Instrproving Coriolis for Custody

Proving Coriolis Flowmeters

October 1998

Proving Coriolis Flowmeters

Copyright 1998, Micro Motion, Inc. All rights reserved.

Micro Motion, ELITE and ProLink are registered trademarks, and ALTUS is a trademark of Micro Motion, Inc., Boulder, Colorado. Rosemount and SMART FAMILY are registered trademarks of Rosemount, Inc., Eden Prairie, Minnesota. HART is a registered trademark of the HART Communication Foundation, Austin, Texas. Modbus is a registered trademark of Modicon, Inc., North Andover, Massachusetts. Microsoft and Windows are registered trademarks of Microsoft Corp., Redmond, Washington. Intel is a registered trademark of Intel Corporation, Santa Clara, California. Hastelloy is a registered trademark of Haynes International, Inc., Kokomo Indiana. Minigrabber is a registered trademark of ITT Corp., New York, New York.

Foreward This manual was published primarily to support the application of Micro Motion Coriolis flowmeters used in custody transfer service, where the meters are proved by common proving methods. This is a comprehensive manual, in that it can be used for training those people who have minimal knowledge of Coriolis meters, and those people who know very little about proving techniques in general. For those experienced with the application of Coriolis flowmeters, or those experienced at proving other types of flowmeters, the manual has been designed in brief sections that can be referred to quickly and completely. It is not necessary to read this entire book to prove a meter.

For example: If an experienced, conventional prover operator wants to prove a Micro Motion meter for the first time, he can turn to Section 8.3 and use the proving form in Appendix A. If an instrumentation engineer is designing a Coriolis meter run, he can refer to the information in Chapters 5 and 6. No need to read the entire manual.

It is hoped that this proving manual will help anyone who is involved in the application of Micro Motion meters that are being proved. For further assistance, please call the Micro Motion Customer Service Department:

In the U.S.A., phone 1-800-522-MASS (1-800-522-6277) Outside the U.S.A., phone 303-530-8400 In Europe, phone +31 (0) 318 549 443 In Asia, phone 65-770-8155

Proving Micro Motion Coriolis Meters i

Contents

Terminology and Mathematical Variables . . . . . . . . . xv

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 General Proving Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Proving Procedures: Conventional and Small Volume Provers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4 Recommended Meters for Custody Transfer. . . . . . 33

5 Coriolis Meter Installation Recommendations . . . 37

6 Interfacing to Coriolis Meter Output Signals. . . . . 43

7 Proving Instrumentation Requirements . . . . . . . . . . . 59

8 Flow Rate Proving Devices . . . . . . . . . . . . . . . . . . . . . . . . . 67

9 Proving Calculations Summary. . . . . . . . . . . . . . . . . . . . . 119

10 Flow Proving Summary and Troubleshooting . . . . . 131

11 Coriolis Meter Density Measurement and Density Proving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

Contents

ii Proving Micro Motion Coriolis Meters

Terminology and Mathematical Variables . . . . . . . . . xix

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Coriolis Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 General Proving Concepts. . . . . . . . . . . . . . . . . . . . . . . . . . . 72.1 What Is Proving Versus Calibration? . . . . . . . . . . . . . . . . 9

2.2 Why Is Proving Performed? . . . . . . . . . . . . . . . . . . . . . . . . . 9Custody Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Quality Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Environmental Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 What Is the Outcome of Proving?. . . . . . . . . . . . . . . . . . . . 10

2.4 When Do You Need To Prove a Coriolis Meter? . . . . . . 11

2.5 How Often Should a Coriolis Meter Be Proved? . . . . . . 11Trend Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Varying Process Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Increasing the Time Between Provings . . . . . . . . . . . . . . . . . . 12Pay and Check Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3 Proving Procedures: Conventional and Small Volume Provers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.1 Meter Configured For Volume Measurement . . . . . . . . . 17

Minimum Volume Proving Requirements . . . . . . . . . . . . . . . . 18Maximum Volume Proving Requirements. . . . . . . . . . . . . . . . 20

3.2 Meter Configured For Mass Measurement . . . . . . . . . . . 22Minimum Mass Proving Requirements . . . . . . . . . . . . . . . . . . 22Using a Density Meter at the Prover . . . . . . . . . . . . . . . . . . . . 25Using the Coriolis Meter Density Measurement. . . . . . . . . . . 27Proving in Volume Units/Measuring in Mass Units . . . . . . . . 29

3.3 Transfer Standard Proving. . . . . . . . . . . . . . . . . . . . . . . . . . 30

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Proving Micro Motion Coriolis Meters iii

4 Recommended Meters for Custody Transfer. . . . . . 33

5 Coriolis Meter Installation Recommendations . . . 375.1 Sensor Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.2 Sensor Flow Tube Orientation . . . . . . . . . . . . . . . . . . . . . 40Liquid Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Gas Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Vertical Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.3 Provisions to Allow Meter Zeroing. . . . . . . . . . . . . . . . . . 40

5.4 Minimizing External Influences on the Meter . . . . . . . 42

5.5 Location of Proving Connections . . . . . . . . . . . . . . . . . . . 42

6 Interfacing to Coriolis Meter Output Signals. . . . . 436.1 Digital Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Interface to Digital Information . . . . . . . . . . . . . . . . . . . . . . . 47Using the RS-485 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Using the Bell 202 Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

6.2 Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48Interfacing to Analog Outputs . . . . . . . . . . . . . . . . . . . . . . . . . 49

6.3 Frequency/Pulse Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Interfacing to Frequency/Pulse Output . . . . . . . . . . . . . . . . . 49K-Factor or Pulse Scaling Factor Determination . . . . . . . . . 52Troubleshooting the Frequency/Pulse Output . . . . . . . . . . . 53

6.4 Additional Flow Measurement Information . . . . . . . . . 53Response Time/Damping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Effects of Damping on Proving Accuracy . . . . . . . . . . . . . . . 54Low-Flow Cutoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Meter Zero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

6.5 Wiring to Allow Field-Access to Meter Information . . 57

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iv Proving Micro Motion Coriolis Meters

7 Proving Instrumentation Requirements . . . . . . . . . . . 597.1 Proving Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

7.2 Pulse Counting Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Frequency Totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Single-Channel Proving Counters. . . . . . . . . . . . . . . . . . . . . . . 62Dual-Channel Proving Counters . . . . . . . . . . . . . . . . . . . . . . . . 62

7.3 Temperature Measurement Device . . . . . . . . . . . . . . . . . . 63

7.4 Pressure Measurement Device . . . . . . . . . . . . . . . . . . . . . . 63

7.5 Density Measurement Device . . . . . . . . . . . . . . . . . . . . . . . 64

7.6 Density Averaging Device . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.7 Density Proving Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

8 Flow Rate Proving Devices . . . . . . . . . . . . . . . . . . . . . . . . . . 678.1 Gravimetric Tank Proving . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Meter Factor Calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Gravimetric Proving Uncertainty . . . . . . . . . . . . . . . . . . . . . . . 74Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Batch Size Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . 76Number of Test Batches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Damping Factor Recommendation . . . . . . . . . . . . . . . . . . . . . 78

8.2 Volumetric Tank Proving . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Meter Factor Calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Volumetric Tank Proving Uncertainty . . . . . . . . . . . . . . . . . . . 80Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Batch Size Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . 83Number of Test Batches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Damping Factor Recommendation . . . . . . . . . . . . . . . . . . . . . 84

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Proving Micro Motion Coriolis Meters v

8.3 Conventional Pipe Prover . . . . . . . . . . . . . . . . . . . . . . . . . . 84Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Meter Factor Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Conventional Pipe Proving Uncertainty . . . . . . . . . . . . . . . . . 86Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Prover Size Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . 90Number of Proving Runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Damping Factor Recommendation . . . . . . . . . . . . . . . . . . . . . 90

8.4 Small Volume Prover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Meter Factor Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Small Volume Prover Uncertainty. . . . . . . . . . . . . . . . . . . . . . 95Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98Small Volume Prover Size Recommendations. . . . . . . . . . . . 100Number of Proving Passes/Runs . . . . . . . . . . . . . . . . . . . . . . . 101Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Damping Factor Recommendations . . . . . . . . . . . . . . . . . . . . 103

