A New Calibration Method for Ultrasonic Clamp-on Flowmeters

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Oliver Carter
6 years ago
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Physikalisch-Technische Bundesanstalt Braunschweig International Flow

1 A New Calibration Method for Ultrasonic Clamp-on Flowmeters Bernhard Funck and Mathias Panicke Flexim GmbH, Berlin Erkan Kublay and Rainer Engel Physikalisch-Technische Bundesanstalt Braunschweig International Flow Measurement Conference 2015: Advances and Developments in Industrial Flow Measurement 1-2 July 2015

2 The real world Requirements on the calibration: Traceability Transferability Repeatability

3 1 Calibrating Ultrasonic Clamp-on Flowmeters 2 Transducer Calibration 3 Transferability and Repeatability 4 Summary 3

4 Concept of Calibration Independent sources of Uncertainty Independent Calibration Meter formula: t V KRe A K 2 t fl Geometry Fluid mechanics Acoustics Time measurement (transmitter) Determined in the field (Option: Field calibration) Transducer calibration (Factory) Transmitter calibration (Factoy)

5 Concept of Calibration Transducer1 Transducer 2 Acoustic calibration factor pipe wall Flow Flow profile pipe wall Geometric calibration factor Fluid mechanic calibration factor

6 Contributions to the uncertainty Meter formular t V KRe A K 2 t fl Contribution Fluid mechanics Pipe geometry Acoustics Time measurement Factory Calibration Field calibration Flow profile O undisturbed Inner Diameter Transducer -- X X X X Electronics

7 1 Calibrating Ultrasonic Clamp-on Flowmeters 2 Transducer Calibration 3 Transferability and Repeatability 4 Summary 7

8 Transducer calibration x x v t vl l F Meter formula x t F v v l k A t 2t F k A v l 2t F t k A 2 x t x t x Displacement of the transducers is equivalent to Displacement of the beam

9 Transducer calibration Uncertainty of the displacement of the transducers: 1 μm. Uncertainty of the time difference measurement: 1/5000 of the signal period The total uncertainty %, depending on transducer type.

10 1 Calibrating Ultrasonic Clamp-on Flowmeters 2 Transducer Calibration 3 Transferability and Repeatability 4 Summary 10

11 Hydrodynamic test field at the PTB

12 Quantification of the Transferability V V K A v REF Re l _ DUT Path velocity Device under test Transferability High accurate reference: HTF Laser Doppler Anemometer Pipe geometry

13 Measurement section Installation area for the transducers >3D Inflow 40D Measuring section 4m Outflow 10D LDA Chamber LDA Chamber

14 14 Measurement section

15 Test matrix Parameter Range Nominal pipe diameter 50 mm 100 mm 300 mm Transducer frequency 2MHz, 4MHz 2MHz, 4MHz 1MHz, 2MHz T v C 0.5 5m/s Re 30E03 2,5E06 Flow profile Non-disturbed 15

16 rel. deviation of the acoustic calibration factor from mean[%] Results: Repeatability Relative deviation of the acoustic calibration factor from mean versus measurement error 1.0% 0.8% 0.6% 0.4% 0.2% 0.0% -0.2% -0.4% lot 1, pos+ lot 1, poslot 2, pos+ lot 2, pos % -0.8% -1.00% -0.50% 0.00% 0.50% 1.00% error [%] Acoustic calibration factor Error Average difference between the two lots 1,062% -0,18% Standard deviation 0,56% 0,22%

17 Results: Transferability

18 Results: Transferability

19 Results: Transferability

20 Uncertainty of the reference for the transferability test Diameter 50mm 100mm 300mm Uncertainty component Symbol Uncertainty contribution Uncertainty contribution Uncertainty contribution Xi ci * u (xi)/xi ci * u (xi)/xi ci * u (xi)/xi Reference flow rate u V.REF 0,010% 0,010% 0,010% Pipe outer diameter u D.o_MUT 0,331% 0,175% 0,062% Pipe thickness u w 0,331% 0,175% 0,062% Mean velocity of the LDA u v.a_lda 0,378% 1,008% 0,289% Path velocity of the LDA u v.l_lda 0,236% 0,195% 0,119% Acoustic calibration factor u K.α 0,150% 0,150% 0,150% Time measurement u r_transm 0,300% 0,300% 0,300% Combined uncertainty 0,728% 1,108% 0,467% Expanded uncertainty (k=2) U ΔV 1,457% 2,215% 0,934%

21 SUMMARY Independent transducer calibration Transducers can be replaced without losing the calibration of the transmitters. The same transmitter can be used with multiple Transducers. Repeatability Before calibration: difference of 1.06 % between the two lots. After calibration: difference reduced to 0.18%. Transferability Errors within the uncertainty estimate of the test setup at two of the three test locations. At the 300 mm pipe the error was 1.3% while the estimated expanded uncertainty of the test setup was 0.93%. The reason for this error was that the inflow conditions were not quite ideal.

22 Thank you!

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