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 c v cos( ) L c v cos( ) L 2c L T fw L α T fw Trev L Trev T fw c 2 T fw Trev Trev 2v cos( ) L v L T fw L Trev Trev T fw L v 2 cos( ) T fw Trev • 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 Theory – Speed of Sound (p, t) Natural Gas 650.0 600.0 550.0 -10 61 5 41 101 121 350.0 81 Absolute Pressure [bar] 400.0 141 161 181 201 450.0 221 241 301 281 261 500.0 1 21 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 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 20 35 Speed of Sound [m/s] 700.0 Temperature [°C] 8 Theory – Speed of Sound (p, t) Nitrogen 600.0 550.0 500.0 -10 61 5 41 101 121 300.0 81 Absolute Pressure [bar] 350.0 141 161 181 201 400.0 221 241 301 281 261 450.0 1 21 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 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 20 35 Speed of Sound [m/s] 650.0 Temperature [°C] 9 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 GC 10” 10” T P T T Piston compressor T • Test pressures: 31, 151, 285 bara • Measurands: SoS, VoG, TUSM, Tbody, Tamb, P 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 11 Experimental set-up – preparation 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 12 Experimental set-up 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 13 Problem solving 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 14 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 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 15 Results – process Pressure Test and Dry Calibration – USM 1 600 500 20.0 Meter pressure P [bara] SoS SoS GERG 2008 [m/s] Ambient t [°C] Meter body t [°C] Gas inside meter t [°C] 18.0 16.0 400 14.0 300 12.0 200 10.0 100 8.0 0 6.0 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 Time [hh:mm] 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 16 Temprature [°C] Pressure [bara] & Speed of Sound [m/s] 700 Results – SoS and theory SoS and theory – Dry Calibration – USM 2 350 300 1.0 200 0.0 150 Meter pressure P [bara] 100 -1.0 SoS rel diff GERG 2008[%] SoS rel diff AGA-10 [%] 50 0 20:00 22:00 target ± 0.30% 0:00 2:00 4:00 6:00 8:00 -2.0 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time [hh:mm] 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 17 SoS rel diff [%] Pressure [bara] 250 Results – SoS path dispersion SoS path dispersion – Dry Calibration – USM 3 Meter pressure P [bara] 6.0 2*stdev Ch_SoS [m/s] Pressure [bara] 300 target ± 0.10% 5.0 250 4.0 200 3.0 150 2.0 100 1.0 50 0.0 0 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 Time [hh:mm] 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 18 6:00 8:00 -1.0 10:00 2·stdev(SoS) [m/s] 350 Results – VoG at zero flow Zero Flow Test – USM 6 Master & Slave 350 Meter pressure P [bara] 0.035 1 Ch Slave VoG [m/s] Pressure [bara] target ± 0.006 m/s 0.025 250 0.015 200 0.005 150 -0.005 100 -0.015 50 -0.025 0 -0.035 4:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time [hh:mm] 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 19 0:00 2:00 VoG [m/s] 4 Ch Avg M VoG [m/s] 300 Results – uncertainty Pressure [bar a] 284.09 ± 0.25 283.26 ± 0.46 151.61 ± 0.06 32.23 ± 0.01 Temperature [°C] 14.59 ± 0.10 13.29 ± 0.18 12.79 ± 0.05 10.22 ± 0.03 # GERG 2008 Average [%] 2791 -0.27 AGA-10 average [%] 2· stdev [%] UCMC, -0.12 0.01 0.12 0.13 GERG [%] Utot, GERG [%] 13010 -0.27 -0.13 0.01 0.12 0.13 1861 -0.15 -0.07 0.00 0.12 0.13 1831 -0.48 -0.45 0.01 0.12 0.13 • GERG2008 uncertainty 0.10% • AGA-10 uncertainty 0.1% - 0.3% - 0.5% • pressure 0.08%, temperature 0.04% 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 20 AGA-10 / GERG2008 – 1 [%] 0.20% 0.10% 0.05% 0.00% -0.05% -0.10% -0.15% -0.20% -10 0 10 20 30 Temperature [°C] 301 40 281 261 241 221 201 181 161 141 121 3rd European Flow Measurement Workshop, Noordwijk, 17 - 19 March 2015 101 81 61 41 21 1 Absolute Pressure [bar] 21 Speed of Sound [m/s] 0.15% 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