8.5 Volumetric Master Meters and Transfer Standards . . 104Master Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104Transfer Standard Meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104Proving Equipment and Procedures . . . . . . . . . . . . . . . . . . . . 105Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106Meter Factor Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107Volumetric Transfer Standard Meter Uncertainty . . . . . . . . 108Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110Proving Duration Recommendation . . . . . . . . . . . . . . . . . . . . 111Number of Proving Runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Damping Factor Recommendation . . . . . . . . . . . . . . . . . . . . . 111

8.6 Coriolis Master Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113Meter Factor Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113Coriolis Master Meter Uncertainty . . . . . . . . . . . . . . . . . . . . . 114Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117Recommended Proving Duration . . . . . . . . . . . . . . . . . . . . . . 117Number of Proving Runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118Damping Factor Recommendation . . . . . . . . . . . . . . . . . . . . . 118

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vi Proving Micro Motion Coriolis Meters

9 Proving Calculations Summary . . . . . . . . . . . . . . . . . . . . . 1199.1 Volume Meter Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

9.2 Mass Meter Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Alternate Method for Determining Mass Meter Factor . . . . . 123

9.3 How Many Proving Runs Are Required? . . . . . . . . . . . . . 123

9.4 Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123Meter Configured for Volume . . . . . . . . . . . . . . . . . . . . . . . . . . 123Meter Configured for Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124Stability of Process Conditions. . . . . . . . . . . . . . . . . . . . . . . . . 124Repeatability Specification for Coriolis Meters . . . . . . . . . . . 125

9.5 Meter Factor Uncertainty. . . . . . . . . . . . . . . . . . . . . . . . . . . 125

9.6 Reproducibility and Trend Charting . . . . . . . . . . . . . . . . . 126

9.7 Applying the Meter Factor to Inventory Calculations 128RFT9739 with Software Version 3.0 or Higher . . . . . . . . . . . . 128RFT9712 and RFT9739 with Software Version Lower

Than 3.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

10 Flow Proving Summary and Troubleshooting . . . . . 13110.1 Summary Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 133

Meter Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133Sensor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133Transmitter Outputs and Configuration . . . . . . . . . . . . . . . . . 134Proving Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

10.2 Proving Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . 135Poor Repeatability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135Poor Meter Factor Reproducibility . . . . . . . . . . . . . . . . . . . . . 136

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Proving Micro Motion Coriolis Meters vii

11 Coriolis Meter Density Measurement and Density Proving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13911.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

11.2 Recommended Meters for Density Measurement . . . . 142

11.3 Interfacing to Coriolis Meter Density Output Signals 143Digital Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143Analog Density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

11.4 Field Proving the Coriolis Meter Density Measurement 146Density Proving Installations. . . . . . . . . . . . . . . . . . . . . . . . . . 148Density Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 151Density Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . 154Density Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . 155Density Factor Reproducibility/Trend Charting . . . . . . . . . . 158Applying the Density Factor to Correct the Coriolis

Meter Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

11.5 Summary Recommendations and Troubleshooting . . . 159Summary Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . 159Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

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viii Proving Micro Motion Coriolis Meters

AppendixesA Proving Forms for Volume Measurement . . . . . . . . . . . . 163

B Proving Forms for Mass Measurement . . . . . . . . . . . . . . . 173

C Proving Forms for Density Measurement . . . . . . . . . . . . 183

D Proving Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

E Determining How Often a Coriolis Meter Should Be Zeroed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

F Mass Flow Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

G Density Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

H Volume Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

I Equation for Predicting Number of Passes Per Run . . 245

J Proving Equipment Manufacturers . . . . . . . . . . . . . . . . . . 251

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Proving Micro Motion Coriolis Meters ix

FiguresFigure 1-1 Components of a Coriolis meter . . . . . . . . . . . . . . . . 3Figure 1-2 Components of a Coriolis sensor . . . . . . . . . . . . . . . 4Figure 2-1 Sample proving trend chart . . . . . . . . . . . . . . . . . . . . 13Figure 3-1 Minimum volumetric proving configuration . . . . . . 19Figure 3-2 Maximum volumetric proving configuration . . . . . 21Figure 3-3 Minimum mass proving configuration . . . . . . . . . . . 23Figure 3-4 Mass proving with a density meter . . . . . . . . . . . . . . 25Figure 3-5 Mass proving using Coriolis density. . . . . . . . . . . . . 28Figure 3-6 Transfer standard proving configuration. . . . . . . . . 31Figure 5-1 Typical sensor installation. . . . . . . . . . . . . . . . . . . . . 39Figure 5-2 Recommended Coriolis sensor orientation . . . . . . . 41Figure 6-1a RFT9739 standard frequency schematic . . . . . . . . . 50Figure 6-1b RFT9739 open collector frequency schematic . . . . 50Figure 6-1c Decreased/limited voltage RFT9739 frequency

schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Figure 6-2 Connection of multiple pulse-counting devices . . . 51Figure 6-3 Coriolis meter response during proving . . . . . . . . . 55Figure 6-4a RFT9739 field-mount local access terminals. . . . . . 57Figure 6-4b RFT9739 rack-mount local access terminals. . . . . . 57Figure 8-1a Gravimetric proving with weigh tank. . . . . . . . . . . . 72Figure 8-1b Gravimetric proving with tanker truck . . . . . . . . . . 72Figure 8-2 Tank proving flow rate ramp-up/ramp-down . . . . . 76Figure 8-3 Outlet piping design for filling tank provers . . . . . . 77Figure 8-4 Volumetric tank proving . . . . . . . . . . . . . . . . . . . . . . 78Figure 8-5 Volumetric proving against a storage tank . . . . . . . 79Figure 8-6 Conventional pipe prover . . . . . . . . . . . . . . . . . . . . . 85Figure 8-7 Small volume prover. . . . . . . . . . . . . . . . . . . . . . . . . . 92Figure 8-8 Double-chronometry pulse interpolation . . . . . . . . 93Figure 8-9 Average meter factors for multiple proving runs . . 102Figure 8-10 Transfer standard proving with volumetric

master meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Figure 8-11 Coriolis master meter proving. . . . . . . . . . . . . . . . . . 112Figure 9-1 Meter Factor trend chart . . . . . . . . . . . . . . . . . . . . . . 127Figure 11-1 Double-walled vacuum-sphere pycnometer . . . . . . 148Figure 11-2 Series density proving installation . . . . . . . . . . . . . . 149Figure 11-3 Parallel density proving installation. . . . . . . . . . . . . 150Figure 11-4 Typical density proving report . . . . . . . . . . . . . . . . . 157

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x Proving Micro Motion Coriolis Meters

TablesTable 6-1 Typical Coriolis meter operating frequencies . . . . . 54Table 8-1 Traceability of proving methods to a fundamental

measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71Table 8-2 Buoyancy correction factors . . . . . . . . . . . . . . . . . . . 73Table 8-3 Typical sensor operating frequencies . . . . . . . . . . . . 99Table 8-4 Brooks Compact prover maximum flow rate for

Micro Motion meters . . . . . . . . . . . . . . . . . . . . . . 101Table 8-5 Repeatability versus number of passes per run . . . . 103Table 9-1 Trend Chart data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

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Proving Micro Motion Coriolis Meters xi

Figures in AppendicesFigure F-1 Components of a Coriolis flow sensor . . . . . . . . . . . 207Figure F-2 Simplified model of an operating Coriolis sensor . 208Figure F-3 RFT9739 signal processing block diagram . . . . . . . 209Figure F-4 Temperature effect on mass flow rate

measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211Figure F-5 Pressure effect on mass flow rate measurement . . 212Figure F-6a RFT9739 wiring connections for pressure

compensation with HART (digital) communications. . . . . . . . . . . . . . . . . . . . . . . . . . 213

Figure F-6b RFT9739 wiring connections for pressure compensation with analog input . . . . . . . . . . . . 214

Figure F-7 Meter uncertainty versus flow rate for ELITE sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Figure F-8 Zero offset error and uncertainty for an ELITE sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

