API Standard 650 Welded Tanks for Oil Storage

✍ Scribed by API

• Publisher: API
• Year: 2020
• Tongue: English
• Leaves: 514
• Category: Library

✦ Synopsis

This Standard is based on the accumulated knowledge and experience of Purchasers and Manufacturers of welded
oil storage tanks of various sizes and capacities for internal pressures not more than 17.2 kPa (21/2 pounds per
square inch) gauge. This Standard is meant to be a purchase specification to facilitate the manufacture and
procurement of storage tanks for the petroleum industry.
If the tanks are purchased in accordance with this Standard, the Purchaser is required to specify certain basic
requirements. The Purchaser may want to modify, delete, or amplify sections of this Standard, but reference to this
Standard shall not be made on the nameplates of or on the Manufacturer’s certification for tanks that do not fulfill the
minimum requirements of this Standard or that exceed its limitations. It is strongly recommended that any
modifications, deletions, or amplifications be made by supplementing this Standard rather than by rewriting or
incorporating sections of it into another complete standard.
The design rules given in this Standard are minimum requirements. More stringent design rules specified by the
Purchaser or furnished by the Manufacturer are acceptable when mutually agreed upon by the Purchaser and the
Manufacturer. This Standard is not to be interpreted as approving, recommending, or endorsing any specific design or
as limiting the method of design or construction.
The verbal forms used to express the provisions in this document are as follows.
Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the standard.
Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order
to conform to the standard.
May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard.
Can: As used in a standard, “can” denotes a statement of possibility or capability.

✦ Table of Contents

Cover
Figures
Figure 4.1a—Minimum Permissible Design Metal Temperature for Materials Used in Tank Shells withoutImpact Testing (SI)
Figure 4.1b—Minimum Permissible Design Metal Temperature for Materials Used in Tank Shells withoutImpact Testing (USC)
Figure 4.2—Isothermal Lines of Lowest One-Day Mean Temperatures (°F)
Figure 4.3—Governing Thickness for Impact Test Determination of Shell Nozzle andManhole Materials
Figure 5.1—Typical Vertical Shell Joints
Figure 5.2—Typical Horizontal Shell Joints
Figure 5.3a—Typical Roof and Bottom Joints
Figure 5.3b—Method for Preparing Lap-welded Bottom Plates under Tank Shell
Figure 5.3c—Detail of Double Fillet-groove Weld for Annular Bottom Plates with a Nominal ThicknessGreater than 13 mm (1/2 in.)
Figure 5.3d—Spacing of Three-Plate Welds at Annular Plates
Figure 5.4—Storage Tank
Figure 5.5—Drip Ring (Suggested Detail)
Figure 5.6—Minimum Weld Requirements for Openings in Shells According to 5.7.3
Figure 5.7a—Shell Manhole
Figure 5.7b—Details of Shell Manholes and Nozzles
Figure 5.8—Shell Nozzles (see Tables 5.6a, 5.6b, 5.7a, 5.7b, 5.8a, and 5.8b)
Figure 5.9—Minimum Spacing of Welds and Extent of Related Radiographic Examination
Figure 5.10—Shell Nozzle Flanges (see Table 5.8a and Table 5.8b)
Figure 5.11—Area Coefficient for Determining Minimum Reinforcement of Flush-type Cleanout Fittings
