Manual of Petroleum Measurement Standards Chapter 17.14.1

Measurement of Bulk Cargoes

by Draft Survey—Ocean-going Vessels

FIRST EDITION, OCTOBER 2019

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms and Definitions 1

4. Significance and Use 4

5. Health and Safety Precautions 4

   1. General 4

   2. Static Electricity Hazards 4

6. Communication and Vessel Familiarization 5

   1. Key Meeting 5

7. The Survey 5

   1. Tools Required for the Survey 6

   2. Determining the Draft 6

   3. Measuring Variable and Consumable Items 8

8. Calculation Process 12

   1. Adjusting the Draft Readings to the Perpendiculars 12

   2. Calculating the Three-Quarter (¾) Mean Draft 13

   3. Determining the Corrected Displacement 14

   4. Determination of Net Weights 16

9. Reporting 17

   1. Initial and Final Survey Spreadsheet 17

Annex A (informative) Tools Required for the Survey 21

Annex B (Informative) Using a Manometer 22

Annex C (informative) Hydrometers 26

Annex D (informative) Salinity Refractometers 28

Annex E (informative) Survey Template 30

Bibliography 31

Figures

1. Draft Marks (Shown in Metric Decimeters) 6

2. Draft Marks (Shown in US Customary Fee) 7

3. Vessel Trimmed by the Stern 9

4. Small Quantity of Liquid in Vessel Trimmed by the Stern 10

5. Reading the Hydrometer 12

6. Initial Survey Worksheet 18

   Contents

   Page

7. Final Survey Worksheet 19

8. Summary Report Worksheet 20

1. Manometer Long Enough to Reach Vessel Sides 23

2. Manometer Not Long Enough to Reach Vessel Sides 24

3. Manometer Showing Plastic Tubing (30–40 m long) 25

C.1 Glass Hydrometer 27

D.1 Refractometer 28

Tables

1 Example of Draft Readings Adjusted to Perpendiculars 13

Measurement of Bulk Cargoes by Draft Survey—Ocean-going Vessels

1. Scope

   
   

   This document describes the procedure for determining the transferred quantity of non-liquid petroleum products loaded onto or discharged from ocean-going vessels by draft survey. This procedure is not an alternative where effective static or dynamic liquid measurement methods can be used.

   
   

2. Normative References

The following documents are referred to in the text in such a way that some or all of their content constitutes requirement of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any addenda) applies.

API MPMS Chapter 11.5, Density/Weight/Volume Intraconversion

API MPMS Chapter 17.4, Method for Quantification of Small Volumes on Marine Vessels (OBQ/ROB)

3 Terms and Definitions

For the purposes of this document, the following definitions apply.

3.1

aft draft

The distance from the bottom of the keel to the waterline on aft perpendicular.

3.2

aft perpendicular

A vertical line drawn at the intersection of the waterline at the vessel’s summer draft marks and the aft edge of the rudder post, or, in the case of most modern ships where no rudder post is fitted, the center line of the rudder stock.

3.3

apparent trim

The difference between the forward draft and the aft draft as read and not corrected to the vessel’s perpendiculars.

3.4

apparent weight

Weight in air.

3.5

beam

The transverse dimensions in a horizontal plane expressing the breadth or width of the ship or ocean-going barge, and measured from side shell plating to side shell plating.

3.6

corrected mean draft (CMD)

The draft as calculated at the center of flotation; may not be equal to the average of the drafts forward and aft. An inland barge's final draft is calculated using the quarter mean method.

3.7

corrected trim

The apparent trim corrected to the perpendiculars.