Understanding API ICP653 Reading 9-Worksheet-04

Understandings API ICP653 

Reading 9 - Q&A Practices 

Work Sheet 04 

API653 储罐认证 , 

Q&A 作业学习 

31 st January 2016 

Charlie Chong/ Fion Zhang

Tank Farms 



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Fion Zhang at Shanghai 

31 st January 2016

API 653 Exam Administration -- Publications 

Effectivity Sheet FOR: November 2015, March 

2016 and July 2016 

Listed below are the effective editions of the publications required for this 

exam for the date(s) shown above. 

API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in 

the Refining Industry, Second Edition, April 2011 


API 653 Exam Administration -- Publications 

Effectivity Sheet FOR: November 2015, March 

2016 and July 2016 

Listed below are the effective editions of the publications required for this 

exam for the date(s) shown above. 

API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in 

the Refining Industry, Second Edition, April 2011 


ATTENTION: Only the following sections / mechanisms from RP 571 are 

included on the exam: 

Section 3, Definitions 

Par. 4.2.7 Brittle Fracture 

4.2.16 Mechanical Fatigue 

4.3.2 Atmospheric Corrosion 

4.3.3 Corrosion Under insulation (CUI) 

4.3.8 Microbiologically Induced Corrosion (MIC) 

4.3.9 Soil Corrosion 

4.3.10 Caustic Corrosion 

4.5.1 Chloride Stress Corrosion Cracking (Cl-SCC) 

4.5.3 Caustic Stress Corrosion Cracking (Caustic Embrittlement) 

5.1.1.10 Sour Water Corrosion (Acidic) 

5.1.1.11 Sulfuric Acid Corrosion 


• API Recommended Practice 575, Inspection of Atmospheric and Low- 

Pressure Storage Tanks, Third Edition, April 2014 

• API Recommended Practice 577 – Welding Inspection and Metallurgy, 

Second Edition, December 2013 

• API Standard 650, Welded Tanks for Oil Storage, Twelfth Edition, March 

2013 with Addendum 1 (September 2014), Errata 1 (July 2013), and 

Errata 2 (December 2014). 

• API Recommended Practice 651, Cathodic Protection of Aboveground 

Petroleum Storage Tanks, Fourth Edition, September 2014. 

• API Recommended Practice 652, Lining of Aboveground Petroleum 

Storage Tank Bottoms, Fourth Edition, September 2014 

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

Reconstruction, Fifth Edition, November 2014. 


• American Society of Mechanical Engineers (ASME), Boiler and Pressure 

Vessel Code, 2013 Edition 

i. ASME Section V, Nondestructive Examination, Articles 1, 2, 6, 7 and 23 

(section SE-797 only) 

ii. Section IX, Welding and Brazing Qualifications (Welding Only) 

See end of this study note for API Official BOK 



http://independent.academia.edu/CharlieChong1 

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The Magical Book of Tank Inspection ICP 



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API 650 PRACTICE QUESTIONS 

Section 1 – Scope 

Q1. API 650 covers the design, materials, fabrication, erection, and testing of 

aboveground steel storage tanks. What is the maximum internal pressure for 

tanks not covered by 

appendix F of this standard? 

a) Maximum pressure shall not exceed 15 psig 

b) Maximum pressure shall not exceed 15 psia 

c) Maximum pressure shall not exceed the weight of the roof plates 

d) Maximum pressure shall not exceed the weight of the floor plates 

Reference: API-650, Paragraph 1.1.1 

ANS:C 


Q2. API-650 applies only to tanks whose entire bottom is uniformly supported 

and tanks in ___ that have a maximum operating temperature of _____°F. 

a) Any petrochemical service and temperature not exceeding 120°F 

b) Non-refrigerated service and temperature not exceeding 200°F 

c) Non-refrigerated service and temperature not exceeding 120°F 

d) Any petrochemical service and temperature not exceeding 200°F 


ANS:B 


Q3. An aboveground storage tank is to be subjected to a small internal 

service pressure. To which standard or Code may the tank be designed? 

a) API-650 providing the requirements of Appendix F are met 

b) API-653 providing the requirements of Appendix F are met 

c) ASME-Section VIII, Div. 1 providing the requirements of Appendix F are 

met 

d) ASME-Section VIII, Div. 2 providing the requirements of Appendix F are 

met 


ANS:A 


Q4. According to Table 1-1, what is the status of Appendix O? 

a) This Appendix is a Recommendation 

b) This Appendix is a Requirement 

c) This Appendix is Mandatory 

d) This Appendix is Purchaser’s option 

Reference: API-650, Paragraph 1.1.19 and Table 1-1 

ANS:D 

Q5. What is the purpose of the ( ) next to a paragraph number? 

a) The paragraph requires a decision or action by the API 

b) The paragraph requires a decision or action by the Inspector 

c) The paragraph requires a decision or action by the purchaser 

d) The paragraph requires a decision or action by the fabricator 

Reference: API-650, Paragraph 1.1.2 and Note 

ANS:C 


Answers to API-Standard 650 Section 1, Scope 


Section 2 – Materials 

Q1. API-650 lists materials to be used in the construction of tanks covered by 

the standard. Is it permissible to use materials other than those listed in the 

standard? 

a) No only materials listed in API-650 may be used in tank fabrication 

b) Yes as long as the manufacturer accepts full liability for tank failure 

c) Yes providing it is certified as meeting all requirements of a material listed 

in API-650 and is approved by the API-653 Inspector 

d) Yes providing it is certified as meeting all the requirements of a material 

listed in API-650 and is approved by the purchaser 


ANS: D 


Q2. If a new or unused plate cannot be completely identified, may it still be 

used in the construction of tanks within the scope of API-650? 

a) Yes only if the material passes the tests prescribed in Appendix S 

b) Yes only if the material passes the tests prescribed in Appendix N 

c) Yes only if the material passes the tests prescribed in ASME Section V 

d) Yes only if the material passes the tests prescribed in ASME Section VIII, 

Div. 2 

Reference: API-650, Paragraph 2.1.2 ANS:B 

Q3. What is the maximum permitted underrun for shell, roof, and bottom 

plates? 

a) 0.10 inch from the computed design thickness or minimum permitted 

thickness 

b) 0.01 inch from the computed design thickness or minimum permitted 

thickness 

c) 0.001 inch from the computed design thickness or minimum permitted 

thickness 

d) 0.02 inch from the computed design thickness or minimum permitted 

thickness 

Reference: API-650, Paragraph 2.2.1.2.3 ANS:B 


Q4. Shell plates are limited to what maximum thickness? 

a) Shell plates are limited to a maximum thickness of 1.250 inches 

b) Shell plates are limited to a maximum thickness of 1.875 inches 

c) Shell plates are limited to a maximum thickness of 1.750 inches 

d) Shell plates are limited to a maximum thickness of 1.075 inches 

Reference: API-650, Paragraph 2.2.1.4 ANS: C 

Q5. Which of the following is not a requirement for shell plates that are thicker 

than 1.5 inches? 

a) Plates thicker than 1.5 inches shall be free of mill scale and painted 

b) Plates thicker than 1.5 inches shall be made to fine-grain practice 

c) Plates thicker than 1.5 inches shall be impact tested 

d) Plates thicker than 1.5 inches shall be normalized or quench tempered 

Reference: API-650, Paragraph 2.2.1.4 ANS: A 


Q6. What is the maximum shell plate thickness permitted for a tank fabricated 

of ASTM A36 material? 

a) This plate material is limited to 1.750 inches 

b) This plate material is limited to 1.075 inches 

c) This plate material is limited to 1.050 inches 

d) This plate material is limited to 1.500 inches 

Reference: API-650, Paragraph 2.2.2 a 

ANS: D 

Q7. What is the maximum shell plate thickness permitted for a tank fabricated 

of ASTM A285, Grade C material? 

a) This plate material is limited to 1.000 inches 

b) This plate material is limited to 1.250 inches 

c) This plate material is limited to 1.500 inches 

d) This plate material is limited to 1.750 inches 

Reference: API-650, Paragraph 2.2.2 d 

ANS: A 


API650: 

4.2.2 ASTM Specifications Plates that conform to the following ASTM 

specifications are acceptable as long as the plates are within the stated 

limitations. a) ASTM A36M/A36 for plates to a maximum thickness of 40 mm 

(1.5 in.). None of the specifications for the appurtenant materials listed in 

Table 1 of ASTM A36M/A36 are considered acceptable for tanks constructed 

under this standard unless it is expressly stated in this standard that the 

specifications are acceptable. 

d) ASTM A285M/A285, Grade C, for plates to a maximum thickness of 25 mm 

(1 in.). 


