API Standard 620

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3 To for 5 F. For Onl Pho Fax APIe, WeldDUCTNO. C620r ordering inforline: : 1-800-8(Toll-free(+1) 303(Local anx: (+1) 303I members receded, Lo012rmation: 54-7179 e in the an3-397-7056 nd Internationa3-397-2740 eive a 30% disow-presd Canada) al) scount where assure applicable. ContentsPage1 Scope .. General .. Coverage.. Limitations .. 1-32 References .. 2-13 Definitions .. Stress and Pressure Terms .. Capacity Terms .. Tank Wall.. Welding Terms .. Other Terms .. 3-34 Materials .. General .. Plates.. Pipe, Flanges, Forging, and Castings .. Bolting Material .. Structural Shapes .. 4-105 Design .. General .. Operating Temperature .. Pressures Used in Design.

4 Loads.. Maximum Allowable Stress for Walls .. Maximum Allowable Stress Values for Structural Members and Bolts .. Corrosion Allowance.. Linings .. Procedure for Designing Tank Walls .. Design of Sidewalls, Roofs, and Bottoms .. Special Considerations Applicable to Bottoms That Rest Directly on Foundations.. Design of Roof and Bottom Knuckle Regions and Compression-ring Girders.. Design of Internal and External Structural Members .. , Locations, and Maximum Sizes of Wall Openings .. Inspection Openings .. Reinforcement of Single Openings .. Reinforcement of Multiple Openings.. Design of Large, Centrally Located, Circular Openings in Roofs and Bottoms.

5 Nozzle Necks and Their Attachments to the Tank .. Flanged Connections .. Cover Plates .. Permitted Types of Joints .. Welded Joint Efficiency .. Plug Welds and Slot Welds.. Stress Relieving .. Radiographic/Ultrasonic Examination .. Flush-type Shell Connection .. 5-64vPage6 Fabrication.. General .. Workmanship .. Cutting Plates.. Forming Sidewall Sections and Roof and Bottom Plates.. Dimensional Tolerances .. Details of Welding .. Qualification of Welding Procedure .. Qualification of Welders .. Matching Plates .. Cleaning Surfaces to be Welded .. Weather Conditions for Welding .. Reinforcement on Welds.. Merging Weld With Plate Surface.

6 Aligning of Main Joints .. Repairing Defects in Welds.. Matching Plates of Unequal Thickness.. Fitting Up of Closure Plates .. Thermal Stress Relief .. Peening Field Welds ..6-87 Inspection, Examination and Testing .. Responsibility of Inspector .. Qualifications of Inspectors .. Access for Inspector .. Facilities for Inspector .. Approval of Repairs.. Inspection of Materials .. Stamping of Plates .. Measuring Thickness of Material.. Inspection of Surfaces Exposed during Fabrication.. Surface Inspection of Component Parts.. Check of Dimensions of Component Parts .. Check of Chemical and Physical Property Data .. Data Required from Manufacturer on Completed Tanks.

7 Check of Stress-relieving Operation .. Examination Method and Acceptance Criteria.. Inspection of Welds.. Radiographic/Ultrasonic Examination Requirements.. Standard Hydrostatic and Pneumatic Tests .. Proof Tests for Establishing Allowable Working Pressures.. Test Gauges ..7-128 Marking .. Nameplates.. Division of Responsibility.. Manufacturer s Report and Certificate .. Multiple Assemblies ..8-29 Pressure- and Vacuum-relieving Devices.. Scope .. Pressure-relieving Devices .. Construction of Devices .. Means of Venting .. Liquid Relief Valves.. Marking .. Pressure Setting of Safety Devices..9-2 Annex A (informative) Inquiries and Suggestions for Change .. A-1 Annex B (normative) Use of Materials That are Not Identified with Listed Specifications.

8 B-1 Annex C (informative) Suggested Practice Regarding Foundations .. C-1 Annex D (informative) Suggested Practice Regarding Supporting Structures .. D-1 Annex E (informative) Suggested Practice Regarding Attached Structures (Internal and External).. E-1 Annex F (informative) Examples Illustrating Application of Rules to Various Design Problems.. F-1 Annex G (informative) Considerations Regarding Corrosion Allowance and Hydrogen-induced Cracking G-1 Annex H (informative) Recommended Practice for Use of Preheat, Post-heat, and Stress Relief.. H-1 Annex I (informative) Suggested Practice for Peening .. I-1 Annex J (Reserved for Future Use) ..J-1 Annex K (informative) Suggested Practice for Determining the Relieving Capacity Required.

9 K-1 Annex L (normative) Seismic Design of Storage Tanks .. L-1 Annex M (informative) Recommended Scope of the Manufacturer s Report .. M-1 Annex N (normative) Installation of Pressure-relieving Devices .. N-1 Annex O (informative) Suggested Practice Regarding Installation of Low-pressure Storage Tanks .. O-1 Annex P (informative) NDE and Testing Requirements Summary .. P-1 Annex Q (normative) Low-pressure Storage Tanks for Liquefied Gases at 325 F or Warmer .. Q-1 Annex R (normative) Low-pressure Storage Tanks Operating Between +40 F and 60 F .. R-1 Annex S (normative) Austenitic Stainless Steel Storage Tanks .. S-1 Annex SC (normative) Stainless and Carbon Steel Mixed Materials Storage Tanks .. SC-1 Annex U (normative) Ultrasonic Examination in Lieu of Radiography.

10 U-1 Annex X (normative) Duplex Stainless Steel Storage Tanks .. X-1 Figures4-1 Isothermal Lines Showing 1-day Mean Ambient Temperature ..4-34-2 Minimum Permissible Design Metal Temperature for Pipe, Flanges, and Forgingswithout Impact Testing ..4-104-3 Governing Thickness for Impact Test Determination of Pipe, Flanges, and Forgings ..4-125-1 Biaxial Stress Chart for Combined Tension and Compression, 30,000 38,000 Strength Steels ..5-55-2 Method for Preparing Lap-welded Bottom Plates under the Tank Sidewall ..5-165-3 Detail of Double Fillet-groove Weld for Bottom Plates with a Nominal Thickness Greater than 1/2in..5-175-4 Typical Free-body Diagrams for Certain Shapes of Tanks ..5-185-5 Compression-ring Region.