Design and Construction of Large, Welded, Low-pressure Storage Tanks

API STANDARD 620

ELEVENTH EDITION, FEBRUARY 2008

Design and Construction of Large, Welded, Low-pressure Storage Tanks

Downstream Segment

API STANDARD 620

ELEVENTH EDITION, FEBRUARY 2008

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.

Copyright © 2008 American Petroleum Institute

Foreword

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.

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 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, N.W., Washington, D.C. 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 and updated quarterly by API, 1220 L Street, N.W., Washington, D.C. 20005.

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW, Washington, D.C. 20005, standards@api.org.

iii

Contents

Page

1. Scope 1-1

   1. General 1-1

   2. Coverage 1-1

   3. Limitations 1-3

2. References 2-1

3. Definitions 3-1

   1. Stress and Pressure Terms 3-1

   2. Capacity Terms 3-1

   3. Tank Wall 3-1

   4. Welding Terms 3-1

   5. Other Terms 3-2

4. Materials 4-1

   1. General 4-1

   2. Plates 4-1

   3. Pipe, Flanges, Forging, and Castings 4-6

   4. Bolting Material 4-9

   5. Structural Shapes 4-9

5. Design 5-1

   1. General 5-1

   2. Operating Temperature 5-1

   3. Pressures Used in Design 5-1

   4. Loads 5-2

   5. Maximum Allowable Stress for Walls 5-3

   6. Maximum Allowable Stress Values for Structural Members and Bolts 5-10

   7. Corrosion Allowance 5-13

   8. Linings 5-13

   9. Procedure for Designing Tank Walls 5-14

   10. Design of Sidewalls, Roofs, and Bottoms. 5-16

   11. Special Considerations Applicable to Bottoms That Rest Directly on Foundations 5-26

   12. Design of Roof and Bottom Knuckle Regions and Compression-ring Girders 5-28

   13. Design of Internal and External Structural Members. 5-33

   14. Shapes, Locations, and Maximum Sizes of Wall Openings 5-36

   15. Inspection Openings 5-37

   16. Reinforcement of Single Openings 5-37

   17. Reinforcement of Multiple Openings 5-47

   18. Design of Large, Centrally Located, Circular Openings in Roofs and Bottoms 5-48

   19. Nozzle Necks and Their Attachments to the Tank 5-50

   20. Bolted Flanged Connections 5-51

   21. Cover Plates 5-51

   22. Permitted Types of Joints 5-57

   23. Welded Joint Efficiency 5-58

   24. Plug Welds and Slot Welds 5-58

   25. Stress Relieving 5-59

   26. Radiographic/Ultrasonic Examination 5-60

   27. Flush-type Shell Connection 5-61

       v

6. Fabrication 6-1

   1. General 1

   2. Workmanship 1

   3. Cutting Plates 1

   4. Forming Sidewall Sections and Roof and Bottom Plates 1

   5. Dimensional Tolerances 1

   6. Details of Welding 4

   7. Qualification of Welding Procedure 4

   8. Qualification of Welders 5

   9. Matching Plates 5

   10. Cleaning Surfaces to be Welded 5

   11. Weather Conditions for Welding 6

   12. Reinforcement on Welds 6

   13. Merging Weld With Plate Surface 6

   14. Aligning of Main Joints 6

   15. Repairing Defects in Welds 6

   16. Matching Plates of Unequal Thickness 7

   17. Fitting Up of Closure Plates 7

   18. Thermal Stress Relief 7

   19. Peening Field Welds 7

7. Inspection, Examination and Testing 7-1

   1. Responsibility of Examiner 7-1

   2. Qualifications of Examiners 7-1

   3. Access for Inspector 7-1

   4. Facilities for Inspector. 7-1

   5. Approval of Repairs 7-1

   6. Inspection of Materials 7-1

   7. Stamping of Plates 7-2

   8. Measuring Thickness of Material 7-2

   9. Inspection of Surfaces Exposed during Fabrication 7-2

   10. Surface Inspection of Component Parts 7-2

   11. Check of Dimensions of Component Parts 7-2

   12. Check of Chemical and Physical Property Data 7-2

   13. Data Required from Manufacturer on Completed Tanks 7-2

   14. Check of Stress-relieving Operation 7-2

   15. Examination Method and Acceptance Criteria 7-3

   16. Inspection of Welds 7-5

   17. Radiographic/Ultrasonic Examination Requirements 7-6

   18. Standard Hydrostatic and Pneumatic Tests 7-8

   19. Proof Tests for Establishing Allowable Working Pressures 7-11

   20. Test Gauges 7-12

8. Marking 8-1

   1. Nameplates 8-1

   2. Division of Responsibility 8-2

   3. Manufacturer’s Report and Certificate 8-2

   4. Multiple Assemblies 8-2

