New Calibration Method for Gas Flow Meters
TQM-5134-1
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Introduction
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Intermediate Checks Between Two Flow Cells of a Piston Prover
Reference Standard
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Calibration Method – Split Method
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Verification and Commissioning of the 100 l/min Flow Cell -
Validation of the Split Method
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Conclusion
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The NMISA Gas Flow laboratory performed intermediate checks on
their piston prover gas flow reference standard (ML-800) using a
series method.
•
When the flow rate was above 25 l/min, an “over-pressure” message
was displayed by the flow cell connected upstream.
•
This indicated that the pressure to the reference standard was higher
than its limits, that is, it exceeded 1,244 kPa above atmosphere.
•
The ML-800 gas flow reference standard is designed to be used at
atmospheric pressures only.
•
A new calibration method, Split Method, was implemented and
validated to have both reference standards venting to atmosphere.
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Intermediate checks were performed between two gas flow reference
standards flow cells, ML-800-44 (50 l/min) and ML-800-75 (100 l/min).
•
This was done to maintain confidence in the calibration of the 50 l/min
flow cell and to commission the 100 l/min flow cell.
TQM-5134-1
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Figure 1: Showing the in line (series) calibration method
for two flow cells
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The results were to be used to verify that the 100 l/min reference
standard was not damaged during shipping from manufacturer.
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Table 1: Measurement results for intermediate checks between
the 50 l/min and 100 l/min flow cells using series method.
•
The Split Method calibration setup positions the reference standard
and the UUT in a parallel configuration.
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This ensures that both the UUT and reference standard vent to
atmosphere.
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Back-pressure is then eliminated.
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Figure 2: Split Method calibration setup. The
arrows show the direction of gas flow.
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Any flow perturbation due to the up/down movement of the reference
standard’s piston is avoided.
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The Split Method was validated using measurement results for the
verification and commissioning of the 100 l/min flow cell.
•
The Split Method was validated against a series calibration method
using a laminar flow system as the reference standard.
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The 100 l/min flow cell was calibrated against the 50 l/min flow cell
using the Split Method.
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It was then calibrated against the laminar flow system using a
validated Series method.
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The results are discussed in the next section.
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Table 2: Shows summarized Split Method validation results.
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The normalized error values (E
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) between the Split Method and the
Series method were all less than or equal to 1.
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The results are also shown graphically in figure 3.
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The graphs shows overlapping uncertainties.
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This indicates satisfactory performance of the Split Method.
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Raw validation data is presented in the full paper.
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Figure 3: Graphical presentation of the Split method
validation results.
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The measurements indicate good agreement between the 50 l/min
and 100 l/min flow cells.
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Using the Split Method, gas flow measurements up to 50 l/min can
be performed without any over-pressure error.
•
This was because the reference standard and UUT were both
venting to atmosphere eliminating any flow restriction which would
cause back pressure.
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The ½”-¼” reducer created flow restriction which resulted in back-
pressure in the flow cell upstream.
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The Split Method has the two flow cells venting to atmosphere,
hence the back-pressure was eliminated.
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Thus, flow measurements up to 50 l/min could be performed.
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The Split Method will also be validated to calibrate other types of
instruments such as mass flow meters.
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Thank You!
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TQM-5134-1
Implementation of a new Split Method calibration to resolve back-pressure effects on gas flow meters used at atmospheric pressures. Intermediate checks, validation, and commissioning process explained with results in the gas flow laboratory. Details on the calibration setup and verification between flow cells.