Q8. All welding to repair surface defects shall be done with ______. 

a) Cellulose coated electrode b) High nickel content electrode 

c) Low-hydrogen electrode d) Gas tungsten process 

Reference: API-650, Paragraph 2.2.6.2 

ANS:C 

Q9. When conducting impact tests, how many specimens are required from a 

single test coupon? 

a) Impact tests shall be performed on a single specimen taken from a single 

test coupon 

b) Impact tests shall be performed on two specimens taken from a single test 

coupon 

c) Impact tests shall be performed on three specimens taken from a single 

test coupon 

d) Impact tests shall be performed on four specimens taken from a single test 

coupon 



Q10. In situations where it is not possible to obtain full size specimens, what 

is the required width along the notch for subsize specimens? 

a) 60% of the material thickness 

b) 80% of the material thickness 

c) 90% of the material thickness 

d) 75% of the material thickness 

Reference: API-650, Paragraph 2.2.8.5 ANS: B 

Q11. Unless data is available to justify a different temperature, what must the 

design metal temperature be for an aboveground storage tank to be installed 

in Birmingham, Alabama? 

a) The design temperature shall be assumed to be 25°F 

b) The design temperature shall be assumed to be 15°F 

c) The design temperature shall be assumed to be 20°F (?) 

d) The design temperature shall be assumed to be 10°F 

Reference: API-650, Paragraph 2.2.9.3 and Figure 2-2 ANS:? 



4.2.9.5 For a plate whose thickness is insufficient to permit preparation of fullsize 

specimens [10 mm × 10 mm (0.394 in. × 0.394 in.], tests shall be made 

on the largest subsize specimens that can be prepared from the plate. 

Subsize specimens shall have a width along the notch of at least 80 % of the 

material thickness. 

Figure 4.2—Isothermal Lines of Lowest One-Day Mean Temperatures (°F) 


Annex L (normative) API Standard 650 Storage Tank Data Sheet 

Design Metal Temperature*: Enter either lowest 1-day mean temperature plus 

8 °C (15 °F) or a lower temperature as specified by the Purchaser if operating 

conditions and/or local atmospheric conditions control fracture toughness 

issues. 

°F 


Q12. Unless data is available to justify a different temperature, what must the 

design metal temperature be for an aboveground storage tank to be installed 

in Indianapolis, Indiana? 

a) The design temperature shall be assumed to be 5°F 

b) The design temperature shall be assumed to be -5°F 

c) The design temperature shall be assumed to be 0°F 

d) The design temperature shall be assumed to be 10°F 

Reference: API-650, Paragraph 2.2.9.3 and Figure 2-2 ANS: -10°F+15°F=5°F 

Q13. What is the required average longitudinal impact value of three 

specimens taken from a 1.375 inch thick A 516M-60(415) normalized Group 

IIIA test coupon? 

a) 30 foot-pounds 

b) 20 foot-pounds 

c) 15 foot-pounds 

d) 13 foot-pounds 

Reference: API-650, Paragraph 2.2.10.2 and Figures 2-3 and 2-4 ANS: C 


Annex L (normative) API Standard 650 Storage Tank Data Sheet 

Design Metal Temperature*: Enter either lowest 1-day mean temperature plus 

8 °C (15 °F) or a lower temperature as specified by the Purchaser if operating 

conditions and/or local atmospheric conditions control fracture toughness 

issues. 


Q14. What is the required average longitudinal impact value of three 

specimens taken from a 1.5 inch thick A 516M-70(485) as rolled Group V test 

coupon? 

a) 35 foot-pounds 

b) 25 foot-pounds 

c) 20 foot-pounds 

d) 30 foot-pounds 

Reference: API-650, Paragraph 2.2.10.2 and Figures 2-3 and 2-4 ANS: D 


Table 4.5b—Minimum Impact Test Requirements for Plates (USC) (See 

Note) 


Q15. Longitudinal impact tests are performed on three specimens, taken from 

a 1.5 inch thick A 516M-70(485) as rolled test coupon with the following 

results: 

• Specimen #1 – 42 foot-pounds, 

• Specimen #2 – 18 foot-pounds, 

• Specimen # 3 – 31 foot-pounds. 

Is the impact test acceptable? 

a) Yes the average impact value exceeds 30 foot-pounds 

b) Yes only one specimen is less than 2/3 the specified minimum value 

c) No the average impact value of Specimen # 1 exceeds 2/3 the required 

average impact value and one specimen is less than 2/3 the specified 

minimum value 

d) No Specimen #2 is less than 2/3 the specified minimum 

Reference: API-650, Paragraph 2.2.8.3 and Figures 2-3 and 2-4 ANS: D 



4.2.9.3 An impact test shall be performed on three specimens taken from a 

single test coupon or test location. 

The average value of the specimens (with no more than one specimen value 

being less than the specified minimum value) shall comply with the specified 

minimum value. 

If more than one value is less than the specified minimum value, or if one 

value is less than two-thirds the specified minimum value, three additional 

specimens shall be tested, and each of these must have a value greater than 

or equal to the specified minimum value. 


Answers to API-Standard 650 Section 2, Materials 


Section 3 – Design 

Q1. According to API-650, tack welds _______ 

a) May be installed by welders who need practice 

b) Can be considered as adding to the strength of a welded joint 

c) Are not considered as having any strength value in the finished structure 

d) Have strength value in the finished structure provided they are performed 

by a qualified welder to a qualified welding procedure 


Q2. What is the minimum size fillet weld permitted when joining a 1” thick 

plate to a ¾” thick plate? 

a) 3/16” 

b) 1/4” 

c) 3/8” 

d) 1/2” 

Reference: API-650, Paragraph 3.1.3.3 ANS: B, 1/3 of ¾ = ¼” 



5.1.3.3 The minimum size of fillet welds shall be as follows: On plates 5 mm 

(3/16 in.) thick, the weld shall be a full- fillet weld, and on plates more than 5 

mm (3/16 in.) thick, the weld thickness shall not be less than one-third the 

thickness of the thinner plate at the joint and shall be at least 5 mm (3/16 in.). 


Q3. For lap-welded joints that are tack welded, what is the minimum amount 

of lap permitted? 

a) The lap need not exceed 2” 

b) The lap need not exceed 1” 

c) The joint shall be lapped at least 5 times the minimum required thickness of 

the thinner plate 

d) The joint shall be lapped at least 5 times the nominal thickness of the 

thinner plate 

Reference: API-650, Paragraph 3.1.3.5 ANS: D 

Q4. The welded joint pictured here is defined as what type of joint? 

a) Double-V butt joint 

b) Square-groove butt joint 

c) Double-U butt joint 

d) Double-square butt joint 



Q5. Vertical shell joints may be partial penetration groove welds welded from 

both sides. 

a) True 

b) False 

Reference: API-650, Paragraph 3.1.5.2 a ANS:B 

Q6. API 650 requires the vertical joints in adjacent shell courses to be offset. 

