Flow Measurement Seminar - SPITZER AND BOYES, LLC · Fluid Flow Fundamentals ... Measurement of...

1

Copyright Copperhill and Pointer, Inc., 2004 (All Rights Reserved) www.spitzerandboyes.com +1.845.623.1830

Industrial Flow Measurement

Seminar Presented by David W. Spitzer

Spitzer and Boyes, LLC


2

Disclaimer

The content of this seminar was developed in an impartial manner from information provided by suppliersDiscrepancies noted and brought to the attention of the presenter will be correctedWe do not endorse, favor, or disfavor any particular supplier or their equipment

Spitzer and Boyes, LLCCopperhill and Pointer, Inc.Seminar Presenter


3

Seminar Outline

IntroductionFluid Flow FundamentalsPerformance MeasuresLinearization and CompensationTotalizationFlowmeter CalibrationMeasurement of Flowmeter PerformanceMiscellaneous ConsiderationsFlowmeter TechnologiesFlowmeter Selection

2


4

Introduction

Working Definition of a ProcessWhy Measure Flow?


5

Working Definition of a Process

A process is anything that changes


6

Why Measure Flow?

Flow measurements provide information about the processThe information that is needed depends on the process

3


7

Why Measure Flow?

Custody transferMeasurements are often required to determine the total quantity of fluid that passed through the flowmeter for billing purposes


8

Why Measure Flow?

Monitor the processFlow measurements can be used to ensure that the process is operating satisfactorily


9

Why Measure Flow?

Improve the processFlow measurements can be used for heat and material balance calculations that can be used to improve the process

4


10

Why Measure Flow?

Monitor a safety parameterFlow measurements can be used to ensure that critical portions of the process operate safely


11

Seminar Outline IntroductionFluid Flow FundamentalsPerformance MeasuresLinearization and CompensationTotalizationFlowmeter CalibrationMeasurement of Flowmeter PerformanceMiscellaneous ConsiderationsFlowmeter TechnologiesFlowmeter Selection


12

Fluid Flow Fundamentals

TemperaturePressureDensity and Fluid ExpansionTypes of FlowInside Pipe DiameterViscosityReynolds Number and Velocity ProfileHydraulic Phenomena

5


13

Temperature

Measure of relative hotness/coldnessWater freezes at 0°C (32°F)Water boils at 100°C (212°F)


14

Temperature

Removing heat from fluid lowers temperature

If all heat is removed, absolute zero temperature is reached at approximately -273°C (-460°F)


15

Temperature

Absolute temperature scales are relative to absolute zero temperature

Absolute zero temperature = 0 K (0°R)Kelvin = °C + 273° Rankin = °F + 460

6


16

Temperature

Absolute temperature is important for flow measurement


17

Temperature

0 K = -273°C 0°R = -460°F

460°R = 0°F273 K = 0°C

373 K = 100°C 672°R = 212°F


18

Temperature

ProblemThe temperature of a process increases from 20°C to 60°C. For the purposes of flow measurement, by what percentage has the temperature increased?

7


19

Temperature

It is tempting to answer that the temperature tripled (60/20), but the ratio of the absolute temperatures is important for flow measurement

(60+273)/(20+273) = 1.13713.7% increase


20




21

Pressure

Pressure is defined as the ratio of a force divided by the area over which it is exerted (P=F/A)

8


22

Pressure

ProblemWhat is the pressure exerted on a table by a 2 inch cube weighing 5 pounds?

(5 lb) / (4 inch2) = 1.25 lb/in2

If the cube were balanced on a 0.1 inch diameter rod, the pressure on the table would be 636 lb/in2


23

Pressure

Atmospheric pressure is caused by the force exerted by the atmosphere on the surface of the earth

2.31 feet WC / psi10.2 meters WC / bar


24

Pressure

Removing gas from a container lowers the pressure in the container

If all gas is removed, absolute zero pressure (full vacuum) is reached at approximately -1.01325 bar (-14.696 psig)

9


25

Pressure

Absolute pressure scales are relative to absolute zero pressure

Absolute zero pressure Full vacuum = 0 bar abs (0 psia)bar abs = bar + 1.01325psia = psig + 14.696


26

Pressure

Atmosphere

Absolute Zero

Vacuum

Absolute Gauge

Differential


27

Pressure

Absolute pressure is important for flow measurement

10


28

Pressure

ProblemThe pressure of a process increases from 1 bar to 3 bar. For the purposes of flow measurement, by what percentage has the pressure increased?


29

Pressure

It is tempting to answer that the pressure tripled (3/1), but the ratio of the absolute pressures is important for flow measurement

(3+1.01325)/(1+1.01325) = 1.99399.3% increase


30



11


31

Density and Fluid Expansion

Density is defined as the ratio of the mass of a fluid divided its volume (ρ=m/V)


32


Specific Gravity of a liquid is the ratio of its operating density to that of water at standard conditions

SG = ρ liquid / ρ water at standard conditions


33


ProblemWhat is the density of air in a 3.2 ft3 filled cylinder that has a weight of 28.2 and 32.4 pounds before and after filling respectively?

12


34


The weight of the air in the empty cylinder is taken into account

Mass =(32.4-28.2)+(3.2•0.075)= 4.44 lb

Volume = 3.2 ft3

Density = 4.44/3.2 = 1.39 lb/ft3


35


The density of most liquids is nearly unaffected by pressureExpansion of liquids

V = V0 (1 + β•ΔT)V = new volumeV0 = old volumeβ = cubical coefficient of expansionΔT = temperature change


36


ProblemWhat is the change in density of a liquid caused by a 10°C temperature rise where β is 0.0009 per °C ?

13


37


Calculate the new volumeV = V0 (1 + 0.0009•10) = 1.009 V0

The volume of the liquid increased to 1.009 times the old volume, so the new density is (1/1.009) or 0.991 times the old density


38


Expansion of solidsV = V0 (1 + β•ΔT)

where β = 3•αα = linear coefficient of expansion

Temperature coefficientStainless steel temperature coefficient is approximately 0.5% per 100°C


39


ProblemWhat is the increase in size of metal caused by a 50°C temperature rise where the metal has a temperature coefficient of 0.5% per 100°C ?

14


40


Calculate the change in size(0.5 • 50) = 0.25%Metals (such as stainless steel) can exhibit significant expansion


41


Boyle’s Law states the the volume of an ideal gas at constant temperature varies inversely with absolutepressure

V = K / P


42


New volume can be calculatedV = K / PV0 = K / P0

Dividing one equation by the other yields

V/V0 = P0 / P

15


43


ProblemHow is the volume of an ideal gas at constant temperature and a pressure of 28 psig affected by a 5 psig pressure increase?


44


Calculate the new volumeV/V0 = (28+14.7) / (28+5+14.7) = 0.895

V = 0.895 V0

Volume decreased by 10.5%


45


Charles’ Law states the the volume of an ideal gas at constant pressure varies directly with absolutetemperature

V = K • T

16


46


New volume can be calculatedV = K • TV0 = K • T0


V/V0 = T / T0


47


ProblemHow is the volume of an ideal gas at constant pressure and a temperature of 15ºC affected by a 10ºC decrease in temperature?


