LNG measurement uncertainty,
review and progressKianoosh Hadidi
LNG workshop, Aberdeen 25th Oktober 2018
Workshop and Training 2018
The content of this presentation has been taken from the work carriedout by the partners in EMPR JRP, ENG03 LNG & ENG60 LNG II.
The related sources have been mentioned at the footnotes.
introduction
Start point ENG03 2009: Real estimation of measurement uncertainty of LNG energy, 1% Equivalent economic value of a reduction of 0.5 % in the energy
uncertainty was predeicted to be 150M€/year
𝐸 = 𝑉𝐿𝑁𝐺 ∙ 𝐷𝐿𝑁𝐺 ∙ 𝐺𝐶𝑉𝐿𝑁𝐺 + 𝐸𝐺𝐴𝑆 𝐷𝐼𝑆𝑃𝐿𝐴𝐶𝐸𝐷 ± 𝐸𝐺𝐴𝑆 𝑡𝑜 𝐸𝑅
These values can be either agreed on a certain value or determind, negligablecontrinution in many cases
The main contribution to theenergy uncertainty
MassLNG
The energy content in the tranfered LNG
LNG performance: Methane Number, an indication of theknocking behavier of a LNG
These two quantities have direct economic impact on LNG trade
introduction
Traceability
Development of calibration standards
Produce Reference data
Uncertainty evaluation
Measurement function
Clear estimation of the uncertainty sources
Uncertainty budget
Modification and developelment
New measurement methods/devices
Calculation methods
Uncertaintyreduction
Content
Mass flow measurement
Small scale mass flow standard
Volume flow measurement
Uncertainty evaluation of tank gauging systems
(LDV) based standard, and mid scale flowmeter calibration standard
Density measurement/calculations
State-of-the-art primary density standard
Development of a speed of sound (SOS) sensor
Development of a new fandamental equation of state
Gas calorific value, model calculation and uncertainty estimation
Energy uncertainty budget in large scales
The effect of small composition variation on the uncertainty of the LNG density and calorific value
The effect of temperature changes on the uncertainty of the LNG density
Methane number
Mass flow measurementSmall scale mass flow standard
A primary LNG mass flow standard at Rotterdam for small scale test and calibration facility Based onweighing method
Start point in development traceability
Measurement model of the reference mass
𝜑𝑀 𝑢𝑇 =𝑚𝑀𝑢𝑇 −𝑚𝑟𝑒𝑓
𝑚𝑟𝑒𝑓× 100
𝑚𝑟𝑒𝑓 = ∆𝑚𝑠𝑐𝑎𝑙𝑒 +𝑚𝑣𝑎𝑝𝑜𝑢𝑟 + 𝐶𝑖𝑛𝑐𝑙𝑖𝑛𝑎𝑡𝑖𝑜𝑛 + 𝐶𝑙𝑖𝑛𝑒𝑝𝑎𝑐𝑘
𝑚𝑣𝑎𝑝𝑜𝑢𝑟= total vapour mass flowing out of the weighing tank during calibration time window
∆𝑚𝑠𝑐𝑎𝑙𝑒 = accumulated cryogenic liquid in the weighing tank during the test time window
𝐶𝑙𝑖𝑛𝑒𝑝𝑎𝑐𝑘= correction due to change in trapped liquid mass between MuT and weighing tank,
𝐶𝑖𝑛𝑐𝑙𝑖𝑛𝑎𝑡𝑖𝑜𝑛= correction due to non-constantinclination of the calance
Results of the evaluation and preliminary validation of a primary LNG mass flow standard Metrologia 51 (2014) 539–551 doi:10.1088/0026-1394/51/5/539
Mass flow measurementSmall scale mass flow standard
The targeted uncertainty of the standard, 0.05%
The reached value of uncertainty 0.12% - 0.15%,
The main contributions to the irreproducibility are related to nonreversible parasitic forces in the weighing system
Potential improvement to reduce the CMC down to 0.1%
Results of the evaluation and preliminary validation of a primary LNG mass flow standard Metrologia51 (2014) 539–551 doi:10.1088/0026-1394/51/5/539
Volume flow measurement
Uncertainty evaluation of tank gauging systems
Ship tank volume measurement model.