What is the minimum required offset between the first course of an AST, 

which is 1.25” thick and the second course which is 1” thick? 

a) The minimum offset shall be 5 times the second shell course height 

b) The minimum offset shall be 5 times the thickness of the second course 

c) The minimum offset shall be 5 times the first shell course height 

d) The minimum offset shall be 5 times the thickness of the first shell course 

Reference: API-650, Paragraph 3.1.5.2 b ANS: D 


API650: 5.1.5.1 General 

b) Vertical joints in adjacent shell courses shall not be aligned, but shall be 

offset from each other a minimum distance of 5t, where t is the plate 

thickness of the thicker course at the point of offset. 


Q7. Three-plate laps in tank bottoms shall be at least ____ from each other, 

from the tank shell, from butt-welded annular-plate joints, and from joints 

between annular plates and the bottom. 

a) 1.2 inches 

b) 12 inches 

c) 1.2 feet 

d) 12 feet 

Reference: API-650, Paragraph 3.1.5.4 ANS:B 

Q8. What is the maximum size of fillet weld permitted in the attachment 

between the lowest course shell plate and the bottom plate? 

a) 3/8 inch 

b) 5/16 inch 

c) 1/2 inch 

d) 1/4 inch 



Q9. What is the minimum size fillet weld required on each side of the shell 

plate attaching shell plate to the annular plate? The shell plate is 1.25” thick. 

a) 3/8 inch 

b) 3/16 inch 

c) 1/4 inch 

d) 5/16 inch 

Reference: API-650, Paragraph 3.1.5.7ANS: D 

Q10. A 110 ft diameter tank shall have a top angle not less than ____ inches. 

a) 2 X 2 X 3/8 

b) 2 X 3 X 3/8 

c) 3 X 3 X 3/8 

d) 3 X 2 X 3/8 



5.1.5.7 Shell-to-Bottom Fillet Welds a) For bottom and annular plates with a 

nominal thickness 13 mm (1/2 in.), and less, the attachment between the 

bottom edge of the lowest course shell plate and the bottom plate shall be a 

continuous fillet weld laid on each side of the shell plate. The size of each 

weld shall not be more than 13 mm (1/2 in.) and shall not be less than the 

nominal thickness of the thinner of the two plates joined (that is, the shell 

plate or the bottom plate immediately under the shell) or less than the 

following values: 


) For annular plates with a nominal thickness greater than 13 mm (1/2 in.), 

the attachment welds shall be sized so that 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 (see Figure 5.3c), but shall not exceed 

the shell plate thickness. 


API650: 5.1.5.9 Roof and Top-Angle Joints 

e) Except as specified for open-top tanks in 5.9, for tanks with frangible joints 

per 5.10.2.6, for self-supporting roofs in 5.10.5, and 5.10.6, and for tanks with 

the flanged roof-to-shell detail described in Item f below, tank shells shall be 

supplied with top angles of not less than the following sizes: 


Q11. The ______ shall state the design metal temperature, the design 

specific gravity, the corrosion allowance, and the design wind velocity. 

a) The purchaser 

b) The fabricator 

c) The Inspector 

d) Erector 

Reference: API-650, Paragraph 3.2.1 ANS: A 

Q12. According to API-650, tanks meeting the minimum requirements of the 

standard may be subjected to a partial vacuum of _____. 

a) One inch of mercury 

b) One inch of water pressure 

c) One pound per square inch absolute 

d) One centimeter of water pressure 

Reference: API-650, Paragraph 3.2.4ANS: B 



5.2 Design Considerations 5.2.1 Loads Loads are defined as follows. 

a) Dead Load (DL): The weight of the tank or tank component, including any 

corrosion allowance unless otherwise noted. b) 

b) Design External Pressure (Pe): Shall not be less than 0.25 kPa (1 in. of 

water) except that the Design External Pressure (Pe) shall be considered 

as 0 kPa (0 in. of water) for tanks with circulation vents meeting Annex H 

requirements. Refer to Annex V for design external pressure greater than 

0.25 kPa (1 in. of water). Requirements for design external pressure 

exceeding this value and design requirements to resist flotation and 

external fluid pressure shall be a matter of agreement between the 

Purchaser and the Manufacturer (see Annex V). Tanks that meet the 

requirements of this standard may be subjected to a partial vacuum of 0.25 

kPa (1 in. of water), without the need to provide any additional supporting 

calculations. 

c) Design Internal Pressure (Pi): Shall not exceed 18 kPa (2.5 lbf/in.2). 


Q13. An AST is 116 ft in diameter and constructed of A 516M-70(485) Group 

V as rolled material. How many hardness tests are required on one 

circumferential weld? 

a) One 

b) Two 

c) Three 

d) Four 

Reference: API-650, Paragraph 3.3.4 ANS: D 

Q14. The purchaser orders an aboveground storage tank and insists on a 

corrosion allowance in the bottom plates of .125 inches. What is the minimum 

thickness permitted for bottom plates in this tank? 

a) Minimum thickness of bottom plate is 1/4 inch 

b) Minimum thickness of bottom plate is 1/2 inch 

c) Minimum thickness of bottom plate is 3/8 inch 

d) Minimum thickness of bottom plate is 5/16 inch 

Reference: API-650, Paragraph 3.4.1 ANS: C 


5.3.4 Weld Hardness 

a) Weld metal and Heat Affected Zone (HAZ) hardnesses shall comply with 

the H2S Supplemental Specification listed on the Data Sheet, Line 5, 

when specified by the Purchaser. 

b) When specified by the Purchaser, the hardness of the weld metal for shell 

materials in Group IV, IVA, V, or VI shall be evaluated by one or both of 

the following methods. 

1. The welding-procedure qualification tests for all welding shall include 

hardness tests of the weld metal and heataffected zone of the test plate. 

The methods of testing and the acceptance standards shall be agreed 

upon by the Purchaser and the Manufacturer. 

2. All welds deposited by machine or an automatic process shall be hardness 

tested on the product-side surface. Unless otherwise specified, one test 

shall be conducted for each vertical weld, and one test shall be conducted 

for each 30 m (100 ft) of circumferential weld. The methods of testing and 

the acceptance standards shall be agreed upon by the Purchaser and the 

Manufacturer. 


Q15. What is the minimum projection, of trimmed bottom plates, beyond the 

outside edge of the weld attaching bottom to the shell? 

a) Minimum projection is 0.01 inch 

b) Minimum projection is 0.10 inch 

c) Minimum projection is 1.00 inch 

d) Minimum projection is 10.0 inch 


Q16. Annular bottom plates shall have a radial width that provides at least 

____ between the inside of the shell and any lap-welded joint in the 

remainder of the bottom. 

a) 12 inches 

b) 24 inches 

c) 1.2 inches 

d) 2.4 inches 



Q17. How far must annular bottom plates project outside the shell? 

a) Annular bottom plates shall project at least 1 inch when trimmed 

b) Annular bottom plates shall project at least 1/2 inch beyond the edge of the 

weld 

c) Annular bottom plates shall project at least 2 inches outside the shell 

d) Annular bottom plates shall project at least 5t (t = thickness of the shell 

course) outside the shell 


• Trimmed bottom plates shall project at least 1 inches 

outside the shell 

• Annular bottom plates shall project at least 2 inches 

outside the shell 


Q18. The thickness of the first shell course of an aboveground storage tank is 

1 5/8th inches. The hydrostatic test stress in the first shell course is 33,000 

psi. What is the minimum permissible thickness of the annular bottom plates? 

a) Minimum permitted thickness is 5/8th inch 

b) Minimum permitted thickness is 9/16th inch 

c) Minimum permitted thickness is 3/4 inch (?) 

d) Minimum permitted thickness is 11/16th inch 

Reference: API-650, Paragraph 3.5.3 and Table 3-1 ANS: A 

Q19. According to API-650, what is the minimum allowable nominal shell 

thickness of an AST that is 86 feet in diameter? 

a) Minimum nominal shell thickness is 3/16th inch 

b) Minimum nominal shell thickness is 1/4 inch 

c) Minimum nominal shell thickness is 9/32nd inch 

d) Minimum nominal shell thickness is 5/16th inch 

Reference: API-650, Paragraph 3.6.1.1ANS: B 


Table 5.1b—Annular Bottom-Plate Thicknesses (tb) (USC) 