9. Pressure- and Vacuum-relieving Devices 9-1

   1. Scope 9-1

   2. Pressure-relieving Devices 9-1

   3. Construction of Devices 9-1

      
      

   4. Means of Venting 9-1

   5. Liquid Relief Valves 9-1

   6. Marking 9-1

   7. Pressure Setting of Safety Devices 9-2

Appendix A Technical Inquiry Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 Appendix B Use of Materials That are Not Identified with Listed Specifications . . . . . . . . . . . . . . . . . . . . . . B-1 Appendix C Suggested Practice Regarding Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Appendix D Suggested Practice Regarding Supporting Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1 Appendix E Suggested Practice Regarding Attached Structures (Internal and External). . . . . . . . . . . . . . . E-1 Appendix F Examples Illustrating Application of Rules to Various Design Problems . . . . . . . . . . . . . . . . . F-1 Appendix G Considerations Regarding Corrosion Allowance and Hydrogen-induced Cracking . . . . . . . . G-1 Appendix H Recommended Practice for Use of Preheat, Post-heat, and Stress Relief . . . . . . . . . . . . . . . . H-1 Appendix I Suggested Practice for Peening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-1

Appendix J (Reserved for Future Use) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .J-1

Appendix K Suggested Practice for Determining the Relieving Capacity Required . . . . . . . . . . . . . . . . . . . K-1 Appendix L Seismic Design of Storage Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-1

Appendix M Recommended Scope of the Manufacturer’s Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M-1

Appendix N Installation of Pressure-relieving Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N-1 Appendix O Suggested Practice Regarding Installation of Low-pressure Storage Tanks . . . . . . . . . . . . . . O-1 Appendix P NDE and Testing Requirements Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-1 Appendix Q Low-pressure Storage Tanks for Liquefied Hydrocarbon Gases . . . . . . . . . . . . . . . . . . . . . . . . Q-1 Appendix R Low-pressure Storage Tanks for Refrigerated Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-1

Appendix S Austenitic Stainless Steel Storage Tanks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-1

Appendix U Ultrasonic Examination in Lieu of Radiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U-1

Figures

1. Isothermal Lines Showing 1-day Mean Ambient Temperature 4-2

2. Minimum Permissible Design Metal Temperature for Pipe, Flanges, and Forgings

   without Impact Testing 4-10

3. Governing Thickness for Impact Test Determination of Pipe, Flanges, and Forgings 4-11

1. Biaxial Stress Chart for Combined Tension and Compression, 30,000 lbf/in.2 – 38,000 lbf/in.2

   Yield Strength Steels 5-5

2. Method for Preparing Lap-welded Bottom Plates under the Tank Sidewall 5-15

3. Detail of Double Fillet-groove Weld for Bottom Plates with a Nominal Thickness

   Greater than 1/2 in 5-15

4. Typical Free-body Diagrams for Certain Shapes of Tanks 5-18

5. Compression-ring Region 5-30

6. Permissible and Non-permissible Details of Construction for a Compression-ring Juncture 5-31

7. Reinforcement of Single Openings 5-38

8. Part 1 Acceptable Types of Welded Nozzles and Other Connections 5-40

5-8 Part 2 Acceptable Types of Welded Nozzles and Other Connections 5-41

5-8 Part 3 Acceptable Types of Welded Nozzles and Other Connections 5-42

1. Part 4 Acceptable Types of Welded Nozzles and Other Connections 5-43

2. Large Head Openings and Conical Shell-reducer Sections 5-49

3. Acceptable Types of Flat Heads and Covers 5-53

4. Spherically Dished Steel Plate Covers with Bolting Flanges 5-55

5. Part 1—Flush-type Sidewall Connection 5-63

1. Part 2—Flush-type Sidewall Connection 5-64

2. Design Factors for Flush-type Connections 5-65

3. Rotation of Sidewall Connection 5-67

1. Shaping of Plates for Steel Tanks 6-2

2. Shaping of Plates for Aluminum Tanks 6-2

3. Butt Welding of Plates of Unequal Thickness 6-8

8-1 Nameplate 8-2

F-1 Reduction of Design Stresses Required to Allow for Biaxial Stress of the Opposite Sign . . . . . . . . F-2 F-2 Examples Illustrating the Use of a Biaxial Stress Chart for Combined Tension and Compression,