Figure 5.12—Flush-Type Cleanout Fittings (see Tables 5.9a, 5.9b, 5.10a, 5.10b, 5.11a, and 5.11b)
Figure 5.13—Flush-type Cleanout Fitting Supports (see 5.7.7)
Figure 5.14—Flush-type Shell Connection
Figure 5.15—Rotation of Shell Connection
Figure 5.16—Roof Manholes (see Table 5.13a and Table 5.13b)
Figure 5.17—Rectangular Roof Openings with Flanged Covers
Figure 5.18—Rectangular Roof Openings with Hinged Cover
Figure 5.19—Flanged Roof Nozzles (see Table 5.14a and Table 5.14b)
Figure 5.20—Threaded Roof Nozzles (see Table 5.15a and Table 5.15b)
Figure 5.21—Drawoff Sump (see Table 5.16a and Table 5.16b)
Figure 5.22—Scaffold Cable Support
Figure 5.23—Grounding Lug
Figure 5.24—Typical Stiffening-ring Sections for Tank Shells (see Table 5.19a and Table 5.19b)
Figure 5.25—Stairway Opening through Stiffening Ring
Figure 5.26—Some Acceptable Column Base Details
Figure 5.27—Overturning Check for Self-anchored Tanks
Figure 5.28—Typical Anchor Chair
Figure 5.29—Typical Anchor Strap Welded Attachment (for Carbon Steel Tank)
Figure 5.30—Typical Hold-down Strap Configuration (for Carbon Steel Tank)
Figure 5.31—Butt Weld Joint with Back-up Bar
Figure 6.1—Shaping of Plates
Figure 8.1—Radiographic Requirements for Tank Shells
Figure 10.1—Manufacturer’s Nameplate
Figure 10.2—Manufacturer’s Certification Letter
Figure AL.1—Cover Plate Thickness for Shell Manholes and Cleanout Fittings
Figure AL.2—Flange Plate Thickness for Shell Manholes and Cleanout Fittings
Figure AL.3—Bottom Reinforcing Plate Thickness for Cleanout Fittings
Figure AL.4—Stresses in Roof Plates
Figure B.1—Example of Foundation with Concrete Ringwall
Figure B.2—Example of Foundation with Crushed Stone Ringwall
Figure E.1—Coefficient Ci
Figure EC.1—Maximum Earthquake Response Spectrum
Figure EC.2—Earthquake Response Spectrum Notation
Figure EC.3—Site Specific Response Spectrum
Figure EC.4—Deterministic Lower Limit on MCE Response Spectrum
Figure EC.5—Relationship of Probabilistic and Deterministic Response Spectra
Figure EC.6—Sloshing Factor, Ks
Figure EC.7—Design Response Spectra for Ground-Supported Liquid Storage Tanks
Figure EC.8—Effective Weight of Liquid Ratio
Figure EC.9—Center of Action of Effective Forces
Figure EC.10—Overturning Moment
Figure F.1—Annex F Decision Tree
Figure F.2—Permissible Details of Compression Rings
Figure G.1—Data Sheet for a Structurally-Supported Aluminum Dome Added to an Existing Tank
Figure G.2—Typical Roof Nozzle
Figure I.1—Concrete Ringwall with Undertank Leak Detection at the Tank Perimeter (Typical Arrangement)
Figure I.2—Crushed Stone Ringwall with Undertank Leak Detectionat the Tank Perimeter (Typical Arrangement)
Figure I.3—Earthen Foundation with Undertank Leak Detection at the Tank Perimeter (Typical Arrangement)
Figure I.4—Double Steel Bottom with Leak Detection at the Tank Perimeter (Typical Arrangement)
Figure I.5—Double Steel Bottom with Leak Detection at the Tank Perimeter (Typical Arrangement)
Figure I.6—Reinforced Concrete Slab with Leak Detection at the Perimeter (Typical Arrangement)
Figure I.7—Reinforced Concrete Slab
Figure I.8—Typical Drawoff Sump
Figure I.9—Center Sump for Downward-Sloped Bottom
Figure I.10—Typical Leak Detection Wells
Figure I.11—Tanks Supported by Grillage Members (General Arrangement)
Figure O.1—Example of Under-Bottom Connection with Concrete Ringwall Foundation
