instruments are


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p

provided with overpressureprotection of 50% to 200% ofrange These protectors satisfy themajority of applications. Wherehigher overpressures areexpected and their nature istemporary (pressure spikes ofshort durationseconds or less),snubbers can be installed.

If excessive overpressure isexpected to be of longer duration,one can protect the sensor byinstalling a pressure relief valve.However, this will result in a lossof measurement when the reliefvalve is open.

Mechanical High pressuresensors

In the case of the button repeater ( figA), the diaphragm can detect extruder pressures up to 10,000 psig and canoperate at temperatures up to 4300C because of its selfcooling design It operates on direct force balance


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operate at temperatures up to 4300 C because of its selfcooling design. It operates on direct force balance

between the process pressure (P1) acting on the sensing diaphragm and the pressure of the output air signal (P2)acting on the balancing diaphragm. The pressure of the output air signal follows the process pressure in inverseratio to the areas of the two diaphragms. If the diaphragm area ratio is 200:1, a 1,000-psig increase in processpressure will raise the air output signal by 5 psig.

Another mechanical high pressure sensor uses a helical Bourdon element (Figure B). This device may include asmany as twenty coils and can measure pressures well in excess of 10,000 psig. The standard element material isheavy-duty stainless steel, and the measurement error is around 1% of span. Helical Bourdon tube sensorsprovide high overrange protection and are suitable for fluctuating pressure service, but must be protected fromplugging. An improvement on the design shown in Figure B detects tip motion optically, without requiring anymechanical linkage.

Vacuum mesurement


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Vacuum gauges in use today fall into threemain categories:

mechanical, thermal,

ionization.

Vacuum mesurement


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Semiconductor-type Sensors


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Static Calibration


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2

cyl

mgp

R



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Converter a.c. / c.c.Amplifier

Output voltage

Pressureservo-transducer


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ArmInductivemotor

Pivotiaphragm

P1 P2Pressure cell

Reluctance detector

Piezoelectric pressuretransducer


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Differentialamplifier

Charge amplifier

Compensation crystal Y2

Crystal Y1

Diaphragm

P1

Power

Preso-sensitive switch


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Relay

C1 C2

A

Pressure admission

B

Fluid Flow Measurements


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Pitot Tube Venturi Meter

Orifice Meter

Rotameter Others

Coriolis (Vortex shedding)

Turbine

Pitot Tube1 atm


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V1 12

h1

h2

2 21 21 1 2 2

1 2

1 1

2 2s

c c c c

P Pg gv h W v h F

g g g g

Pitot Static Tube


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h

V1

1


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t

i

D

D Ratio of throat diameter to pipe ID


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24

2

1

V

cC Pv g

CV = coefficient of discharge (accounts for friction losses)

Usually CV = 0.98, see Figure 5.9, p 155 for CV as a function of Re.

If a manometer is used to measure P, then

2 4 21V

m fCv gh

Orifice Meter

Vena contracta


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h

V1

P1

Di is the pipe ID and Do is the orifice diameter

Do/Di

Orifice Design Equation

2 4m


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20.61 2i c fD g P

With 0.2


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W

V

If calibrated for one fluid, then

1/ 2

12 1

2

Q Q

Others


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1. Vortex-shedding flow meter flow past a bluntobject causes vortexes2. Turbine meters paddle wheel speed measures

flow rate

3. Thermal gas mass flow meter a slip stream isheated by a constant heat input and temperaturerise is related to the gas mass flow

4. Magnetic flow meters a magnetic field isgenerated across a conducting fluid with the

induced voltage proportional to the flow velocity5. Coriolis mass flow meter fluid enters two U-tubeside channels where coriolis forces cause a twist inthe tubes. Twist angle is proportional to mass flowrate.

Unsteady FlowD1, v1


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1

2

h

z1

z2

Toricellis Equation

D2, v2

2 2v gh

Velocity of surface 1

1

dhv

dt

From the equation of continuity

2

12 1

2

Dv v

D

Flow Measurement, Q


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Tracer method BS5857 Ultrasonic flow measurement

Tank filling method

Installation of an on-line flowmeter

Tracer Method


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The Tracer method is particularly suitable for cooling water flow measurement becauseof their sensitivity and accuracy.

This method is based on injecting a tracer into the cooling water for a few minutes at an

accurately measured constant rate. A series of samples is extracted from the system at a point

where the tracer has become completely mixed with the cooling water. The mass flow rate is

calculated from:

qcw = q1 x C1/C2

where qcw = cooling water mass flow rate, kg/s

q1 = mass flow rate of injected tracer, kg/s

C1 = concentration of injected tracer, kg/kg

C2 = concentration of tracer at downstream position during the plateau periodof constant concentration, kg/kg

The tracer normally used is sodium chloride.