Figure F-9 Mounting for sensor vibration isolation. . . . . . . . . . 219Figure G-1 Components of a Coriolis flow sensor . . . . . . . . . . . 225Figure G-2 RFT9739 signal processing block diagram . . . . . . . 227Figure G-3 Temperature effect on density measurement . . . . . 228Figure G-4 Pressure effect on density measurement. . . . . . . . . 229Figure G-5a RFT9739 wiring connections for pressure

compensation with HART (digital) communication . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Figure G-5b RFT9739 wiring connections for pressure compensation with analog input . . . . . . . . . . . . 231

Figure G-6 Fluid flow rate effect on density measurement . . . 232Figure G-7 Mounting for sensor vibration isolation. . . . . . . . . . 234Figure G-8 Effect of wall thickness reduction on density

measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236Figure H-1 Temperature effect on volumetric flow rate

measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242Figure H-2 Pressure effect on volumetric flow rate

measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242Figure H-3 Effect of mass flow rate on volumetric flow rate

measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242Figure I-1 Meter factors and repeatability versus flow rate . . 247

Contents

xii Proving Micro Motion Coriolis Meters

Tables in AppendicesTable A-1 Proving conversion factors . . . . . . . . . . . . . . . . . . . . . 172Table A-2 Buoyancy correction factors . . . . . . . . . . . . . . . . . . . 172Table B-1 Proving conversion factors . . . . . . . . . . . . . . . . . . . . . 182Table B-2 Buoyancy correction factors . . . . . . . . . . . . . . . . . . . 182Table C-1 Density conversion factors . . . . . . . . . . . . . . . . . . . . . 187Table F-1 Pressure coefficients for flow . . . . . . . . . . . . . . . . . . 210Table F-2 Zero uncertainty specifications . . . . . . . . . . . . . . . . . 217Table F-3 Typical sensor operating frequencies . . . . . . . . . . . . 219Table G-1 Pressure coefficients for density . . . . . . . . . . . . . . . . 230Table G-2 FD and K3 values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233Table G-3 Typical sensor operating frequencies . . . . . . . . . . . . 234Table G-4 Velocity of sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Table I-1 Number of passes per run. . . . . . . . . . . . . . . . . . . . . . 248

Contents

Proving Micro Motion Coriolis Meters xiii

Forms and ChartsForm A-1 Coriolis Meter Volume vs. Conventional Pipe

Prover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166Form A-2 Coriolis Meter Volume vs. Small Volume Prover . . 167Form A-3 Coriolis Meter Volume vs. Volumetric Tank

Prover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168Form A-4 Coriolis Meter Volume vs. Volumetric Master

Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169Form A-5 Coriolis Meter Volume vs. Coriolis Master Meter

Mass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170Form A-6 Coriolis Meter Volume vs. Gravimetric Tank

Prover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171Form B-1 Coriolis Meter Mass vs. Conventional Pipe Prover 176Form B-2 Coriolis Meter Mass vs. Small Volume Prover . . . . 177Form B-3 Coriolis Meter Mass vs. Volumetric Tank Prover . . 178Form B-4 Coriolis Meter Mass vs. Volumetric Master Meter . 179Form B-5 Coriolis Meter Mass vs. Coriolis Master Meter

Mass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180Form B-6 Coriolis Meter Mass vs. Gravimetric Tank Prover . 181Form C-1 Coriolis Meter Density Proving Report . . . . . . . . . . 186Form C-2 Correcting the Coriolis Meter Density to Prover

Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187Form D-1 Meter Factor Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . 192Form D-2 Density Factor Chart . . . . . . . . . . . . . . . . . . . . . . . . . 193Form E-1 Meter Zero Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

xiv Proving Micro Motion Coriolis Meters

Proving Micro Motion Coriolis Meters xv

Terminology and Mathematical Variables

The following terms and mathematical variables are used throughout this document.

Coriolis Meter TermsDriver or drive coil Coil and magnet assembly, used to vibrate the sensor flow tubes.

Flow calibration factor A coefficient, initially determined during factory calibration, which is used to convert sensor pickoff signals to a mass flow rate. The calibration factor resides in the transmitter. The calibration factor usually is not adjusted after the initial factory calibration.

K-factor or pulse scaling factor Pulses per unit mass (volume); an adjustable value that is configured into the transmitter by the manufacturer or a user. The K-factor is a value that is divided into the pulses output from the meter, to determine the total mass or gross volume measured by the Coriolis meter.

Maximum full-scale flow The maximum flow rating of the meter. This value is defined by the meter manufacturer.

Maximum operating flow rate The maximum flow rate at which the meter is to be used. This value is defined by the meter user.

Meter or flowmeter Combination of the mechanical flow sensor and the electronics transmitter. To have a functional Coriolis flowmeter, both components are required. See Figure 1-1, page 3.

Meter factor A number obtained by dividing the actual quantity of fluid passed through the meter (as determined from the prover) by the quantity registered by the meter.

Minimum full-scale flow The minimum flow rate that enables the meter to produce the maximum analog output of 20 mA. This value is defined by the meter manufacturer.

Nominal full-scale flow The nominal flow rating of the meter. This value is defined by the meter manufacturer.

Peripheral device An additional electronic instrument used for supplementary computations, totalization, or display of the meters output information.

Pickoffs or pickoff coils Coil and magnet assembly, used to measure the effect of the Coriolis force on the vibrating sensor flow tubes and to monitor tube vibration.

Process connections Flanges or fittings that are used to connect the sensor to the process piping.

RTD Resistance temperature detector, used to compensate the meter measurement for the effect of temperature on the elasticity of the sensor flow tube.

Sensor The mechanical component of a Coriolis meter, through which the process fluid flows. The sensor consists of the components shown in Figure 1-2, page 4

Sensor flow tubes Tube or tubes, which are vibrated using the driver, through which the process fluid flows. Small-scale distortion of the tubes caused by the Coriolis force, which is induced by the flowing fluid, is measured to determine the mass flow rate of the fluid.

xvi Proving Micro Motion Coriolis Meters

Terminology and Mathematical Variables Proving Terms

Sensor case The housing that surrounds the sensor flow tubes to prevent them from being damaged and to keep potential environmental contamination from the sensor pickoffs. Optional devices such as burst disks, drains and vents can be supplied to accommodate hazardous area installations.

Stored zero The zero value stored in the transmitter, determined when the meter is zeroed.

Transmitter The electronics assembly that powers the driver and processes the signals from the sensor pickoffs to provide meaningful mass flow and density output.

True zero The true zero value of the meter under the current process conditions. This is the value that represents the time difference between the right and left sensor pickoff signals when there is no flow through the sensor.

Zero stability or zero uncertainty A number that represents the statistical variation in the stored zero value, obtained from multiple meter zeroings. The source of this uncertainty is limitations in the transmitters ability to sample and measure the small signal levels from the pickoffs. Each sensor size and model has a unique zero stability value, which can be found in the sensor specifications.

Zero offset The difference between the true zero value and the stored zero value, caused by external influences such as changes in temperature or mounting conditions.

Zeroing A procedure to determine a zero value that represents the baseline offset between the sensor pickoffs at zero flow. The zero value is used by the transmitter to calculate flow rate. (The zeroing operation should not be confused with resetting the totalizer).

Proving TermsBase prover volume The volume of the prover corrected to standard conditions of 60F and 14.73 psia or 15C and 101 kPa.

Calibration The process of using a reference standard to determine a calibration factor. Calibration adjusts the output of the meter to bring it to a value which is within the specified accuracy tolerance. This process is normally conducted by the meter manufacturer.

Prover prerun The time between launching the piston or ball and the start of pulse accumulation from the meter.

Proving The process of comparing the indicated quantity that passes through a meter under test, at operating conditions, to a

reference of known quantity, in order to establish a meter factor that equates the two quantities. This process is normally conducted in the field.

Proving pass The operation of the prover displacer traversing the calibrated volume of the prover, between its detector switches.

Proving run A complete proving cycle, which can consist of one or more proving passes.

Waterdraw The process of calibrating a volumetric proving device against a NIST-certified volumetric field-standard test measure.

Proving Micro Motion Coriolis Meters xvii

Terminology and Mathematical Variables Mathematical Terms

Density TermsBase density The density of the liquid at the base conditions (typically at 60F and 14.73 psia or 15C and 101 kPa).

Density factor A number obtained by dividing the actual density of the fluid measured by a density reference (typically a pycnometer), by the density registered by the meter.

Flowing density The density of the liquid at actual flowing temperature and pressure.

Pycnometer A vessel of known volume and mass, which is filled with fluid and weighed to determine the density of the fluid.

Mathematical Termsp Fluid density at flowing conditions at the prover

m Fluid density at flowing conditions at the meter

BPV Base prover volume

Ctsp Correction for thermal expansion of steel at the prover

Cpsp Correction for pressure effect on steel at the prover

Ctlp Correction for thermal expansion of process fluid at the prover

Cplp Correction for pressure effect on process fluid at the prover

Ctlm Correction for thermal expansion of process fluid at the meter

Cplm Correction for pressure effect on process fluid at the meter

DF Density factor

MFm Meter factor when the meter is configured to indicate mass

MFv Meter factor when the meter is configured to indicate volume

Pm Fluid pressure at the meter

Pp Fluid pressure at the prover

Tm Fluid temperature at the meter

Tp Fluid temperature at the prover

xviii Proving Micro Motion Coriolis Meters

Proving Micro Motion Coriolis Meters 1

1 Introduction

1.1 Coriolis Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Figure 1-1 Components of a Coriolis meter . . . . . . . . . . . . . . . . . . . . . 3Figure 1-2 Components of a Coriolis sensor. . . . . . . . . . . . . . . . . . . . . 4

2 Proving Micro Motion Coriolis Meters


1 Introduction

1.1 Coriolis MetersA unique feature of Coriolis meters is that they measure mass flow rate directly. The mass flow rate measurement is not calculated from volume and density measurements. The volume of a fluid will change with varying temperature, due to thermal expansion; and pressure, due to fluid compression. The advantage of measuring mass is that mass is unaffected by changes in process conditions.

A Coriolis meter consists of a mechanical sensor and an electronic transmitter, as shown in Figure 1-1. The sensors primary measurement components are vibrating flow tubes and flow detectors (pickoffs), which are illustrated in Figure 1-2. The pickoffs provide a signal from which the mass flow rate can be determined. A density measurement, which is independent of the mass flow measurement, is also obtained from the vibrating flow tube. If desired, the

Figure 1-1. Components of a Coriolis meter. Shown are an ELITE CMF200 sensor and RFT9739 field-mount transmitter in an explosion-proof housing.


Introduction1Figure 1-2. Components of a Coriolis sensor. Shown is an ELITE CMF300 sensor.

Coriolis meter mass flow and density measurements can be used to calculate the volumetric flow rate of the fluid.

Coriolis meters have inherent features that are well suited to custody transfer measurement. The sensors have no rotating parts such as bearings or gears, which provides the following advantages:

Low maintenance, because there are no parts that wear with time.

Solids can flow through the sensor without damage; strainers are optional.

Vapor/gas in the process fluid will not cause damage due to overspin, as is common with turbine meters.

The meters can be significantly overranged without causing damage to the sensor.

Coriolis meters provide a multivariable measurement:

Mass flow rate to 0.1% Density to 0.0005 g/cc Volumetric flow rate to 0.15% Temperature to 1C

Because Coriolis meters measure mass flow rate directly, they are ideally suited to products that are accounted for on a mass basis, such as LPG, NGL, ethylene, and CO2. Traditionally, mass measurement is achieved indirectly by using a volumetric meter, a density meter, and a flow computer. The flow

computer determines the mass from the measured volume and density. A Coriolis meter replaces these three pieces of equipment, reducing the requirements for installing and maintaining multiple instruments. Because a Coriolis meter measures the entire process fluid stream, the need for a sampling system for density measurement is eliminated. Sampling systems are prone to maintenance problems, and there is always uncertainty as to whether the sample is representative of the actual fluid stream. In addition, Coriolis meters are capable of measuring flow in either the forward or reverse direction, which is particularly advantageous in loading/unloading applications.

Custody transfer measurement typically requires the meter accuracy to be proved in the field. Commonly available field proving devices are volume references, which are used to verify a meters volumetric flow rate measurement. If the Coriolis meter is configured for volumetric flow rate measurement, it is proved just like any volumetric meter would be proved. However, if the meter is being used to measure mass, then the fluid density must be determined to convert the prover volume measurement to mass units, to allow comparison to the meter mass measurement. Another concern is the time required for performing a proving run. There are timing considerations associated with proving a Coriolis meter that can result

Resistancetemperature

detector (RTD)

Pickoff coil andmagnet

Drive coil and magnet

Flow tubes

Pickoff coil and magnet

Introduction 1


in poor results if the proving time is too short. Because the prover volume is fixed, higher flow rates will result in shorter proving times. Using a prover that is too small for the Coriolis meter will affect the accuracy and repeatability of the proving results.

The purpose of this document is to discuss the methods available for proving, and to provide guidelines to help ensure that the

proving results are reliable. Significant details about the operation of Coriolis meters are included, to enhance the understanding of technical issues that may arise during meter proving. Both flow rate and density proving will be discussed. However, the primary focus is flow rate proving. This document focuses on proving for custody transfer, but the principles presented are applicable to any type of proving application.


2 General Proving Concepts

2.1 What Is Proving Versus Calibration? . . . . . . . . . . . . . . . . . . . . . 9

2.2 Why Is Proving Performed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Custody Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Quality Audit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Environmental Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 What Is the Outcome of Proving? . . . . . . . . . . . . . . . . . . . . . . . . 10

2.4 When Do You Need To Prove a Coriolis Meter? . . . . . . . . . . . 11

2.5 How Often Should a Coriolis Meter Be Proved? . . . . . . . . . . . 11Trend Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Varying Process Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Increasing the Time Between Provings. . . . . . . . . . . . . . . . . . . . . . . 12Pay and Check Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 2-1 Sample proving trend chart. . . . . . . . . . . . . . . . . . . . . . . . . . 13


2 General Proving Concepts

2.1 What Is Proving Versus Calibration?Calibration is typically performed in a laboratory at several different flow rates, densities, or temperatures. When a calibration is performed, the meters calibration factors are determined. Every Micro Motion meter is calibrated in a gravimetric calibration lab to determine the meters fundamental mass flow calibration factor, and to verify that meter accuracy is within specification over a range of flow rates.

The Micro Motion calibration lab employs weigh scales whose calibration is traceable to the National Institute of Standards and Technology (NIST). The calculated uncertainty of the calibration facility is better than 0.05%, based on ISO 5168. The calibration lab employs water as the flowing medium. The weigh-scale readings are corrected for buoyancy effect. During the flow calibration procedure, the density calibration factors for the meter are also

determined. The density calibration is performed using two fluids air and water.

Proving differs from calibration in that it is performed in the field under operating conditions. When a meter is proved in the field, a meter correction factor is determined. The correction factor is multiplied by the reading from the meter to offset the meter measurement. Proving is usually performed under one set of conditions, and should be conducted when the operating conditions are most representative of the typical operating conditions. If the operating conditions vary significantly during operation, it is beneficial to prove the meter under the different operating conditions, to determine if different meter factors are needed for each set of conditions.

This is accomplished by comparing the reading from the meter to a calibrated reference device.

2.2 Why Is Proving Performed?The need for proving arises because operating conditions differ significantly from the conditions under which the meter is calibrated. Verification is necessary to determine whether variations in fluid properties and process conditions cause a shift in the meters calibration under actual operating conditions. The proving process allows the user to correct the reading from the meter to provide the true quantity of fluid that went through the meter.

The meter measurement being proved can be flow rate or density. Meter proving is generally conducted for one of three reasons:

Custody transfer

Quality audit Environmental audit

Custody TransferThere are two types of custody transfer measurement: (1) legal, which falls under government Weights and Measures requirements, and (2) contract, under which a contractual agreement between a buyer and seller specifies requirements. Custody transfer flow measurements are performed for accounting of product quantities in order to establish monetary value of deliveries between sellers and buyers. The meter is proved to ensure product inventory accounting is of the highest accuracy.


General Proving ConceptsWhat Is the Outcome of Proving?2

Proving must be performed under actual operating conditions. A field reference device is used to prove the meter.

Quality AuditA routine meter verification plan should be established to comply with ISO 9000 quality requirements, to ensure product quality remains consistent. If a meter is used for controlling the addition of various fluid components to make a final product, meter performance must be repeatable to ensure product quality does not decline.

Environmental AuditAn environmental audit might be required by the EPA, OSHA, or other governing body, to ensure material balances in manufacturing and pipeline transfers are correct. The primary purpose of such an audit is to verify that transferred material is accounted for, so that there is no loss of product along the way.

Because environmental regulation requirements are escalating, it is more important today than ever to have a sufficient number of measurement points to provide evidence that no environmental violations have occurred at a site. As part of this environmental accounting, it is essential to show that a plan is in place for routinely verifying equipment accuracy, and to provide evidence that meter verification is being conducted on a regularly scheduled basis.

For quality and environmental audits, field proving is not specifically required. A more flexible meter verification plan can be used. The objective is to verify the meter is performing within specification, and to recalibrate if it is out of specification. Therefore, the meter can be removed and tested in a separate calibration facility or be sent out for reverification by the manufacturer. Master meter verification methods are also acceptable.

2.3 What Is the Outcome of Proving?The objective of proving a meter is to determine what the meter reading is, compared to a known reference. The basic calculation that applies to all provings, whether the measurement being proved is flow or density, is described by Equation 2-1.

(Eq. 2-1)

The meter correction factor defined in Equation 2-1 is commonly referred to as a meter factor. The information obtained from proving can be used in a number of ways:

The meter reading can be multiplied by the meter factor to obtain the correct measurement.

Proving results can be used to determine new meter calibration factors.

A decision can be made whether to return equipment to the manufacturer for checkup/recalibration.

The most common result of proving is to use a calculated meter factor to correct the meters flow rate indication. The meters flow measurement is multiplied by the meter factor to provide the correct inventory. Therefore, a meter factor greater than 1.0000 indicates that the meter is under-registering (reading low). A meter factor less than 1.0000 indicates that the meter is over-registering (reading high).

The discussion thus far has been general, and can be applied to proving either the meters flow rate or density measurement. The remaining discussion, presented in Sections 3 through 10, applies only to flow rate proving. Density proving is covered in Section 11.

Meter Correction Factor Prover ValueMeter Reading-------------------------------------------=

General Proving ConceptsHow Often Should a Coriolis Meter Be Proved? 2


2.4 When Do You Need To Prove a Coriolis Meter?For custody transfer measurement it is common practice to prove the meter when it is first put into service, and on a regularly scheduled basis thereafter. Also, proving is typically performed anytime the meter is subjected to changes in conditions which might cause a change in measurement accuracy. The following list details all of the conditions under which a meter might need to be proved. However, these are not requirements.

1. When the meter is initially brought into service.

2. If the meter is being used to measure bi-directional flow (forward and reverse flow), provings should be performed to establish meter factors for each direction. Although, the meter calibration factor does not change between forward and reverse flow, a zero offset would result in different meter factors for the forward and reverse directions. Refer to Appendix E, page 195, for a discussion on meter zeroing.

3. As required by the contract or proving schedule.

4. Anytime the accuracy of a meter is ques-tioned by either party involved in the cus-tody transfer.

5. When the sensor is returned to service

after having been removed from the pro-cess pipeline, or anytime the sensor mounting conditions are changed.

6. When the sensor or transmitter is replaced.

7. When the meter is rezeroed. (Characteriz-ing the meters zero can preclude having to prove when the meter is zeroed. Refer to Appendix E, page 195.)

8. When a change in flow rate occurs, if the change might cause the meter to exceed the accuracy limits set forth in the con-tract. Proving the meter over a range of flow rates might be necessary to deter-mine acceptable flow rate tolerances. In lieu of any test data, the meter should be reproved if the flow rate varies signifi-cantly from the normal operating flow rate.

9. When there is a significant change in the system temperature, pressure, or density, that would affect meter accuracy. (Refer to Appendix F, page 205.)

Because the objective of proving is to obtain the most accurate product accounting that is possible, more provings might be required for a new installation. As confidence in the meter performance becomes established, the level of proving can be decreased.

2.5 How Often Should a Coriolis Meter Be Proved?Typically, the proving contract specifies how often proving must be performed. However, the real determinant should be the performance of the meter from one proving to the next. One way to determine the frequency of proving is to collect proving data on an initial group of meters, and the proving frequency determined for these meters can be applied to all meters on similar service. If there is little or no change in meter factor between provings, the proving frequency can be reduced. Conversely, if the

meter factor changes each time the meter is proved, then more frequent proving is appropriate.

It is generally recommended that new users who have little experience with Coriolis meters should prove their first meters at least monthly, to provide data on their particular applications. Proving the meter more frequently after the meter is initially installed will speed up the process of determining the required meter proving frequency.


General Proving ConceptsHow Often Should a Coriolis Meter Be Proved?2

Trend ChartsA trend chart of meter factor and meter repeatability should be developed. It is desirable to record the parameters listed below directly on the trend chart, for each proving, to gain an understanding of any influences on the meter.

Date Name of proving company Flow rate Temperature at meter Pressure at meter Density at meter Ambient temperature Whether the meter was zeroed or not Prover base volume Temperature at prover Pressure at prover Density at prover

Figure 2-1 shows an example of a meter trend chart, which could be used for tracking meter performance. A blank trend chart, which may be reproduced, is included on page 192. It is common practice that the meter factor vary by no more than 0.25% from one proving to the next. However, the actual requirement is either specified in the contract or required by Weights and Measures authorities. Additional information on using trend charts is presented in Section 9.6, page 126.

Varying Process ConditionsIf the meter will be operated over a range of process conditions, it is useful to perform several provings across the entire operating range, to determine whether using a single meter factor will suffice for all operating conditions, or whether multiple meter factors are necessary for different operating conditions. If the operating conditions will

not be constant from one day to the next it is beneficial to characterize the influence of the following parameters on the meter factor:

Flow range Temperature range Pressure range Different products, varying composition

and viscosity

Trend charts can be used to collect this type of information. Trend charts are also an excellent means of tracking variations in the meters zero offset, and establishing requirements for rezeroing the meter. Refer to Appendix E, page 195, for a discussion on determining meter zeroing requirements.

Increasing the Time Between ProvingsAfter sufficient data is accumulated, it might be acceptable to increase the time between provings quarterly, semiannually or annually. The ability to go to longer times between provings depends on collecting sufficient data to convince the user of meter factor stability. The frequency of proving will also depend on contract requirements. Semiannual or annual provings might be sufficient for ISO 9000 certification, but might not be acceptable for custody transfer measurement. Corrosive or erosive process fluids warrant more frequent proving. It is never recommended to go any longer than one year between meter provings.

After the user has demonstrated the required proving frequency on an initial group of meters, all subsequent meters that are used on similar applications can have this proving frequency applied without having to repeat the entire confidence determination for every new meter.

General Proving ConceptsHow Often Should a Coriolis Meter Be Proved? 2


Figure 2-1. Sample proving trend chart.

Location Sensor Model

Fluid Sensor Serial Number

Proving Co. Transmitter Model

Prover Base Volume Transmitter Serial No.

Passes Per Run Calibration Factor

Meter Measuring/Mass or Volume KFactor

Met

er F

acto

r

1.0075

1.0050

1.0025

1.0000

0.9975

0.9950

0.9925

Date: 2/4/98 3/8/98 4/5/98 5/3/98 6/7/98 7/5/98 8/2/98 9/6/98Flow Rate: gal/min 420 400 395 440 450 445 435 410Tmeter: F Pmeter: psig Densitymeter: g/cc Tambient: F 70 65 75 85 92 95 94 93Was meter rezeroed? No No No No No No No NoTprover: F 73 73 76 78 80 82 84 82Pprover: psig 87 90 88 88 90 89 87 89Densityprover: g/cc .6196 .6175 .6154 .614 .6126 .6112 .6098 .6111

Re

pea

tabi

lity

0.15%

0.10%

0.05%

0.00%

ABC Company

Butadiene

CMF300

123456789

RFT9739

987654321

667.584.75

Mass 60 pulse/lb

XYZ Proving Co.