Figure O.2—Example of Under-Bottom Connection with Concrete Ringwall Foundation and Improved TankBottom and Shell Support
Figure O.3—Example of Under-Bottom Connection with Earth-Type Foundation
Figure P.1—Nomenclature for Piping Loads and Deformation
Figure P.2a—Stiffness Coefficient for Radial Load: Reinforcement on Shell (L/2a = 1.0)
Figure P.2b—Stiffness Coefficient for Longitudinal Moment: Reinforcement on Shell (L/2a = 1.0)
Figure P.2c—Stiffness Coefficient for Circumferential Moment: Reinforcement on Shell (L/2a = 1.0)
Figure P.2d—Stiffness Coefficient for Radial Load: Reinforcement on Shell (L/2a = 1.5)
Figure P.2e—Stiffness Coefficient for Longitudinal Moment: Reinforcement on Shell (L/2a = 1.5)
Figure P.2f—Stiffness Coefficient for Circumferential Moment: Reinforcement on Shell (L/2a = 1.5)
Figure P.2g—Stiffness Coefficient for Radial Load: Reinforcement in Nozzle Neck Only (L/2a = 1.0)
Figure P.2h—Stiffness Coefficient for Longitudinal Moment: Reinforcement in Nozzle Neck Only (L/2a = 1.0)
Figure P.2i—Stiffness Coefficient for Circumferential Moment: Reinforcement in Nozzle Neck Only (L/2a = 1.0)
Figure P.2j—Stiffness Coefficient for Radial Load: Reinforcement in Nozzle Neck Only (L/2a = 1.5)
Figure P.2k—Stiffness Coefficient for Longitudinal Moment: Reinforcement in Nozzle Neck Only (L/2a = 1.5)
Figure P.2l—Stiffness Coefficient for Circumferential Moment: Reinforcement in Nozzle Neck Only (L/2a = 1.5)
Figure P.3a—Construction of Nomogram for b1, b2, c1, c2 Boundary
Figure P.3b—Construction of Nomogram for b1, c3 Boundary
Figure P.4a—Obtaining Coefficients YF and YL
Figure P.4b—Obtaining Coefficient YC
Figure P.5a—Determination of Allowable Loads from Nomogram: FR and ML
Figure P.5b—Determination of Allowable Loads from Nomogram: FR and MC
Figure P.6—Low-type Nozzle with Reinforcement on Shell
Figure P.7—Allowable-load Nomograms for Sample Problem
Figure V.1a—Dimensions for Self-Supporting Cone Roof
Figure V.1b—Dimensions for Self-Supporting Dome Roof
Tables
Table 4.1—Maximum Permissible Alloy Content
Table 4.2—Acceptable Grades of Plate Material Produced to National Standards (See 4.2.6)
Table 4.3a—Linear Equations for 4.1a (SI)
Table 4.3b—Linear Equations for 4.1b (USC)
Table 4.4a—Material Groups (SI)
Table 4.4b—Material Groups (USC)
Table 4.5a—Minimum Impact Test Requirements for Plates (SI) (See Note)
Table 4.5b—Minimum Impact Test Requirements for Plates (USC) (See Note)
Table 5.1a—Annular Bottom-Plate Thicknesses (tb) (SI)
Table 5.1b—Annular Bottom-Plate Thicknesses (tb) (USC)
Table 5.2a—Permissible Plate Materials and Allowable Stresses (SI)
Table 5.2b—Permissible Plate Materials and Allowable Stresses (USC)
Table 5.3a—Thickness of Shell Manhole Cover Plate and Bolting Flange (SI)
Table 5.3b—Thickness of Shell Manhole Cover Plate and Bolting Flange (USC)
Table 5.4a—Dimensions for Shell Manhole Neck Thickness (SI)
Table 5.4b—Dimensions for Shell Manhole Neck Thickness (USC)
Table 5.5a—Dimensions for Bolt Circle Diameter Db and Cover Plate Diameter Dc for Shell Manholes (SI)
Table 5.5b—Dimensions for Bolt Circle Diameter Db and Cover Plate Diameter Dc for Shell Manholes (USC)
Table 5.6a—Dimensions for Shell Nozzles (SI)
Table 5.6b—Dimensions for Shell Nozzles (USC)