Ultrasonic Flow meter

Operating under Doppler effect principle these meters are non-invasive, meaning


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measurements can be taken without disturbing the system. Scales and rust in the pipes arelikely to impact the accuracy.

Ensure measurements are taken in a sufficiently long length of pipe free from flow

disturbance due to bends, tees and other fittings.

The pipe section where measurement is to be taken should be hammered gently to enable

scales and rusts to fall out.

For better accuracy, a section of the pipe can be replaced with new pipe for flow

measurements.

Tank filing method


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In open flow systems such as water getting pumped to an overhead tank or a sump, the flow

can be measured by noting the difference in tank levels for a specified period during which

the outlet flow from the tank is stopped. The internal tank dimensions should be preferabletaken from the design drawings, in the absence of which direct measurements may be

resorted to.

Installation of an on-lineflowmeter


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If the application to be measured is going to be critical and periodic then the best option

would be to install an on-line flowmeter which can rid of the major problems encountered

with other types.


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additional

PumpsBernoullis Theorem Pressure head: measure of fluids mech. PE


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Velocity head: measure of fluids mech. KE Friction head: measure of energy lost that heats fluid

Z1 + P1/ + V12/2g = Z2 + P2/ + V2

2/2g + [(U2 U1) W Q]

q + wshaft = (h2 h1) + (v22 v12)/2 + g(z2z1)

Z/z: fluid height; P: fluid pressure; : fluid density

V/v: fluid velocity U: internal energy W/w: work

Q/q: heat transferred h: enthalpy g: grav. acceleration

BOTTOM LINE: Total energy within the control volume isconstant under SS conditions.

Flow of Fluids in Pipes

ASSUMPTIONS:

S d fl (fl d i

GOALS: Understand how the fluid pressure and flow speed change frompoint to point along the pipe.

2

2

2


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Steady state flow (flow speed isconstant in time at any givenpoint along pipe).

No internal energy change (notransformation of mechanical

energy to thermal energy, noviscousdrag).

Irrotational flow (no vorticity, nowhirlpools, eddies, etc.)

ANALYSIS:

Conservation of Mass. Work Energy Theorem.

111

Principle of Continuity

v1

Consider the amount (mass m1) of fluid passing into the region betweenpoints 1 and 2 in the pipe during a time t:


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1

2

1111 Atvm

A1 1

length

volume

This is the mass of the fluidthat passed point 1.


1

v1

v2


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12

Conservation of mass (along with steady state flow) says that whateverflowed into the region between 1 and 2 MUSThave flowed out:

222111

222111

21

AvAv

AtvAtv

mm

The productv A is called mass flow rate with units kg/s.


1

v1v2


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12

ASSUMPTION: The fluid density remains constant (liquid).

2211

2211

AvAvAvAv

The productv A is called (volume) flow rate with units m3/s.

For the flow of liquids, pipe cross-sectional area A (and A alone) governs

flow speed. In particular, flow speed increases through a constriction.

Check Question on Principle of Continuity

Water flowing at 0.4 m/s through a pipe of circular cross section 2.0 cm indiameter meets a constriction of diameter 1.0 cm.

a) What is the flow speed within the constricted portion of the pipe in m/s?b) What is the volume flow rate of the water in the pipe?


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The Bernoulli Equation

2

y

y2

v2


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1

y1

111

222

gyAtv

gyAtvPE

Principle of Continuity says:

VAtvAtv 2211

yggygyV

PE

12The change in gravitational PEperunit volume swept out.

v1


2

y

y2

v2

1


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1

y1

v1

2111

2222

2

1

2

1

vAtv

vAtvKE


VAtvAtv 2211

221222

1

2

1

2

1vvv

V

KE

The change in gravitational KEper unit volume swept out.


2

y

y2

v2

p2A2


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1

y1

v1

tvAp

tvApW

222

111


VtvAtvA 2211

pppV

W

21The work done on system by adjacent fluidper unit volume swept out.

p1A1


V

PE

V

KE

V

W

The Work Energy Theorem relates the net work to the change in totalmechanical energy:


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VVV

021 2 ygvp

22221

211

2

1

2

1gyvpgyvp

Thereby giving us Bernoullis equation in its two common forms:


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http://vaccum%20pump.swf/


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BASIC VACUUM

PRACTICE

Why is a Vacuum Needed?


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To move a particle in a (straight) line over a large distance

(Page 5 manual)

Why is a Vacuum Needed?

