Manual of Petroleum Measurement Standards Chapter 17.5

El Hydrocarbon Management HM 64

Guidelines for Voyage Analysis and Reconciliation of Cargo Quantities

3rd edition, April 2012

API MPMS Chapter 17.5/EI HM 64

Guidelines for Voyage Analysis and Reconciliation of Cargo Quantities

3rd Edition April 2012

Published jointly by

API

and

ENERGY INSTITUTE LONDON

The Energy Institute is a professional membership body incorporated by Royal Charter 2003 Registered charity number 1097899

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Foreword

This publication was prepared jointly by the American Petroleum Institute Committee on Petroleum Measurement and the Energy Institute Hydrocarbon Management Committee.

The American Petroleum Institute Committee on Petroleum Measurement (COPM) and the Energy Institute's Hydrocarbon Management Committee (HMC) are responsible for the production and maintenance of standards and guides covering various aspects of static and dynamic measurement of petroleum. API COPM and EI HMC, their sub- committees and work groups consist of technical specialists representing oil companies, equipment manufacturers, service companies, terminal and ship owners and operators. API COPM and EI HMC encourage international participation and when producing publications their aim is to represent the best consensus of international technical expertise and good practice. This is the main reason behind the production of joint publications involving cooperation with experts from both the API and EI.

API/EI standards are published as an aid to procurement of standardized equipment and materials and/or as good practice procedures. These standards are not intended to inhibit purchasers or producers from purchasing or producing products made to specifications other than those of API or EI.

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 publication was produced following API/EI standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API/EI 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, USA, or the Technical Department, Energy Institute, 61 New Cavendish Street, London, W1G 7AR, UK.

Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the Director of Standards (API) or the Technical Department (EI). Generally, API/EI 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, 1220 L Street, NW, Washington, DC 20005, USA, or the EI Technical Department, Energy Institute, 61 New Cavendish Street, London, W1G 7AR, UK.

A catalogue of API publications can be found at www.api.org/publications. A catalogue of EI publications can be found at www.energypublishing.org.

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, DC 20005, USA, standards@api.org or to the Technical Department, Energy Institute, 61 New Cavendish Street, London, W1G 7AR, UK.

iii

Contents

Page

1. Scope 1

2. Normative References 1

   1. General 1

   2. API/EI Joint Documents 1

   3. API Documents 1

   4. Other Documents. 1

3. Definitions 2

4. Cargo Reconciliation 3

   1. General 3

   2. Collecting Information and Data 3

   3. The Voyage Analysis Report (VAR) 3

   4. The Voyage Summary and Reconciliation Report (VSRR)6

5. Possible Causes of Losses or Gains 7

   1. General 7

   2. Cargo Transfer Measurement Points 7

   3. Shore Measurements 8

   4. Vessel Measurements 11

   5. Water Determination 14

   6. Additional Factors 16

   7. Measurement Uncertainties and Errors 18

Annex A (informative) Instructions for Completion of Voyage Analysis Forms 20

Annex B (informative) Examples of Cargo Analysis and Reconciliation 27

Bibliography 39

Figures

1 Four Point Reconciliation 8

1. Voyage Analysis Report (VAR) 23

2. Summary of Vessel-to-Vessel Transfers 24

3. Field Facts 25

4. Voyage Summary and Reconciliation Report (VSRR) 26

1. Voyage Analysis Report (VAR) Summary 31

2. Voyage Analysis Report (VAR) 32

3. Voyage Analysis Report (VAR) 33

4. Voyage Analysis Report (VAR) 34

5. Voyage Analysis Report (VAR) 35

6. Voyage Analysis Report (VAR) 36

7. Voyage Summary and REconciliation Report (VSRR) 37

8. Voyage Analysis Report (VAR) 38

Tables

1. Bill of Lading to Outturn Comparison 5

2. Shore to Vessel Comparison—Load Port(s) 5

3. Vessel to Shore Comparison—Discharge Port(s) 5

4. Vessel Transit Comparison 6

5. OBQ/ROB Comparison 6

A.1 Recommended Forms for Complex Voyage Analysis 22

v

Introduction

The shipment of petroleum or petroleum products by marine vessels may result in a difference between the load port and discharge port quantities. This difference, gain or loss, will be caused by one or more of the following:

1. Physical Loss/Gain is an actual loss or gain of cargo (sometimes referred to as “Real Loss or Gain”). Physical losses can be the result of evaporation, unmeasured ROB, line fill, cargo diversion, spillage or theft.