Applicable for Membrane tank and a Moss tank
This work was fully in accordance with GUM and included real shipment data
Model measurement function
𝑉 = 𝑉𝑡𝑎𝑏𝑙𝑒 + 𝑐𝑉 𝐶𝑡𝑎𝑛𝑘,𝑡 𝑇 𝐶𝑡𝑎𝑛𝑘,𝑝 𝑝∆𝑉𝑇𝐴𝐵𝐿𝐸
∆ℎℎ − 𝑇𝑟𝑢𝑛𝑐(ℎ)
h = ℎ𝑖𝑛𝑑 𝐶𝑔𝑎𝑢𝑔𝑒,𝑇 𝑇𝑔𝑎𝑢𝑔𝑒 𝐶𝑔𝑎𝑢𝑔𝑒,𝑝 𝑝𝑔𝑎𝑢𝑔𝑒 + ∆ℎ𝑡𝑟𝑖𝑚 + ∆ℎ𝑙𝑖𝑠𝑡 + ∆ℎ𝜌 +
∆ℎ𝑐𝑜𝑚𝑝 + ∆ℎ𝑐𝑎𝑙 + ∆ℎ𝑑𝑟𝑖𝑓𝑡
Trim expressed in metres or fractions of a metre, according to the difference in bow and stern drafts
List represented by the angle α in degrees to port. In this illustrative case, the correction will be negative
Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/
Moss type Membrane type
Volume flow measurementUncertainty evaluation of tank gauging systems
An overview of relevant input quantities is given. Red color indicates that they may significantly influence the measurement of transferred volume.
Tank
Calibration
Drift/stabilit
Resolution
Temp. dim. structure
Hydrostaticpressure
Sagging/ Hogging
Temp. sensors
Inclinometer
Calibration
Drift/stabilit
Resolution
Disper. in readings
Sagging/ Hogging
Pressure gauge
CalibrationDrift
Float level gauge
Tape temp.
Liquid densityBoyancy
Calibration Location
Drift
Disper. in readings
Calibration
Drift/stabilit
Disper. in readings
Radar level gauge
Calibration
Mount. position
Temp.
Drift
Disper. readings
Surface detection
Measurand Value Uncertainty
Distribution
Standard uncertainty
Rel. Uncertaint
ySensitivity Contributio
n
hind,stop [m] 4,000 0,0075 normal 0,00 0,09 % 1 0,0038Dhcal [m] 0,000 0,002 normal 0,00 NA 1 0,0010Dhdrift [m] 0,000 0,01 normal 0,01 NA 1 0,0050
Dhtrim,stop[m] -0,009 0,000 rectangular 0,00 0,10 % 1 0,0000Trim [m] 0,033 0,01 rectangular 0,01 15,38 % -0,038 -0,0002
cTrim,loc,cal [m] 0,200 0,1 normal 0,05 25,00 % -0,038 -0,0019Dhlist,stop[m] -0,013 0,002 rectangular 0,00 -7,50 % 1 0,0010
List [°] 0,019 0,01 rectangular 0,01 26,32 % -0,007 0,0000cList,loc,cal [m] 2,000 0,5 standard 0,50 25,00 % -0,007 -0,0033Ttank,start [°C] -150,000 5 rectangular 2,50 -1,67 % 4,00E-06 0,0000Tref,tank [°C] -160,000 2 standard 2,00 -1,25 % -4,00E-06 0,0000
Tgauge,start [°C] -130,000 5 standard 5,00 -3,85 % -4,00E-06 0,0000Tref,gauge [°C] 20,000 0,5 standard 0,50 2,50 % 4,00E-06 0,0000
a 1,000E-06 standard
0,000,00 % 40 0,0000
b 1,000E-06 standard
0,000,00 % -600 0,0000
hstop 3,978 uh,empty 0,0075
Uh,empty 0,0149
Uh,empty* 0,38 %
Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/
Volume flow measurementUncertainty evaluation of tank gauging systems
Uncertainty budget of Moss type tank
Volume measurementUncertainty evaluation of tank gauging systems
• 𝐔𝑽=0.21%, GIIGL third edition 2010
• 𝐔𝑽=0.20 % to 0.55 % (k = 2) GIIGL fifth edition 2017
Measurand Value Uncertainty Distribution Standard uncertainty
Rel. st. uncertainty Sensitivity Contributi
onVtable (Trunc(hstart)) 34000 70,00 normal 35,000 0,10 % 1 35,00
hstart 22,84943 0,03774 standard 0,03774 0,17 % -1273,062204 -48,05DVSaggingHogging,start 0,000 70,000 rectangular 35,000 NA 1 35,00DVHydrostatic,start 0,000 70,000 rectangular 35,000 NA 1 35,00DVTable,drift,start 0,000 0,000 rectangular 0,000 NA 1 0,00
