CORIOLIS

MASS FLOW
METERS
R. Mascomani
Chief Research Engineer
FCRI, PALAKKAD.

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 MASS FLOW
 Determination of energy balances
 Measuring efficiency of Engines
 Energy content of natural gas/Crude
 Mass is constant independent of pressure,
temperature, gravity, viscosity, pressure,
temperature, density
 Mass Flow tops the list

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MASS FLOW MEASUREMENT

 Area x velocity x density

 True mass flow meters :
Output is direct function of
mass flow.
• Coriolis meters

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 MASS FLOW MEASUREMENT

 Inferential
mass flow meters :
Employs simultaneous
measurements of flowing volume
and density.
 Product gives mass flow.

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 CORIOLIS MASS FLOWMETERS

 Movement of particle across the surface of

a rotating body
 Acceleration by a force called Coriolis force
 Normal to both particle direction axis of
rotation of the body.
 Magnitude directly proportional to the
product of the mass of the particle and
Coriolis acceleration.

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 Oscillating Flow Tube, No Flow

Inlet Side Outlet Side

Outlet Support
Inlet Axis Outlet
Side

Inlet Side

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 Oscillating Flow Tube – Response
to Flow

Fluid Reactive
Outlet Force (Outlet)
Twist
Axis Support
Inlet
Axis
Outlet Side

Inlet
Side
Fluid Reactive
Force (Inlet)

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 Dual-Tube Sensor

Fluid Reactive Fluid Reactive

Force (Inlet) Force (Outlet)

Inlet Outlet

Fluid Reactive Fluid Reactive

Force (Inlet) Force (Outlet)

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Oscillating Flow Tube, No Flow

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 Dual-tube Sensor

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 Mass Flow Measurement
SENSOR SIGNAL , NO SENSOR SIGNAL , WITH
FLOW FLOW

Outlet Side
C1 OutletSide
C1

Inlet Side
C2
Inlet Side
C2 ∆T ∆T

Time Time

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Flow Calibration Factor (FCF)

3.8552 5.13
Flow Factor
(grams/sec/µ second of ∆ T)

Temperature Correction Factor

(% / 100 oC)

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How Transmitter Computes Mass
Flow-Calibration Constants

 Flow Calibration Flow rate in grams per

Constant (determined second that produces 1
during factory or field microsecond of ∆ t.
calibration)
Value of ∆ t when there is no
 Zero Flow Offset flow through the sensor.
(determined during
field calibration)
Percent change in tube
rigidity resulting from a
 Flow Temperature
Coefficient (specified change in temperature of 100
for the sensor) ºC.

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MECHANISM OF VIBRATION
 Tube anchored at two points vibrate
up&down
 Vibration at resonance
 Vibration at free end
 Forces operate in opposite directions and
the tube twists
 Twist angle or change in phase between two
transducers detecting the movement of legs
is measured

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 m = K × ∆T / 8 / r 2

K : Constant for tube material

∆ T : Time interval
 r: Tube radius

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MATERIAL OF CONSTRUCTION

 Common material SS316

 Special materials such as Titanium,
Hastelloy, Zirconium and tantalum
for chemical compatibility

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 PARALLEL TUBE
CONSTRUCTION

 Two tubes vibrate in out of phase giving equal and

opposite signal. Effect of vibration cancels out
 Drive coil an one tube and an opposing magnet on the
other to vibrate the tube.
 Motion sensors electro magnetic types.
 Miniature temperature sensor on the surface of the
tube.
 AC/DC powered versions and power consumption 10
W typically.
 Output pulsed /frequency/4-20 mA

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 DESIGN MASS FLOWMETERS
 Fullscale deflections less than 0.001”
 Chemical compatibility and material.

 Pressure Rating

 Flow Range

 Pressure Drop

 Signal amplitude to noise ratio.

 Electronics to resolve times in ns range.

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TUBE CONFIGURATIONS
 Variety of shapes
 sensitivity

 increase range

 reduce stress

 Straight tube reduced pressure drop

• Easier installation
• Needs sensitive detectors
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 PERFORMANCE
 Size : 1/16" up to 6"
 Flow Range : g/h - 10 t/m

 Range : 25 : 1 (Typical) and 100 : 1 in some

application.
 Accuracy : ±0.15% - ± 0.25% R+ Zero shift error.

