Regulations for custody transfer measurements: meeting the needs? Focus on liquid flow measurement systems/applications

Transcription

1 Regulations for custody transfer measurements: meeting the needs? Focus on liquid flow measurement systems/applications

2 Contents - Requirements in OIML publications - Uncertainty effects on trade - Back to the basics - Metrological design of flow applications - Examples how things can go wrong while you think you have done things perfectect - Conclusion / considerations - Answer to the question Regulations for custody transfer measurements: meeting the needs? P 2

3 Requirements in OIML publications - OIML R49 (1 to 3) Water meters - OIML R81 Cryogenic meters - OIML R75 (1 to 3) Heat meter - OIML R117-1 Dynamic measuring system for liquids other then water - meter, transfer point and hydraulic path with particular characteristics - gas elimination device, filter, pump and correction device Lets focus on accuracy and repeatability P 3

4 OIML R117-1 Accuracy Classes (1) P 4

5 OIML R117-1 Accuracy Classes (2) Repeatability 2/5 of the value in line A. Measurement uncertainty for a verification1/3 of the value in line A or B depending on test and 1/5 for type approval. P 5

6 Uncertainty effects on trade, example class 0.5 Truck Price 1 tank 6x p/d 5 days 52 weeks Class 0.5 [ /L] /] L [ ] [] [ ] [] [ ] [] [ ] [] Petrol 1, Diesel 1, Pipeline application: class 0.3 however non stop flow! Do re-calibrations, better flow meters, other equipment help to reduce these effects? P 6

7 Back to the basics - The measurement proces is leading, not the instruments (we buy or sell m 3 and kg) - Instruments need to be selected based on the measurement proces - Study the physics behind measurement proces - Best design: on basis of this study and written standards (selection instruments) - Perform a Metrological review and calculate the expected measurement uncertainty (redesign if needed) P 7

8 Metrological design of flow applications Effects of surrounding environment on reliability, comparability of a measuring system in operation Piping (flow profile) Fluid properties Pressure Temperature Human errors Design errors Air in liquid Liquid in air P 8 Vibrations Pulsations EMC Leaking valves Environmental conditions Etc.

9 Impacting parameters on your measurement (uncertainty) proces - Procedures (people and automated processes) - Instruments (calibration, turn down ratio, offset, span, signal type, etc...) - Fluid properties (viscosity, density, composition etc..) - Flow conditions and design on application (flow profile, high and low temperatures, pressures, pulsations, flashing, cavitation etc..) - Sampler systems and analysing instruments - Flow computers and automatic ti correction devices (correct equations, etc..)

10 Examples - Flow meter calibrated in a laboratory and operated in slightly different circumstances - I/O input for flow computer - Conversions to reference conditions - Flow cut off and zero offset electronic flow meters P 10

11 Example BIPM key-comparison CCM.FF-K2 Hydrocarbon flow Institute (NMI) NEL SP CMI VSL (NMI-VSL) Force CMS NMI-J CENAM MC Country United Kingdom (pilot) Sweden Czech Republic The Netherlands Denmark Chinese Taipei Japan Mexico Canada May July 2007

12 CCM.FF-K2 package

13 Procedure of CCM.FF-K2 - Flow meters - PD and turbine meter (4 & 3 ) measurements at the same time - Viscosity range 1 to 10 mm 2 /s (cst) Used viscosities between 1.51 to 4.32 mpa/s - Test with and without straightener - Flow rates between 5 and 30 l/s ( gal/min [US]) - One cardinal point at Reynolds

14 PD meter, Configuration 1 (1)

15 PD meter, Configuration 1 (2)

16 Turbine meter, Configuration 1

17 I/O input example Flow computers and other issues - Correct all input and output I/O s that influence the result of the measurement - Enough correction points for the I/O s - Use the correct Volume Correction Factor table selected (what is the uncertainty of the VCF for your liquid?) - Rounding of measurements - Flow cut off on electronic flow meters! See example

18 Meter Factor correction +0,30 +0,25 +0,20 +0,15 +0,10 Measurement error [%] +0,05 +0,00 0,05 0,10 0,15 0,20 0,25 0, Flow rate [%]

19 Density (VCF) 0,10 Difference between calculated density and reference density 0,08 0,06 0,04 Density error [%] 0,02 0,00 0,02 0,04 0,06 0,08 0, Temperature [ C]

20 Flow cut off and zero offset - OIML R117-1: - Flow cut off maximum 20% Q min = 2% Q max (1:10) - Zero offset maximum 0.1% at Q min (line C) - Zero offset can drift in time Zero needs to be checked on a regular basis. If a low flow cut off is set: a big positive zero drift can be detected.

21 Live zero monitoring +0,03 Zero check IKS SKID after tests 17 th March 2011 Flow rate [kg/min] Mass Total [kg] +0,02 flow rate [kg/min] In ndicated mass [kg] Indicated +0,01 +0,00 0,01 0,02 Zero specification = 0, kg/min 0, Time [s] Zero spec conform OIML R117-1 equals 0.1% Q min +/ kg/min

22 What do you need to do for a good measurement? - During the design of an application think deeply about metrology (uncertainty sources) and specify what accuracies and uncertainties need to be achieved - Use proven procedures (use standards) - Train operators in good measurement practice (Metrology college) - Determine the system uncertainty and evaluate it on a regular basis - Audit the procedures on a regular basis

23 Conclusion / considerations - Metrology is an art, and can be learned - Take every input parameter seriously (sensitivity study) - Perform a metrological design review. (Even existing applications) - Don t forget to evaluate the measurement accuracy and uncertainty of the application P 23

24 Regulations for custody transfer measurements: meeting the needs? Depends highly on measurement system / application and the intrinsic value of the transported product!

25 VSL PO Box AR Delft The Netherlands T F E [email protected] I Erik Smits E [email protected]