Q20. Unless otherwise agreed to by the purchaser, what is the minimum 

nominal width of shell plates? 

a) Minimum width of shell plates is 84 inches 

b) Minimum width of shell plates is 96 inches 

c) Minimum width of shell plates is 72 inches 

d) Minimum width of shell plates is 120 inches 


Q21. Aboveground storage tank manufacturers are required to furnish a 

drawing to the purchaser listing all but which of the following for each course? 

a) The material specification 

b) The allowable stress 

c) The nominal thickness used 

d) The nominal thickness of coatings 



Q22. In calculating the net plate thickness for an AST fabricated of A 516M 

Grade 450(60) material, what would be the product design stress value used 

in the calculation? 

a) 24,000 

b) 21,300 

c) 32,000 

d) 23,300 

Reference: API-650, Paragraph 3.6.2.1 and Table 3-2 ANS: B 

Q23. The fabricator of an AST obtains the approval of the purchaser to use 

the alternative shell design permitted in Appendix A in the design of a 60 foot 

diameter tank using 3/8th inch A 516M Grade 450(60) plate. What allowable 

stress would be used in the design calculations? 

a) 21,300 b) 24,000 c) 21,000 d) 32,000 




A.3 Design A.3.1 The maximum tensile stress before the joint efficiency 

factor is applied shall be 145 MPa (21,000 lbf/in.2). A.3.2 Stresses shall be 

computed on the assumption that the tank is filled with water (specific gravity 

= 1.0) or with the liquid to be stored if it is heavier than water. A.3.3 The 

tension in each ring shall be computed 300 mm (12 in.) above the centerline 

of the lower horizontal joint of the course in question. When these stresses 

are computed, the tank diameter shall be taken as the nominal diameter of 

the bottom course. 


Q24. What is the maximum diameter of tank that permits the 1-foot method of 

calculation for required thickness? 

a) Tanks 50 feet in diameter and less 

b) Tanks 120 feet in diameter and less 

c) Tanks 180 feet in diameter and less 

d) Tanks 200 feet in diameter and less 

Reference: API-650, Paragraph 3.6.3.1: ANS: D 

Q25. Openings in tank shells, larger than that required to accommodate a 

____ flanged or threaded nozzle shall be reinforced. 

a) 2 inch 

b) 2.5 inch 

c) 3 inch 

d) 3.5 inch 



Q26. When installing openings in a shell plate, the edge of the fillet weld 

around the periphery of the reinforcing pad shall be spaced at least the 

greater of _______ from the centerline of any butt-welded shell joints. 

a) Eight inches or ten times the weld size 

b) Eight times the weld size or ten inches 

c) Eight times the weld size or six inches 

d) Eight inches or six times the weld size 

Reference: API-650, Paragraph 3.7.3.1 a ANS: B 

Q27. When installing openings adjacent to each other, how much space must 

there be between the welds around the periphery of the reinforcing plate? 

a) Eight times the larger weld or ten inches from each other 

b) Eight inches or six times the larger weld from each other 

c) Eight times the larger weld or six inches from each other 

d) Eight times the larger weld or eight inches from each other 

Reference: API-650, Paragraph 3.7.3.1 b ANS: C 


5.7.3 Spacing of Welds around Connections 

5.7.3.1 For non-stress-relieved welds on shell plates over 13 mm (1/2 in.) 

thick, the minimum spacing between penetration connections and adjacent 

shell-plate joints shall be governed by the following. 

a) The toe of the fillet weld around a non-reinforced penetration or around the 

periphery of a reinforcing plate, and the outer edge of a butt-weld around 

the periphery of a thickened insert plate or insert plate, shall be spaced at 

least the greater of eight times the weld size or 250 mm (10 in.) from the 

centerline of any butt-welded shell joints, as illustrated in Figure 5.6, 

dimensions A or B. 

b) The toe of the fillet weld around a non-reinforced penetration or around the 

periphery of a reinforcing plate, and the outer edge of a butt-weld around 

the periphery of a thickened insert plate or insert plate, shall be spaced at 

least the greater of eight times the larger weld size or 150 mm (6 in.) from 

each other, as illustrated in Figure 5-6, dimension E. 


Figure 5.6—Minimum Weld Requirements for Openings in Shells 

According to 5.7.3 








Q28. A minimum distance of ____ shall be maintained between the toe of a 

weld around a non-reinforced penetration and the toe of the shell-tobottom 

weld. 

a) Ten inches b) Eight inches c) Six inches d) Three inches 


Q29. Subject to the acceptance of the purchaser, the manufacture may locate 

a circular shell opening in a horizontal butt-welded shell joint provided 

______. 

a) Minimum spacing dimensions are met and a liquid penetrant examination 

of the welded joint is conducted 

b) Minimum spacing dimensions are met and a radiographic examination of 

the welded joint is conducted 

c) Minimum spacing dimensions are met and an ultrasonic examination of 

the welded joint is conducted 

d) Minimum spacing dimensions are met and a magnetic particle examination 

of the welded joint is conducted 






API650: 5.7.3.4 Nozzles and manholes should not be placed in shell weld 

seams and reinforcing pads for nozzles and manholes should not overlap 

plate seams (i.e. Figure 5.9, Details a, c, and e should be avoided). If there is 

no other feasible option and the Purchaser accepts the design, circular shell 

openings and reinforcing plates (if used) may be located in a horizontal or 

vertical butt-welded shell joint provided that the minimum spacing dimensions 

are met and a radiographic examination of the welded shell joint is conducted. 

The welded shell joint shall be fully radiographed for a length equal to three 

times the diameter of the opening, but the weld seam being removed need 

not be radiographed. Radiographic examination shall be in accordance with 

8.1.3 through 8.1.8. 


Q30. All flush-type clean-out fittings and flush-type shell connections shall be 

thermally stress relieved after assembly and prior to installation in the tank. 

What are the temperature range and time requirements for this stress relief 

activity? 

a) 1100°F to 1200°F for 1 hour per inch of reinforcing plate thickness 

b) 1100°F to 1200°F for 1/2 hour per inch of shell thickness 

c) 1100°F to 1200°F for 1 hour per inch of shell thickness 

d) 1100°F to 1200°F for 1 & 1/2 hour per inch of shell thickness 


Q31. Subject to the acceptance of the purchaser, the fabricator may stress 

relieve at a temperature of 1000°F when it is impractical to stress relieve at a 

minimum temperature of 1100°F providing _____. 

a) The shell plate is first pre-heated to 300°F 

b) The holding time is increased to 2 hours per inch of thickness 

c) The holding time is increased to 4 hours per inch of thickness 

d) The holding time is increased to 10 hours per inch of thickness 



Q32. What is the minimum required thickness for a manhole cover plate to be 

used with a 24 inch manhole? The maximum design liquid level of the tank is 

45 feet. 

a) Minimum thickness of cover plate is 9/16th inch 

b) Minimum thickness of cover plate is 5/8th inch 

c) Minimum thickness of cover plate is 1/2 inch 

d) Minimum thickness of cover plate is 11/16th inch 

Reference: API-650, Paragraph 3.7.5.1 and Table 3-3 ANS: A 

Q33. What is the bolt circle diameter for a cover plate used with a 30 inch 

diameter manhole? 

a) 32 ¾ inch 

b) 36 ¼ inch 

c) 38 ¾ inch 

d) 42 ¼ inch 

Reference: API-650, Paragraph 3.7.5.2 and Table 3-5 ANS: B 


Q34. The purchaser has ordered a 36 inch manhole to be installed in the first 

course of an AST. The thickness of the shell plate and the reinforcing plate 

is 1.375 inches. What is the required hole diameter that must be cut in the 

tank to accommodate this manhole? 

