Calibration of Pipe Provers in the field

Transcription

1 Calibration of Pipe Provers in the field Erik Smits, Senior Metrologist Liquid Flow & Volume at VSL March 30 th 2016 All pictures have been removed for the pdf version!

2 Content - Where and when are pipe provers used? - Methods to calibrate pipe provers - Measurement traceability (SI and/or USC) - What uncertainty is achievable? - Metering system accuracies and uncertainties - Water draw method vs master meter method - Some errors due to procedures - Conclusions

3 Where and when are pipe provers used? - Initial (and re-) calibration and verification of flow meters - At flow meter manufacturing site (calibration capabilities preferred to be ISO/IEC17025 accredited) - In flow calibration facility of a 3rd party. A National Metrology Institute with CIPM MRA (e.g. VSL), an ISO/IEC17025 accredited company or a non accredited company - Field proving (calibration) of flow meters in a metering system. Fixed and mobile units. Calibration at real conditions

4 Methods to calibrate pipe provers - Gravimetric method API MPMS (2012) - Water draw method API MPMS Master Meter method API MPMS Diameter and length measurements What is an acceptable calibration method? What are the advantage and disadvantage of the different calibration methods?

5 Measurement traceability SI measurement units or USC measurement units by conversion

6 What uncertainty is achievable? - Water draw method API MPMS % to 0.05% in base (reference) volume - Master Meter method API MPMS % to 0.07% in base (reference) volume Measurement uncertainty for a pipe prover is not just the API range repeatability! What uncertainty is requested for a metering system?

7 Metering system accuracies and uncertainties (1)

8 Metering system accuracies and uncertainties (2) - Design (flow profile, upstream pipes etc..) - Fluid properties (viscosity, density, temperature, pressure etc..) - Electrical connections (RTD, transmitters, flow computer etc..) - Calculations - Use of standards (for example incorrect fluid property data made for general fluids) - Etc

9 Metering system accuracies and uncertainties (3) Meter Factor vs Pipe Prover API MPMS section

10 Metering system accuracies and uncertainties (4) Pipe Prover calibration uncertainty Stability of Pipe Prover calibration Flow meter calibration Stability of flow meter Design errors Stability due to changing conditions Other Measurement uncertainty When the measurement uncertainty for the metering system is large there is no need for a pipe prover calibration with low measurement uncertainty Not real measurement data!

11 Metering system accuracies and uncertainties (5) When the impact is small one can select the calibration method that suits the location of the pipe prover best. (provided that the service company executing the calibration can perform both methods!) What are the advantages of the different methods?

12 Water draw method vs Master meter method (1) Water draw method: - Method is described in API MPMS (calculation in ) - Method with possibly the lowest measurement uncertainty - Traceability direct to test measures (proving tanks) however, always at very low flow rate! - Pipe prover needs to be cleaned before filling it with water - A solid transfer point needed - Only one pair of detectors per calibration run

13 Water draw method vs Master meter method (2)

14 Water draw method vs Master meter method (3) Master meter method: - Method is described in API MPMS (calculation in ) - Traceability is indirect via a master meter. Directly before and after the calibration runs the master meter is calibrated with a master prover or proving tank - The pipe prover does not need to be cleaned in when the liquid of the metering system can be used (big advantage) - Calibration is done by counting pulses between detectors - More pairs of detectors can be calibrated per run - Repeatability requirements for runs, for calibration results of master meter before and after runs etc

15 Water draw method vs Master meter method (4)

16 Water draw method vs Master meter method (5)

17 Some errors due to procedures - Stopping the sphere just behind the detector will result in an incorrect temperature measurement in the pipe prover - Using grease on the sphere only to produce smooth movement of the sphere through the pipe. Not to fill up holes, scratches and other defects on the sphere or the pipe wall - Make sure the calibration unit is as close as possible to the pipe prover. The connection can cause all kinds of challenges

18 Conclusions When the required measurement uncertainty of the metering system is medium to high there is no need for a pipe prover calibration with low measurement uncertainty In the field choose a calibration method that meets your needs not of the needs of the service provider

19 VSL PO Box AR Delft The Netherlands T F E I info@vsl.nl Erik Smits E fsmits@vsl.nl Erik Smits: VSL group: VSL Fluid Flow Metrology group: