Manual of Petroleum Measurement Standards Chapter 21.1

Flow Measurement Using Electronic Metering Systems—Electronic Gas Measurement

ANSI/API MPMS CHAPTER 21.1 SECOND EDITION, FEBRUARY 2013

AGA REPORT NO. 13

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

Users of this Standard should not rely exclusively on the information contained in this document. Sound business, scientific, engineering, and safety judgment should be used in employing the information contained herein.

All rights reserved. No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005.

Copyright © 2013 American Petroleum Institute

Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification.

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order to conform to the specification.

This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually by API, 1220 L Street, NW, Washington, DC 20005.

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, standards@api.org.

iii

Contents

Page

1. Scope 1

2. Normative References 2

3. Descriptions, Definitions, and Symbols 2

   1. Description of an Electronic Gas Measurement System 2

   2. Elements of a Gas Measurement System 2

   3. Definitions 3

   4. Symbols 9

4. Electronic Gas Measurement System Algorithms 11

   1. General 11

   2. Overview 11

   3. Quantity Calculation Period (QCP) 12

   4. Differential Meter Measurement 12

   5. Linear Meter Measurement 18

   6. Value Determination For Live Inputs 24

   7. Compressibility, Density, Heating Value, and Composition 24

5. Audit and Record Requirements 24

   1. Introduction 24

   2. Quantity Transaction Record (QTR) 24

   3. Software/Firmware Identifiers 27

   4. Configuration Log 28

   5. Event Log 28

   6. Alarm and Operating Data 28

   7. Corrected Quantity Transaction Record (QTRcorr) 28

   8. Test Record 29

6. Data Availability 29

   1. General 29

   2. Onsite Data Requirements 30

   3. Off-Site Data Requirements 30

   4. Data Retention 31

7. Commissioning 31

   1. General 31

   2. Documentation Review 31

   3. Final Integrated EGM System Site Commissioning 32

   4. Commissioning Documentation 34

8. Equipment Verification and Calibration 34

   1. Components Requiring Verification/Calibration 34

   2. Verification and Calibration 35

   3. Ambient Temperature, Line Pressure, and Atmospheric Pressure Effects 41

   4. Verification and Calibration Equipment 41

9. Security and Data Integrity 42

   1. Introduction 42

   2. Restricting Access 42

   3. Intelligent Device Data Communication Integrity 42

   4. Integrity of Logged Data 43

   5. Algorithm Protection 43

      v

      Page

   6. EGM Memory Protection 43

   7. Integrity of Transferred Data 43

Annex A (informative) Rans Methodology for Estimating Sampling Frequency and Calculation

Algorithm Errors 44

Annex B (normative) Averaging Techniques 59

Annex C (informative) Correction Methodology 62

Annex D (normative) Calculation of Normal Operating Range and Percent Fluctuation 64

Annex E (informative) Example Flow Computer Variable Input Type Testing - Differential Meters 67

Annex F (informative) Example Commissioning Checklist 76

Annex G (informative) Examples of Configuration Log Data 77

Annex H (informative) Calculation of Differential Pressure “As-Found” 80

Annex I (informative) Example of a Redundancy Verification Report 83

Annex J (informative) Examples of Applying Linear Meter Equations 85

Annex K (informative) Example of Using DPIV , DPY , and a Volumetric Flow Rate Calculator to

Recalculate a QCP or QTR 91

Bibliography 94

Figures

1. Graphical Representation of an Electronic Gas Measurement (EGM) System and Its

   Relationship to Other Devices 1

2. Estimated Expansion Factor Errors Based Hourly QTRs and DP/SP Ratios 17

3. Conceptual Representation of an EGM System. 33

4. Verification/Calibration Process 36

A.1 46

A.2 46

A.3 47

A.4 47

1. Flow Rate Fluctuation Correction Factor 52

2. One Second Logged Data 53

3. One Minute Flow Time Linear Averages of Logged Data 53

4. Comparison of Differential Pressure Averages 54

5. Estimated Expansion Factor Error Using Hourly QTR Recalcs and DP/SP Ratios 56

6. Example Calculations Plotted on the Expansion Factor Error Graph 58

1. Typical Operating Pressure/Calculated Normal Operating Range 65

2. Frequency Distribution Showing 5th Percentile and 95th Percentile 65

3. Example of Operating Pressure that is Not Normally Distributed 66

1. Block Diagram of Test Set-up and Algorithm Verification Process 68

2. Example of an Over-damped I/P Output 70

3. Example of an Over-damped I/P Output 71

4. I/P with Poor Output Control 72

5. I/P with Good Output Control 72

6. Example of One Hour Differential Pressure Trend with a Five Minute Offset 74

   vi

   Page

7. Notice Late Trend Last Five Minutes Matches First Five Minutes of the On-time Trend 75

1. Calculation of “Equivalent” Working Pressure As-found and Calibration Error 81

2. Atmospheric Pressure/Calculation of “Equivalent” Working Pressure As-left 82

3. Calculated “Equivalent” Working Pressure As-Found/As-Left Verifications 82

1. Differences Between DPIV and DPLinear and Recalculated Volumes, Using Hourly QTR Data for

   a Plunger Lift Production Area 91

2. Differences Between DPIV, DPlinear, and DPY Calculated from Hourly QTR Data for

   a Plunger Lift Protection Area 92

3. Differences Between Expansion Factor (Y) Calculated Using DPIV, DPlinear, and DPY

for a Plunger Lift Production Area 93

Tables

1 Maintenance Practices 35

1. Algorithm Flow Pattern/Calculation Frequency Check of Data in Figure A.6 55

2. Table of Example QTRs Used to Check DPY vs. DPLinear Expansion Factor Errors 57

vii

Flow Measurement Using Electronic Metering Systems— Electronic Gas Measurement

1 Scope

This standard describes the minimum specifications for electronic gas measurement systems used in the measurement and recording of flow parameters of gaseous phase hydrocarbon and other related fluids for custody transfer applications utilizing industry recognized primary measurement devices.

Electronic gas measurement (EGM) systems may be comprised of a number of components which work together to measure and record gas flow as shown in Figure 1. The components contained in the cloud are considered part of the EGM system. The components may be considered individually or be integral parts of the EGM system and the calculations may be performed onsite and/or off-site.

This standard provides the minimum reporting and change management requirements of the various intelligent components required for accurate and auditable measurement. The requirements can be met by a combination of electronically and/or manually recorded configuration, test reports, change record reporting of the electronic gas measurement system components and flow parameters. It is recognized that diagnostic capabilities of the newer meter and transmitter technologies are important but due to the device specific complexity, intelligent device diagnostics are out of scope for this standard.

For all existing installations, the decision to upgrade the system to satisfy the current standard is at the discretion of the parties involved.

EGM System

Volume and energy quantity calculation devices

PT FT

TT AT

Note Figure 1 uses ISA symbols where the first letter of the symbol is the process variable and the second letter is the type of instrument. For example for the symbol PI, (P) stands for pressure instrument and (I) stands for indicator. The process variables in the figure are pressure (P), flow rate (F), temperature (T), and analytical (A) and the types of instruments are indicator (I), transmitter (T), element (E).

EGM

component manually or electronically recorded configuration, test reports, change logs

Figure 1—Graphical Representation of an Electronic Gas Measurement (EGM) System and Its Relationship to Other Devices

1