Atmosphere (High)Vacuum


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Contamination

(usually water)Clean surface

Atmosphere (High)Vacuum

To provide a clean surface


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HOW DO WE CREATE A

VACUUM?

VACUUM PUMPING METHODSVACUUM PUMPS

(METHODS)

Gas Transfer

Vacuum Pump

Entrapment

Vacuum Pump

Positive Displacement Kinetic Adsorption


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Sliding Vane

Rotary Pump

Molecular

Drag Pump

Turbomolecular

Pump

Fluid Entrainment

Pump

Reciprocating

Displacement Pump

Drag

Pump

Positive Displacement

Vacuum Pump

Kinetic

Vacuum Pump

Rotary

Pump

Diaphragm

Pump

Piston

Pump

Liquid Ring

Pump

Rotary

Piston Pump

Rotary

Plunger Pump

Roots

Pump

Multiple Vane

Rotary Pump

Dry

Pump

Adsorption

Pump

Cryopump

Getter

Pump

Getter Ion

Pump

Sputter Ion

Pump

Evaporation

Ion Pump

Bulk Getter

Pump

Cold TrapIon Transfer

Pump

Gaseous

Ring Pump

Turbine

Pump

Axial Flow

Pump

Radial Flow

Pump

Ejector

Pump

Liquid Jet

Pump

Gas Jet

Pump

Vapor Jet

Pump

Diffusion

Pump

Diffusion

Ejector Pump

Self Purifying

Diffusion Pump

Fractionating

Diffusion Pump

Condenser

Sublimation

Pump

BAROMETER


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WATER MERCURY

760

mm

Mercury: 13.58 times

heavier than water:

Column is 13.58 x shorter :

10321 mm/13.58=760 mm

(= 760 Torr)

10.321

mm

29,9

in

(Page 12 manual)

PRESSURE OF 1 STANDARD

ATMOSPHERE:


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ATMOSPHERE:

760 TORR, 1013 mbar

AT SEA LEVEL, 0O C AND 45O LATITUDE

Pressure Equivalents

Atmospheric Pressure (Standard) =


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0

14.7

29.9

760

760

760,000

101,3251.013

1013

gauge pressure (psig)

pounds per square inch (psia)

inches of mercury

millimeter of mercury

torr

millitorr or microns

pascalbar

millibar

THE ATMOSPHERE IS A MIXTURE OF GASES

PARTIAL PRESSURES OF GASES CORRESPOND TO THEIR RELATIVE VOLUMES


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GAS SYMBOL

PERCENT BY

VOLUME

PARTIAL PRESSURE

TORR PASCAL

Nitrogen

Oxygen

ArgonCarbon Dioxide

Neon

Helium

Krypton

HydrogenXenon

Water

N2

O2

ACO2

Ne

He

Kr

H2X

H2O

78

21

0.930.03

0.0018

0.0005

0.0001

0.000050.0000087

Variable

593

158

7.10.25

1.4 x 10-2

4.0 x 10-3

8.7 x 10-4

4.0 x 10

-4

6.6 x 10-5

5 to 50

79,000

21,000

94033

1.8

5.3 x 10-1

1.1 x 10-1

5.1 x 10

-2

8.7 x 10-3

665 to 6650

(Page 13 manual)

VAPOR PRESSURE OF WATER AT

VARIOUS TEMPERATURES


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T (O C)

100

25

0

-40

-78.5-196

P (mbar)

1013

32

6.4

0.13

6.6 x 10 -4

10 -24

(BOILING)

(FREEZING)

(DRY ICE)

(LIQUID NITROGEN)

(Page 14 manual)


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(Page 15 manual)

Vapor Pressure of some Solids


269/348

(Page 15 manual)

PRESSURE RANGES


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RANGE

ROUGH (LOW) VACUUM

HIGH VACUUM

ULTRA HIGH VACUUM

PRESSURE

759 TO 1 x 10 -3 (mbar)

1 x 10 -3 TO 1 x 10 -8 (mbar)

LESS THAN 1 x 10 -8 (mbar)

(Page 17 manual)


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GAS FLOW

CONDUCTANCE

(Page 24 manual)

Viscous and Molecular Flow


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Viscous Flow(momentum transfer

between molecules)

Molecular Flow(molecules move

independently)

FLOW REGIMES

Viscous Flow:

Distance between molecules is small; collisions betweenl l d i t fl th h t t f


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Distance between molecules is small; collisions betweenmolecules dominate; flow through momentum transfer;

generally P greater than 0.1 mbar

Transition Flow:

Region between viscous and molecular flow

Molecular Flow:

