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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 4
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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 5
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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 6
Theory – USM principle
• If increased pressure causes no change of the
geometry, c will match theory and consequently
v will be measured correctly
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 7
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)
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 8
-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)
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 9
-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]
Absolute Pressure [bar]
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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 10
Experimental set-up
• Test pressures: 31, 151, 285 bara
• Measurands: SoS, VoG, TUSM, Tbody, Tamb, P
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T
10” 10”
P
T
T
GC
T
Piston compressor
Experimental set-up – preparation
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Experimental set-up
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Problem solving
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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
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Results – process
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 16
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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 17
-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
Meter pressure P [bara]
SoS rel diff GERG 2008[%]
SoS rel diff AGA-10 [%]
target ± 0.30%
Results – SoS path dispersion
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 18
-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
Meter pressure P [bara]
2*stdev Ch_SoS [m/s]
target ± 0.10%
Results – VoG at zero flow
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 19
-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
Meter pressure P [bara]
1 Ch Slave VoG [m/s]
4 Ch Avg M VoG [m/s]
target ± 0.006 m/s
Results – uncertainty
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 20
• 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 [%]
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 21
-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]
Absolute Pressure [bar]
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
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 22
Thank you !
3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 23