3.08661

4


General Proving ConceptsHow Often Should a Coriolis Meter Be Proved?2

Pay and Check MetersAnother common means for checking meter performance is to install two or more meters in a single pipeline. The multiple meters verify one anothers performance. This is most commonly performed with a pay meter and a check meter. The pay meter is used for billing purposes and the check meter is used to ensure the pay meter is reading properly.

In a typical pay-and-check metering application, multiple meters are proved upon installation. Then the inventory readings of the meters are checked against one another on a regular basis usually monthly or weekly. It is important that the readings of the meters be taken at the same time every

reporting period, to minimize discrepancies between the readings of the meters. If possible, it is advantageous to record the inventory readings from both meters simultaneously.

The larger the reporting period, the smaller the errors associated with recording the inventory readings will be. The meters should agree with each other within some predefined specification. If the deviation between the meters exceeds the specification, both meters should be proved to determine where the source of the discrepancy lies. In addition, it is considered good practice to prove the pay meter on at least an annual basis.


3 Proving Procedures: Conventional and Small Volume Provers

3.1 Meter Configured For Volume Measurement. . . . . . . . . . . . . . 17Minimum Volume Proving Requirements . . . . . . . . . . . . . . . . . . . . . 18

Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Maximum Volume Proving Requirements . . . . . . . . . . . . . . . . . . . . 20Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.2 Meter Configured For Mass Measurement . . . . . . . . . . . . . . . . 22Minimum Mass Proving Requirements . . . . . . . . . . . . . . . . . . . . . . . 22

Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Using a Density Meter at the Prover . . . . . . . . . . . . . . . . . . . . . . . . . 25Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Using the Coriolis Meter Density Measurement . . . . . . . . . . . . . . . 27Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Proving in Volume Units/Measuring in Mass Units . . . . . . . . . . . . . 29Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.3 Transfer Standard Proving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Proving Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Proving Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Proving Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 3-1 Minimum volumetric proving configuration . . . . . . . . . . . 19Figure 3-2 Maximum volumetric proving configuration . . . . . . . . . . . 21Figure 3-3 Minimum mass proving configuration . . . . . . . . . . . . . . . . 23Figure 3-4 Mass proving with a density meter . . . . . . . . . . . . . . . . . . . 25Figure 3-5 Mass proving using Coriolis density . . . . . . . . . . . . . . . . . . 28Figure 3-6 Transfer standard proving configuration . . . . . . . . . . . . . . 31


3 Proving Procedures: Conventional and Small Volume Provers

Proving is performed by using a field reference device to verify the meters flow measurement accuracy. The field reference device can be stationary or portable. Although the methods for proving Coriolis meters and volumetric meters are very similar, there are differences in the operation of the Coriolis meter that will require special consideration. Available equipment for proving Coriolis meters includes:

Gravimetric tanks Volumetric tanks Conventional pipe provers Small volume provers Volumetric master meters Mass (Coriolis) master meters

This section provides a general overview of the procedures required to prove a Coriolis meter with a conventional pipe prover. These

procedures are also directly applicable to small volume provers (or Compact Provers). Both conventional pipe provers and small volume provers are flow through volumetric proving device. These procedures are generally applicable to master meters methods and tank proving methods, with some modification. Proving methods using other equipment listed above are discussed in detail in Section 8, page 67.

This discussion on proving procedures is divided into three main topics:

1. Proving a Coriolis meter configured for volume measurement;

2. Proving a Coriolis meter configured for mass measurement; and

3. Using a transfer standard to prove a Coriolis meter when the prover is undersized.

3.1 Meter Configured For Volume MeasurementA Coriolis meter measures mass flow rate and density independently. Details of how these measurements are performed are presented in Appendices F and G. Because the meter measures both mass and density, it can also be used for determining volumetric flow rate. The measured volume is calculated as shown in Equation 3-1.

(Eq. 3-1)

where

q =Calculated volume flow

=Measured mass flow

=Measured density

When a Coriolis meter is configured for volume flow measurement, it can be treated like any volumetric meter. Additional technical details about the meters volume measurement are presented in Appendix H, page 239.

For reasons of accounting tradition, many companies prefer to account for product on a standard volume basis. Standard volume is generally determined by applying temperature and pressure correction factors to the actual volumetric flow rate to adjust the volume to standard conditions, generally 60F and 14.73 psia, as shown in Equation 3-2.

q m

-----=

m


Proving Procedures: Conventional and Small Volume ProversMeter Configured For Volume Measurement3

(Eq. 3-2)

where

qstd = Standard volume

qactual = Actual measured volume

Ctlm = Correction factor for thermal expansion of process fluid at the meter

Cplm = Correction factor for pressure effect at the meter

Actual volume cannot be used for product accounting, because product volume changes with variations in temperature and pressure. If a Coriolis meters volumetric flow rate is corrected to a standard volume, the calculation being performed is:

(Eq. 3-3)

where

actual = Actual measured density

The correction factors Ctlm and Cplm are used to correct for the effect of temperature and pressure on the density of the fluid, so what is actually being calculated is:

(Eq. 3-4)

where

std=Standard density

The method described above is a roundabout way to obtain a flow rate measurement that is independent of changes in process conditions. Accounting on a mass basis is less complicated.

Model RFT9739 and RFT9712 transmitters have a special units feature, which can be used to display a standard volume. If the product being measured is a pure product, the standard density (std) is known, and a special units conversion factor can be entered into the transmitter. With the conversion factor in place, the transmitter

performs the calculation shown in Equation 3-4. The meter then measures mass flow, yet displays the flow rate and flow total in standard volume units for accounting purposes. This approach cannot be used for products with a composition that varies.

For petroleum products the RFT9739 transmitter is capable of performing a standard volume computation using API equation 2540. The measured temperature from the sensor is used to correct to a standard temperature of 60F. The transmitter is not capable of correcting to standard pressure. The algorithm used by an RFT9739 is only for generalized petroleum products.

The advantage of configuring the meter for volume measurement is that it can be proved in the same fashion as any volumetric meter. This simplifies the proving process, because the meters measured volume can be compared directly to the prover volume. Details of proving equipment and procedures are presented in the following sections.

Minimum Volume Proving RequirementsFigure 3-1 illustrates the minimum equipment requirement for proving a Coriolis meter configured for volumetric measurement. This system can only be used under the following conditions:

1. Pressure and temperature at the prover and meter are essentially the same. Requirements for temperature and pressure agreement and distance between the meter and prover will depend upon the properties of the fluid.

2. A single shutoff valve can be used to completely halt fluid flow through the sensor, to allow zeroing. Products that expand significantly when flow is halted will require two valves to block the meter in.

qstd qactual* Ctlm* Cplm=

qstdm

actual----------------* Ctlm* Cplm=

qstdm

std---------=

Proving Procedures: Conventional and Small Volume ProversMeter Configured For Volume Measurement 3


Figure 3-1. Minimum volumetric proving configuration. Minimum requirements for proving a Coriolis meter configured for volumetric measurement.

Proving Equipment

Key components of this volume metering/proving system include:

Coriolis meter Proving connections consisting of block

and bleed valves: V1, V2, and V3. Valve V2 is also used to halt flow to allow zeroing of the Coriolis meter.

Prover that has a calibrated volume between the prover detectors

Pressure measured at the prover to correct for the effect of pressure on the prover volume (Cpsp)

Temperature measured at the prover to correct for the effect of temperature on the prover volume (Ctsp)

Pulse counter, which is used to accumulate flow pulses from the Coriolis meter. The counter is triggered by the prover detectors.

Proving Procedure

The steps involved in proving a meter are:

1. Prior to proving, the Coriolis meters zero reading should be checked as discussed on page 56, and in Appendix E, page 195.