a) 36 & 1/4 inch b) 36 & 1/2 inch c) 36 & 3/4 inch d) 36 & 5/8 inch 

Reference: API-650, Paragraph 3.7.5.3 and Table 3-7 ANS: C 

Q35. API 650 requires telltale holes in reinforcing plates. What is the required 

dimension of this hole and what should be done with it after the initial repad 

pressure test? 

a) The hole shall be 3/8 inch diameter and shall be left open to the 

atmosphere 

b) The hole shall be 1/4 inch diameter and shall be left open to the 

atmosphere 

c) The hole shall be 3/8 inch diameter and shall be closed after testing 

d) The hole shall be 1/4 inch diameter and shall be closed after testing 

Reference: API-650, Paragraph 3.7.6.1 ANS: 


Table 5.7b—Dimensions for Shell Nozzles: Pipe, Plate, and Welding 

Schedules (USC) 


Table 5.7b—Dimensions for Shell Nozzles: Pipe, Plate, and Welding 

Schedules (USC) 


Q36. What is the maximum size un-reinforced opening permitted in flat cover 

plates without increasing the thickness of the cover plate? 

a) 4 inch pipe size providing the edge of the opening is not more than ¼ the 

height or diameter of the opening closer to the center of the cover plate 

b) 3 inch pipe size providing the edge of the opening is not more than ¼ the 


c) 2 inch pipe size providing the edge of the opening is not more than ¼ the 


d) 1 & ½ inch pipe size providing the edge of the opening is not more than ¼ 

the height or diameter of the opening closer to the center of the cover plate 


Q37. What is the maximum size opening that may be placed in a cover plate? 

a) 12 inches pipe size 

b) 8 inches pipe size 

c) 6 inches pipe size 

d) 3 inches pipe size 



Q38. An aboveground storage tank has a design liquid height of 40 feet. The 

purchaser intends to install product mixing equipment in the cover plate of a 

30 inch manhole. What is the required minimum thickness of the cover plate? 

a) The minimum thickness shall be at least .625 inches 

b) The minimum thickness shall be at least .75 inches 

c) The minimum thickness shall be at least .9375 inches 

d) The minimum thickness shall be at least .875 inches 



API650: 5.8.3 Cover Plates 

A cover plate with a nozzle attachment for product-mixing equipment shall 

have a thickness at least 1.4 times greater than the thickness required by 

Table 5.3a and Table 5.3b. The added thickness (or pad plate) for 

replacement of the opening cutout in the cover plate shall be based on Table 

5.3a and Table 5.3b. The 40 % increase in thickness within a radius of one 

diameter of the opening may be included as part of the area of replacement 

required. The mixer- nozzle attachment to the cover plate shall be a fullpenetration 

weld. The manhole bolting-flange thickness shall not be less than 

1.4 times the thickness required by Table 5.3a and Table 5.3b. The manhole 

nozzle neck shall be designed to support the mixer forces with a minimum 

thickness not less than the requirements 


Table 5.3b—Thickness of Shell Manhole Cover Plate and Bolting Flange 

(USC) 

11/16 x 1.4 x 40/43.9 = 0.877” 


Q39. A 24 inch manhole is to be installed in a roof plate and it is anticipated 

that work may be carried on through the manhole while the tank is in use. 

What is the diameter of the opening to be cut in the roof plate and what is 

the outside diameter of the reinforcing plate? 

a) The diameter of the opening is 24.625” and the OD of the reinforcing plate 

is 42” 

b) The diameter of the opening is 24.625” and the OD of the reinforcing plate 

is 46” 

c) The diameter of the opening is 24.750” and the OD of the reinforcing plate 

is 42” 

d) The diameter of the opening is 24.750” and the OD of the reinforcing plate 

is 46” 

Reference: API-650, Paragraph 3.8.4 ANS: B 


Figure 5.16—Roof Manholes (see Table 5.13a and Table 5.13b) 


Q40. What is the minimum thickness permitted for rectangular roof opening 

cover plates? 

a) Minimum thickness shall not be less than .875 inches 

b) Minimum thickness shall not be less than .750 inches 

c) Minimum thickness shall not be less than .625 inches 

d) Minimum thickness shall not be less than .500 inches 


Q41. Stiffening ring splice welds shall be located at least _____ from any 

vertical shell weld. 

a) 24 inches 

b) 18 inches 

c) 12 inches 

d) 6 inches 



API650: 5.9.3.4 Welds joining stiffening rings to the tank shell may cross 

vertical tank seam welds. Any splice weld in the ring shall be located a 

minimum of 150 mm (6 in.) from any vertical shell weld. Stiffening rings may 

also cross vertical tank seam welds with the use of coping (rat hole) of the 

stiffening ring at the vertical tank seam. Where the coping method is used, the 

required section modulus of the stiffening ring and weld spacing must be 

maintained. 


Q42. When stiffening rings are to be used as walkways, what is the required 

width of the stiffening ring? 

a) The width shall be not less than 36 inches clear of the projecting curb 

angle on the top of the tank shell 

b) The width shall be not less than 3 feet 6 inches clear of the projecting curb 


c) The width shall be not less than 24 inches clear of the projecting curb 


d) The width shall be not less than 2 feet 4 inches clear of the projecting curb 



Q43. How far below the top of the curb angle should a stiffening ring, that is to 

be used as a walkway, be located? 

a) 3 feet 6 inches b) 36 inches c) 6 feet 3 inches d) 63 inches 

Reference: API-650, Paragraph 3.9.4ANS: A 


API650: 5.9.4 Stiffening Rings as Walkways A stiffening ring or any portion 

of it that is specified as a walkway shall have a width not less than 710 mm 

(28 in.) clear of projections including the angle on the top of the tank shell. 

The clearance around local projections shall not be less than 610 mm (24 in.). 

Unless the tank is covered with a fixed roof, the stiffening ring (used as a 

walkway) shall be located 1100 mm (42 in.) below the top of the curb angle 

and shall be provided with a standard railing on the unprotected side and at 

the ends of the section used as a walkway. 


Q44. All roofs and supporting structures shall be designed to support dead 

loads plus a uniform live load of not less than _____ of projected area 

a) 25 pounds per square inch 

b) 25 pounds per square foot 

c) 25 pounds per square yard 

d) 25 pounds per square meter 


Q45. What is the minimum nominal thickness permitted for roof plates? 

a) 3/16 inch or 5.76 pounds per square foot 

b) 3/16 inch or 6.75 pounds per square foot 

c) 3/16 inch or 7.65 pounds per square foot 

d) 3/16 inch or 12-gauge sheet 



Q46. A roof where the continuous fillet weld between the roof plates and the 

top angle does not exceed 3/16", the slope at the top angle attachment does 

not exceed 2" in 12", and the shell-to-roof compression ring details are limited 

to Figure F-2 (a)-(d) may be considered what type of roof? 

a) A 1 in 6 roof 

b) A dangerous roof design and should be avoided 

c) A roof with inherent compensation 

d) A frangible roof 

Reference API-650, Paragraph 3.10.2.5.1 ANS: D 

Q47. Rafters shall be spaced so that in the outer ring, their centers are not 

more than _____ apart measured along the circumference of the tank. 

a) 3π feet or 9.42 feet b) 2π feet or 6.28 feet 

c) 4π feet or 12.56 feet d) 2.5π feet or 7.85 feet 

Reference: API-650, Paragraph 3.10.4.4ANS: B 


Answers to API-Standard 650 Section 3, Design 


Section 4 – Fabrication 

Q1. What method(s) is/are permitted for straightening material? 

a) Pressing or other non-injurious method prior to layout or shaping 

b) Heating and hammering after layout or shaping 

c) Jacking into shape after final assembly 

d) Jacking into shape and holding with tack welds 


Q2. When plates are to be butt-welded, shearing is limited to what maximum 

thickness? 

a) 5/8th inch 

b) 3/8th inch (9.5mm) 

c) 3/16th inch 

d) Shearing is not permitted 

Reference: API-650, Paragraph 4.1.2ANS: B 


Q3. When plates are to be used in lap-welded joints, shearing is limited to 

what maximum thickness 

a) 3/16th inch b) 3/8th inch 

c) 1/2 inch d) 5/8th inch (15mm) 


