selection of flow meter
DESCRIPTION
flow meterTRANSCRIPT
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FLOWMETERSELECTIONSEMINAR
AlanGraff
RLStoneCoI&CSalesManager
UpstateNY&NewEngland
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A Leading Supplier of Flowmetersto HVAC & Industrial Marketplace
Magmeters Vortex & Swirl Turbine Thermal & Coriolis Mass BTU Meter Pitot, Wedge Orifice Plates, Venturi Positive Displacement Rotameter, Variable Area
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DefineApplication BasicFacts
FlowingMedia(Steam,Water,Air,Gasetc) Density pressureandtemperature FlowRange,minimumtomaximum(turndownneeded)
Accuracy howstated?%ofrangeorspan Repeatability Straightrunrequirements&available EconomicConsiderations Initialcost,maintenancecost&operatingcosts
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Whyarewehere?
Thereisno 1meterthatwillmeeteveryapplication
Everyapplicationneedstobelookedatindividually
Wecanmakesomegeneralizations!!!!!!
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HOWMUCH (TOTAL)
HOWFAST (RATE)
FLOWMEASUREMENT
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Flow Through A Pipe
Real WorldIdealized
Pipe Velocity Profile
VV
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Flow Profile Correlation
Velocity profile is a predictable function of Reynolds number. Fluids with the same Reynolds number will have similar velocity profiles.
SteamWaterHeavy Crude
V
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General Flow Terminology
Reynolds Number (RE) A single dimensionless parameter formed as the ratio of inertial to viscous forces . Magnitude indicates whether flow is laminar or turbulent
=
CharacteristicDimension*
(D)
Fluid Viscosity ()RE=
FluidDensity
(p)
FluidVelocity
(V)Inertia ForcesViscous Forces
* Usually inside pipe diameter.
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Characterization of Fluid Flow
Types of FlowRE < 2100
RE >3000
*** Well documented & proven fully developed flow profiles
Transitional
Turbulent ***
Laminar
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Volumetric Flowrate (Q)
Volume = Area x LengthVolume Flow = Area x Velocity
VA
Q
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Mass Flowrate (m)
Where m = Mass FlowQ = Volume Flow = Fluid Density
= AV
Mass = Volume x Density
Mass Flow m = Qp
VA
m
Q=VA
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MassvsVolumeFlowmeters
Whyareweconcerned? Howmuchdoesitreallymatter? Flowthrougha4linemeasuredinaAveragingPitot
Flow Rate 1000 cfm 1000 cfm
Pressure 5 psi 5 psi
Temperature 100 F 70 F
DP in WC 12.181 11.532
Thereisa6%errorjustbychangingdensity/temperatureslightlycanyoumetercope??
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General Flow Terminology
Factors affecting flowmeter performance Process media
Liquid Gas
Density (Specific Gravity) Viscosity Pressure
Temperature Velocity
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Flowmeter Performance
Accuracy Repeatability Linearity Rangeability
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Types of Accuracy
% Rate % Full Scale % Span % Max DP
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Accuracy
% Rate The percent accuracy value is constant and applied to the actual (or indicated) flowrate
Example:Flowrate 1% rate100 GPM 1 GPM50 GPM 0.5 GPM10 GPM .01 GPM
% Full Scale The absolute value of error (as expressed in engineering units)
Flowrate 1% Full Scale % Rate100 GPM 1 GPM 1%50 GPM 1 GPM 2%10 GPM 1 GPM 10%
Example:
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Accuracy
Percent Error Versus Flow
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Poor Repeatability Means Poor Accuracy
Good Accuracy Means Good Repeatability
Good Repeatability Does Not Necessarily Mean Good Accuracy
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VolumetricFlowmeters
DP Turbine Vortex/Swirl Magnetic Target Ultrasonic Displacement
Note:canbeinferredmasswithcompensatingtransmitter
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Differential Pressure Flowmeters
Flow Measurement Principles
PQ = K
ORIFICE PLATE(or FLOW TUBE) VENA
CONTRACTA
MANOMETER(or DP TRANSMITTER)h
Direction of Flow
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DP Primary Elements
VariousOrificeConfiguration
FlowNozzle
VenturiFlowmeter
FlowTube
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DPPrimaryElements
AveragingPitot
Accelabar CombinedPitot&Venturi
WedgeElement
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Secondary Flow / DP Transmitter
Differential Pressure / Flow Transmitter
Square Root Extraction
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DP Flowmeters
DIFFERENTIAL PRESSUREADVANTAGES
Use On Liquid, Gas, and Steam
Suitable for Extreme Temperatures and Pressures
No Moving Parts
Low Cost
DISADVANTAGES
Limited Rangeability
Effected By Changes In Density, Pressure, and Viscosity
Maintenance Intensive
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Magnetic FlowmetersTheory of Operation
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Magmeter Requirements
Process must be a liquid Minimum conductivity Meter must be full
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Magnetic Flowmeters
MAGNETICADVANTAGES
No Moving Parts
Very Wide Rangeability
Ideal For Slurries
Unobstructed Flow Path
DISADVANTAGES
Liquid Must Be Conductive
Physical Pressure and Temperature Limits
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Magnetic Flowmeters
No moving parts No pressure drop Flowrate independent of viscosity, temperature, and density Minimum upstream piping requirements Electronics interchangeable without regard to size Measure dirty liquids with solids Measure highly corrosive fluids Very large turndown Linear output
Advantages Over Other Technologies
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Vortex Meter
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Vortex MeterPrinciple of Operation
Q = V x A
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Vortex
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Vortex/Swirlmeter
ADVANTAGES
No Moving Parts
For Liquid, Gas, or Steam
Uneffected by Pressure, Temperature, or Density Changes.