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Presentation Transcript
Implementation of a New Calibration Method to Resolve Back-Pressure Effects on the Calibration of Gas Flow Meters By : M. Dlamini D. Jonker E. P. Tarnow TQM-5134-1
Overview Introduction Intermediate Checks Between Two Flow Cells of a Piston Prover Reference Standard Calibration Method Split Method Verification and Commissioning of the 100 l/min Flow Cell - Validation of the Split Method Conclusion TQM-5134-1
Introduction The NMISA Gas Flow laboratory performed intermediate checks on their piston prover gas flow reference standard (ML-800) using a series method. When the flow rate was above 25 l/min, an over-pressure message was displayed by the flow cell connected upstream. This indicated that the pressure to the reference standard was higher than its limits, that is, it exceeded 1,244 kPa above atmosphere. The ML-800 gas flow reference standard is designed to be used at atmospheric pressures only. A new calibration method, Split Method, was implemented and validated to have both reference standards venting to atmosphere. TQM-5134-1
Intermediate Checks Between Two Flow Cells of the Piston Prover Reference Standard Intermediate checks were performed between two gas flow reference standards flow cells, ML-800-44 (50 l/min) and ML-800-75 (100 l/min). This was done to maintain confidence in the calibration of the 50 l/min flow cell and to commission the 100 l/min flow cell. Figure 1: Showing the in line (series) calibration method for two flow cells TQM-5134-1
Intermediate Checks Between Two Flow Cells of the Piston Prover Reference Standard The results were to be used to verify that the 100 l/min reference standard was not damaged during shipping from manufacturer. Table 1: Measurement results for intermediate checks between the 50 l/min and 100 l/min flow cells using series method. ML-800-44 (ml/min) ML-800-75 (ml/min) Correction (ml/min) Expanded Unc. (ml/min) 5 017,4 5 034,3 -17,0 8,1 9 981,4 10 006 -24 17 15 004 14 992 12 23 20 045 20 032 13 32 25 087 25 073 15 42 TQM-5134-1
Calibration Method Split Method The Split Method calibration setup positions the reference standard and the UUT in a parallel configuration. This ensures that both the UUT and reference standard vent to atmosphere. Back-pressure is then eliminated. Figure 2: Split Method calibration setup. The arrows show the direction of gas flow. TQM-5134-1
Calibration Method Split Method Any flow perturbation due to the up/down movement of the reference standard s piston is avoided. The Split Method was validated using measurement results for the verification and commissioning of the 100 l/min flow cell. The Split Method was validated against a series calibration method using a laminar flow system as the reference standard. The 100 l/min flow cell was calibrated against the 50 l/min flow cell using the Split Method. It was then calibrated against the laminar flow system using a validated Series method. The results are discussed in the next section. TQM-5134-1
Verification and Commissioning of the 100 l/min Flow Cell Split Method Correction (ml/min) (ml/min) 5 000 -25,8 -27,5 10 000 -39 -42 15 000 38 -8 20 000 29 -10 25 000 18 -58 30 000 17 -106 35 000 4 -109 40 000 -13 -133 45 000 -10 -167 50 000 -9 -173 Table 2: Shows summarized Split Method validation results. Series Method Correction Split Method Exp. Unc. (ml/min) 105 105 112 109 110 116 117 121 132 132 Series Method Exp. Unc. (ml/min) 11,7 24 34 46 58 72 81 92 102 112 Nominal Flow (ml/min) Calculated |En| values 0,02 0,03 0,39 0,33 0,61 0,90 0,79 0,78 0,94 0,95 TQM-5134-1
Verification and Commissioning of the 100 l/min Flow Cell The normalized error values (En) between the Split Method and the Series method were all less than or equal to 1. The results are also shown graphically in figure 3. The graphs shows overlapping uncertainties. This indicates satisfactory performance of the Split Method. Raw validation data is presented in the full paper. TQM-5134-1
Verification and Commissioning of the 100 l/min Flow Cell Calibration of the 100 l/min flow cell using the Split Method and using the Series Method. 250.00 200.00 150.00 Correction (ml/min) 100.00 50.00 0.00 Series -50.00 Split -100.00 -150.00 -200.00 -250.00 -300.00 0 10 20 30 40 50 60 Nominal Flow Rate ( 1000 ml/min) Figure 3: Graphical presentation of the Split method validation results. TQM-5134-1
Verification and Commissioning of the 100 l/min Flow Cell The measurements indicate good agreement between the 50 l/min and 100 l/min flow cells. Using the Split Method, gas flow measurements up to 50 l/min can be performed without any over-pressure error. This was because the reference standard and UUT were both venting to atmosphere eliminating any flow restriction which would cause back pressure. TQM-5134-1
Conclusion The - reducer created flow restriction which resulted in back- pressure in the flow cell upstream. The Split Method has the two flow cells venting to atmosphere, hence the back-pressure was eliminated. Thus, flow measurements up to 50 l/min could be performed. The Split Method will also be validated to calibrate other types of instruments such as mass flow meters. TQM-5134-1
The End Thank You! TQM-5134-1