Q4. What are the requirements regarding mill test reports according to API- 

650? 

a) No material shall be used in the construction of an AST unless it is 

accompanied by a mill test report 

b) Mill test reports are required only on shell plate material 

c) Mill test reports shall be furnished to the purchaser only when specified in 

the original purchase order 

d) Mill test reports shall be furnished to the purchaser prior to final acceptance 

of the AST 

Reference: API-650, Paragraph 4.2.1ANS: C 


Q5. Mill and shop inspection releases the manufacturer from responsibility for 

replacing defective material. 

a) True 

b) False 



Answers to API-Standard 650 Section 4, Fabrication 


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Section 5 – Erection 

Q1. What welding process is not permitted when impact testing of the 

material is required? 

a) Shielded metal-arc 

b) Gas metal-arc 

c) Oxyfuel 

d) Submerged arc 


Q2. Welding may be performed manually, automatically, or semiautomatically 

according to the procedures described in ____ of the ASME 

Code. 

a) Section VIII, Division 1 

b) B31.3 

c) Section VIII, Division 2 

d) Section IX 



Q3. No welding of any kind shall be performed when the temperature of the 

base metal is less than ____°F 

a) Sixty b) Thirty-two c) Zero d) Negative fifteen 


Q4. When base metal thickness is greater than 1.25 inches or the base metal 

temperature is 0°F -32°F, what requirement must be met? 

a) The base metal within 3 inches of the starting point of the welding shall be 

heated to a temperature warm to the hand (140°F) 

b) The base metal within 3 inches of the starting point of the welding shall be 

heated to a temperature of not less than 200°F 

c) The base metal within 3 inches of the starting point of the welding shall be 


d) The base metal within 3 inches of the starting point of the welding shall be 




API653: 10.4.2.3 No welding of any kind shall be performed when the 

surfaces of the parts to be welded are wet from rain, snow, or ice; when rain 

or snow is falling on such surfaces; or during periods of high winds unless the 

welder and the work are properly shielded. No welding of any kind shall be 

performed when the temperature of the base metal is less than 0 °F. When 

the temperature of the base metal is between 0 °F and 32 °F or the thickness 

is in excess of 1 in., the base metal within 3 in. of the place where welding is 

to be started shall be heated to a temperature warm to the hand 

(approximately 140 °F) before welding. (See 10.4.4.3 for preheat 

requirements for shell plates over 1½ in. thick.) 

10.4.4.3 For horizontal and vertical joints in tank shell courses constructed of 

material over 1 ½ in. thick (based on the thickness of the thicker plate at the 

joint), multi-pass weld procedures are required, with no pass more than 3/4-in. 

thick permitted. A minimum preheat of 200 °F is required of these welds. 


Q5. What is the maximum acceptable undercut for horizontal butt joints? 

a) 1/64th inch 

b) 1/32nd inch 

c) 3/64th inch 

d) 3/32nd inch 


Q6. What is the maximum acceptable undercut for vertical butt joints? 

a) 3/32nd inch 

b) 3/64th inch 

c) 1/32nd inch 

d) 1/64th inch 



Q7. What is the maximum permissible weld reinforcement for a vertical joint in 

plate thickness 1.25”? 

a) 3/16th inch b) 1/8th inch c) 1/4th inch d) 3/32nd inch 


Q8. When tack welds are used during the assembly of vertical joints, what 

requirement is stipulated by API-650? 

a) Tack welds that are to be removed do not require a qualified procedure or 

welder 

b) Tack welds that are to be left in place shall be made using a qualified 

procedure only 

c) Tack welds that are to be removed may be made using a welder in training 

d) Tack welds that are to be left in place shall be made using a qualified 

procedure and welder 



API650: 8.1.3.4 The finished surface of the weld reinforcement at the location 

of the radiograph shall either be flush with the plate or have a reasonably 

uniform crown not to exceed the following values: 


API653: Table 10.1—Maximum Thicknesses on New Welds 


Q9. What is the requirement when protective coatings are used on surfaces 

to be welded? 

a) The coating must be removed prior to welding 

b) The coating shall be included in the welder’s performance qualification 

tests 

c) The coating shall be included in the welding procedure qualification 

d) The coating shall be identified on the purchase order 


Q10. The welding of the ____ shall be practically complete prior to weldingout 

the bottom joints. 

a) Nozzle reinforcement periphery welds 

b) Shell-to-bottom weld 

c) All vertical and horizontal shell welds 

d) All external attachment welds 



Q11. In a vertical joint of an AST, what is the maximum misalignment of 1.5” 

thick plate? 

a) Maximum misalignment is .150 inch 

b) Maximum misalignment is .145 inch 

c) Maximum misalignment is .135 inch 

d) Maximum misalignment is .125 inch 

Reference: API-650, Paragraph 5.2.3.1 ANS: D (10% of 1.5” or 1/8”, max) 

Q12. In a horizontal joint of an AST, what is the maximum projection of an 

upper plate beyond the face of the plate below it? The plate thickness is .25 

inch. 

a) Maximum projection is .0625 inch 

b) Maximum projection is .0500 inch 

c) Maximum projection is .1250 inch 

d) Maximum projection is .09375 inch 

Reference: API-650, Paragraph 5.2.3.2 ANS: A, for t

API653: 10.4.4 Shells 

10.4.4.1 Plates to be joined by butt welding shall be matched accurately and 

retained in position during welding. Misalignment in completed vertical joints 

over 5/8-in. thick shall not exceed 10 % of the plate thickness, with a 

maximum of 1/8 in. Misalignment in joints 5/8-in. thick or less shall not exceed 

1/16 in. Vertical joints shall be completed before the lower horizontal weld is 

made. 

10.4.4.2 In completed horizontal butt joints, the upper plate shall not project 

beyond the face of the lower plate at any point by more than 20 % of the 

thickness of the upper plate, with a maximum projection of 1/8 in., except that 

a projection of 1/16 in. is acceptable for upper plates less than 5/16-in. thick. 


material over 1 1/2-in. thick (based on the thickness of the thicker plate at the 

joint), multi-pass weld procedures are required, with no pass more than 3/4-in. 

thick permitted. A minimum preheat of 200 °F is required of these welds. 


Q13. Multi-pass weld procedures are required for circumferential and vertical 

joints in tank shell courses constructed of material that is more than 1.5 

inches thick. What is the maximum weld pass size permitted and what is the 

minimum pre-heat temperature? 

a) No weld pass over ¾ inch with a minimum pre-heat of 300°F 

b) No weld pass over ½ inch with a minimum pre-heat of 200°F 

c) No weld pass over ¾ inch with a minimum pre-heat of 200°F 

d) No weld pass over ½ inch with a minimum pre-heat of 300°F 



material over 1 1/2-in. thick (based on the thickness of the thicker plate at the 

joint), multi-pass weld procedures are required, with no pass more than 

3/4-in. thick permitted. A minimum preheat of 200 °F is required of these 

welds. 