48


Calculate the new volumeV/V0 = (273+15-10) / (273+15) = 0.965

V = 0.965 V0


17


49


Ideal Gas Law combines Boyle’s and Charles’ Laws

PV = n R T


50


New volume can be calculatedP • V = n • R • TP0 • V0 = n • R • T0


V/V0 = (P0 /P) • (T / T0)


51


ProblemHow is the volume of an ideal gas at affected by a 10.5% decrease in volume due to temperature and a 3.5% decrease in volume due to pressure?

18


52


Calculate the new volumeV/V0 = 0.895 • 0.965 = 0.864

V = 0.864 V0



53


Non-Ideal Gas Law takes into account non-ideal behavior

PV = n R T Z


54


New volume can be calculatedP • V = n • R • T • ZP0 • V0 = n • R • T0 • Z0


V/V0 = (P0 /P) • (T / T0) • (Z / Z0)

19


55


For liquids, specific gravity is the ratio of the density of the liquid to the density of water at standard conditions


56


For gases, specific gravity is the ratio of the density of the gas to the density of air at standard conditions

Specific gravity is commonly used to describe the ratio of the density of the gas at standard conditions to the density of air at standard conditions


57


Standard conditionsPressure

14.696 psia, 1 atmosphere14.7 psia14.4 psia1 bar absolute4 oz.

20


58


Standard conditionsTemperature

15°C (59°F) 68°F70°F0°C


59




60

Types of Flow

Q = A • vQ is the volumetric flow rateA is the cross-sectional area of the pipev is the average velocity of the fluid in the pipe

21


61

Types of Flow

Typical Volumetric Flow Units(Q = A • v)ft2 • ft/sec = ft3/secm2 • m/sec = m3/secgallons per minute (gpm)liters per minute (lpm)cubic centimeters per minute (ccm)


62

Types of Flow

W = ρ • QW is the mass flow rateρ is the fluid densityQ is the volumetric flow rate


63

Types of Flow

Typical Mass Flow Units (W = ρ • Q)lb/ft3 • ft3/sec = lb/seckg/m3 • m3/sec = kg/secstandard cubic feet per minute (scfm)standard liters per minute (slpm)standard cubic centimeters per minute(sccm)

22


64

Types of Flow

Q = A • vW = ρ • Q

Q volumetric flow rateW mass flow rate v fluid velocity½ ρv2 inferential flow rate


65




66

Inside Pipe Diameter

The inside pipe diameter (ID) is important for flow measurement

Pipes of the same size have the same outside diameter (OD)

Welding considerationsPipe wall thickness, and hence its ID, is determined by its schedule

23


67


Pipe wall thickness increases with increasing pipe schedule

Schedule 40 pipes are considered “standard” wall thicknessSchedule 5 pipes have thin wallsSchedule 160 pipes have thick walls


68


Nominal pipe sizeFor pipe sizes 12-inch and smaller, the nominal pipe size is the approximate ID of a Schedule 40 pipeFor pipe sizes 14-inch and larger, the nominal pipe size is the OD of the pipe


69



24


70

Viscosity

Viscosity is the ability of the fluid to flow over itselfUnits

cP, cStSaybolt Universal (at 100ºF, 210 ºF)Saybolt Furol (at 122ºF, 210 ºF)


71

Viscosity

Viscosity can be highly temperature dependent

WaterHoney at 40°F, 80°F, and 120°F Peanut butter


72

Viscosity

At a given temperature: Newtonian fluids have constant viscositythe viscosity of a Non-Newtonian fluid varies when different amounts of sheer stress is applied

25


73

Viscosity

Stress versus Flow Curves

Flow

Stress

Newtonian

Inverted Plastic

Ideal Plastic

Thixotropic


74




75

Velocity Profile and Reynolds Number

Reynolds number is the ratio of inertial forces to viscous forces in the flowing stream

RD = 3160 • Q gpm • SG / (μcP • Din)

26


76


Reynolds number can be used as an indication of how the fluid is flowing in the pipe Flow regimes based on RD

Laminar < 2000Transitional 2000 - 4000Turbulent > 4000


77


Not all molecules in the pipe flow at the same velocityMolecules near the pipe wall move slower; molecules in the center of the pipe move faster


78


Flow

Velocity Profile

Laminar Flow RegimeMolecules move straight down pipe

27


79


Flow

Velocity Profile

Turbulent Flow RegimeMolecules migrate throughout pipe


80


Transitional Flow RegimeMolecules exhibit both laminar and turbulent behavior


81


Many flowmeters require a good velocity profile to operate accuratelyObstructions in the piping system can distort the velocity profile

Elbows, tees, fittings, valves

28


82


Flow

Velocity Profile (distorted)

A distorted velocity profile can introduce significant errors into the measurement of most flowmeters


83


Good velocity profiles can be developedStraight run upstream and downstream

No fittings or valvesUpstream is usually longer and more important

Flow conditioner


84


Good velocity profiles can be developedLocate control valve downstream of flowmeter

Upstream control valve should be a warning that all aspects of the flow measurement system should be checked carefully

29







30


88




89

Hydraulic Phenomena

Vapor pressure is defined as the pressure at which a liquid and its vapor can exist in equilibrium

The vapor pressure of water at 100°C is atmospheric pressure (1.01325 bar abs) because water and steam can coexist


90

Hydraulic Phenomena

A saturated vapor is in equilibrium with its liquid at its vapor pressure

Saturated steam at atmospheric pressure is at a temperature of 100°C

31


91

Hydraulic Phenomena

A superheated vapor is a saturated vapor that is at a higher temperature than its saturation temperature

Steam at atmospheric pressure that is at 150°C is a superheated vapor with 50°C of superheat


92

Hydraulic Phenomena

Flashing is the formation of gas (bubbles) in a liquid after the pressure of the liquid falls below its vapor pressure

Reducing the pressure of water at 100°C below atmospheric pressure (say 0.7 bar abs) will cause the water to boil


93

Hydraulic Phenomena

Cavitation is the formation and subsequent collapse of gas (bubbles) in a liquid after the pressure of the liquid falls below and then rises above its vapor pressure

Can cause severe damage in pumps and valves

32


94

Hydraulic Phenomena

Distance

Pressure

Flashing

Cavitation

Piping Obstruction

Vapor Pressure (typical)


95

Hydraulic Phenomena

Energy ConsiderationsClaims are sometimes made that flowmeters with a lower pressure drop will save energy


96

Hydraulic Phenomena

Energy Considerations

Pressure

Flow

CentrifugalPump Curve

33


97

Hydraulic Phenomena


Pressure

Flow

System Curve(without flowmeter)


98

Hydraulic Phenomena


Flow

Pressure


99

Hydraulic Phenomena


Flow

P

Q

System, Flowmeterand Control Valve

Pressure

System

Flowmeter andControl ValvePressure Drop

System and Flowmeter

34


100

Hydraulic Phenomena


Flow

P

Q

System, Flowmeterand Control Valve

Pressure

System

Flowmeter andControl ValvePressure Drop

System and Flowmeter(Low Pressure Drop)