Wide Rangeability
DISADVANTAGES
Span Limitations Due to Viscosity
Flow Profile Sensitive (Vortex)
VORTEX / SWIRLMETER
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Swirlmeter
Principle of OperationPreamplifier
Swirler Sensor Deswirler
r = local radiusVA = axial velocity of flowVT = angular velocity of flowp = static pressure
Backflow
Housing
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Swirlmeters
Benefits High Accuracy 0.50% of Rate
No Moving Parts
Minimal Upstream Piping
Measures Low Flows
Versatile
Electronics can be used for Diagnostics
Works with Entrained Liquids
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Swirlmeter
Cut-Away ViewTechnical Data Measures liquids, gases and steam Available integral, remote, or flow
computer electronics Accuracy 0.50% rate Sizes 0.75" thru 16.0" Minimal upstream piping req. Flow as low as 1 GPM Excellent in light gas applications
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Installation Length
Swirlmeter
15 D 5 D
25 D 5 D
50 D 5 D
Vortex 4Swirlmeter
90 elbow
Processcontrol valve
Reduction
3 D 1 D
3 D 1 D
5 D 1 D
min. 1.8 D
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Turbine Meter
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Turbine Meter
Principle of Operation
Rotor velocity is proportional to fluid velocity
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Turbine Meter
High accuracy (.5% of rate) High rangeability (up to 50:1) Compact design Fast response time Broad range of sizes Clean water applications only NIST Traceable Factory Calibration Low cost, Easy to install In and out of line, under pressure
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Turbine Meter
Straight pipe run requirements Process fluid lubricity Reynolds number constraintsViscosityDensity
Maintenance & recalibration
Performance Considerations
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Turbine Flowmeters
TURBINEADVANTAGES
High Accuracy
Suitable for Extreme Temperatures and Pressures
Can Be Used On Gas or Liquid
DISADVANTAGES
Only For Low Viscosities
Moving Parts
Sensitive to Flow Profile
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Positive Displacement Flowmeters
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PD Flowmeters
Helical gear Nutating disk Oscillating
piston Oval gear Rotary
Types
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Positive Displacement Meter
Typical Principle of Operation
Schematic of a nutating-disk meter
Schematic of a rotary-vane flowmeter Schematic of a
lobed-impeller flowmeter
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PD Flowmeters
Ideal for viscous fluids Custody transfer Batching Minimal straight piping
requirements
Advantages
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Ultrasonic Flowmeters
Doppler Time of
flight
Types
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DopplerFlowmeter
Ultrasonic FlowmetersPrinciple of Operation
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Ultrasonic FlowmetersPrinciple of Operation
Transit-TimeFlowmeter
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Ultrasonic Flowmeters
Reynolds number constraints Entrained gas or particles for doppler Clean liquids for time of flight Installed without process shut down Straight upstream piping
requirements
Performance Considerations
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Ultrasonic
ULTRASONICADVANTAGES
No Moving Parts
Unobstructed Flow Passage
Wide Rangeability
DISADVANTAGES
For Liquids Only (limited gas)
Flow Profile Dependent
Errors Due To Deposits
V
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MassFlowmeter
DirectMeasurement
ThermalDispersion Coriolis
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CoriolisMassFlowmeter
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Coriolis
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Coriolis
CORIOLISADVANTAGES
Direct Mass Measurement
High Accuracy
Additional Density Measurement
Uneffected By Flow Profile
DISADVANTAGES
High Purchase Price
High Installation Cost
Size Limitations
Vibration Sensitive
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ThermalDispersion
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ThermalDispersionMassFlowmeter
Gasapplicationonly Relativelyinexpensive Easytoinstallandremoveunderpressure Accuracy0.5% Turndown,100:1 Capableofmonitoringextremelylowflows Truemassflowmeter(compensatesfortemperature/pressure)
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PipingConsiderations
Alwaysneedafullpipe
Properup/downdiameter
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BTUMonitoring
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Summary Each Application is Different
FlowingMedia(egSteam,Water,Air,Gasetc)Density pressureandtemperatureFlowRange,minimumtomaximum(turndownneeded)Accuracy howstated?%ofrangeorspanRepeatabilityStraightrunrequirements&availableMaintenanceandreliability
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GeneralHVACRecommendations
Steam:AccelabarorSwirl
ChilledorHotWater:HotTapInsertTurbine
NaturalGasorAir:ThermalDispersion
FuelOil:CoriolisorWedge