rectangular 0,000 NA 0,00Vtable (Trunc(hstop)) 1600 3,20 rectangular 1,600 0,10 % 1 1,60
hstop 0,15000 0,00786 standard 0,00786 5,24 % -19,05461974 -0,15DVSaggingHogging,stop 0,000 3,500 rectangular 1,750 NA 1 1,75DVHydrostatic,stop 0,000 3,500 rectangular 1,750 NA 1 1,75DVTable,drift,stop 0,000 0,800 rectangular 0,400 NA 1 0,4Ttank,start (°C) 20 20,0 rectangular 10,000 50,00 % 1,1E+00 11,22Ttank.stop (°C) 20 20,0 rectangular 10,00 50,00 % 5,3E-02 0,53Ttank,ref (°C) 20,00 2 rectangular 1,00 5,00 % -1,1E+00 -1,12
a 1,10E-05 1,1E-06 rectangular 0,00 5,00 % 0 0,0Vtank unloaded 33242,13 uVloaded 87.97
UV,loaded 175.95
UV,loaded* 0.53%
Evaluation uncertainty in transferred LNG, https://lngmetrology.info/publications/project-reports/
Uncertainty budget of membrane type tank
• Larger than twice the uncertainty mentioned in third edition of GIIGNL 2010
• Better agreement in GIIGNL 2017
Volume flow measurement(LDV) based standard, and mid-scale flowmeter calibration standard
Uncertainty budget flow rate measurements in LNG by Laser Doppler Velocimetry https://lngmetrology.info/publications/project-reports/
A new Laser Doppler Velocimetry (LDV) based standard
Mid-scale flow meter calibration has been built at Rotherdam
It is presently under testing
The master flow meter calibrated based on weighing method in the first LNG project
When operational this facility will enabletreacible calibration with an establisheduncertainty
Developed in ENG03 LNG and ENG60 LNG II
Further modification in LNG III to be validated in croyogrnic canditions and defined as primary reerence standard for LNGstandard
LDV standard can be a great support to cross valide this novel and traceable calibration standards facility
Measurement function:
Uncertainty budget flow rate measurements in, LNG by Laser Doppler Velocimetry https://lngmetrology.info/publications/project-reports/
Volume flow measurement(LDV) based standard, and mid-scale flowmeter calibration standard
𝑄𝑣 =𝑣𝑎𝑥𝑖𝑠 ∙ 𝜋 ∙ 𝑑
2
4(𝑎 + 𝑏 ∙ 𝑙𝑛(𝜌 ∙ 𝑣𝑎𝑥𝑖𝑠∙ 𝑑
𝜇 + 𝜖)
𝑄𝑣 Volumetric flowrate obtained from the LDV system
𝑣𝑎𝑥𝑖𝑠 Measured axial velocity using the LDV system
d Internal diameter of the LDV convergent throat
𝑎 Intercept of the model function
b Slope of the model function
𝜌 Density of LNG at local conditions of pressure and temperature
𝜇 Viscosity of LNG at local conditions of pressure and
𝜖 Model function error
A full uncertainty budget has been defined for LNG measurements. Field data was not acceible to apply. A randomly measurement data of liquid nitrogen at laboratory conditions shows a relative uncertainty of 0.63%.
A new Laser Doppler Velocimetry (LDV) based standard
Density measurementState-of-the-art primary density standard
Results of the LNG density measurements including uncertainty, https://lngmetrology.info/publications/project-reports/
Density measurement Single-Sinker Densimeter for cryogenic liquid mixtures
A special single-sinker densimeter
T-range: 90 K to 300 K
p-range: 0.05 MPa to 12 MPa
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