101

Hydraulic Phenomena

Energy ConsiderationsThe pump operates at the same flow and pressure, so no energy savings are achieved by installing a flowmeter with a lower pressure drop


102

Hydraulic Phenomena


Flow

P

Q

Pressure

System

System and Flowmeter

Full Speed

Reduced Speed

35


103

Hydraulic Phenomena

Energy ConsiderationsOperating the pump at a reduced speed generates the same flow but requires a lower pump discharge pressure

Hydraulic energy generated by the pump better matches the loadEnergy savings are proportional to the cube of the speed


104



105

Performance Measures

Performance CriteriaPerformance StatementsRepeatabilityLinearityAccuracyComposite AccuracyTurndownRangeability

36


106

Performance Criteria

Installation complexity and costMaintenanceAccuracyLinearityRepeatability


107

Performance Criteria

Dependence on fluid propertiesHydraulic considerations of flowmeterHydraulic considerations of fluidOperating CostsReliabilitySafety


108

Performance Statements

Percent of ratePercent of full scalePercent of meter capacity (upper range limit)Percent of calibrated span

37


109


1% of rate performance at different flow rates with a 0-100 unit flow range

100% flow 0.01•100 1.00 unit50% flow 0.01•50 0.50 unit25% flow 0.01•25 0.25 unit10% flow 0.01•10 0.10 unit


110


Flow%RateError

0

10

-10

1% Rate Performance


111


1% of full scale performance at different flow rates with a 0-100 unit flow range

100% flow 0.01•100 1 unit = 1% rate50% flow 0.01•100 1 unit = 2% rate25% flow 0.01•100 1 unit = 4% rate10% flow 0.01•100 1 unit = 10% rate

38



Flow%RateError

0

10

-10

1% Full Scale Performance


113


1% of meter capacity (or upper range limit) performance at different flow rates with a 0-100 unit flow range (URL=400)

100% flow 0.01•400 4 units = 4% rate50% flow 0.01•400 4 units = 8% rate25% flow 0.01•400 4 units = 16% rate10% flow 0.01•400 4 units = 40% rate



Flow0

10

-10

1% Meter Capacity Performance

39


115


Performance expressed as a percent of calibrated span is similar to full scale and meter capacity statements where the absolute error is a percentage of the calibrated span


116


1% of calibrated span performance at different flow rates with a 0-100 unit flow range (URL=400, calibrated span=200)

100% flow 0.01•200 2 units = 2% rate50% flow 0.01•200 2 units = 4% rate25% flow 0.01•200 2 units = 8% rate10% flow 0.01•200 2 units = 20% rate



Flow0

10

-10

1% of Calibrated Span Performance(assuming 50% URL)

40


118


A calibrated span statement becomes a full scale statement when the instrument is calibrated to full scaleA calibrated span statement becomes a meter capacity statement when the instrument is calibrated at URL


119


Performance specified as a percent of rate, percent of full scale, percent of meter capacity, and percent of calibrated span are different



Flow%RateError

0

10

-10

1% Rate

1% Meter Capacity1% Full Scale

1% Calibrated Span(50%URL)

41


121


Performance statements can be manipulated because their meaning may not be clearly understoodTechnical assistance may be needed to analyze the statements


122

Repeatability

Repeatability is the ability of the flowmeter to reproduce a measurement each time a set of conditions is repeated


Repeatability

FlowError 0

Repeatability

42


124

Linearity

Linearity is the ability of the relationship between flow and flowmeter output (often called the characteristic curve or signature of the flowmeter) to approximate a linear relationship


Linearity

FlowError 0

Linearity


126

Accuracy

Accuracy is the ability of the flowmeter to produce a measurement that corresponds to its characteristic curve

43


Accuracy

FlowError 0

Accuracy


128

Composite Accuracy

Flowmeter suppliers often specify the composite accuracy that represents the combined effects of repeatability, linearity and accuracy


Composite Accuracy

FlowError 0

Flow Range

Composite Accuracy (in Flow Range)

44


Composite Accuracy


Composite Accuracy


132

Turndown

Performance statements apply over a range of operationTurndown is the ratio of the maximum flow that the flowmeter will measure within the stated accuracy to the minimum flow that can be measured within the stated accuracy

45


133

Rangeability

Rangeability is a measure of how much the range (full scale) can be adjusted


134



135

Linearization and Compensation

Linear and nonlinear flowmetersGas density compensation

PressureTemperatureTap location

Liquid temperature compensationFlow computers

46


136

Linear Flowmeters

Flow

% FlowSignal

Linear Output Signal


137

Nonlinear Flowmeters

Flow

% FlowSignal

Squared Output Signal


138

Linear and Nonlinear Flowmeters

Output Linear Flowmeter Nonlinear Flowmeter1 % 1 % 10 %

10 % 10 % 31.6 %25 % 25 % 50 %50 % 50 % 70.7 %

100 % 100 % 100 %

* Note the large gain at low flows for nonlinear flowmeters

47


139

Gas Density Compensation

Temperature

Pressure Nominal Conditions

Standard Conditions

Range of Operation


140


Temperature


Standard Conditions

Flowmeter Factors


141


Temperature


Actual Conditions

Standard Conditions

Compensation

48


142


Gas LawsLaboratory dataHandbook informationMathematical relationship

Typically a function of pressure, temperature, and composition)


143


Gas Laws

(P • T nom • Z nom) • VV nom = -------------------

(Pnom • T • Z)


144


Gas Laws

PV nom = constant • -------- • V

(T • Z)

49


145


Effects can be large (see table in text)Temperature

1% per 3°C at 300K

Pressure10% per bar at 9 bar (gauge)1% per psi at 85 psig


146


Density affects the output of squared output flowmeters approximately half as much as linear output flowmeters

Pressure effects are lower for squared output flowmetersTemperature effects are lower for squared output flowmeters


147

Liquid Density Compensation

Typically temperature correction

50


148

Pressure Tap Location

Pressure tapUsually upstreamMay be in the flowmeter bodySome flowmeters allow downstream


149

Pressure Tap Location

Temperature tapUsually downstream to reduce turbulence

Upstream temperature tap should be a warning that all aspects of the flow measurement system should be checked carefully

May be within the flowmeter body


150

Flow Computers

Density compensationPressure, temperature, and compressibility

Reynolds number compensationFlowmeter expansionOther…

51


151



152

Analog Flowmeter (Linear)

Flow

% FlowSignal Output

Proportionalto Flow


153

Analog Flowmeter (Nonlinear)

Flow

% FlowSignal

OutputProportional toSquare of Flow

52


154

Digital Flowmeter (Linear)

Flow

% FlowSignal Output

Proportionalto Flow

Flowmeter may turnoff at low flows


155

Totalization

Analog flowmeterIntegrator (0.5% rate performance)Indicator (optional)


156

Totalization

Digital flowmeterCount pulses (±1 pulse)f/I converter (0.5% rate) and indicator (optional)