±0.5% R for gases

Uncertainty of measurement facilities ±0.3% - ± 0.6%
R

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Calibration with different fluids

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Effect of Pressure

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Effect of Temperature

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 C A L IBR A T IO N C UR VE (3 ")
E& H Sl N o.99 08 -30 08 1-1-1 8

0 .60 0
0 .50 0
% erro r in indic a te d ma s s

0 .40 0
0 .30 0
0 .20 0
0 .10 0
0 .00 0
-0 .10 0
-0 .20 0
-0 .30 0
-0 .40 0
-0 .50 0
-0 .60 0
0 50 0 1 00 0 1 50 0 2 00 0 2 50 0
A ctu al flow rate in kg /m in

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 CALIBR ATION C URV E
6",F R,M eter serial no .217458

Before final adjustment of cal factor

After final adjustment of cal fac tor

0.500
0.400
% error in indicated mass

0.300
0.200
0.100
0.000
-0.100
-0.200
-0.300
-0.400
-0.500
0 50 100 150 200 250 300 350
Ac tual flow r ate in tons /hr

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 C alibra tion curv e o f a ma ss flow m ete r
3",FR,M ete r S eria l n o.:3446 01

0.40
0.30
% Error in indicated m ass

0.20
0.10
0.00
-0.10
-0.20
-0.30
-0.40
0 1 00 2 00 3 00 400 5 00 600 7 00 800 900 10 00 1100 12 00 13 00
Actu al flo w rate kg /m in

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 ZERO STABILITY

 Well balanced meter vibrates freely independent of

external environment
 Minimum potential for zero error effects.
 Tube balance (Passing of energy to pipes)
 Stress affect fundamental oscillation of meter causing
zero shift
 Errors highest at bottom range of the meter
 Importance for gas measurement due to low density

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 OPERATIONAL SAFETY

 Material compatibility
 Tube under continuous stress
 Stress corrosion cracking may result failure
 Residual liquid may be potentially corrosive if liquid
carry over
 Secondary containment for hazardous/explosive gases

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 POTENTIAL FLUID EFFECTS

 Quoted uncertainty accounts for fluid effects

 Certain tubes sensitive to pressure

 Bourdon effect due to pressure increase

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 ADVANTAGES
 A clear tube provides a fundamental means of
measuring mass flow.
 No moving components and requires less
maintenance.
 Corrosion resistant materials.
 Calibration independent of viscosity and flow
profile.
 Immune to swirl and asymmetrical flows
 Output linear with mass flow.
 High turn down ratio
 Very repeatable
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 COST OF OWENERSHIP
(Comparison of Coriolis and inferential meters)

 Metering accuracy ( % of reading)

 Human intervention ( Number per year)
 Safety ( points of leakage)
 Recalibration frequency ( Times per year)
 Long-term drift ( % per year)
 System components ( number required for
measurement)
 Turndown ratio
 Reliability

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Comparison of meters

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 DISADVANTAGES

 Accuracy degraded at low flow rates due to zero

shifts.
 Performance affected by air/gas pockets.
 Sensitive to vibration.
 Need careful installation
 Difficult to prove at site
 High pressure drop at full flow
 Bulky in some designs.
 Size limitation
 Expensive.

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 SIZING
 Flow rate and line size.
 Pressure and temperature ratings

 Materials of construction.

 Resistance to corrosion and pitting

 Fatigue strength.

 Pressure drop.

 Liquids.

 Gases, Flowing velocity

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 FLUID VELOCITY

 Maximum flowrate 0.5 Mach

 For airflow 160 m/s
 Sonic effects at higher velocities

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 CALIBRATION

 Mastermeter system
 Gravimetric methods

 Volumetric methods

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 CALIBRATION

 With some meters , there are shifts between

water calibration and site fluid
 Variation depends on design
 Site calibration with PD meters
 Compact provers may be used

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Calibration Schematic

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 INSTALLATION

 Mechanical Installation, Vibration reduction

 For Liquid measurement,keeping out of gas
 For Gas Measurement,keeping out of particle
 Vertical pipe with flow upward preferred.
 No condensate or other liquids should be trapped in the flowmeter
 Adequate rigid pipe supports on either side,close to the meter
 By pass loop.
 Stress due to bolting will change calibration

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 Use of antivibration mounts to reduce the effects of stress.
 Avoid vibration in the range of 40 - 200 Hz. ( Near pumps and motors )
 Alignment of gaps to reduce stress
 Downstream shut off valve to zero the meter.
 No special up/down stream piping requirement.
 Flow meter size can be less than process piping for low density gases.
 20 - 30 pipe diameters in between meters to avoid "Cross Talk".

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 APPLICATIONS

 Batch production of chemicals

 Blending systems

 Truck loading

 Food, drink industry.

 Photographic emulsions, polypropylene

 Dispensing of LPG ,GNG

 Air,CO2, ,Nitrogen and Chlorine

 Ethylene,Hydrogen

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 ACCURACY OF INFERRED
TECHNIQUES
 Volume

 Pressure

 Temperature

 GasComposition
 Compressibility Factor and

 Measurement to be made simultaneously.