2. Connect the prover to the proving connections. For stationary provers, the piping should already be in place. For portable proving systems, the connection is typically made with flexible hose. Make sure the hose is rigid enough that its volume doesnt change during proving, and that its pressure rating is adequate. Ground the proving skid to prevent potential sparking.

3. Divert fluid through the prover by opening valves V1 and V3, and closing valve V2. Fluid should flow through the prover for at least 10 minutes to allow the prover steel temperature to stabilize to the process fluid temperature.

Flow Sensor

Prover loop

Coriolis meter

Pulse counter

Pressure

TemperatureProver

detectors

Transmitter


Proving Procedures: Conventional and Small Volume ProversMeter Configured For Volume Measurement3

4. Check for leaks, and bleed any gas out of the prover as necessary.

5. Connect the meters pulse output to the proving counter. Connect the prover detector outputs to the pulse counter. For stationary provers this is typically accomplished by activating an electrical switch.

6. Enable the prover pressure and temperature instrumentation. Specific procedures will depend on whether the instrumentation is manual or electronic.

7. Insert the proving ball into the receiver.

8. Perform two or three trial proving runs to ensure the temperature and pressure has stabilized (generally done by tripping a switch that releases the prover ball from the receiver into the prover). A proving run is completed once the prover ball has gone through an entire measurement cycle.

9. Conduct the actual proving by performing a series of proving runs. Five proving runs are recommended for conventional provers, and three runs of 10 to 15 passes each is recommended for small volume provers.

10. Record the pressure and temperature at the prover during each proving run. Record the approximate fluid flow rate during the proving. After each run record the pulses accumulated from the meter from the pulse counter.

11. Perform proving calculations.

Proving Calculations

The repeatability of the proving is determined by taking the results of the three or five provings and performing the following calculation:

(Eq. 3-5)

Generally the proving results must have a repeatability of less than 0.05% in order for the proving to be considered to be valid. If the repeatability is acceptable, Equation 3-6 is used to calculate the meter factor for the proving. The Ctsp and Cpsp correction factors for the effects on the prover steel are determined from standard equations, using the appropriate coefficients for the prover material of construction.

(Eq. 3-6)

where

MFv = Meter factor, meter configured to indicated volume

BPV = Base prover volume

Ctsp = Correction factor for thermal expansion of steel at the prover

Cpsp = Correction factor for pressure effect on steel at the prover

Section 9, page 119, provides additional details on proving calculations. Proving form A-1, page 166 (Appendix A), can be used to record the proving data and perform the proving calculations.

Maximum Volume Proving RequirementsFigure 3-2, page 21, illustrates the maximum equipment requirement for proving a Coriolis meter configured for volumetric measurement. Components have been added to the minimum system to accommodate the following special circumstances:

1. Pressure and temperature at the prover is not representative of the conditions at the meter.

2. The flow of process fluid cannot be stopped to allow the meter to be zeroed, and must be diverted around the meter.

3. The meter must be blocked in to obtain zero flow through the meter.

Repeatability(%)PulsesMAX PulsesMIN

PulsesMIN----------------------------------------------------------* 100=

MFvBPV * Ctsp* Cpsp

Meter PulsesKFactor

------------------------------------- ----------------------------------------------=

Proving Procedures: Conventional and Small Volume ProversMeter Configured For Volume Measurement 3


Figure 3-2. Maximum volumetric proving configuration. Maximum requirements for proving a Coriolis meter configured for volumetric measurement.

Proving Equipment

Additional components of this system, beyond those shown in Figure 3-1, page 19, include:

Bypass loop, which includes valves V1, V2, and V3. The bypass allows flow to be diverted around the meter to allow meter zeroing. This is required for applications in which the flow through the pipeline cannot be stopped.

Pressure measured at the meter to correct the measured fluid volume to standard pressure (Cplm)

Temperature measured at the meter to correct the measured fluid volume to standard temperature (Ctlm)

Pressure measured at the prover is also used to correct the fluid volume to standard pressure (Cplp)

Temperature measured at the prover is also used to correct the fluid volume to standard temperature (Ctlp)

Proving Procedure

The additional steps involved in proving a meter, beyond those described on page 19, are described below:

1. If the fluid is expansive, closing a single valve downstream of the meter may result in reverse flow through the meter. This would result in an incorrect zero value being determined. Therefore, the meter may have to be blocked in by closing both valves V2 and V3, which are depicted in Figure 3-2.

2. If the process demands that flow through the system cannot be halted, then the process fluid must be diverted around the meter by opening valve V1 during the zeroing operation.

3. If pressure and temperature instrumentation at the meter is required, these devices will also have to be enabled.

4. In addition to recording the pressure and temperature at the prover, it might be necessary to record pressure and temperature at the meter.

Flow Sensor

Prover loop

Coriolis meter

Pulse counter

Pressure

TemperatureProver

detectors

Transmitter

TemperaturePressureBypass loop (optional)


Proving Procedures: Conventional and Small Volume ProversMeter Configured For Mass Measurement3


The repeatability of the proving is determined by taking the results of the three or five provings and performing the calculation shown in Equation 3-5. A repeatability of less than 0.05% is commonly required. If the repeatability is acceptable, Equation 3-7 is used to calculate the meter factor for the proving, using the average number of pulses from the proving runs. The Ctlp and Cplp correction factors are

determined from API MPMS look-up tables, or from API equation 2540 and compressibility equations.

(Eq. 3-7)

These calculations are detailed in proving form A-1, page 166 (Appendix A).

3.2 Meter Configured For Mass MeasurementWhen a Coriolis meter is configured for mass measurement and is being proved against a volumetric prover, the prover volume must be converted to mass units to allow comparison to the mass measured by the meter. In order to convert the prover volume to mass, an accurate density determination at the prover must be made. Any error in the determination of the density will result in an equivalent error in the meter factor. The fluid density can be determined from any of the following methods:

1. Calculated from measured temperature and pressure. This method is limited to well characterized products of known composition.

2. Determined from an in-line density meter located at the prover. A density sampling system is used to determine a density factor for the density meter.

3. Determined from the Coriolis meter density measurement. The Coriolis meter should be located close to the prover. A density sampling system is used to determine a density factor for the Coriolis meter.

For many process fluids the actual flowing density (not the density at standard conditions) does not remain constant, due to fluctuations in product composition or process conditions. This is particularly true of light hydrocarbons. If the fluid density varies while the meter is being proved, it will be difficult to obtain acceptable repeatability, and the meter factor may be in error. In this

situation, it is recommended that the average fluid density during the proving run be determined, and this average density be used in the meter factor calculation.

If a density measurement device is used, it will be necessary to prove the density measurement to obtain a density factor (DF). It would be reasonable to prove the density measurement every time the Coriolis meters flow measurement is proved. The frequency of determining the density factor may be reduced if the density factor continually remains consistent from one proving to the next. Actual field practice may vary from these recommendations based on the required accuracy levels.

Minimum Mass Proving RequirementsFigure 3-3 illustrates the minimum equipment requirement for proving a Coriolis meter configured for mass measurement. This system can only be used under the following conditions:

1. The fluid density at the prover can be accurately determined from the pressure and temperature measurements.

2. A single shutoff valve can be used to completely halt fluid flow through the sensor to allow zeroing. Products that expand significantly when flow is halted will require two valves to block the meter in.

MFvBPV * Ctsp* Cpsp* Ctlp* Cplp

Meter PulsesKFactor

--------------------------------- * Ctlm* Cplm---------------------------------------------------------------------------=

Proving Procedures: Conventional and Small Volume ProversMeter Configured For Mass Measurement 3


Figure 3-3. Minimum mass proving configuration. Minimum requirements for proving a Coriolis meter configured for mass measurement.

Proving Equipment

Key components of this mass metering/proving system include:

Coriolis meter Proving connections consisting of block

and bleed valves V1, V2, and V3. Valve V2 is used to halt flow to allow zeroing of the Coriolis meter.