53


157

Totalization

Digital flowmeter with analog outputInherent flowmeter performanceAnalog output circuit

Add approximately 0.06% of full scale

f/I converter (0.5% rate) and indicator


158

Totalization

Digital flowmeters seem to be superior to analog flowmeter

Inherent performance may not be equalDigital flowmeters generally turn off at flow flow ratesAnalog output circuit

Add approximately 0.06% of full scale


159


54


160

Calibration

Calibration is performing adjustments to the instrument so that it measures within accuracy constraints

Comparison of measurement with “true”value


161

Flowmeter Calibration

Calibration of many variables is staticLevel – tape, rulerPressure – force and areaTemperature – freezing/boiling water


162


Calibration of flowmeters is dynamicPrimary standard uses time and weight

55


163


Ideally, flowmeter calibration should be performed under operating conditions

Usually not practical and often impossibleUse another calibration technique as a surrogate


164


Wet calibrationPrimary flow laboratoryFlow calibration facility

Dry calibrationPhysical dimensionsElectronic techniques

Verification of operation


165

WaterTank

WeighTank

Load Cells

Diverter ValveMeterUnderTest

Primary Flowmeter Laboratory

56


166


WaterTank

WeighTank

Load Cells

Diverter Valve

MeterUnderTest


167

WaterTank

WeighTank

Load Cells

Diverter ValveMeterUnderTest



168

WaterTank

MeterUnderTest

Flow Calibration Facility

MasterMeter

ProductionMeters

57


169

Dry Calibration

Dry calibrationVerify physical dimensionsElectronic techniques

ZeroSpanScaling factorAnalog output


170

Effect of Zero Calibration

Flow

% FlowSignal

Ideal Calibration

Effect of 1% ZeroCalibration Error(1% of full scale)


171

Effect of Span Calibration

Flow

% FlowSignal

Ideal Calibration

Effect of 1% SpanCalibration Error

(1% of rate)

58


172

Calibration

Instruments with zero and span adjustments tend to have percent of full scale accuracyInstruments with a span adjustment and no zero adjustment tend to have percent of rate accuracyThere are exceptions


173



174

Measurement of Flowmeter Performance

Flow measurement system componentsFlow rangeFlowmeterTransmitter

59


175


Flow measurement system componentsLinearizationDigital conversionIndicatorTotalization


176


Overall flow measurement system performance

Combine components statistically (do not add mathematically)AccuracyUncertainty (ISO GUM)


177


60


178

Miscellaneous Considerations

Materials of constructionCorrosionAbrasion/erosionPressure and temperatureFlange ratingsContamination


179


Velocity profileStraight run

Reductions up/downstream of straight runFlanges are part of straight run

Remove internal welding beads

Align gaskets so they do not intrude into pipeAlign flowmeter so it is centered in the pipe


180


Velocity profileFlow conditionerControl valve downstreamTemperature tap downstreamPressure tap upstream

61


181


Piping considerationsOrientation

Full pipeSingle phase flowHomogeneous flow


182


Piping considerationsSupport flowmeter

Do not have flowmeter supporting piping

AlignmentAxialFace-to-faceDo not “spring” pipe


183


Piping considerationsBypass pipingHydro-test considerationsDirtCoating

62


184


Wiring2-wire

Signal wires provide loop power

3-wireExtra wire for power

4-wireSeparate signal and power wires (in separate conduits unless low voltage power is used)


185


SafetyGrounding

Required for some flowmetersSafety consideration for some services (oxygen)

LeakageArea electrical classificationLubricants and contamination


186


63


187

Flowmeter Technologies

Introduction ThermalDifferential Pressure TurbineMagnetic UltrasonicMass Variable AreaOpen Channel CorrelationOscillatory InsertionPositive Displacement BypassTarget


188

Flowmeter Classes

Wetted moving partsPositive displacementTurbineVariable area


189

Flowmeter Classes

Wetted with no moving partsDifferential pressureOscillatoryTargetThermal

64


190

Flowmeter Classes

ObstructionlessCoriolis massMagneticultrasonic


191

Flowmeter Classes

Non-wetted (external)UltrasonicCorrelation


192

Flowmeter Measurements

VolumePositive displacement

65


193


VelocityMagneticOscillatoryTurbineUltrasoniccorrelation


194


InferentialDifferential pressureTargetVariable area


195


MassCoriolis massThermal

66


196

Flowmeter Technology Sections

Technologies are in alphabetical orderTechnology sections have similar organization


197




198

Principle of Operation

A piping restriction is used to develop a pressure drop that is measured and used to infer fluid flow

Primary Flow ElementTransmitter (differential pressure)

67


199


Bernoulli’s equation states that energy is approximately conserved across a constriction in a pipe

Static energy (pressure head)Kinetic energy (velocity head)Potential energy (elevation head)


200


Bernoulli’s equationP/(ρ•g) + ½v2/g + y = constant

P = absolute pressureρ = densityg = acceleration of gravityv = fluid velocityy = elevation


201


Equation of ContinuityQ = A•v

Q = flow (volumetric) A = cross-sectional areav = fluid velocity (average)

68


202


Apply the equation of continuity and Bernoulli’s equation for flow in a horizontal pipe

Acceleration of gravity is constantNo elevation change


203


Apply Bernoulli’s equation upstream and downstream of a restriction

P1 + ½ ρ•v12 = P2 + ½ ρ•v2

2


204


Solve for the pressure difference and use the equation of continuity(P1 - P2) = ½ ρ•v2

2 - ½ ρ•v12

= ½ ρ [v22 - v1

2]= ½ ρ [(A1/A2)2 – 1]•v1

2

= ½ ρ [(A1/A2)2 – 1]•Q2/A12

= constant • ρ • Q2

69


205


ΔP = constant • ρ • Q2

Fluid density affects the measurementPressure drop is proportional to the square of the flow rate

Squared output flowmeterDouble the flow… four times the differential


206


Q = constant • (ΔP/ρ)½

Fluid density affects the measurementFlow rate is proportional to the square root of the differential pressure produced

Often called “square root flowmeter”


207


Q is proportional to 1/ρ½

Fluid density affects the measurement by approximately -1/2% per % density change

70


208


Liquid density changes are usually smallGas and vapor density changes can be large and may need compensation for accurate flow measurement

Flow computersMultivariable differential pressure transmitters


209


ProblemWhat is the effect on a differential pressure flowmeter when the operating pressure of a gas is increased from 6 to 7 bar?

To simplify calculations, assume that atmospheric pressure is 1 bar abs


210


The ratio of the densities is (7+1)/(6+1) = 1.14

The density of the gas increased 14 percentThe flow measurement is proportional to the inverse of the square root of the density which is (1/1.14)½ = 0.94

The flow measurement will be approximately 6 percent low

71


211


ProblemCalculate the differential pressures produced at various percentages of full scale flow

Assume 0-100% flow corresponds to 0-100 differential pressure units


212


Differential pressure as a function of flowFlow ΔP100 % 100 dp units50 % 25 “ “20 % 4 “ “10 % 1 “ “


213


Low flow measurement can be difficultFor example, only ¼ of the differential pressure is generated at 50 percent of the full scale flow rate. At 10 percent flow, the signal is only 1 percent of the differential pressure at full scale.

