FLOWMETERSELECTION
SEMINAR
AlanGraff
RLStoneCo
I&CSalesManager
UpstateNY&NewEngland
A Leading Supplier of Flowmeters
to HVAC & Industrial Marketplace
Magmeters
Vortex & Swirl
Turbine
Thermal & Coriolis Mass
BTU Meter
Pitot, Wedge
Orifice Plates, Venturi
Positive Displacement
Rotameter, Variable Area
DefineApplication BasicFacts
FlowingMedia(Steam,Water,Air,Gasetc)
Density pressureandtemperature
FlowRange,minimumtomaximum(turndown
needed)
Accuracy howstated?%ofrangeorspan
Repeatability
Straightrunrequirements&available
EconomicConsiderations Initialcost,maintenance
cost&operatingcosts
Whyarewehere?
Thereisno 1meterthatwillmeetevery
application
Everyapplicationneedstobelookedat
individually
Wecanmakesomegeneralizations!!!!!!
FLOWMEASUREMENT
HOWMUCH (TOTAL)
HOWFAST (RATE)
Flow Through A Pipe
Idealized
Real World
Pipe
Velocity Profile
Flow Profile Correlation
Steam
Water
Heavy Crude
Velocity profile is a predictable function of Reynolds
number. Fluids with the same Reynolds number will have
similar velocity profiles.
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
RE=
Inertia Forces
Viscous Forces
Fluid
Density
(p)
Fluid
Velocity
(V)
Characteristic
Dimension*
(D)
Fluid Viscosity ()
* Usually inside pipe diameter.
Characterization of Fluid Flow
Types of Flow
RE < 2100
Laminar
Transitional
RE >3000
Turbulent ***
*** Well documented & proven fully
developed flow profiles
Volumetric Flowrate (Q)
V
A
Volume = Area x Length
Volume Flow = Area x Velocity
Mass Flowrate (m)
Q=VA
Mass Flow m =
Qp
= AV
V
A
Where
m
Q
= Mass Flow
= Volume Flow
= Fluid Density
Mass = Volume x Density
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/temperatureslightlycan
youmetercope??
General Flow Terminology
Factors affecting flowmeter performance
Process
Liquid
Gas
Density
media
Temperature
Velocity
(Specific Gravity)
Viscosity
Pressure
Flowmeter Performance
Accuracy
Repeatability
Linearity
Rangeability
Types of Accuracy
% Rate
% Full Scale
% Span
% Max DP
Accuracy
% Rate
The percent accuracy value is constant and
applied to the actual (or indicated) flowrate
Flowrate
Example: 100 GPM
50 GPM
10 GPM
1% rate
1 GPM
0.5 GPM
.01 GPM
% Full Scale The absolute value of error (as expressed in
engineering units)
Flowrate
Example: 100 GPM
50 GPM
10 GPM
1% Full Scale
1 GPM
1 GPM
1 GPM
% Rate
1%
2%
10%
Accuracy
Percent Error Versus Flow
Poor Repeatability Means
Poor Accuracy
Good Accuracy Means
Good Repeatability
Good Repeatability Does Not
Necessarily Mean Good Accuracy
VolumetricFlowmeters
DP
Turbine
Vortex/Swirl
Magnetic
Target
Ultrasonic
Displacement
Note:canbeinferredmasswithcompensatingtransmitter
Differential Pressure Flowmeters
Flow Measurement Principles
Q=K
ORIFICE PLATE
(or FLOW TUBE)
VENA
CONTRACTA
Direction of Flow
MANOMETER
(or DP TRANSMITTER)
DP Primary Elements
Various
Orifice
Configuration
Flow
Tube
Flow
Nozzle
Venturi
Flowmeter
DPPrimaryElements
AveragingPitot
Accelabar Combined
Pitot&Venturi
WedgeElement
Secondary Flow / DP Transmitter
Differential Pressure /
Flow Transmitter
Square Root Extraction
DP Flowmeters
DIFFERENTIAL PRESSURE
ADVANTAGES
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
Magnetic Flowmeters
Theory of Operation
Magmeter Requirements
Process must be a liquid
Minimum conductivity