Prover that has a calibrated volume between the prover detectors

Pressure measured at the prover to correct for the effect of pressure on the prover volume (Cpsp)

Temperature measured at the prover to correct for the effect of temperature on the prover volume (Ctsp)

Density at the prover, determined from the process fluid temperature and pressure

Pulse counter, which is used to accumulate flow pulses from the Coriolis meter. The counter is triggered by the prover detectors.

Proving Procedure

The steps involved in proving a meter configured for mass measurement are described below:

1. Prior to proving, the Coriolis meters zero reading should be checked as discussed on page 56, and in Appendix E, page 195.

2. Connect the prover to the proving connections. For stationary provers, the piping should already be in place. For portable proving systems, the connection is typically made with flexible hose. Make sure the hose is rigid enough that its volume doesnt change during proving, and that its pressure rating is adequate. Ground the proving skid to prevent potential sparking.

3. Divert fluid through the prover by opening valves V1 and V3, and closing valve V2. Fluid should flow through the prover for at least 10 minutes to allow the prover steel temperature to stabilize to the process fluid temperature.

4. Check for leaks and bleed any gas out of the prover as necessary.

5. Connect the meters pulse output to the proving counter. Connect the prover detector outputs to the pulse counter. For stationary provers this is typically accomplished by activating an electrical switch.

V1

V2

V3

Flow Sensor

Prover loop

Coriolis meter

Pulse counter

Pressure

Temperature

Prover detectors

Transmitter Density determined from P & T



6. Enable the prover pressure and temperature instrumentation. Specific procedures will depend on whether the instrumentation is manual or electronic.

7. Insert the proving ball into the receiver.

8. Perform two to three trial proving runs to ensure the temperature and pressure has stabilized (generally done by tripping a switch that releases the prover ball from the receiver into the prover). A proving run is completed once the prover ball has gone through an entire measurement cycle.

9. Conduct the actual proving by performing a series of proving runs. Five proving runs are recommended for conventional provers, and three runs of 10 to 15 passes each is recommended for small volume provers.

10. Record the pressure and temperature at the prover during each proving run. Record the approximate fluid flow rate during the proving. After each run record the pulses accumulated from the meter from the pulse counter.

11. Perform proving calculations.


A significant difference between mass and volume proving is the method that is used to determine proving repeatability. For volume-to-volume proving, the repeatability can be based on the number of pulses accumulated. However, for mass-to-volume proving, the pulse repeatability would not account for variations in product density. If the product density were to vary during the proving, the pulse repeatability may be unacceptable. Therefore, when performing a mass-to-volume proving, the repeatability should be based on the meter factor for the individual provings, not the accumulated pulses. This

calculation is shown in Equation 3-8. The meter factors for the individual proving runs are determined from Equation 3-9, and the repeatability is based on the maximum and minimum meter factors from the runs.

(Eq. 3-8)

Generally the proving results must have a repeatability of less than 0.05% in order for the proving to be considered to be valid. The product density during the proving should vary by no more than 0.0002 g/cc. Based on a fluid with a density of 0.8 g/cc, this level of density variation would take up 0.025% of the repeatability specification. This leaves only a 0.025% repeatability allowance for the meter and the rest of the proving system.

Before calculating the meter factor, the product density must first be determined. A look-up table or an equation is used to obtain the density of the fluid from the recorded pressure and temperature. Next, the Ctsp and Cpsp correction factors for the effects on the prover steel are determined from standard equations, using the appropriate coefficients for the prover material of construction. Then the meter factors for the individual proving runs are calculated as shown in Equation 3-9.

(Eq. 3-9)

where

p = fluid density under flowing conditions at the prover

Section 9, page 119, provides additional information on proving calculations. Proving form B-1, page 176 (Appendix B), can be used to record data, and shows the calculation steps.

Repeatability(%)MFMAX MFMIN

MFMIN------------------------------------------* 100=

MFmBPV* Ctsp* Cpsp* p

Meter Factor KFactor

--------------------------------------- -------------------------------------------------------=

Proving Procedures: Conventional and Small Volume ProversMeter Configured For Mass Measurement 3


Figure 3-4. Mass proving with a density meter. Requirements for using a density meter at the prover for proving a Coriolis meter configured for mass measurement.

Using a Density Meter at the ProverThis example is a variant of the procedure described above for minimum mass proving requirements. It applies when the density cannot be determined from pressure and temperature measurements at the prover. Figure 3-4 illustrates the equipment requirement for this scenario. Components have been added to the minimum mass proving system to accommodate the following circumstances:

1. The density at the prover cannot be determined from pressure and temperature measurements.

2. The density of the fluid cannot be held constant (within 0.0002 g/cc) during the proving pass or run, requiring an average density to be determined.

3. The flow of process fluid cannot be stopped to allow the meter to be zeroed, and must be diverted around the meter.

4. The meter must be blocked in to obtain zero flow through the meter.

Proving Equipment

Additional components of this mass metering/proving system, beyond those shown in Figure 3-3, page 23, include:

A density meter at the prover (a small Coriolis meter installed at the prover can be used to provide density measurement)

A density proving system for the density meter

An optional density averager, if the fluid density does not remain constant during the proving pass or run

An optional bypass loop, which includes valves V1, V2, and V3. The bypass allows flow to be diverted around the meter to allow meter zeroing. This is required for applications in which the flow through the pipeline cannot be stopped.

All of these components may not be required. Add only those items that are needed for the particular application.

Proving Procedure

The additional steps involved in proving a meter configured for mass measurement

V1

V2 V3

V4

V5

V6V7

V8

V9V10

V11

Flow Sensor

Prover loop

Coriolis meter

Pulse counter

Pressure

Temperature

Prover detectors

Transmitter

Bypass loop (optional)

Density averager (optional)

Density sampler

Density meter



using a density meter at the prover, beyond those described beginning on page 23, are described below:

1. If the fluid is expansive, closing a single valve downstream of the meter may result in reverse flow through the meter.

This would result in an incorrect zero value being determined. Therefore, the meter may have to be blocked in by closing both valves V2 and V3, which are depicted in Figure 3-4, page 25.

2. If the process demands that flow through the system cannot be halted, then the process fluid must be diverted around the meter by opening valve V1 during the zeroing operation.

3. The density meter must be enabled.

4. Prior to proving the Coriolis meter, the density meters density factor (DF) must be determined. This is accomplished by opening valves V7, V10, and V9. Valve V11 is used to generate sufficient pressure drop to obtain a representative fluid sample in the density loop. Care should be taken to ensure that flashing or cavitation does not result from dropping the pressure. Fluid is circulated through the density meter and density sampling container until the temperature at both locations has stabilized and the two temperatures agree to within 0.2C. (Figure 3-4 does not show the details of the density proving equipment. Refer to Section 11.4, page 146, for a complete description of this process.) Once conditions have stabilized, a density sample is collected and the density meters density reading is recorded simultaneously. This process is repeated two to three times, to ensure the density factor is repeatable.

5. After the density factor has been determined, the system is returned to normal operation by opening valve V8 and closing valves V10 and V9. For safety reasons valve V8 would need to be opened before closing valves V10 and V9. Valve V11 is still used to generate sufficient pressure drop to obtain a representative fluid sample in the density loop.

6. While the meter is being proved, the density reading from the density meter is recorded along with the other proving data.

7. If the optional density averager is used, it must be enabled. The density averager is connected to the prover detectors and the density meters density measurement output. The prover detectors trigger the averager to average the density meters density measurement during the proving run. The average density is recorded at the end of the proving pass or run.


As discussed for minimum mass proving, the repeatability value is calculated by using the meter factor, not the meter pulses (as shown in Equation 3-8, page 24). An additional calculation is also performed: the determination of the density meters density factor, as shown in Equation 3-10.

(Eq. 3-10)

The density of the fluid at the prover (p) is obtained from the density meter reading. This will either be obtained from the density meter or the density averager, if required. The Ctsp and Cpsp correction factors for the effects on the prover steel are determined from standard equations, using the appropriate coefficients for the prover material of construction. The meter factors for the individual proving runs are then calculated as shown in Equation 3-1

Documents

Instrproving Coriolis for Custody