Manual of Petroleum Measurement Standards Chapter 2.2A

Measurement and Calibration of Upright Cylindrical Tanks

by the Manual Tank Strapping Method

SECOND EDITION, NOVEMBER 2019

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Contents

Page

1. Scope 1

2. Normative References 1

3. Safety 1

4. Terms and Definitions 2

5. Significance 3

6. Equipment 3

   1. General 3

   2. Tapes for Height Measurement 3

   3. Tapes for Circumference Measurement 4

   4. Accessory Equipment 4

7. Calibration of Working Tape with the Master Tape 5

8. General Practices 7

9. Tank Status Before Calibration 7

10. Descriptive Data 7

11. Tolerances 11

12. Shell Plate Thickness 11

13. Vertical Tank Measurements 15

14. Circumferential Measurements 21

    1. Preparation 21

    2. Physical Measurements 22

15. Deadwood Management 22

16. Tank Bottoms 23

17. Floating Roofs 25

    1. General 25

    2. Floating Roof Weight 26

    3. Deadwood Determination 26

    4. Deducting Floating Roof Displacement 26

18. Insulated Tanks 27

19. Tank Capacity Table Development-Calculation Procedures 27

    1. General 27

    2. Capacity Table Requirements 28

    3. Calibration of the Master Tape to 60 °F 31

    4. Conversion of Outside to Inside Circumferences 31

    5. Deductions for Circumference Tape Rises 31

    6. Expansion and Contraction of Steel Tank Shells due to Liquid Head 32

    7. Expansion and Contraction of Steel Tank Shells due to Temperature 35

    8. Effect of Tilt on Cylindrical Portion of Tank 36

    9. Floating Roofs 36

    10. Summary Data on the Capacity Table 39

    11. Recalibration Requirements 39

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        Contents

        Page

    12. Certification of Capacity Tables 40

Annex A (normative) Tank Calibration Frequency and Recomputation of Calibration Tables 41

Annex B (informative) Example Calculations for Upright Cylindrical Steel Tank—Aboveground 48

Annex C (informative) Guidelines for Computer Input 65

Annex D (informative) Shell Temperature Correction Factors 67

Annex E (informative) Underground Tanks 72

Annex F (informative) Tank Calibration Method Selection 78

Bibliography 81

Figures

1. Height Measuring Tape and Bob 3

2. Strapping Tapes for Circumference Measurements 4

3. Jointed-type Tape Guides 5

4. Record Form for Deadwood 8

5. Measurement Locations for Welded Upright Tanks 12

6. Measurement Locations for Riveted Shingled Arrangement 13

7. Measurement Locations for Bolted Tanks 14

8. Vertical Tank Measurements (Welded) 16

9. Vertical Tank Measurements (Bolted) 17

10. Vertical Tank Measurements (Riveted) 18

11. Effective Inside Tank Height (Cone Roof) 19

12. Effective Inside Tank Height (Floating Roof) 20

13. Spherical Segment (Dished), Hemispherical and Semiellipsoidal Bottoms Convex,

    and Accessible Measurements of Upright Tanks 24

14. Coned Downward Bottom and Accessible Measurements of Upright Tanks 25

15. Diagram of Floating Roof at Rest (A) and Floating (B) 26

16. Typical Steel Pontoon Floating Roof with Single Center Deck 27

17. True Circumference vs Tape Path at Axial Lap Joint Away from Circumferential Joint 33

1. Uniform Zone As Identified on an Increment Table 44

2. Summary of Tank Volume Shift (%) Relationship to Tank Calibration Interval (years) 45

1. Upright Cylindrical Tank, Composite Construction 51

2. Typical NIST Report of Calibration 52

1. Locations of Measurements on Upright Cylindrical Concrete Underground Tanks 74

2. Locations of Measurements on Rectangular Steel or Concrete Underground Tanks 76

1. External Floating Roof Tank Decision Chart 79

2. Fixed Roof Tank Decision Chart 79

3. Chart for Internal Floating Roof Tanks 80

Tables

1. Suggested Record Form “A” for Measurements of Upright Cylindrical Tanks 9

2. Suggested Record Form “B” for Measurements of Upright Cylindrical Tanks 10

3. Elevations for Circumference Measurements on Various Types of Upright Cylindrical Tanks 21

4. Circumferential Tolerances 22

5. Customary Version Capacity Table—Example Capacity Table—Tank No. 117 Floating Roof 29

6. SI Version Capacity Table—Example Capacity Table—Tank No. 117 Floating Roof 30

Contents

Page

1. Next Calibration Interval Calculation. 45

2. Examples of Tank Calibration Interval Calculation Results 45

3. Product Specific Gravity Impact to Volume (Illustrative) 46

1. Typical Measurement Record of an Upright Cylindrical

   Steel Tank for Example Calculations 53

2. Summary of Circumference Corrections 54

B.3A Tank Table Run Sheet 62

B.3B Run Sheet for Soft Conversion to Metric 63

Measurement and Calibration of Upright Cylindrical Tanks by the Manual Tank Strapping Method

1. Scope

   
   

   1. This standard describes the procedures for calibrating upright cylindrical tanks used primarily for the storage of petroleum liquids. It first addresses procedures for making necessary measurements to determine total and incremental tank volumes and then presents the recommended procedures for computing volumes.

      
      

   2. Both SI (metric) and U.S. customary (USC) units are presented where appropriate in the document. SI and USC conversions may not necessarily be exact. The SI units often reflect what is available in commercial equipment.

      
      

   3. The standard also provides guidelines for recalibration and for computerization of capacity tables.

      
      

2. Normative References

   
   

   The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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 Manual of Petroleum Measurement Standards (MPMS) Chapter 2.2B, Calibration of Upright Cylindrical Tanks Using the Optical Reference Line Method

   
   

   API Standard 650, Welded Steel Tanks for Oil Storage

   
   

   API Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction

   
   

   API Standard 2555, Method for Liquid Calibration of Tanks

   
   

   ICS 1/OCIMF 2/IAPH 3, International Safety Guide for Oil Tankers and Terminals (ISGOTT) 4

   
   

   IP 5 Petroleum Measurement Manual, Part 2, “Tank Calibration,” Section 1, “Vertical Cylindrical Tanks, Measurement Methods”

   
   

   NFPA 306 6, Standard for the Control of Gas Hazards on Vessels

   
   

3. Safety

   
   

   1. Before entering any tank, permission shall be obtained from the terminal supervisor, authorized official, or other responsible person in charge. This responsible person should supply information regarding particular materials and conditions or the applicable Material Safety Data Sheet (MSDS).

      
      

   2. Due consideration should be given to applicable safety procedures. Safety considerations include, but are not limited to, potential electrostatic hazards, potential personnel exposure (and associated protective

1 International Chamber of Shipping, 38 St Mary Axe Street, London EC3A 8BH, United Kingdom, www.ics-shipping.org.

2 Oil Companies International Marine Forum, 27 Queen Anne’s Gate, London, SW1H 9BU, United Kingdom, www.ocimf.com.

3 International Association of Ports and Harbors, 7th Floor, South Tower New Pier Takeshiba 1-16-1 Kaigan, Minato-ku, Tokyo 105-0022, www.iaphworldports.org.

4 ISGOTT is available from Witherby Publishing Group Ltd. (Marine Publishing), 32/36 Aylesbury Street, London ECIR OET, United Kingdom.

5 Institute of Petroleum, 61 New Cavendish Street, London W1M 7AR, United Kingdom, www.energyinst.org.uk.

6 National Fire Protection Association, 1 Batterymarch Park, Quincy, Massachusetts 02169-7471, www.nfpa.org.

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