72


214


ProblemWhat is the differential pressure turndown for a 10:1 flow range?

0.12 = 0.01, so at 10% flow the differential pressure is 1/100 of the differential pressure at 100% flowThe differential pressure turndown is 100:1


215


Noise can create problems at low flow rates

0-10% flow corresponds to 0-1 dp units90-100% flow corresponds to 81-100% dp units


216


Noise at low flow rates can be reduced by low flow characterization

Force to zeroLinear relationship at low flow rates

73


217


Square root relationship generally applies when operating above the Reynolds number constraint for the primary flow element

Operating below the constraint causes the flow equation to become linear with differential pressure (and viscosity) Applying the incorrect equation will result in flow measurement error


218


ProblemIf the Reynolds number at 100% flow is 10,000, what is the turndown for accurate measurement if the primary flow element must operate in the turbulent flow regime?

10,000/4000, or 2.5:1


219


ProblemWill the flowmeter operate at 10% flow?

It will create a differential pressure…however, Reynolds number will be below the constraint, so the flow measurement will not conform to the square root equation (and will not be accurate)

74


220

Orifice PlatePrimary Flow Element

Flow

Orifice Plate


221

Orifice PlatePrimary Flow Elements

ConcentricConicalEccentricIntegralQuadrantSegmental


222

Orifice Plate Taps

Upstream DownstreamCorner 0D 0DFlange 1 inch 1 inchFull flow 2.5D 8DRadius 1D 0.5DVena Contracta 1D vena contracta

75


223

VenturiPrimary Flow Element

Flow

Throat


224

Flow Nozzle Primary Flow Element

Flow

Nozzle


225

V-Conetm

Primary Flow Element

Flow

V-Conetm

76


226

Differential PressureMulti-Valve Manifold Designs

Multi-valve manifolds are used to isolate the transmitter from service for maintenance and calibration

One-piece integral assemblyMounted on transmitter


227


Upstream Tap

Downstream Tap

High

Low

TransmitterImpulse Tubing (typical)

Three ValveManifold


228


Upstream Tap

Downstream Tap

High

Low

TransmitterImpulse Tubing (typical)

Five ValveManifold

Drain/Vent

Calibration

77


229


Removal from serviceOpen bypass valve (hydraulic jumper)Close block valvesBe sure to close bypass valve to calibrateUse calibration and vent/drain valves (five valve manifold)


230


Return to serviceOpen bypass valve (hydraulic jumper)Open block valvesClose bypass valve


231


Removal and return to service procedure may be different when flow of fluid in tubing/transmitter is dangerous

High pressure superheated steam

78


232

Impulse Tubing

Liquid

No! (gas)

No! (dirt)

Liquid FlowTransmitters

HL

OrificePlate


233

Impulse Tubing

Gas

No! (dirt, condensate)

Gas Flow

Transmitters LHOrificePlate


234

Impulse Tubing

Steam

No! (dirt, condensate)

Steam Flow

Transmitters

HL

OrificePlate

Condensate legs(typical)

79


235

Impulse Tubing

SteamFlow

HL

OrificePlate

Condensate legs(same height)

Same Elevation(shown offset)


236

Impulse Tubing

Liquids avoid collection of gasGas avoid collection of liquidVapor form condensate legsHot locate transmitter far from tapsCold insulate and/or heat trace


237



80


238


Faraday’s Law of Electromagnetic Induction defines the magnitude of the voltage induced in a conductive medium moving at a right angle through a magnetic field

Most notably applied to electrical power generation


239


Faraday’s Law

E = constant • B • L • v

B is the magnetic flux densityL is the path lengthv is the velocity of the medium


240


ExperimentGalvanometer with wire between terminalsHorseshoe magnetMoving the wire through the magnetic field moves the galvanometer indicator

Moving wire in opposite direction moves indicator in opposite directionMoving wire faster moves indicator higher

81


241


Flow

Electrode

Magnet

Tube (non-magnetic) Liner (insulating)

Magnetic Field


242


Magnetic flowmeters direct electromagnetic energy into the flowing streamVoltage induced at the electrodes by the conductive flowing stream is used to determine the velocity of fluid passing through the flowmeter


243


Induced voltageE = constant • B • D • v

Substituting Q = A • v and assuming that A, B, and D are constant yields:

E = constant • Q

82


244


The induced voltage at the electrodes is directly proportional to the flow rate

E α Q


245

Principle of OperationAC Excitation

Magnet is excited by an AC waveformVoltage waveform at electrode is also an AC waveform


246


AC excitation was subject to:Stray voltages in the process liquidElectrochemical voltage potential between the electrode and process fluid

83


247


AC excitation was subject to:Inductive coupling of the magnets within the flowmeterCapacitive coupling between signal and power circuitsCapacitive coupling between interconnection wiring


248


Zero adjustments were used to compensate for these influences and the effect of electrode coating

Percent of full scale accuracy


249


Feeding power to the primary element, then back to the transmitter reduces the possibility of inducing voltage from the power wiring

Electromagnet is the large power drawSignal voltage could be induced from wiring carrying current to the magnet

84


250

Principle of OperationDC Excitation

Pulsed DC excitation reduces drift by turning the magnet on and off

Magnet On = Signal + Noise

Magnet Off = Noise


251


Noise is canceled by subtracting these two measurements

Signal + Noise – Noise = Signal


252


DC magnetic flowmeters automatically self-zero

Percent of rate accuracyThe 4mA analog output zero adjustment is not set automatically and still maintains a percent of full scale accuracy

85


253


Response time can be compromised


254

Magnetic Flowmeter Designs

CeramicElectrodelessLow FlowMedium FlowHigh Flow


255


High NoiseLow ConductivityPartially-fullResponse - FastSanitaryTwo-wire

86


256


External/Internal CoilsFlangedWaferMiniature


257




258


Coriolis mass flowmeters use the properties of mass to measure mass

Thermal mass flowmeters assume constant thermal properties

87


259


Coriolis acceleration

r

ω

Man Standing Still

r

ω

Man Moving Outward

Δr

Coriolis Force


260


Man Standing StillVelocity in tangential plane is constant

F tang = m • a tang= m • Δ v tang / Δ t= m • (r • ω – r • ω) / Δ t= m • 0 / Δ t= 0 (no force in tangential plane)


261


Man Moving OutwardVelocity in tangential plane changes

F tang = m • a tang= m • Δ v tang / Δ t= m • ((r + Δ r) • ω – r • ω) / Δ t= m • Δ r • ω / Δ t≠ 0 (force in tangential plane)

88


262


Components that produce Coriolis forceRotationMotion towards/away from center of rotationResultant Coriolis acceleration


