Effects of Pressure and Temperature on
Coriolis Flow Meters
Steve Smith
Business Manager
Micro Motion Coriolis, Density & Viscosity
Agenda
Coriolis Basics
What factors affect Coriolis Accuracy?
Zero/Span Effect
Temperature Span Effect
Pressure Span Effect
Temperature Zero Effect
Combined Pressure and Temp Effect
Working Example
EU MID
Coriolis Metering Workshop
What is Coriolis?
What Does Coriolis Measure?
70 Litres 110 Litres
-10° C
65 kgs +10° C
65 kgs
Theory of Operation - Density
Density measurement is based on the natural frequency of the system including
the flow tubes and the process fluid.
– As the mass increases, the natural frequency of the system decreases.
– As the mass decreases, the natural frequency of the system increases.
Theory of Operation
Density Measurement
As the density of the process
fluid increases, the natural
frequency decreases.
As the density of the process
fluid decreases, the natural
frequency increases.
Theory of Operations – Mass Flow During a no flow condition, there is no Coriolis effect and the sine waves are in
phase with each other.
When fluid is moving through the sensor's tubes, Coriolis forces are induced
causing the flow tubes to twist in opposition to each other. The time difference
between the sine waves is measured and is called Delta-T which is directly
proportional to the mass flow rate.
Theory of Operations – Mass Flow The Flow Calibration Factor consists of 10 characters, including
two decimal points. – The first five digits are the flow calibration factor. This calibration factor,
multiplied by a given Delta-T, yields mass flow rate in grams/sec.
– The last three digits are a temperature coefficient for the sensor tube material.
This coefficient compensates for the effect of temperature on tube rigidity (%
change in rigidity per 100°C).
Three wire platinum RTD measures tube temperature on inlet side of sensor
– Accurate to +/- 1.0oC
– Available as additional process variable
Applies to liquid
and gas, and is
linear throughout
the entire range of
the meter
Theory of Operation – Volume (indirect or calculated)
Volumetric Flow is a calculated variable.
Volume can be referenced to standard temperature using the temperature input.
Coriolis meters are preferred for volume measurements.
– Low pressure drop
– Wide turndown
– High accuracy
– High degree of linearity
Density
Flow MassFlow Volume
Coriolis Sensor Geometries
All Geometries are not created equal
Design trade-offs are made for such things as;
– Flow sensitivity & turndown
– Density accuracy
– Fluid S.G. range (gas/liquid)
– Materials of construction
– Temperature effects
– Drainability and Cleanability
– Pressure limits
Micro Motion provides several geometries to meet the wide
measurement requirements of the industries and customers we serve.
Factors that Effect Meter Accuracy
Coriolis Meter Accuracy
Span:
• Affects Coriolis Tubes
• Pressure
• Temperature
Zero Effects
• Influences Sensor Coils
• Temperature
Zero v’s Span effects
0.995
0.997
0.999
1.001
1.003
1.005
1.007
1.009
1.011
0 200 400 600 800 1000 1200
Rate
MF
Note: For clarity, zero error shown
is 4X larger than MMI spec
Span Error Zero Error
Span Effects - Temperature
– As Temperature increases, Tubes Get Wobblier
Three wire platinum RTD measures tube temperature on inlet side of sensor
– Accurate to +/- 1.0oC
– Available as additional process variable
Span Effects - Temperature
Actual Flow Rate
Temperature Span Effect
Actual Flow Rate
Ind
ica
ted
Flo
w R
ate
Typical Values:
•316 SS = 4.26
•Hasteloy = 3.25
•Titanium = 5.48
This is Always a
Positive % Value
Span Effects - Pressure
Actual Flow Rate
Pressure Span Effect
Ind
ica
ted
Flo
w R
ate
Actual Flow Rate
This is Always a
Negative % Value
– As Pressure increases, Tubes Get Stiffer
Span Effects - Pressure
– As Pressure increases, Tubes Get Stiffer
Zero Effects - Temperature
Zero Effects - Temperature
0
1
2
3
4
5
6
7
8
9
10
11
1 2 3 4 5 6 7 8 9
Actual Rate
Zero Accuracy
Zero Offset
Zero Effects - Temperature
“Process temperature effect is defined as:
• For mass flow measurement, the worst-case
zero offset due to process fluid temperature
change away from the zeroing temperature.”
Combined Pressure & Temp. Effect
Influencing Factors:
Tube Shape
Wall Thickness
Tube Geometry
Materials
Twin v’s Straight Tubes
Required Density Accuracy
» Although the Combined Pressure and Temp effect is present, the effect on Mass Flow and Density measurements on Coriolis
Meters is Negligible.
Working Example
Starting point = 0.1% “Flat Spec”
• However, when flow rate is less than zero stability / 0.001:
• Accuracy = ±[(zero stability / flow rate) × 100]% of rate, and repeatability = ±[½(zero
stability / flow rate) × 100]%.
CMFHC2
• Zero Stability = 68 kg/hr
• Temperature Span = +4.25%/100degC
• Pressure Span = -0.023%/bar
• Temp Zero Effect = ±0.00025%/degC
Summary
• Zero Calibration
• Temperature Span
Affects
• Pressure Span
Affects
• Temperature Zero
Affects
Coriolis flow meters offer unrivalled potential within O&G
metering applications.
However, correct attention must be paid to
environmental compensation and correct zero
calibration procedures
MID Approvals – UK Call to action
Summary
Coriolis Basics
What factors affect Coriolis Accuracy?
Zero/Span Effect
Temperature Span Effect
Pressure Span Effect
Temperature Zero Effect
Combined Pressure and Temp Effect
Working Example
EU MID
Coriolis Metering Workshop
F-series (0,1% )
Perf
orm
ance a
nd functionalit
y
Price
H-series (0,1% )
T-series (0,15% )
H-series (0,15% )
F-series (0,2% )
R-series (0,5% )
LF-series
ELITE-series (0,1% )
ELITE-series (0,05%)
Direct
Connect
1500
1700
2500
2700
2200S
2400S
1500
filling
3500
3700
Measuring range
1 gr/hr – 2,550 T/hr
Flexible solutions for your processes
Installation Considerations
Entrained Gas Performance
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
0 250 500 750 1000 1250 1500 1750 2000 2250
Sensor
Mas
s F
low
Err
or
(%)
New ELITE
CMF300
Sensor improvements
• Sensor stability • Sensor design
Low Drive Frequency – typical 80Hz
Electronics Improvements
•Processing speed
•Optimizing the Signal processing
Maximising Efficiency with Additional Process Information
Maximising Installed Base Potential
Limited I/O? – No Problem!
Customer Challenge: Make it easy to determine the health of my meter
“We calibrate manually by taking meters out of the process, and it is a pain. It is an all-day deal and we pay £2k to 3k per meter per year for this. We can spend more than £200,000 per year, and the calibration factors
never seem to change” --- Chemical Customer
• “Can I tell if my Coriolis meter has changed?”
• “Can I detect when the meter is being coated?”
• “How often do I need to recalibrate my meter?”
Erosion Cracking Pitting Coating
Characteristics that alter meter performance
Micro Motion Smart Meter Verification Overview
Coriolis meters have no moving parts
– Expectation that meter calibration will never change
Mechanical stiffness is directly related to flow calibration factor
– Damage or degradation will affect both
Meter Verification precisely tests mechanical stiffness
– And associated electrical components
Measurement is validated – or – warning is issued
1
10
100
1000
0 20 40 60 80 100 120 140 160
Frequency
Am
plit
ud
e
D
dDrive
Frequencies