Meter must be full
Magnetic Flowmeters
MAGNETIC
ADVANTAGES
No Moving Parts
Very Wide Rangeability
Ideal For Slurries
Unobstructed Flow Path
DISADVANTAGES
Liquid Must Be Conductive
Physical Pressure and Temperature
Limits
Magnetic Flowmeters
Advantages Over Other Technologies
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
Vortex Meter
Vortex Meter
Principle of Operation
Q=VxA
Vortex
Vortex/Swirlmeter
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)
Swirlmeter
Principle of Operation
Preamplifier
Housing
Swirler
Sensor Deswirler
Backflow
r
VA
VT
p
=
=
=
=
local radius
axial velocity of flow
angular velocity of flow
static pressure
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
Swirlmeter
Cut-Away View
Technical 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
Installation Length
Swirlmeter
Swirlmeter
Vortex 4
Process
control valve
5D
1D
3D
1D
50 D
5D
25 D
5D
15 D
5D
90 elbow
min. 1.8 D
Reduction
3D
1D
Turbine Meter
Turbine Meter
Principle of Operation
Rotor velocity is proportional to fluid velocity
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
Turbine Meter
Performance Considerations
Straight pipe run requirements
Process fluid lubricity
Reynolds number constraints
Viscosity
Density
Maintenance & recalibration
Turbine Flowmeters
TURBINE
ADVANTAGES
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
Positive Displacement Flowmeters
PD Flowmeters
Types
Helical gear
Nutating disk
Oscillating
piston
Oval gear
Rotary
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
PD Flowmeters
Advantages
Ideal for viscous fluids
Custody transfer
Batching
Minimal straight piping
requirements
Ultrasonic Flowmeters
Types
Doppler
Time of
flight
Ultrasonic Flowmeters
Principle of Operation
Doppler
Flowmeter
Ultrasonic Flowmeters
Principle of Operation
Transit-Time
Flowmeter
Ultrasonic Flowmeters
Performance Considerations
Reynolds number constraints
Entrained gas or particles for doppler
Clean liquids for time of flight
Installed without process shut down
Straight upstream piping
requirements
Ultrasonic
ULTRASONIC
ADVANTAGES
No Moving Parts
Unobstructed Flow Passage
Wide Rangeability
DISADVANTAGES
For Liquids Only (limited gas)
Flow Profile Dependent
Errors Due To Deposits
MassFlowmeter
DirectMeasurement
ThermalDispersion
Coriolis
CoriolisMassFlowmeter
Coriolis
Coriolis
CORIOLIS
ADVANTAGES
Direct Mass Measurement
High Accuracy
Additional Density Measurement
Uneffected By Flow Profile
DISADVANTAGES
High Purchase Price
High Installation Cost
Size Limitations
Vibration Sensitive
ThermalDispersion
ThermalDispersionMassFlowmeter
Gasapplicationonly
Relativelyinexpensive
Easytoinstallandremoveunderpressure
Accuracy0.5%
Turndown,100:1
Capableofmonitoringextremelylowflows
Truemassflowmeter(compensatesfor
temperature/pressure)
PipingConsiderations
Alwaysneedafullpipe
Properup/downdiameter
BTUMonitoring
Summary Each Application is
Different
FlowingMedia(egSteam,Water,Air,Gasetc)
Density pressureandtemperature
FlowRange,minimumtomaximum(turndownneeded)
Accuracy howstated?%ofrangeorspan
Repeatability
Straightrunrequirements&available
Maintenanceandreliability
GeneralHVACRecommendations
Steam:AccelabarorSwirl
ChilledorHotWater:HotTapInsertTurbine
NaturalGasorAir:ThermalDispersion
FuelOil:CoriolisorWedge