263


U-tube Coriolis mass flowmeterRotation

Oscillation about a plane parallel to the centerline of the piping connections


264


U-tube Coriolis mass flowmeterMotion towards/away from center of rotation

Mass flow through U-tube towards/away from the centerline of piping connections

89


265


U-tube Coriolis mass flowmeterCoriolis force

Twist of U-tube


266


Flow

Centerline ofRotation

Motion Away fromCenterline of Rotation

Motion TowardCenterline of Rotation

Coriolis ForcesTwist U-tube


267


ExperimentHold a garden hose with both hands so it sags near the floor (like a U-tube)

Turning water on/off has little affect on the position of the hose

90


268


ExperimentSwing the hose toward and away from your body

Turning on the water will cause the sides of the U-tube to move towards/away from youStopping the swinging will stop the movement and relax the U-tube


269


Coriolis acceleration is proportional to the mass flow Coriolis acceleration generates a forceCoriolis force twists the U-tube


270


Mass flow is proportional to the Coriolis force that twists the U-tube

Measure the twist of the U-tube

91


271


Amount of twist depends on mechanical properties of the U-tube

MaterialWall thicknessTemperature


272


Temperature MeasurementPipe wall temperature is measured to compensate for material propertiesMany Coriolis mass flowmeters offer (an optional) temperature measurement output

Not process temperatureOutside pipe wall temperature


273


Density MeasurementThe frequency of oscillation is related to fluid densityMany Coriolis mass flowmeters offer (an optional) density measurement output

92


274


Viscosity MeasurementIn the laminar flow regime, the mass flow measurement, temperature measurement, and external differential pressure measurement across the flowmeter is used to calculate viscosity


275


Viscosity MeasurementTo counteract the effects of pipe vibration, one Coriolis mass flowmeter uses a weight that twists the tubeMeasurement of the forces due this twist are used to determine the fluid viscosity


276

Tube Geometry – Single U-tube

FlowSensor

(attached to case)

Outer Case

Drive Coil

93


277

Tube Geometry – Single U-tube

First practical designSensors connected to case

Measure movement relative to caseSusceptible to pipe vibrationRigid support structures

Metal plateConcrete foundation


278

Tube Geometry – Dual U-tube

Flow Sensor Detects MovementBetween the Tubes

Outer Case

Drive Coil

Flow split betweenupper and lower tubes

(one tube shown)

Recombined Flow


279

Tube Geometry – Dual U-tube

Flow split between two tubesSensors connected to case

Measure relative movement of tubesReduced susceptibility to pipe vibrationMount flowmeter in piping

94


280

Tube Geometry – B-Tube

Foxboro

B-tube Design

Two Single Tubes

Flow Inlet


281

Tube Geometry – Curved Tube

Endress+Hauser, Micromotion, Oval

Curved Tube Design

Flow Splitters

Flow

Dual Tubes


282

Tube Geometry – Curved Tube

ABB

Curved Tube Design

Flow Splitters

Flow

Dual Tubes

95


283

Tube Geometry – Delta

Micromotion

Delta Tube Design

Flow Splitters

Flow

Dual Tubes


284

Tube Geometry – Diamond

Kueppers

Diamond Tube Design

Flow Splitters

Flow

Dual Tubes


285

Tube Geometry – Omega

Actaris (Schlumberger)

Omega Tube Design

Flow Splitters

Flow

Dual Tubes

96


286

Tube Geometry – Omega

Heinrichs

Omega Tube Design

Flow Splitters

Flow

Dual Tubes


287

Tube Geometry – Round

Rheonik

Round Tube Design

Flow Splitters

Flow

Dual Tubes


288

Tube Geometry – Straight

Endress+Hauser

Straight Dual Tube Design

Flow Splitters

Flow

Dual Tubes

97


289

Tube Geometry – Straight

Brooks, Endress+Hauser, Krohne, Micromotion, Oval

Straight Single Tube Design

Flow

Single Tube


290

Tube Geometry – S-Tube

S-Tube Design

Flow Splitter

Flow

Dual Tubes

Flow Splitter

FMC Energy Systems


291


FMC Energy SystemsS-Tube Design

Flow Splitter

Flow

Dual Tubes

Flow Splitter

98


292


KrohneS-Tube Design

Flow Splitter

Flow

Dual Tubes

Flow Splitter


293

Tube Geometry– U-Tube

Brooks, MicromotionSingle U-Tube Design

Flow

Single Tube


294

Tube Geometry– U-Tube

Micromotion, Oval, YokogawaDual U-Tube Design

Flow Splitter

Flow

Dual Tubes

Flow Splitter

99


295

Tube Geometry – U-Tube

DanfossU-Tube Design

Flow

Single Tube


296

Fluid Characteristics

Single-phase homogeneousLiquidGasVapor


297


Two-phaseLiquid/solidLiquid/gas

Avoid flashing

100


298


Within accurate flow rangeCorrosion and erosionImmiscible fluids


299

Piping and Hydraulics

For liquid applications, keep the flowmeter full of liquid

Hydraulic designVertical riser preferredAvoid inverted U-tube


300


For liquid applications, orient to self-fill and self-drain

Self-filling is important to ensure a full pipeIf not, special precautions must be taken when zeroing the flowmeterIf not, gas/vapor can accumulate, especially at low flow conditions

101


301


For liquid applications, keep the flowmeter full of liquid

Hydraulic designBe careful when flowing downwardsBe careful when flowing by gravity


302


For gas/vapor applications, keep the flowmeter full of gas/vapor

Hydraulic designSelf-drainingVertical preferredAvoid U-tube


303


For gas/vapor applications, calculate pressure drop carefully

Mass flow range of a given size flowmeter is fixedRelatively small mass occupies a relatively large volumeHigh velocity and high pressure drop resultFlowmeter will operate low in its range

102


304

Performance

PremiumTypical: 0.1% rate plus zero stability

Low costTypical: larger of 0.5% rate or zero stability

Analog outputTypical: up to 0.1% of full scaleSometimes not available


305




306

Open Channel - FlumePrimary Flow Element

Flow

Throat

ConvergingSection

DivergingSection

Level Measurement

103


307

Open Channel - WeirPrimary Flow Element

Rectangular Cipolletti Triangular

WeirLevel Measurement

Flow


308




309


Fluidic flowmeters are flowmeters that generate oscillations as a result of flow

The number of oscillations can be related to the flow rate

104


310


Examples of fluidic phenomenaWind whistling through branches of treesSwirls downstream of a rock in a flowing streamFlag waving in breeze


311


Fluidic flowmetersFluidic flowmeter (Coanda effect)Vortex precession flowmeter (swirl)Vortex shedding flowmeter


312

Coanda Effect Fluidic Flowmeter

Coanda EffectFlow tends to attach itself to flat surface

Fluidic oscillatorPassages allow portion of flow to feed back and impinge on incoming streamAlternating attachment

105


313


Frequency of alternating attachments is proportional to flow

Doubling the flow doubles the number of attachments


314


Reynolds number constraintsOver 500


315


Flow

FeedbackPassage Sensor

106


316


SensorsDeflectionThermal


317

Vortex Precession Flowmeter

Often called a “swirlmeter”Inlet vanes cause the flow to spin and form a cycloneThe tip of the cyclone moves around the inside pipe wall (precession)Outlet vanes remove swirl from the flow


318


Speed that vortex rotates around the pipe is proportional to flow

Doubling the flow doubles the precession

107


319


Flow

Sensor

Inlet Guide Vanes Outlet Guides


320


SensorsPiezoelectric


321

Vortex Shedding Flowmeter

An obstruction (bluff body or strut) is located in the flow stream

Low flow - fluid flows around obstructionHigh flow - alternating vortices are formed

Number of vortices formed is proportional to fluid velocity

108


322


The sensing system detects the vortices createdThe frequency of the vortices passing the sensing system is proportional to fluid velocity


323


Flow

Sensor

VortexL

L

L


324


Bluff body is typically approximately 20% of the pipe ID

Pressure drop across similar vortex shedders in the same service is similar

For liquids: 5 psid at 15 ft/sec400 mbar at 5 m/s

109


325


ProblemWhat is the approximate pressure drop across a vortex shedder at 7.5 ft/sec?


