Manual of Petroleum Measurement Standards Chapter 4—Proving Systems

Section 9—Methods of Calibration for

Displacement and Volumetric Tank Provers

Part 4—Determination of the Volume of Displacement and Tank Provers by the Gravimetric Method of Calibration

FIRST EDITION, OCTOBER 2010

Manual of Petroleum Measurement Standards Chapter 4—Proving Systems

Section 9—Methods of Calibration for Displacement and Volumetric Tank Provers

Part 4—Determination of the Volume of Displacement and Tank Provers by the Gravimetric Method of Calibration

Measurement Coordination

FIRST EDITION, OCTOBER 2010

Special Notes

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Copyright © 2010 American Petroleum Institute

Foreword

This multi-part publication consolidates and standardizes calibration procedures for displacement and volumetric tank provers used in the metering of petroleum liquids. It provides essential information on the operations involved in obtaining a valid, accurate and acceptable prover volume by different calibration methods. Units of measure in this publication are in the International System (SI) and United States Customary (USC) units consistent with North American industry practices. The parts consist of the following:

• Part 1—Introduction to the Determination of the Volume of Displacement and Tank Provers;

  
  

• Part 2—Determination of the Volume of Displacement and Tank Provers by the Waterdraw Method of Calibration;

  
  

• Part 3—Determination of the Volume of Displacement Provers by the Master Meter Method of Calibration;

  
  

• Part 4—Determination of the Volume of Displacement and Tank Provers by the Gravimetric Method of Calibration.

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.

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

   1. General 1

   2. U.S. Customary (USC) and International System (SI) Units 1

   3. National Metrology Institute 1

   4. Safety Considerations. 1

2. Normative References 1

3. Terms and Definitions 2

4. Prover Preparation 3

5. Preliminary and General Calibration Procedures 3

   1. General 3

   2. Preliminary Calibration Procedures 3

   3. General Calibration Procedures 10

6. Calibration Procedures 12

   1. General 12

   2. Calibration Preparation 12

   3. Displacement Type Bidirectional Provers with Free Displacers 14

7. Troubleshooting Calibration Problems 18

   1. General 18

   2. Weighing System 18

   3. Water Quality 19

Annex A (normative) Calculation Procedures for the Determination of Base Prover Volume (BPV) of Displacement Provers by the Gravimetric Method (GM) 20

Annex B (informative) Dynamic Prover Volume Calculation, Gravimetric Method (GM)—SI Units 31

Annex C (informative) Dynamic Prover Volume Calculation, Gravimetric Method (GM)—USC Units 33

Annex D (informative) Weigh Scale Verification Gravimetric Method (GM) (Example) 35

Annex E (informative) Run Datasheet Gravimetric Method (GM) (Example) 36

Annex F (informative) Tank Prover Volume Calibration Gravimetric Method (GM)—USC Units

(Distilled Water Example) 37

Annex G (informative) Figures 38

Bibliography 48

Figures

1 Gravimetric Calibration of a Displacement Type Unidirectional Prover with a Free Displacer 39

2A Gravimetric Calibration Displacement Type Bi-Directional Prover with a Free Piston

Displacer and Check Valves in the Manifold 40

2B Gravimetric Calibration of a Displacement Type Bi-directional Prover with a Free

Sphere Displacer 41

3A Gravimetric Calibration of the Downstream Volume of a Displacement Prover

with a Captive Displacer and External Directors 42

3B Gravimetric Calibration of the Upstream Volume of a Displacement Prover

with a Captive Displacer and External Detectors 43

v

Contents

3C A Gravimetric Calibration of a Displacement Prover with Equal Size Diameter Shafts

Page

on Both Sides of a Captive Displacer, with External Detectors 44

4A Waterdraw Calibration of a Volumetric Tank Prover with a Bottom-Weir 45

4B Gravimetric Calibration of a Volumetric Tank Prover with a Dry Bottom using the Water-fill Method . . 46 4C Gravimetric Calibration of a Volumetric Tank Prover with a Wet Bottom 47

Table

A.1 Equation Reference Standards and Publications 30

vi

Introduction

This standard describes the gravimetric method of calibration (GM), which is used to determine the calibrated volume of both displacement and tank provers. All prover volumes shall be determined by calibration and not by calculation.

The GM differs from the waterdraw (volumetric) method found in API MPMS Ch. 4.9.2. The main difference between the methods is that a field standard test measure is replaced with a weighing system (weigh scale and container).

A majority of the activities necessary to prepare the prover, conduct calibration runs, and record all the required data necessary to calculate the base volumes of displacement and tank provers are identical for the waterdraw and GMs. This standard will describe activities that are different from the waterdraw method. Therefore, it will be necessary for the user to reference API MPMS Ch. 4.9.1 and API MPMS Ch. 4.9.2 to perform all activities necessary for a calibration. Detailed volume calculation procedures for this method are included in Annex A.

vi

Chapter 4—Proving Systems

Section 9—Methods of Calibration for Displacement and Volumetric Tank Provers Part 4—Determination of the Volume of Displacement and Tank Provers by the Gravimetric Method of Calibration

1. Scope

   1. General

      
      

      This standard covers the specific procedures, equipment, and calculations required to determine the Base Prover Volume (BPV), of both tank and displacement provers by the gravimetric method of calibration (GM).

      
      

   2. U.S. Customary (USC) and International System (SI) Units

      
      

      This standard presents both International Systems (SI) and U.S. Customery (USC) units, and may be implemented in either system of units. The presentation of both units is for the convenience of the user, and is not necessarily the exact conversions. The system of units to be used is typically determined by contract, regulatory requirement, the manufacturer, or the user’s calibration program.

      
      

   3. National Metrology Institute

      
      

      Throughout this document issues of traceability are addressed by references to National Institute of Standards and Technology (NIST). However, other appropriate national metrology institutes can be referenced.

      
      

   4. Safety Considerations

      
      

      There is no intent to cover safety aspects of conducting the work described in this standard, and it is the duty of the user to be familiar with all applicable safe work practices. It is also the duty of the user to comply with all existing federal, state, or local regulations [e.g. the Occupational Safety and Health Administration (OSHA)] that govern the types of activities described in this standard, and to be familiar with all such safety and health regulations.

      
      

2. Normative References

The following referenced documents are indispensable for the application of this document. For date references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Manual of Petroleum Measurement Standards (MPMS) Chapter 1, Vocabulary

API MPMS Chapter 4 (All Sections), Proving Systems

API MPMS Chapter 5 (All Sections), Metering

API MPMS Chapter 7 (All Sections), Temperature Determination

API MPMS Chapter 9 (All Sections), Density Determination

API MPMS Chapter 11 (All Sections), Physical Properties Data

API MPMS Chapter 12 (All Sections), Calculation of Petroleum Quantities

API MPMS Chapter 13 (All Sections), Statistical Aspects of Measuring and Sampling

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