Manual of Petroleum Measurement Standards Chapter 17.4

Method for Quantification of Small Volumes on Marine Vessels (OBQ/ROB)

SECOND EDITION, SEPTEMBER 2016

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Foreword

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Contents

1. Scope 1

2. Normative References 1

3. Terms and Definitions 1

4. Safety and Health Considerations 2

   1. General 2

   2. Static Electricity Hazards 3

   3. Health Hazards 3

5. Quantification Procedures 3

   1. General 3

   2. Gauging 4

   3. Temperatures 4

   4. Sampling 4

   5. Vessel Cargo Lines and Pumps 4

   6. Slops 4

6. OBQ/ROB Characteristics 4

   1. General 4

   2. Liquid Material 5

   3. Nonliquid Material 5

7. Calculating Quantities 5

Annex A (normative) Small Volume Calculations and Configuration Equations 6

Annex B (informative) On Board Quantity/Remaining On Board Report 18

Annex C (normative) Wedge Calculation 21

Bibliography 25

Figures

1. Nonliquid Only 7

2. Single Liquid in Contact with All Four Bulkheads 8

3. Single Liquid in Contact with Three Bulkheads Only 9

4. Single Liquid above Nonliquid (Liquid in Contact with All Four Bulkheads) 11

5. Single Liquid above Nonliquid (Liquid in Contact with Three Bulkheads Only) 12

6. Two Liquids (Both Liquids in Contact with All Four Bulkheads) 13

7. Two Liquids (Lower Liquid in Contact with Three Bulkheads Only) 14

8. Two Liquids (Both Liquids in Contact with Three Bulkheads Only) 15

9. Two Liquids with a Nonliquid Lower Layer (Lower Layer Liquid in Contact with Three Bulkheads Only) . . 15

10. Two Liquids with a Nonliquid Lower Layer (Lower Layer Liquid in Contact with All Four Bulkheads) . . . 17

11. Two Liquids with a Nonliquid Lower Layer (Both Liquids in Contact with Three Bulkheads Only) 17

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Introduction

The purpose of this standard is to provide a method for determining the small volumes of on board quantity (OBQ) prior to loading a vessel or material remaining on board (ROB) a vessel upon completion of discharge.

Method for Quantification of Small Volumes on Marine Vessels (OBQ/ROB)

1. Scope

   
   

   This standard applies only to quantification by manual gauging of small volumes on marine vessels prior to loading or upon completion of discharge. It does not address clingage, hydrocarbon vapors, cargoes in transit, or cargo pumpability. Refer to API Manual of Petroleum Measurement Standards (MPMS) Chapter 3.

   
   

2. Normative References

   
   

   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.

   
   

   API MPMS Chapter 3 (all relevant sections), Tank Gauging

   
   

   API MPMS Chapter 3.1A, Standard Practice for the Manual Gauging of Petroleum and Petroleum Products

   
   

   API MPMS Chapter 7, Temperature Determination

   
   

   API MPMS Chapter 8.1, Manual Sampling of Petroleum and Petroleum Products

   
   

   API MPMS Chapter 12.1.1, Calculation of Static Petroleum Quantities—Upright Cylindrical Tanks and Marine Vessels

   
   

   API MPMS Chapter 17.1, Guidelines for Marine Inspection

   
   

   API MPMS Chapter 17.2, Measurement of Cargoes On Board Tank Vessels

   
   

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

   
   

3. Terms and Definitions

For the purposes of this standard, the following terms and definitions apply. Other terms used in this standard are defined in API MPMS Chapter 1 or other API petroleum-measurement standards.

3.1

clingage

Cargo that adheres to all surfaces of the emptied portion of the tank other than bottom surfaces.

3.2

liquid volume

The measurable amount of material that is free-flowing at the time of measurement.

3.3

multipoint gauging

The activity of measuring cargo in a vessel tank through two or more openings in the top of the tank.

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