326


(5 • 7.5/15) = 2.5 psig might be tempting, but in the turbulent flow regime, the pressure drop across a restriction varies as the square of the flow

Double the flow, four times the differentialThe pressure drop will be 5 • (7.5/15)2 = 1.25 psig approximately


327


Strut design is like a “piano wire”Gas flow measurementLow pressure drop

110


328


Flow

Strut

VortexL

L

L

UltrasonicSensor


329

Vortex Shedding FlowmeterSensing Systems

Shedder and sensing system tradeoffs are made in the design process to:

operate linearlyoperate at low velocityoperate at low Reynolds numbers


330



reduce the effect of short straight runreduce the effects of misalignmentreduce the effects of vibration

111


331



reduce the possibility of leaksAll-welded body designs


332


Hydraulic energy to operate the sensing system is usually provided by the fluid

Flowmeter turns off at low velocity


333


Velocity constraint is a function of density

Lower density increases low velocity limitHigher density decreases low velocity limit

112


334


Typical Velocity ConstraintsWater 0.35 m/s 1 ft/secFree air 6.5 m/s 21 ft/secAir (8 bar) 3.5 m/s 11.5 ft/sec


335


Reynolds Number ConstraintSufficient Reynolds number is needed to generate oscillations

Flowmeter turns off at low Reynolds numbers


336


Reynolds number constraintsLinear operation over 10-30,000Turn off 3-10,000Nonlinear between turn off / linearSmall sizes

Lower Reynolds number limits

113


337


Both Reynolds number and velocity constraints must be satisfied for vortex shedding flowmeters to operate


338


ProblemWill a vortex shedding flowmeter measure the flow of a liquid operating at a Reynolds number of 1,000,000 at a velocity of 0.1 m/s?

No --- the velocity is below the minimum velocity constraint


339


ProblemWill a vortex shedding flowmeter measure the flow of a liquid operating at a Reynolds number of 100 at a velocity of 10 m/s?

No --- the velocity is below the minimum Reynolds number constraint

114


340

Vortex Shedding SensorDeflection

Flow

Sensor

VortexL

L

L


341

Vortex Shedding SensorDeflection

Flow

Sensor

VortexL

L

L


342

Vortex Shedding SensorDifferential Pressure

Flow

Sensor

VortexL

L

L

115


343

Vortex Shedding SensorDifferential Pressure

Flow

Sensor

VortexL

L

L


344

Vortex Shedding SensorShedder Twist

Flow

Sensor

VortexL

L

L


345

Vortex Shedding SensorThermal

Flow

ThermalSensor

VortexL

L

L

116


346

Vortex Shedding SensorTorque Tube

Flow

Torque Tube

VortexL

L

L


347

Vortex Shedding SensorUltrasonic

Flow VortexL

L

L

UltrasonicSensor


348


Vibration effectsAcceleration compensation

Fishtail design with embedded sensorFishtail design with counterbalancingTorque tube designShedder twist design

117


349

Vortex Shedding SensorFishtail Design

Flow

Embedded Sensor

VortexL

L

L


350

Vortex Shedding SensorFishtail Design

Flow

External Sensor

VortexL

L

L


351

Vortex Shedding SensorTorque Tube

Flow

Torque Tube

VortexL

L

L

118


352

Vortex Shedding SensorShedder Twist

Flow

Center of Rotation(offset for clarity)

VortexL

L

L


353


Early designs were not balancedSubsequent designs were balancedNo mass designs (such as thermal and ultrasonic) do not have to be acceleration compensated


354

Vortex Shedding Sensor Multivariable

Embedded temperature sensorsEmbedded flow computer

Pressure and temperature compensationReynolds number compensation

119


355




356

Positive Displacement Flowmeter

Positive displacement flowmeters measure flow by repeatedly entrapping fluid within the flowmeter

Moving parts with tight tolerancesBearingsMany shapes


357

Positive Displacement Flowmeters

Oval Gear

OscillatingPiston

NutatingDisk

120


358


Sensing systemsMechanicalMagneticRadio frequencyOptical


359


MaintenancePluggingBearing wearAbrasionLeaks



Flow%RateError

10

-10

3 cP

1-1

1 10 1000.1

>1000 cP

121



Flow

PressureDrop asPercent ofMaximumRating

100

0

3 cP

1 10 1000.1

30,000 cP


362




363

Target Flowmeter

Target flowmeters determine flow by measuring the force exerted on a body (target) suspended in the flow stream

122


364

Target Flowmeter

Flow

Target


365

Target Flowmeter

Dynamic balance with flowing streamSame equations as differential pressure flowmeters

Affected by density (+1% specific gravity change affects flowmeter by -0.5%)


366

Target Flowmeter

MaintenanceTarget wearCoatingLeaksDrift

123


367




368

Thermal Flowmeter

Thermal flowmeters use the thermal properties of the fluid to measure flow

Hot Wire AnemometerThermal Profile


369

Thermal FlowmeterHot Wire Anemometer

Hot wire anemometers determine flow by measuring the amount of energy needed to heat a probe whose heat loss changes with flow rate

124


370

Thermal FlowmeterHot Wire Anemometer

Flow

ThermalSensor


371

Thermal FlowmeterThermal Profile

Thermal profile flowmeters determine flow by measuring the temperature difference that results in a heated tube when the fluid transfers heat from the upstream portion to the downstream portion of the flowmeter


372

Thermal FlowmeterThermal Profile

Flow

Heater

Temperature Sensors

Heater

Zero Flow

125


373




374

Turbine Flowmeter

Fluid flow causes a rotor to spin whereby the rotor speed is proportional to fluid velocity

Primary Flow ElementTransmitter


375

Turbine Flowmeter

FlowRotor

Sensor/Transmitter

126


376

Turbine Flowmeter

The sensor detects the rotor bladesThe frequency of the rotor blades passing the sensor is proportional to fluid velocity


377

Turbine Flowmeter

Operating constraintsTurbulent flow regime10-600mm (0.5 to 24 inch)Application-specific designs have limited temperature capability (natural gas)Minimum/maximum velocityLubricity (often difficult to quantify)


