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

http://www.swri.org/default.htm

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