The document discusses standards for the design, fabrication, and construction of cylindrical steel tanks for oil storage according to API Standard 650. It summarizes key chapters and sections of the standard, including requirements for materials selection and testing, joint design and inspection, shell and bottom plate thickness calculations, and erection procedures. The standard provides guidance for tank manufacturers to ensure structural integrity and safety according to industry best practices.

1. STORAGE
VESSELS
 Ministry of Electricity, Iraq
By
MASU KUMARA
Chartered Mechanical Engineer
Consultant, GPP Projects

2. Storage Vessel Design
 Storage of
 Petroleum oils
 Biogenic oil
 Fertilizers
 Food Grains
 Plastic Pellets etc.
liquids
Solids

3. Petroleum Oil Storage
 Cylindrical Tanks designed and constructed based
on API codes of practice
 API Standard 650 – Welded Steel Tanks for Oil
Storage
 API Standard 651- Cathodic Protection of
Aboveground Storage Tanks
 API Standard 653, Tank Inspection, Repair,
Alteration, and Reconstruction
 And other API standards also useful

4. API STANDARD 650 (API 650)
 Chapter 01. Scope
 Chapter 02. Materials
 Chapter 03. Design
 Chapter 04. Fabrication
 Chapter 05. Erection
 Chapter 06. Methods of Inspecting Joints
 Chapter 07. Welding Procedure and Welder
Qualifications
 Chapter 08. Markings
 Appendices A to U

5. Chapter 01. Scope
 Scope of this standard (API 650)
 Limitations and references
 Tanks with internal pressures approximately in the
region of atmospheric pressure (Appendix F gives
provisions for smaller pressure storages)
 The entire bottom should be uniformly supported
 In non refrigerated services
 Maximum operating temperature 90oC (Appendix M
gives provisions for the operating temperature range
from 90oC to 260 oC)
 In SI units or US customary units

6. Chapter 01. Scope
 COMPLIANCE
The manufacturer is responsible for complying
with all provisions of this standard. Inspection
by the purchaser’s inspector (the term inspector
as used herein) does not negate the
manufacturer’s obligation to provide quality
control and inspection necessary to ensure
such compliance.

7. Chapter 02 Materials (Plates)
 Group i through iiiA is lower stress steels
 Group v through viA is higher stress steels

8. Chapter 02. Materials
 Killed steel is steel that has been completely
deoxidized by the addition of an agent before
casting, so that there is practically no evolution of
gas during solidification. They are characterized
by a high degree of chemical homogeneity and
freedom from gas porosity. The steel is said to
be "killed" because it will quietly solidify in the
mould, with no gas bubbling out. It is marked
with a "K" for identification purposes

9. Chapter 02. Materials
 Semi-killed steel is mostly deoxidized steel,
but the carbon monoxide leaves blowhole
type porosity distributed throughout the ingot.
The porosity eliminates the pipe found in
killed steel and increases the yield to
approximately 90% by weight. Semi-killed
steel is commonly used for structural steel
with a carbon content between 0.15 to 0.25%
carbon.

10. Chapter 02. Materials (Lower Stress Group)
Group I Group II Group III Group IIIA
Semi killed Killed or semi
killed
As rolled, killed
fine grain practice
Normalized Killed,
fine grain practice
A 283 C A 131 B A 573-58 A 131 CS
A 285 C A 36 A516-55 A 573-58
A 131 A G40.21M-26-M A516-60 A 516-55
A 36 Grade 250 G40.21M-260W A 516-60
Grade 235 Grade 250 G40.21M-260W
Grade 250 Grade 250

11. Chapter 02. Materials (Higher Stress Group)

12. Chapter 02: Materials (SA 283/SA 283M Plates)
Chemical Requirement Grade A Grade B Grade C Grade D
C, Max % 0.14 0.17 0.24 0.27
Mn, Max % 0.90 0.90 0.90 0.90
P, Max % 0.035 0.035 0.035 0.035
S, Max % 0.04 0.04 0.04 0.04
Si, Max %
40mm & Under 0.40 0.40 0.40 0.40
Over 40 mm 0.15-0.40 0.15-0.40 0.15-0.40 0.15-0.40
Cu, Max % 0.2 0.2 0.2 0.2
Tensile requirement
Tensile strength (MPa) 310-415 345-450 380-515 415-550
Yield Point (MPa) 165 185 205 320

13. Chapter 02: Materials (SA 285/SA 285M Plates)
Chemical requirement Grade A Grade B Grade C
C, Max % 0.17 0.22 0.28
Mn, Max % 0.90 0.90 0.90
P, Max % 0.035 0.035 0.035
S, Max % 0.035 0.035 0.035
Tensile requirement
Tensile strength (MPa) 310-450 345-485 380-515
Yield Point (MPa) 165 185 205

14. Chapter 02: Materials (Colours Designated)

15. Chapter 02 Materials (Piping)

16. Chapter 02 Materials (Flanges)

17. Chapter 02 Materials (Bolting)

18. Chapter 02 Materials (Welding
Electrodes)

19. Chapter 03. Design
No Description
1 Joints
2 Design Considerations
3 Special Considerations
4 Bottom Plates
5 Annular bottom plates
6 Shell Design
7 Shell Openings
8 Shell Attachments and Tank appurtenances
9 Top and intermediate wind girders
10 Roofs
11 Wind Load on Tanks
12 Tank Anchorage