   Evaporative loss may occur during load/discharge operations and during transit. Daily temperature variations and movement of the cargo during the voyage (sloshing) will increase evaporative losses. Cargos with higher vapor pressure are likely to suffer greater evaporative losses.

   
   

   The ROB (quantity remaining on board) is the liquid and non liquid cargo left on board the vessel after discharge. The ROB measurement can only include cargo which remains on the tank floor and can be measured from available gauge points. Unmeasured ROB can occur when a vessel is out of trim and it is not possible to measure the cargo from the tank available gauge points. That cargo which remains as clingage on the tank sides or other internal structure is not included in the ROB measurement and will result in a real loss when the outturn is considered. The amount of clingage will be dependent upon cargo viscosity and temperature.

   
   

   Line fill losses result from transfer lines which contain more cargo after the movement than before, leading to reduced quantities being measured in the receiving tanks. This can occur during loading or discharge.

   
   

   Cargo diversion can occur inadvertently as a result of incorrectly set or leaking valves, operator error, or intentionally as theft.

   
   

   While physical gains are not common, some cargos with the ability to absorb water or to blend with other components or additives may show physical gain. In addition, gains may be caused by physical operations and equipment errors or failures such as cargo diversion, Crude Oil Washing (COW) recovering clingage from previous cargo, etc.

   
   

2. Apparent Loss/Gain is a difference in quantity which is not related to a physical loss. Apparent losses include errors which can possibly be corrected and also differences due to uncertainties in the measurement systems which generally cannot be removed. The majority of individual losses and gains are apparent rather than real and fall into the following categories.

Measurement error includes all the errors associated with measurement procedures, equipment and operator performance. These errors can be in liquid level or meter measurements, determining temperature, sampling, tank calibration, and laboratory testing methods.

Procedural error occurs when operations deviate from the industry measurement standards and good practice. An example would be the failure to ensure pipeline fullness at the start of the cargo transfer.

Calibration error relates to accuracy (calibration) of the measurement equipment. Only the base international standards are deemed to be exact. The possibility of introducing a fixed error or bias increases with every step in the calibration chain, moving from the base standard to the field device. Random error or uncertainty increases with each step.

Further, all measurement equipment is affected by use and handling, so regular field checks and calibrations are necessary to ensure that equipment continues to provide accurate measurements.

Paper Loss/Gain is a term frequently used to include all Apparent Losses/Gains. It is the result of calculation errors which may occur when converting basic measurement data into cargo quantities. Computer programmes and calculators have reduced the risk of mathematical errors but the cargo calculations should always be checked when a large discrepancy occurs.

vi

Guidelines for Voyage Analysis and Reconciliation of Cargo Quantities

1. Scope

   This standard covers guidelines for the reconciliation of marine cargo quantities. These guidelines are intended to provide a basis for analyzing and reconciling the quantity differences (gains/losses) resulting from marine custody transfer movement(s) of petroleum and petroleum product cargoes. As such, the guidelines are complementary to, but do not replace, normal inspection procedures.

   
   

2. Normative References

   1. General

      
      

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

      
      

      The following documents may be referenced to supplement the information presented in this chapter:

      
      

   2. API/EI Joint Documents

      
      

      API MPMS Chapter 17.6/EI HM66, Guidelines for Determining the Fullness of Pipelines between Vessels and Shore Tanks

      
      

      API MPMS Chapter 17.9/EI HM49, Vessel Experience Factor

      
      

      API MPMS Chapter 17.11/EI HM52, Measurement and Sampling of Cargoes On Board Tank Vessels Using Closed/ Restricted Equipment

      
      

   3. API Documents

      
      

      API MPMS Chapter 17.1, Guidelines for Marine Cargo Inspection

      
      

      API MPMS Chapter 17.3, Guidelines for Identification of the Source of Free Waters Associated with Marine Petroleum Cargo Movements

      
      

   4. EI Document

      
      

      EI HM40 1, Guidelines for the crude oil washing of ships’ tanks and the heating of crude oil being transported by sea

      
      

   5. Other Documents

Marpol 73/78 2, The International Convention for the Prevention of Pollution from Ships

1. Energy Institute, formerly the Institute of Petroleum, 61 New Cavendish Street, London W1G 7AR, UK.

2. International Maritime Organization (IMO) Publishing, 4 Albert Embankment, London SE1 7SR, United Kingdom, sales@imo.org.

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