Q14. The initial weld pass inside the shell of the shell-to-bottom weld shall be 

cleaned and examined for its entire circumference. This examination shall be 

visually and by which of the following? 

a) Magnetic particle or ultrasonic or suitable liquid penetrant process 

b) Magnetic particle or suitable liquid penetrant process or a vacuum box and 

bubble method 

c) Magnetic particle or radiography or vacuum box and bubble method 

d) Magnetic particle or acoustic emission or eddy current 



Q15. The required examination of the initial weld pass as described in API- 

650 may be waived subject to agreement between the purchaser and the 

AST manufacturer provided all but which of the following examinations are 

performed on the entire circumference of the weld(s) 

a) Examine either side of the finished weld by MT, PT, or right angle vacuum 

box 

b) Visually examine the initial weld (inside and outside) 

c) Visually examine the finished joint welded surfaces (inside and outside the 

shell) 

d) Examine either side of the finished weld by MT, PT, UT, or RT 



Q16. What are the dimensions of a standard vacuum testing box? 

a) 6” wide by 30” long 

b) 6” wide by 24” long 

c) 6” wide by 36” long 

d) 6” wide by 32” long 


Q17. In an examination of a tank’s bottom weld seams by vacuum box testing, 

what is the required partial vacuum pressure? 

a) At least 1 lbf/in 2 gauge (psig) 

b) At least 2 lbf/in 2 gauge (psig) 

c) At least 3 lbf/in 2 gauge (psig) 

d) At least 4 lbf/in 2 gauge (psig) 



Q18. If an alternative to vacuum box testing is used, whose approval is 

required? 

a) The Manufacturer 

b) The API-653 Inspector 

c) The local jurisdiction 

d) The purchaser 


Q19. After fabrication is completed but prior to filling an aboveground storage 

tank with test water, reinforcing plates shall be tested. What method of test 

and pressure shall be used? 

a) A hydrostatic pressure test at up to 15 lbf/in 2 (psig) 

b) A pneumatic pressure test at up to 15 lbf/in 2 (psig) 

c) A vacuum test at a partial pressure of 2 lbf/in 2 (psig) 

d) A pneumatic pressure test at up to 25 lbf/in 2 (psig) 



Q20. A new aboveground storage tank must be tested. If water is available for 

testing the shell, the tank shall be filled to any of the following levels except? 

a) To the maximum design liquid level 

b) Tanks with tight roofs, to 2 inches above the weld connecting the roof plate 

of compression bar to the top angle of the shell 

c) To overflowing to ensure all air is vented from the tank 

d) To a level lower than specified in a) or b) when restricted by overflows or 

freeboard agreement between the manufacturer and the purchaser 



API650: 7.3.5 Testing of the Shell After the entire tank and roof structure is 

completed, the shell (except for the shell of tanks designed in accordance with 

Annex F) shall be tested by one of the following methods, as specified on the Data 

Sheet, Line 14. 1) If water is available for testing the shell, the tank shall be filled 

with water as follows: 

(1) to the maximum design liquid level, H; 

(2) for a tank with a tight roof, to 50 mm (2 in.) above the weld connecting the roof 

plate or compression bar to the top angle or shell; 

(3) to a level lower than that specified in Sub-item 1 or 2 when restricted by overflows, 

an internal floating roof, or other freeboard by agreement between the Purchaser 

and the Manufacturer, or 

(4) to a level of seawater producing a bottom of shell hoop stress equal to that 

produced by a full-height fresh water test. 

The tank shall be inspected frequently during the filling operation, and any welded 

joints above the test-water level shall be examined in accordance with Item 2 below. 

This test shall be conducted before permanent external piping is connected to the tank. 

Attachments to the shell defined in 5.8.1.1, located at least 1 m (3 ft) above the water 

level, and roof appurtenances may be welded during the filling of the tank. After 

completion of the hydro-test, only non-structural small attachments may be welded to 

the tank in accordance with 7.2.1.11. 


Q21. The purchaser of an AST that is designed to be gas tight required the 

roof to be tested pneumatically. What maximum pressure would be applied to 

a tank with ¼” thick roof plates? 

a) The maximum pneumatic pressure permitted is .053 psi 

b) The maximum pneumatic pressure permitted is .071 psi 

c) The maximum pneumatic pressure permitted is .083 psi 

d) The maximum pneumatic pressure permitted is .091 psi 

Reference: API-650, Paragraph 5.3.7.1 and 3.10.2.2 

Solution: 3/16” thick plate = 7.65 lb/ft ∴1/16” = 2.55 lb/ft ANS: B 


API650: 7.3.7 Testing of the Roof 7.3.7.1 Upon completion, the roof of a 

tank designed to be gas-tight (except for roofs designed under 7.3.7.2, F.4.4, 

and E.7.5) shall be tested by one of the following methods. a) Applying 

internal air pressure not exceeding the weight of the roof plates and applying 

to the weld joints a bubble solution or other material suitable for the detection 

of leaks. b) Vacuum testing the weld joints in accordance with 8.6 to detect 

any leaks. 7.3.7.2 Upon completion, the roof of a tank not designed to be gastight, 

such as a tank with peripheral circulation vents or a tank with free or 

open vents, shall receive only visual examination of its weld joints, unless 

otherwise specified by the Purchaser. 


Q22. During the filling of an aboveground storage tank for testing, leakage 

was observed in a horizontal seam. Repairs are to be completed with the test 

water in the tank. The tank is 61 feet high and the leak is discovered 29 feet 

below the top of the tank. Where must the water level be during the repair? 

a) The water level shall be not less than 30 feet from the top of the tank 

b) The water level shall be not more than 32 feet from the bottom of the tank 

c) The water level shall be at the maximum design liquid level 

d) The water shall be removed from the tank 

Reference: API-650, Paragraph 5.4.4 ANS:A, 61-29=32’, answer The water 

level shall be more than 31 feet from the top of the tank 

API650: 7.4.4 Repairs of defects discovered after the tank has been filled with water 

for testing shall be made with the water level at least 0.3 m (1 ft) below any point being 

repaired or, if repairs have to be made on or near the tank bottom, with the tank empty. 

Welding shall not be done on any tank unless all connecting lines have been 

completely blinded. Repairs shall not be attempted on a tank that is filled with oil or 

that has contained oil until the tank has been emptied, cleaned, and gas freed. 

Repairs on a tank that has contained oil shall not be attempted by the Manufacturer 

unless the manner of repair has been approved in writing by the Purchaser and the 

repairs are made in the presence of the Purchaser’s inspector. 


Q23. A 60 foot high aboveground storage tank is designed with an internal 

floating roof. What is the maximum out-of-plumbness permitted on the 54.5 

foot fixed roof columns? 

a) 2.94 inches 

b) 3.27 inches 

c) 1.31 inches 

d) 1.18 inches 

Reference: API-650, Paragraph 5.5.2 ANS:B/ 57.5x12/200 = 3.27, smaller 

than 5 

Q24. What is the maximum roundness tolerance (radius tolerance) permitted 

on an AST that is 110 feet in diameter and where is this tolerance applied? 

a) ¾” measured 10 feet above the bottom corner weld 

b) ¾” measured 1 foot below the top shell angle joint 

c) ¾” measured 1 foot above the bottom corner weld 

d) ¾” measured 10 feet below the top shell angle joint 



7.5.2 Plumbness a) The maximum out-of-plumbness of the top of the shell 

relative to the bottom of the shell shall not exceed 1/200 of the total tank 

height. The out-of-plumbness in one shell course shall not exceed the 

permissible variations for flatness and waviness as specified in ASTM 

A6M/A6, ASTM A20M/A20, or ASTM A480M/A480, whichever is applicable. b) 

The maximum out-of-plumbness of roof columns, guide poles, or other 

vertical internal components shall not exceed 1/200 of the total height. The 

1/200 criteria shall also apply to fixed roof columns. For tanks with internal 

floating roofs, apply the criteria of this section or Annex H, whichever is more 

stringent. 

H.4.5 Roof Penetrations Columns, ladders, and other rigid vertical 

appurtenances that penetrate the deck shall be provided with a seal that will 

permit a local deviation of ±125 mm (±5 in.). Appurtenances shall be plumb 

within a tolerance of ±75 mm (±3 in.). 


7.5.3 Roundness Radii measured at 0.3 m (1 ft) above the bottom corner 

weld shall not exceed the following tolerances: 


Q25. Peaking at vertical welds and banding at horizontal welds shall not 

exceed ____. 

a) 1 inch b) ¾ inch c) ½ inch d) ¼ inch 

Reference: API-650, Paragraph 5.5.4 (a and b) ANS: C 

Q26. Peaking and banding are determined using a horizontal sweep board for 

peaking and a straight edge vertical sweep board for banding. What is the 

required length of these 

sweep boards? 

a) 48 inches 

b) 24 inches 

c) 42 inches 

d) 36 inches 

Reference: API-650, Paragraph 5.5.4 (a and b) ANS: D 


API650: 7.5.4 Local Deviations Local deviations from the theoretical shape (for 

example, weld discontinuities and flat spots) shall be limited as follows. 

a) Deviations (peaking) at vertical weld joints shall not exceed 13 mm (1/2 in.). 