Distance between molecules is large; collisions between

molecules and wall dominate; flow through random motion;generally P smaller than 10 mbar-3

(Page 25 manual)

MEAN FREE PATH

MOLECULAR DENSITY AND MEAN FREE PATH


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MOLECULAR DENSITY AND MEAN FREE PATH

1013 mbar (atm) 1 x 10-3 mbar 1 x 10-9 mbar

#

mol/cm3

MFP

3 x 10 19

(30 million trillion)4 x 10 13

(40 trillion)4 x 10 7

(40 million)

2.5 x 10-6 in

6.4 x 10-5

mm

2 inches

5.1 cm

31 miles

50 km

FLOW REGIMES


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Mean Free Path

Characteristic DimensionViscous Flow: is less than 0.01

Mean Free Path

Characteristic Dimension

Molecular Flow: is greater than 1

Mean Free PathCharacteristic Dimension

Transition Flow: is between 0.01 and 1

Conductance in ViscousFlow


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Under viscous flow conditions doubling thepipe diameter increases the conductance

sixteen times.

The conductance is INVERSELY related to

the pipe length

(Page 28 manual)

Conductance in MolecularFlow


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Under molecular flow conditions doubling

the pipe diameter increases the conductance

eight times.

The conductance is INVERSELY related tothe pipe length.

SYSTEM

Series Conductance

RT

= R1

+ R2


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SYSTEM

PUMP

C1

C2

1 = 1 + 1C1 C2CT

1 = C1 + C2C1 x C2CT

CT = C1 x C2

C1 + C2

(Page 29 manual)

GAS LOAD

Outgassing Permeation


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Outgassing

Leaks

Virtual

Real

Backstreaming

Diffusion

GAS LOAD (Q) IS EXPRESSED IN:mbar liters per second

Pumpdown Curve10+1

10-1

Volume


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Pressur

e(mbar)

Time (sec)

10-1110 1 10 3 10 5 10 7 10 9 10 11 10 13 10 15 10 17

10-3

10-5

10-7

10-9

Surface Desorption

Diffusion

Permeation

Roughing Pumps


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2(Page 39 manual)

VACUUM PUMPING METHODSVACUUM PUMPS

(METHODS)

Gas Transfer

Vacuum Pump

Entrapment

Vacuum Pump

Positive Displacement

Vacuum Pump

Kinetic

Vacuum Pump

Adsorption

Pump


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Sliding Vane

Rotary Pump

Molecular

Drag Pump

Turbomolecular

Pump

Fluid Entrainment

Pump

Reciprocating

Displacement Pump

Drag

Pump

Vacuum Pump Vacuum Pump

Rotary

Pump

Diaphragm

Pump

Piston

Pump

Liquid Ring

Pump

Rotary

Piston Pump

Rotary

Plunger Pump

Roots

Pump

Multiple Vane

Rotary Pump

Dry

Pump

Pump

Cryopump

Getter

Pump

Getter Ion

Pump

Sputter Ion

Pump

Evaporation

Ion Pump

Bulk Getter

Pump

Cold TrapIon Transfer

Pump

Gaseous

Ring Pump

Turbine

Pump

Axial Flow

Pump

Radial Flow

Pump

Ejector

Pump

Liquid Jet

Pump

Gas Jet

Pump

Vapor Jet

Pump

Diffusion

Pump

Diffusion

Ejector Pump

Self Purifying

Diffusion Pump

Fractionating

Diffusion Pump

Condenser

Sublimation

Pump

PUMP OPERATING RANGES

Rough VacuumHigh VacuumUltra High

Vacuum

Rotary Vane Mechanical Pump


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10-12 10-10 10-8 10-6 10-4 10-2 1 10+2

P (mbar)

Venturi Pump

y p

Rotary Piston Mechanical Pump

Sorption Pump

Dry Mechanical Pump

Blower/Booster Pump

High Vac. Pumps

Ultra-High Vac. Pumps

VACUUM SYSTEM USE

98

1

23

Chamber

High Vac. PumpR hi P


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1

2

4

6

5

8

7

3

3a

4

56

7

8

9

g pRoughing Pump

Foreline Pump

Hi-Vac. Valve

Roughing ValveForeline Valve

Vent Valve

Roughing Gauge

High Vac. Gauge

7

33a

(Page 44 manual)

Rotary Vane, Oil-SealedMechanical Pump


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(Page 45 manual)

Pump Mechanism


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How the Pump Works


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(Page 46 manual)

OIL BACKSTREAMING


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2

PRESSURE LEVELS: LESS THAN 0.2 mbar

The Molecular Sieve/Zeoli

pumps &pumping system

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