20. Chapter 03 Design (Joints)
some terminologies
 tack weld: A weld made to hold the parts of a weldment in proper
alignment until the final welds are made.
 fillet weld: A weld of approximately triangular cross section that
joins two surfaces at approximately right angles, as in a lap joint, tee
joint, or corner joint.
 full-fillet weld: A fillet weld whose size is equal to the thickness of
the thinner joined member.
 butt-weld: A weld placed in a groove between two abutting
members. Grooves may be square, V-shaped (single or double), or
U-shaped (single or double), or they may be either single or double
beveled.
 lap joint: A joint between two overlapping members
 butt joint: A joint between two abutting parts lying in approximately
the same plane

21. Chapter 03 Joint Design
BUTT JOINT
STRAP JOINT
LAP JOINT
FILLET JOINT
CORNER JOINT

22. Chapter 03 Design (joints)
Fusion Weld Zones

23. Chapter 03 Design (Joints)
 Shell joints (Vertical and horizontal) shall be butt joints
with complete penetration and complete fusion.
 Bottom joints may be butt welded or lap welded
 Butt welded bottom joints
 with or without backing strips
 Complete penetration
 At least 3mm backing strip when use
 Root opening less than 6 mm
 Three-plate joints in the tank bottom shall be at least 300 mm
(12 in.) from each other and from the tank shell.

24. Chapter 03 Design (Joints)
 Bottom Joints may be Butt welded or Lap welded
 Lap welded bottom joints
 Complete penetration
 Reasonably rectangular and square edged
 Full fillet on all seams
Three-plate laps in tank bottoms shall be at
least 300 mm (12 in.) from each other, from
the tank shell, from butt-welded annular-plate
joints, and from joints between annular plates
and the bottom.

25. Chapter 03 Design (Joints)
 Shell to bottom Fillet Welds
 If shell plates less than 12.5 mm, shall be continuous fillet
weld on both sides of shell.
 If shell plate are grater than 12.5 mm, either the legs of the fillet welds or
the groove depth plus the leg of the fillet for a combined weld is of a size
equal to the annular-plate thickness
Nominal thickness of
shell plate
Minimum size of fillet
weld
5 mm 5 mm
5 mm to 20 mm 6 mm
20 mm to 32 mm 8 mm
32 mm to 45 mm 10 mm

26. Chapter 03 Design
 Bottom plates and annular plates
 Minimum thickness of bottom plates 6mm, if
any corrosion allowance is specified by the
purchaser, add c.a. to 6mm
 Unless otherwise agreed, plates shall be of
minimum width of 1800 mm (72 ft)
 at least a 25 mm (1 in.) width will project
beyond the outside edge of the weld attaching
the bottom to the shell plate

28. Chapter 03 Design

29. Chapter 03. Design
 Shell Design
 Above thickness is the minimum, and hence could be altered based on other
parameters as well
 Minimum nominal plate width shall be of 1800mm
 The design shell thickness shall be computed on the basis that the tank is filled to a
level with a liquid that has a specific gravity specified by the purchaser
Nominal Tank Diameter
(m)
Nominal Plate thickness
(mm)
Less than 15 5
Between 15 to 36 6
Between 36 to 60 8
Above 60 10

30. Chapter 03 Design

31. Chapter 03. Design

32. Chapter 03 Design
 Calculation of Thickness by the 1-Foot
Method
 Calculation of Thickness by the Variable
Design-Point Method
 Calculation of Thickness by Elastic
Analysis

35. Chapter 03 Design
Shell Openings
Shell Manholes
Shell nozzles and flanges
Flush-Type Cleanout Fittings
Spacing of Welds Around
Connections
Reinforcement and Welding

37. Chapter 03 Design
 SHELL ATTACHMENTS AND TANK
APPURTENANCES
 Shell Attachments
 Bottom Connections
 Cover Plates
 Roof Manholes
 Roof Nozzles
 Water Drawoff Sumps
 Scaffold-Cable Support
 Threaded Connections

38. Chapter 03 Design
 Wind Girders Draw off sumps
 Wind girders are stiffening rings to maintain
roundness when the tank is subjected to wind loads.
 Wind girders may be made of structural sections,
formed plate sections, sections built up by welding,
or combinations of such types of sections assembled
by welding.
 Minimum structural member sizing would be
65x65x6 and may cross vertical tank weld seam
welds with coping of stiffening rings at vertical seam.
 Could be used as a walkway if minimum width of
stiffening ring to be 610 mm and to be located
1100mm below the top angle.

40. Chapter 03 Design
 Top wind girders
 Intermediate wind girders
 Top angle and curb angle
 Dome roof, umbrella roof
 Tank anchorage

43. Chapter 04 Fabrication

44. Chapter 04 Fabrication

45. Chapter o4 Fabrication

46. Chapter 04 Fabrication

47. Chapter 05 Erection
 Tank Bottom

48. Chapter 05 Erection
 Two methods used
 From bottom to roof – using cranes
 From roof to bottom – using hydraulic jacks

49. Chapter 05 Erection

50. Chapter 05 Erection
 Tank Shells
 Some other guide lines are also there in the code

51. Chapter 05
 Shell to bottom welds
The initial welds pass
inside of the shell have
to be examined by using
applicable method
agreed by the purchaser
and manufacturer

52. Chapter 05 Erection

53. Chapter 05 Erection

54. Chapter 06 Method of Inspecting Joints
 1. Radiographic Method
 2. Magnetic Particle Examination
 3. Ultrasonic Examination
 4. Liquid Penetrant Examination
 5. Visual Examination
 6. Vacuum testing

55. Chapter 06
 Radiographic Method

56. Chapter 06

57. Chapter 06 Inspection of joints

58. Chapter 06 Inspection of joints
 Magnetic Particle Examination
 Liquid Penetrant Examination

59. Chapter 07 Welding Procedure
 Welding Procedure Specification (WPS)
 Procedure Qualification Records (PQR)
 Welder Performance Qualification (WPQ)

60. Chapter 08 Marking

61. Thank you very much