30,000 – 38,000 Pounds per Square Inch Yield Strength Steels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-7 F-3 Form for Use in Graphical Solutions of Problems Involving Biaxial Tension and Compression,

30,000 – 38,000 Pounds per Square Inch Yield Strength Steels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-8 F-4 Free-body Sketch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-9

F-5 Example of a Reinforced Opening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-17

F-6 Example of a Reinforced Opening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-21

F-7 Example of a Reinforced Opening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-26

F-8 Example of a Reinforced Opening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-28

L-1 Part 1—Seismic Zone Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-5

L-1 Part 2—Seismic Zone Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-6

1. Curves for Obtaining Factors W1/WT and W2/WT for the Ratio D/H . . . . . . . . . . . . . . . . . . . . . . . . . . . L-7

2. Curves for Obtaining Factors X1/H and X2/H for the Ratio D/H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-7

L-4 Curve for Obtaining Factors k for the Ratio D/H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-7 L-5 Curve for Obtaining the Value of b when M[D2(wt + wL)] Exceeds 0.785 . . . . . . . . . . . . . . . . . . . . . . . L-9 Q-1 Typical Stiffening-ring Weld Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-11 Q-2 Radiographic/Ultrasonic Examination Requirements for Butt-welded Shell Joints in Cylindrical

Flat-bottom Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-19

R-1 Typical Stiffening-ring Weld Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-9 R-2 Radiographic/Ultrasonic Examination Requirements for Butt-welded Shell Joints in Cylindrical

Flat-bottom Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-15

Tables

1. Minimum Requirements for Plate Specifications to be Used for Design Metal Temperatures 4-3

2. Maximum Permissible Alloy Content 4-5

3. Minimum Charpy V-notch Requirements for Plate Specimens 4-7

1. Maximum Allowable Stress Values for Simple Tension 5-6

2. Maximum Allowable Efficiencies for Arc-welded Joints 5-8

3. Maximum Allowable Stress Values for Structural Members. 5-11

4. Sidewall-to-Bottom Fillet Weld for Flat-bottom Cylindrical Tanks 5-15

5. Factors for Determining Values of R1 and R2 for Ellipsoidal Roofs and Bottoms 5-21

6. Tank Radius Versus Nominal Plate Thickness 5-24

7. Allowable Tension Stresses for Uplift Pressure Conditions 5-27

8. Minimum Size of Fillet Weld 5-32

9. Factors for Determining Values of k for Compression-ring Bracing 5-35

10. Dimensions of Flush-type Shell Connections (Inches) 5-61

1. Diameter Range Versus Radius Tolerance 6-3

2. Minimum Preheat Temperatures 6-6

3. Maximum Thickness of Reinforcement on Welds 6-7

4. Stress-relieving Temperatures and Holding Times 6-8

7-1 Maximum Thickness of Reinforcement on Welds for Radiography Examined Joints 7-3

F-1 Computed Values of (t – c)R, sc, st, and N for the Assumed Thicknesses: Example . . . . . . . . . . . . F-5 F-2 Computed Values of (t – c)R, sc, st, and N for the Assumed Thicknesses: Example 2 . . . . . . . . . . . F-9 F-3 Cross-Sectional Area of Standard Angles: Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-13 L-1 Seismic Zone Tabulation for Some Areas Outside the United States . . . . . . . . . . . . . . . . . . . . . . . . . . L-3 L-2 Seismic Zone Factor (Horizontal Acceleration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-3 L-3 Site Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L-8 Q-1 ASTM Materials for Primary Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-2

Q-2 Charpy V-notch Impact Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-4

Q-3 Maximum Allowable Stress Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-7

Q-4A Minimum Thickness for the Annular Bottom Plate: Steel Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-9

Q-4B Minimum Thickness for the Annular Bottom Plate: Aluminum Tanks . . . . . . . . . . . . . . . . . . . . . . . . . Q-9

