Dry Calibration of Ultrasonic Flowmeters with Natural · PDF fileDry Calibration of Ultrasonic...

Dry Calibration of Ultrasonic

Flowmeters with Natural Gas

up to 285 bar

Jos van der Grinten - NMi EuroLoop

Dry Calibration of

Ultrasonic Flow Meters with

Natural Gas up to 285 bar

Jos van der Grinten

Chief Metrologist, NMi EuroLoop

Contents

• Introduction

• Metering accurately at 285 bar?

• Theory

• Experimental set-up

• Results

• Conclusions

3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 3

Introduction

Pipelines

• BBL

• Northstream

• Southstream

Metering

• >> 100 bar

• USMs

• No calibration

facilities


Metering accurately at 285 bar?

Method

• Calibrate at highest available pressure (60 bar)

covering the meter’s flowrate range

• Check speed of sound (SoS)

– at zero flow conditions,

– at pressures up to the operational pressure ,

– using natural gas

• If criteria are met,

use 60 bar curve at 285 bar

expand uncertainty


Metering accurately at 285 bar?

Assumptions

• Meter curve weakly dependent on pressure

USM is real flow velocity meter

evidenced by type approval tests

• Change in path length << path length

or is compensated

• If speed of sound is correctly measured,

then flow velocity is measured correctly as well


Theory – USM principle

• If increased pressure causes no change of the

geometry, c will match theory and consequently

v will be measured correctly


L v α

revfw

fwrev

revfw

revfw

fwrev

revfw

rev

fw

TT

TTLv

TL

TLv

TT

TTLc

TL

TLc

TLvc

TLvc

)cos(2)cos(2

22

)cos(

)cos(

Theory – Speed of Sound (p, t)


-105

20

35

350.0

400.0

450.0

500.0

550.0

600.0

650.0

700.0

1

21

41

61

8110

11211

4116

118120

122124

126128

1301

Temperature [°C]

Spe

ed

of

Sou

nd

[m

/s]

Absolute Pressure [bar]

650.0-700.0

600.0-650.0

550.0-600.0

500.0-550.0

450.0-500.0

400.0-450.0

350.0-400.0

Natural Gas

Theory – Speed of Sound (p, t)


-105

20

35

300.0

350.0

400.0

450.0

500.0

550.0

600.0

650.0

1

21

41

61

8110

11211

4116

118120

122124

126128

1301

Temperature [°C]

Spe

ed

of

Sou

nd

[m

/s]


600.0-650.0

550.0-600.0

500.0-550.0

450.0-500.0

400.0-450.0

350.0-400.0

300.0-350.0

Nitrogen

Experimental set-up

• 6 x USM 16” ANSI 2500# NorSok

• Gauge pressure 0 – 350 bar at Pr point

• Barometer in control room

• Pt100 temperature transmitters (HART)

– Inside temperature

– Body temperature

– Ambient temperature

• All instruments interfaced with our CMS that logs

all transmitters

• Meter log recorded at our diagnostics computer

• Gas composition averaged during filling process


Experimental set-up

• Test pressures: 31, 151, 285 bara

• Measurands: SoS, VoG, TUSM, Tbody, Tamb, P


T

10” 10”

P

T

T

GC

T

Piston compressor

Experimental set-up – preparation


Experimental set-up


Problem solving


Criteria for acceptance

• Max deviation between measured SoS and the

SoS calculated from the gas composition:

within ± 0.3% (originally ± 0.2%)

– Equation of State both AGA-10 and GERG2008

– Average SoS

• Dispersion of SoS values between chords,

high – low or 2·s(c1..n) ≤ 0.5 m/s

• Zero flow velocity: average within ± 0.006 m/s


Results – process


6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0

100

200

300

400

500

600

700

14:00 20:00 2:00 8:00 14:00 20:00 2:00 8:00 14:00 20:00 2:00 8:00 14:00 20:00 2:00 8:00

Tem

pra

ture

[°C

]

Pre

ssu

re [b

ara]

& S

pe

ed o

f So

un

d [

m/s

]

Time [hh:mm]

Pressure Test and Dry Calibration – USM 1

Meter pressure P [bara]

SoS

SoS GERG 2008 [m/s]

Ambient t [°C]

Meter body t [°C]

Gas inside meter t [°C]

Results – SoS and theory


-2.0

-1.0

0.0

1.0

0

50

100

150

200

250

300

350

20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

SoS

rel d

iff

[%]

Pre

ssu

re [b

ara]

Time [hh:mm]

SoS and theory – Dry Calibration – USM 2


SoS rel diff GERG 2008[%]

SoS rel diff AGA-10 [%]

target ± 0.30%

Results – SoS path dispersion


-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0

50

100

150

200

250

300

350

14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00

2·s

tde

v(So

S) [

m/s

]

Pre

ssu

re [b

ara]

Time [hh:mm]

SoS path dispersion – Dry Calibration – USM 3


2*stdev Ch_SoS [m/s]

target ± 0.10%

Results – VoG at zero flow


-0.035

-0.025

-0.015

-0.005

0.005

0.015

0.025

0.035

0

50

100

150

200

250

300

350

8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00

Vo

G [

m/s

]

Pre

ssu

re [b

ara]

Time [hh:mm]

Zero Flow Test – USM 6 Master & Slave


1 Ch Slave VoG [m/s]

4 Ch Avg M VoG [m/s]

target ± 0.006 m/s

Results – uncertainty


• GERG2008 uncertainty 0.10%

• AGA-10 uncertainty 0.1% - 0.3% - 0.5%

• pressure 0.08%, temperature 0.04%

Pres-

sure

[bar a]

Temper-

ature

[°C]

# GERG

2008

Average

[%]

AGA-10

average

[%]

2·

stdev

[%]

UCMC,

GERG

[%]

Utot,

GERG

[%]

284.09 ±

0.25

14.59

± 0.10

2791 -0.27 -0.12 0.01 0.12 0.13

283.26 ±

0.46

13.29

± 0.18

13010 -0.27 -0.13 0.01 0.12 0.13

151.61 ±

0.06

12.79

± 0.05

1861 -0.15 -0.07 0.00 0.12 0.13

32.23

± 0.01

10.22

± 0.03

1831 -0.48 -0.45 0.01 0.12 0.13

AGA-10 / GERG2008 – 1 [%]


-100

1020

3040

-0.20%

-0.15%

-0.10%

-0.05%

0.00%

0.05%

0.10%

0.15%

0.20%

121

4161

81101

121141

161181

201221

241261

281301

Temperature [°C]

Spe

ed

of

Sou

nd

[m

/s]


0.15%-0.20%

0.10%-0.15%

0.05%-0.10%

0.00%-0.05%

-0.05%-0.00%

-0.10%--0.05%

-0.15%--0.10%

-0.20%--0.15%

Conclusions

• Dry calibrations

– Nitrogen generally used

– EuroLoop can also use natural gas

• Advantage of nat. gas is that dry calibrations are

performed with substantially higher SoS values:

Nat. Gas 660 m/s versus Nitrogen 470 m/s

• At 151 bar and 5°C ~ 15°C SoS is hardly

depending on temperature

• SoS calculations between AGA-10 and

GERG2008 differ at 285 bar by 0.15% and

match within their uncertainties


Thank you !


Dry Calibration of Ultrasonic Flowmeters with Natural · PDF fileDry Calibration of Ultrasonic...

Documents

Transcript of Dry Calibration of Ultrasonic Flowmeters with Natural · PDF fileDry Calibration of Ultrasonic...