Table 5.7a—Dimensions for Shell Nozzles: Pipe, Plate, and Welding Schedules (SI)
Table 5.7b—Dimensions for Shell Nozzles: Pipe, Plate, and Welding Schedules (USC)
Table 5.8a—Dimensions for Shell Nozzle Flanges (SI)
Table 5.8b—Dimensions for Shell Nozzle Flanges (USC)
Table 5.9a—Dimensions for Flush-type Cleanout Fittings (SI)
Table 5.9b—Dimensions for Flush-type Cleanout Fittings (USC)
Table 5.10a—Minimum Thickness of Cover Plate, Bolting Flange, and Bottom Reinforcing Plate for Flush-typeCleanout Fittingsf (SI)
Table 5.10b—Minimum Thickness of Cover Plate, Bolting Flange, and Bottom Reinforcing Plate forFlush-type Cleanout Fittingsf (USC)
Table 5.11a—Thicknesses and Heights of Shell Reinforcing Plates for Flush-type Cleanout Fittings (SI)
Table 5.11b—Thicknesses and Heights of Shell Reinforcing Plates for Flush-type Cleanout Fittings (USC)
Table 5.12a—Dimensions for Flush-type Shell Connections (SI)
Table 5.12b—Dimensions for Flush-type Shell Connections (USC)
Table 5.13a—Dimensions for Roof Manholes (SI)
Table 5.13b—Dimensions for Roof Manholes (USC)
Table 5.14a—Dimensions for Flanged Roof Nozzles (SI)
Table 5.14b—Dimensions for Flanged Roof Nozzles (USC)
Table 5.15a—Dimensions for Threaded Roof Nozzles (SI)
Table 5.15b—Dimensions for Threaded Roof Nozzles (USC)
Figure 5.19—Flanged Roof Nozzles (see Table 5.14a and Table 5.14b)
Figure 5.20—Threaded Roof Nozzles (see Table 5.15a and Table 5.15b)
Table 5.16a—Dimensions for Drawoff Sumps (SI)
Table 5.16b—Dimensions for Drawoff Sumps (USC)
Table 5.17—Requirements for Platforms and Walkways
Table 5.18—Requirements for Stairways
Table 5.19a—Section Moduli (cm3) of Stiffening-Ring Sections on Tank Shells (SI)
Table 5.19b—Section Moduli (in.3) of Stiffening-Ring Sections on Tank Shells (USC)
Table 5.20a—Uplift Loads (SI)
Table 5.20b—Uplift Loads (USC)
Table 5.21—Unfactored (Working Stress) Downward Reactions on Foundations
Table 7.1a—Minimum Preheat Temperatures (SI)
Table 7.1b—Minimum Preheat Temperatures (USC)
Table A.1a—Typical Sizes and Corresponding Nominal Capacities (m3) for Tanks with 1800-mm Courses (SI)
Table A.1b—Typical Sizes and Corresponding Nominal Capacities (Barrels) for Tanks with 72-in. Courses (USC)
Table A.2a—Typical Sizes and Corresponding Nominal Capacities (m3) for Tanks with 2400-mm Courses (SI)
Table A.2b—Typical Sizes and Corresponding Nominal Capacities (Barrels) for Tanks with 96-in. Courses (USC)
Table AL.1—Material Specifications
Table AL.2—Joint Efficiency
Table AL.3a—Minimum Mechanical Properties (SI)
Table AL.3b—Minimum Mechanical Properties (USC)
Table AL.4a—Annular Bottom Plate Thickness (SI)
Table AL.4b—Annular Bottom Plate Thickness (USC)
Table AL.5a—Minimum Shell Thickness (SI)
Table AL.5b—Minimum Shell Thickness (USC)
Table AL.6a—Allowable Tensile Stresses for Tank Shell (for Design and Test) (SI)
Table AL.6b—Allowable Tensile Stresses for Tank Shell (for Design and Test) (USC)
Table AL.7a—Allowable Stresses for Roof Plates (SI)
Table AL.7b—Allowable Stresses for Roof Plates (USC)
Table AL.8a—Compressive Moduli of Elasticity E (MPa) at Temperature C) (SI)
Table AL.8b—Compressive Moduli of Elasticity E (ksi) at Temperature (F) (USC)
Table AL.9a—Shell Nozzle Welding Schedule (SI)
Table AL.9b—Shell Nozzle Welding Schedule (USC)
Table E.1—Value of Fa as a Function of Site Class