378

Turbine Flowmeter

MaintenanceBearing wearRotor damageSensor failure

127


379

Turbine Flowmeter

DesignsAxialPaddle wheelPropellerTangential


380




381


Ultrasonic flowmeters direct ultrasonic energy into the flowing streamInformation from the remnants of this energy is used to determine the velocity of fluid passing through the flowmeter

128


382


Sensing the remnants is predicated upon a complete ultrasonic circuit

Transmitting deviceEntry pipe wall (and liner)Fluid (and reflections off pipe wall)Exit pipe wall (and liner)Receiving device


383


To function properly, all parts of the ultrasonic circuit must allow sufficient energy to pass


384


Weak signals may cause the flowmeter to be erratic or cease to function

PaintDry ultrasonic coupling compoundPipe wall coating or corrosionPoorly bonded linerTuberculation (barnacles)

129


385


Ultrasonic noise may cause the flowmeter to be erratic or cease to function

Nearby radio transmitterControl valve with “quiet” trim


386

Principle of OperationDoppler Ultrasonic

Doppler ultrasonic flowmeters reflect ultrasonic energy from particles, bubbles and/or eddies flowing in the fluid


387


Flow

Transmitter Receiver

Bubbles or Solids

Reflection

130


388


Under no flow conditions, the frequencies of the ultrasonic beam and its reflection are the sameWith flow in the pipe, the difference between the frequency of the beam and its reflection increases proportional to fluid velocity


389


Doppler Equationvf = K • Δf

K = constantvf = velocity of fluid where ultrasonic energy is reflectedΔf = difference between the transmitted and reflected frequencies


390

Principle of OperationTransit Time Ultrasonic

Transit time (time-of-flight) ultrasonic flowmeters alternately transmit ultrasonic energy into the fluid in the direction and against the direction of flow

131


391


Flow

Sensor

Sensor


392


The time difference between ultrasonic energy moving upstream and downstream in the fluid is used to determine fluid velocity


393

Under no flow conditions, the time for the ultrasonic energy to travel upstream and downstream are the same

Flow

Sensor

Sensor


132


394


With flow in the pipe, the time for the ultrasonic energy to travel upstream will be greater than the downstream time

Flow

Sensor

Sensor


395


Transit Time Equationvp = K • (Tu – Td)

Tu • Tdvp = average fluid velocity in the pathK = constantTu = upstream transit time in fluidTd = downstream transit time in fluid


396


Tu and Td are dependent upon the speed of sound in the fluidSome designs use measurements and equations that are not dependent upon the speed of sound in the fluid

133


397

Principle of OperationPulse Repetition Ultrasonic

Pulse repetition (sing-around) ultrasonic flowmeters alternately transmit ultrasonic energy into the fluid in the direction and against the direction of flowThe receipt of one ultrasonic pulse triggers the sending of a new ultrasonic pulse


398


The frequency that the pulses are repeated is used to determine fluid velocity


399


Pulse Repetition Equationvp = K • (fu – fd)

vp = average fluid velocity in the pathK = constantfu = frequency of upstream transit time periodfd = frequency of downstream transit time

period

134


400

Single Path Geometry

Flow

Sensor

Sensor


401


Flow

Sensor

Sensor


402


Flow

Sensor

SensorOne Reflection

135


403


Flow

Sensor

Sensor

Two Reflections


404


Flow

Sensor Sensor

Three Reflections


405


SensorSensor

In Out

136


406

Multiple Path Geometry

Sensor


407

Chordal Path Geometry

Sensor


408

Ultrasonic Flowmeters

Applications (general)Large pipesFlashing fluidsCorrosive fluidsHazardous fluids

137


409

Ultrasonic Flowmeters

Applications (specific)Custody transfer

Natural gasPetroleum products

Stack gasFlare gas


410




411


Flow

MeteringFloat

MeteringTube

138


412


Pressure due tofluid velocity

Weight of float minusweight of fluid it displaces

DynamicBalance


413




414

Correlation Flowmeters Principle of Operation

Correlation flowmeters determine fluid velocity by measuring parameters associated with the flowing stream at different places in the piping

139


415

Correlation FlowmetersUltrasonic

Flow

Sensor

Distance


416

Correlation FlowmetersPressure Sensor Array

Flow

Sensor Array(wraps around pipe)


417



140


418

Insertion Flowmeter

Insertion flowmeter infer the flow in the entire pipe by measuring flow at one or more strategic locations in the pipe


419

Insertion Flowmeter

Flow

Theoretical Velocity Profile

Average velocity

Rd = 4000

Rd = 4,000,000


420

Insertion Flowmeter

Flow

Sensor

141


421

Insertion Flowmeter

TechnologiesDifferential PressureMagneticTargetThermalTurbineVortex


422




423


Divide the flowing fluid into a large and small flowing stream

It is important to ensure a known ratio between these flows

Measure the flow of the small stream to infer the total flow of the fluid

142


424

Bypass FlowmeterOrifice Plate

Flow

Orifice Plate

Bypass Flowmeter


425



426

Factors in Flowmeter Selection

Flowmeter classesWetted moving partsNo wetted moving partsObstructionlessNon-wetted (external)

143


427


Flowmeter measurementsVolumeVelocityMassInferential


428


PerformanceAccuracy

End useIndicationControlTotalizationAlarm


429


Power requirementsSafetyRangeabilityMaterials of constructionMaintainability

144


430


Ease of applicationEase of installationInstalled costOperating costMaintenance cost


431

Data for Flowmeter Selection

PerformanceFluid properties

Fluid nameFluid state(s)Compatibility of materialsPressure and temperature


432


Fluid propertiesSpecific gravity and densityFluid viscosityOperating rangeOther (conductivity, thermal capacity, vapor pressure…)

145


433


InstallationPipe sizeDifferential pressurePipe vibrationPulsating flowStraight runAmbient conditions


434


OperationMaintenanceAvailability of parts and serviceInstalled costOperating cost


435


Future considerationsPlant expansion

Risk

146


436

Flowmeter Selection

Typical selection processTrial and error until one “works”Potential lost opportunity


437

Flowmeter Selection

Proposed selection processDisqualify inappropriate technologies using technical and non-technical criteriaSelect the best flowmeter from the remaining technologies


438

Flowmeter Selection

Technical criteriaItems or issues that absolutely disqualify a technology

Non-technical criteriaPreferences

147


439

Review and Questions IntroductionFluid Flow FundamentalsPerformance MeasuresLinearization and CompensationTotalizationFlowmeter CalibrationMeasurement of Flowmeter PerformanceMiscellaneous ConsiderationsFlowmeter TechnologiesFlowmeter Selection


Industrial Flow Measurement

Seminar Presented by David W. Spitzer

Spitzer and Boyes, LLC

Date post:	18-May-2018
Category:	Documents
Upload:	trinhnhan
View:	219 times
Download:	1 times

Flow Measurement Seminar - SPITZER AND BOYES, LLC · Fluid Flow Fundamentals ... Measurement of...

Documents