Q-5 Nominal Thickness of Inner Tank Cylindrical Sidewall Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-13 Q-6 Radius Tolerances for the Inner Tank Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q-13

R-1 Material for Primary Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-3

R-2 Minimum Charpy V-notch Impact Requirements for Primary-component Plate Specimens (Transverse) and Weld Specimens Including the Heat-affected Zone. . . . . . . . . . . . . . . . . . . . . . . . . . R-4

R-3 Material for Secondary Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-5 R-4 Minimum Permissible Design Metal Temperature for Plates Used as Secondary Components

without Impact Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-6

1. Minimum Charpy V-notch Impact Requirements for Secondary-component Plate

   Specimens (Transverse) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-7

2. Thickness Requirements for the Annular Bottom Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-8

S-1a ASTM Materials for Stainless Steel Components (SI Units) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-2

S-1b ASTM Materials for Stainless Steel Components (US Customary Units) . . . . . . . . . . . . . . . . . . . . . . . S-3 S-2 Maximum Allowable Stress Values for Simple Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-4

S-3 Allowable Stresses for Plate Ring Flanges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-5

S-4 Yield Strength Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-5

S-5 Modulus of Elasticity at the Design Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-5 U-1 Flaw Acceptance Criteria for UT Indications (May be Used for All Materials and 201LN) . . . . . . . . . U-5 U-2 Alternate Flaw Acceptance Criteria for UT Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U-6 U-3 Charpy V-notch Impact Values Required to Use Table U-2 for 9% Nickel Steel . . . . . . . . . . . . . . . . . . U-6

Design and Construction of Large, Welded, Low-pressure Storage Tanks

Section 1—Scope

1. General

   
   

   The API Downstream Segment has prepared this standard to cover large, field-assembled storage tanks of the type described in 1.2 that contain petroleum intermediates (gases or vapors) and finished products, as well as other liquid products commonly handled and stored by the various branches of the industry.

   
   

   The rules presented in this standard cannot cover all details of design and construction because of the variety of tank sizes and shapes that may be constructed. Where complete rules for a specific design are not given, the intent is for the Manufacturer—subject to the approval of the Purchaser’s authorized representative—to provide design and construction details that are as safe as those which would otherwise be provided by this standard.

   
   

   The Manufacturer of a low-pressure storage tank that will bear the API 620 nameplate shall ensure that the tank is constructed in accordance with the requirements of this standard.

   
   

   The rules presented in this standard are further intended to ensure that the application of the nameplate shall be subject to the approval of a qualified inspector who has made the checks and inspections that are prescribed for the design, materials, fabrication, and testing of the completed tank.

   
   

2. Coverage

   
   

   1. This standard covers the design and construction of large, welded, low-pressure carbon steel above ground storage tanks (including flat-bottom tanks) that have a single vertical axis of revolution. This standard does not cover design procedures for tanks that have walls shaped in such a way that the walls cannot be generated in their entirety by the rotation of a suitable contour around a single vertical axis of revolution.

      
      

   2. The tanks described in this standard are designed for metal temperatures not greater than 250°F and with pressures in their gas or vapor spaces not more than 15 lbf/in.2 gauge.

      
      

   3. The basic rules in this standard provide for installation in areas where the lowest recorded 1-day mean atmospheric temperature is –50°F. Appendix S covers stainless steel low-pressure storage tanks in ambient temperature service in all areas, without limit on low temperatures. Appendix R covers low-pressure storage tanks for refrigerated products at temperatures from +40°F to –60°F. Appendix Q covers low-pressure storage tanks for liquefied hydrocarbon gases at temperatures not lower than –270°F.

      
      

   4. The rules in this standard are applicable to tanks that are intended to (a) hold or store liquids with gases or vapors above their surface or (b) hold or store gases or vapors alone. These rules do not apply to lift-type gas holders.

      
      

   5. Although the rules in this standard do not cover horizontal tanks, they are not intended to preclude the application of appropriate portions to the design and construction of horizontal tanks designed in accordance with good engineering practice. The details for horizontal tanks not covered by these rules shall be equally as safe as the design and construction details provided for the tank shapes that are expressly covered in this standard.

      
      

   6. Appendix A provides information on the preparation and submission of technical inquiries as well as responses to recent inquiries.

      
      

   7. Appendix B covers the use of plate and pipe materials that are not completely identified with any of the specifications listed in this standard.

1-1