Table E.2—Value of Fv as a Function of Site Class
Table E.3—Site Classification
Table E.4—Response Modification Factors for ASD Methods
Table E.5—Importance Factor (I) and Seismic Use Group Classification
Table E.6—Anchorage Ratio Criteria
Table E.7—Minimum Required Freeboard
Table E.8—Design Displacements for Piping Attachments
Table J.1a—Minimum Roof Depths for Shop-assembled Dome-roof Tanks (SI)
Table J.1b—Minimum Roof Depths for Shop-assembled Dome-roof Tanks (USC)
Table K.1a—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 2400-mm Courses and an Allowable Stress of 159 MPa for the Test Condition (SI)
Table K.1b—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 96-in. Courses and an Allowable Stress of 23,000 lbf/in.2 for the Test Condition (USC)
Table K.2a—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 2400-mm Courses and an Allowable Stress of 208 MPa for the Test Condition (SI)
Table K.2b—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 96-in. Courses and an Allowable Stress of 30,000 lbf/in.2 for the Test Condition (USC)
Table K.3a—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 2400-mm Courses and an Allowable Stress of 236 MPa for the Test Condition (SI)
Table K.3b—Shell-Plate Thicknesses Based on the Variable-design-point Method (See 5.6.4) Using 96-in. Courses and an Allowable Stress of 34,300 lbf/in.2 for the Test Condition (USC)
Table L.1—Index of Decisions or Actions That May be Required of the Tank Purchaser
Table M.1a—Yield Strength Reduction Factors (SI)
Table M.1b—Yield Strength Reduction Factors (USC)
Table M.2a—Modulus of Elasticity at the Maximum Design Temperature (SI)
Table M.2b—Modulus of Elasticity at the Maximum Design Temperature (USC)
Table O.1a—Dimensions of Under-Bottom Connections (SI)
Table O.1b—Dimensions of Under-Bottom Connections (USC)
Table P.1a—Modulus of Elasticity and Thermal Expansion Coefficient at the Design Temperature (SI)
Table P.1b—Modulus of Elasticity and Thermal Expansion Coefficient at the Design Temperature (USC)
Table S.1a—ASTM Materials for Stainless Steel Components (SI)
Table S.1b—ASTM Materials for Stainless Steel Components (USC)
Table S.2a—Allowable Stresses for Tank Shells (SI)
Table S.2b—Allowable Stresses for Tank Shells (USC)
Table S.3a—Allowable Stresses for Plate Ring Flanges (SI)
Table S.3b—Allowable Stresses for Plate Ring Flanges (USC)
Table S.4—Joint Efficiencies
Table S.5a—Yield Strength Values in MPa (SI)
Table S.5b—Yield Strength Values in psi (USC)
Table S.6a—Modulus of Elasticity at the Maximum Design Temperature (SI)
Table S.6b—Modulus of Elasticity at the Maximum Design Temperature (USC)
Table U.1a—Flaw Acceptance Criteria for UT Indications May be Used for All Materials (SI)
Table U.1b—Flaw Acceptance Criteria for UT Indications May be Used for All Materials (USC)
Table X.1—ASTM Materials for Duplex Stainless Steel Components
Table X.2a—Allowable Stresses for Tank Shells (SI)
Table X.2b—Allowable Stresses for Tank Shells (USC)
Table X.3—Joint Efficiencies
Table X.4a—Yield Strength Values in MPa
Table X.4b—Yield Strength Values in PSI
Table X.5a—Modulus of Elasticity at the Maximum Design Temperature (SI)
Table X.5b—Modulus of Elasticity at the Maximum Design Temperature (USC)
Table X.6a—Hot Forming Temperatures (SI)
Table X.6b—Hot Forming Temperatures (USC)
Special Notes