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 ACCURACY OF INFERRED TECHNIQUES
 PV = n. R. T.Z. (real gas law relationship)
 Z = 0.6 (for CNG at 2000 PSI and 50
deg.F with specific gravity of 0.7)
 If compressibility is not accounted a
correction of about 40% is required in
mass flow.
 Over 8000 meters for past 10 years

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CRITERIA FOR GAS MEASUREMENT
 Zero stability
 Operational safety

 Fluid velocity

 Meter Uncertainty

 Precision losses

 Potential fluid effects

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 ZERO STABILITY METER BALANCE /
INSTALLATION

 Meters employ twin or dual tube

 Well-balanced tube vibrates freely
 Poorly balanced meter pass energy into the flange
 Stresses or pipe forces
 Zero drift and its associated errors
 Brackets de-couples meter
 Errors highest at bottom range
 Gas densities 30-40 times lower
 Physical checking of vibration

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 FLUID VELOCITY – GAS PROPERTIES

 Maximum flowrate 0.5 MACH

 Air Velocity 160m/s
 Calculated in relation to the measuring tube diameter
 Flow velocity / the speed of sound in gas

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 ACCEPTABLE PRESSURE LOSS

 Low pressure gases due to high

velocity
 Fluid vapor pressure to ensure no
condensate formation

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 OPERATIONAL SAFETY

 Complete material compatibility

 Vibrating under stress
 Incompatibility causes stress corrosion
cracking
 Liquid “carry over” can occur due to failure
of gas scrubber or dryer
 Residual liquid potentially corrosive to the
tubes
 Range of wetted in 316, 904L stainless steel,
Hasteloy C, Titanium, Zirconium

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 METER UNCERTAINTIES

 Performance better than 0.5% across a

20:1 turn down
 Uncertainties for gas flow facilities
range from +/-0.3% to 0.6%.

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 POTENTIAL FLUID EFFECTS

 Fluid effects taken into account normally

 Certain tube designs sensitive to pressure
 “Bourden”effect at high pressure
 Predictable and results in a shift in the K-
factor
 Compensated for continuous pressure
 Optional pressure compensation with
external pressure transducer

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 CORIOLIS METERS IN THE NATURAL
GAS FIELD

 GPU Gasnet, Victoria, Australia

 36 meters from 6mm upto 50mm with flows <4,000
scm/hr
 High costs for removing and recalibration
 Field proving techniques using portable meters
 Metering facilities permit series flow testing and
validation

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CORIOLIS METERS IN THE NATURAL GAS
FIELD

 Five reference meters (6mm to 75mm)

 Calibrated on air and / or on natural gas
at pressure and water calibration
 The results of proving relies stability and
repeatability
 Coriolis meters “finger print” the field
meters

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 METER PROVING OF CORIOLIS METERS
 Coriolis meters rarely require field calibration
 Water calibration meets specifications on natural
gas
 Performance verification by gravimetric scales or
fixed volume tank
 Proving on natural with sonic nozzles or piston
provers
 Coriolis meters in-situ calibration
 Coriolis meters practical choice in quantifying
orifice and turbine meter

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APPLICATION OF CORIOLIS METERS FOR
NATURAL GAS

 Over 8,000 for CNG

 Verified gravimetrically to ±0.3%

 Local weights and Measures authorities

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 PRODUCTION

 90M to 10MM scfd at a 550 psig and 150 deg.F

 Factory calibration matched with multiple orifice
run to within +/-1%
 Density measurement detect periodic slight crude
carry over
 Additional 30 gas meters

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 COMPRESSION / TRANSPORTATION

 120 Coriolis meter for compressor stations

 More accurate mass fuel measurement

 Non-mechanical design

 No straight run requirements

 Immunity to extensive vibration inherent to station design

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 COMPRESSION / TRANSPORTATION

 Improved accounting gas consigned for

compression
 Vibration testing and proving against
sonic nozzles
 On-shore and off-shore gas compression
stations

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 TRANSMISSION / DISTRIBUTION
 A grid for remote region
 To reduce the metering maintenance and
proving
 Multiple orifice run costly

 Cost savings $100 K per skid for Coriolis

in place of turbine

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 TRANSMISSION / DISTRIBUTION
 Coriolis eliminated the need for skids
 No need for flow conditioning and filters

 Conversion from mass to standard

volume
 Eliminates uncertainties related to
temperature and pressure

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 CNG METER CALIBRATION

 Storage Banks (13.5 m3)

 High-precision weighing
 High pressure at 250 bar
 Flow rates up to 4500 kg/h
 Extensive instrumentation and remote operation
 Real time PC based process control and DAS
 DAS records temperatures, mass, pressures

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 CORIOLIS METER AS A SIMPLE ENERGY
METER
 Energy content of natural gas
 Estimation of energy content of the
natural gas
 Coriolis measures the mass

 Assumption of constant inert gas

composition
 Scaling the output for a fixed Btu/lbs
(kJ/kg)

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 TESTING AND APPROVAL FOR CORIOLIS
METERS
 Compressed air & natural gas, pipeline natural
gas
 Against sonic nozzles, turbine master meters
and bell provers
 Coriolis installation, application practices and
accuracy specifications
 PTB & NMI approval for coriolis metering in NIST
approved dispensers
 US (NIST), Canada, Mexico, Japan, Russia
 Argentina, S.Africa, Venezuela, Chile, Colombia

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