Instructions for Submitting a Proposed Revision to this Standard Under ContinuousMaintenance
Foreword
Important Information Concerning Use of Asbestos or Alternative Materials
Table of Contents
SECTION 1—SCOPE
1.1 General
1.2 Limitations
1.3 Responsibilities
1.4 Documentation Requirements
1.5 Formulas
SECTION 2—NORMATIVE REFERENCES
SECTION 3—TERMS AND DEFINITIONS
SECTION 4—MATERIALS
4.1 General
4.2 Plates
4.3 Sheets
4.4 Structural Shapes
4.5 Piping and Forgings
4.6 Flanges
4.7 Bolting
4.8 Welding Electrodes
4.9 Gaskets
SECTION 5—DESIGN
5.1 Joints
5.2 Design Considerations
5.3 Special Considerations
5.4 Bottom Plates
5.5 Annular Bottom Plates
5.6 Shell Design
5.7 Shell Openings
5.8 Shell Attachments and Tank Appurtenances
5.9 Top and Intermediate Stiffening Rings (Wind Girders)
5.10 Roofs
5.11 Wind Load on Tanks (Overturning Stability)
5.12 Tank Anchorage
5.13 Downward Reactions on Foundations
SECTION 6—FABRICATION
6.1 General
6.2 Shop Inspection
SECTION 7—ERECTION
7.1 General
7.2 Details of Welding
7.3 Examination, Inspection, and Repairs
7.4 Repairs to Welds
7.5 Dimensional Tolerances
SECTION 8—METHODS OF EXAMINING JOINTS
8.1 Radiographic Method
8.2 Magnetic Particle Examination
8.3 Ultrasonic Examination
8.4 Liquid Penetrant Examination
8.5 Visual Examination
8.6 Vacuum Testing
SECTION 9—WELDING PROCEDURE AND WELDER QUALIFICATIONS
9.1 Definitions
9.2 Qualification of Welding Procedures
9.3 Qualification of Welders
9.4 Identification of Welded Joints
SECTION 10—MARKING
10.1 Nameplates
10.2 Division of Responsibility
10.3 Certification
Annex A (normative) Optional Design Basis for Small Tanks
Annex AL (normative) Aluminum Storage Tanks
Annex B (informative) Recommendations for Design and Construction of Foundations forAboveground Oil Storage Tanks
Annex C (normative) External Floating Roofs
Annex D (informative) Inquiries and Suggestions for Change
Annex E (normative) Seismic Design of Storage Tanks
Annex EC (informative) Commentary on Annex E
Annex F (normative) Design of Tanks for Small Internal Pressures
Annex G (normative) Structurally-Supported Aluminum Dome Roofs
Annex H (normative) Internal Floating Roofs
Annex I (normative) Undertank Leak Detection and Subgrade Protection
Annex J (normative) Shop-Assembled Storage Tanks
Annex K (informative) Sample Applications of the Variable-Design-Point Method to DetermineShell-Plate Thickness
Annex L (normative) API Standard 650 Storage Tank Data Sheet
Annex M (normative) Requirements for Tanks Operating at Elevated Temperatures
Annex N (normative) Use of New Materials That Are Not Identified
Annex O (normative) Under-Bottom Connections
Annex P (normative) Allowable External Loads on Tank Shell Openings
Annex R (informative) References for Tanks in Non-petroleum Product Service
Annex S (normative) Austenitic Stainless Steel Storage Tanks
Annex SC (normative) Stainless and Carbon Steel Mixed Materials Storage Tanks
Annex T (informative) NDE Requirements Summary
Annex U (normative) Ultrasonic Examination in Lieu of Radiography
Annex V (normative) Design of Storage Tanks for External Pressure
Annex W (normative) Commercial and Documentation Recommendations
Annex X (normative) Duplex Stainless Steel Storage Tanks
Annex Y (informative) API Monogram ProgramUse of the API Monogram by Licensees
Bibliography