Peaking at vertical weld joints shall be determined using a horizontal sweep board 

900 mm (36 in.) long. The sweep board shall be made to the nominal radius of the 

tank. 

b) Deviations (banding) at horizontal weld joints shall not exceed 13 mm (1/2 in.). 

Banding at horizontal weld joints shall be determined using a straight edge vertical 

sweep board 900 mm (36 in.) long. 

c) Flat spots measured in the vertical plane shall not exceed the appropriate plate 

flatness and waviness requirements given in 7.5.2. 

API563: 10.5.4 Peaking 

With a horizontal sweep board 36-in. long, peaking shall not exceed 1/2 in. The sweep 

board shall be made to the true outside radius of the tank. 

API563: 10.5.5 Banding 

With a vertical sweep board 36-in. long, banding shall not exceed 1 in. 


Horizontal Peaking Board, peaking of vertical weld. 

Vertical Banding Board, banding of horizontal weld. 


http://www.naehss.org/PastSchools/2011/LargeTankStorageIntegrity.pdf

Q27. The top of the concrete ringwall (where installed) of an AST must be 

level within ± 1/8” in any 30 feet of circumference. What is the total 

circumferential tolerance measured from the average elevation? 

a) ±1/8” b) ±3/16” c) ±1/2” d) 1/4” 

Reference API-650, Paragraph 5.5.5.2 (a) ANS: D 

Q28. Where a concrete ringwall is not provided, the foundation under the 

shell shall be level to within what tolerances? 

a) ±1/8” in any 30’ of the circumference and ±1/2” in the total circumference 

measured from the average elevation 

b) ±1/8” in any 10’ of the circumference and ±1/2” in the total circumference 


c) ±1/8” in any 10’ of the circumference and ±1/4” in the total circumference 


d) ±1/8” in any 30’ of the circumference and ±1/4” in the total circumference 


Reference API-650, Paragraph 5.5.5.2 (b) ANS: B 


Q29. For foundations specified to be sloped from a horizontal plane, the 

actual elevation shall not deviate from the calculated differences by more than 

which of the following where concrete ringwalls are provided? 







Reference API-650, Paragraph 5.5.5.3 (a) ANS: D 


Q30. For foundations specified to be sloped from a horizontal plane, the 

actual elevation shall not deviate from the calculated differences by more 

than which of the following where concrete ringwalls are not provided? 







Reference API-650, Paragraph 5.5.5.3 (b) ANS: B 


Answers to API-Standard 650 Section 5, Erection 


Section 6 – Methods of inspecting Joints 

Q1. With regards to radiographic examination of welded joints, API-650 

considers plates to be the same thickness when the difference in their 

specified or design thickness is not greater than ____. 

a) 1/32nd inch 

b) 1/16th inch 

c) 3/32nd inch 

d) 1/8th inch 

Reference: API-650, Paragraph 6.1 ANS: D 

API650: 8.1 Radiographic Method 

For the purposes of this paragraph, plates shall be considered of the same 

thickness when the difference in their specified or design thickness does not 

exceed 3 mm (1/8 in.). 


Q2. Which of the following joints do not require radiographic examination? 

a) Bottom-plate welds 

b) Shell butt welds 

c) Flush-type connections with butt welds 

d) Annular-plate butt welds 


Q3. Vertical butt welds in plates not greater than 3/8th inch thick, require one 

spot radiograph to be taken in the first _____ of completed vertical joint of 

each type and thickness by each welder or welding operator. 

a) 100 feet 

b) 50 feet 

c) 25 feet 

d) 10 feet 

Reference: API-650, Paragraph 6.1.2.2(a) ANS: D 


Q4. One additional spot radiograph shall be taken in each additional ____ of 

vertical joint of 

the same type and thickness. 

a) 10 feet 

b) 200 feet 

c) 100 feet 

d) 25 feet 

Reference: API-650, Paragraph 6.1.2.2(a) ANS: C 

Q5. What percentage of the selected spot radiographs must be at junctions of 

vertical and horizontal welded joints? 

a) 25 percent 

b) 50 percent 

c) 75 percent 

d) 15 percent 

Reference: API-650, Paragraph 6.1.2.2(a) ANS: A 


Q6. For butt welded joints in plates over 3/8” to not over 1” in thickness are 

required to be radiographically examined to the same extent as plates 3/8” 

and less. What additional spot examination does API-650 require for these 

welded joints? 

a) 50 percent of all vertical and horizontal junctions 

b) 75 percent of all vertical and horizontal junctions 

c) 100 percent of all vertical and horizontal junctions 

d) 25 percent of all horizontal joints between the first and second course 

Reference: API-650, Paragraph 6.1.2.2(b) ANS: C 

Q7. The radiographic film for all junctions of vertical and horizontal joints shall 

show at least ____ of weld length on each side of the vertical intersection. 

a) 3 inches 

b) 2 inches 

c) 1 inch 

d) 4 inches 

Reference: API-650, Paragraph 6.1.2.2(b) and (c) ANS: B 


API650: 8.1.2.2 

b) For butt-welded joints in which the thinner shell plate is greater than 10 mm 

(3/8 in.) but less than or equal to 25 mm (1 in.) in thickness, spot radiographs 

shall be taken according to Item a. In addition, all junctions of vertical and 

horizontal joints in plates in this thickness range shall be radiographed; each 

film shall clearly show not less than 75 mm (3 in.) of vertical weld and 50 mm 

(2 in.) of weld length on each side of the vertical intersection. In the lowest 

course, two spot radiographs shall be taken in each vertical joint: one of the 

radiographs shall be as close to the bottom as is practicable, and the other 

shall be taken at random (see the center panel of Figure 8.1). 


Q8. The butt weld around the periphery of an insert manhole or nozzle shall 

be ____. 

a) Completely examined by liquid penetrant methods 

b) Completely examined by ultrasonic methods 

c) Completely examined by magnetic particle methods 

d) Completely examined by radiographic methods 

Reference: API-650, Paragraph 6.1.2.2(d) ANS: D 

Q9. After the initial spot radiograph in the first 10 feet of horizontal butt joint, 

additional spot radiographs shall be taken at what increment? 

a) One radiograph shall be taken in each additional 200 feet 

b) One radiograph shall be taken in each additional 100 feet 

c) One radiograph shall be taken in each additional 300 feet 

d) One radiograph shall be taken in each additional 150 feet 



Q10. What is the minimum weld length that must be clearly shown on each 

radiograph? 

a) 2 inches 

b) 3 inches 

c) 6 inches 

d) 8 inches 


Q11. Personnel who perform and evaluate radiographic examinations 

according to API-650 shall be qualified and certified by the manufacturer as 

meeting the requirements as generally outlined in _____. 

a) Level II or Level III of ASNT SNAT-TC-1B 

b) Level II or Level III of ASNT SNT-TC-1B 

c) Level II or Level III of ASNT SNAT-TC-1A 

d) Level II or Level III of ASNT SNT-TC-1A 



Q12. The acceptance standards for radiographic examinations shall be in 

accordance with which of the following? 

a) Paragraph UW-51(b) in Section VIII of the ASME Code 

b) Paragraph PW-51(b) in Section I of the ASME Code 

c) Paragraph 341.3.2 in B31.3 Process Piping of the ASME Code 

d) Paragraph RB-3233 in the National Board Inspection Code (NBIC) 


Q13. If a section of weld is shown by a radiograph to be unacceptable under the 

provisions of API-650, paragraph 6.1.5 or the radiograph does not define the 

limits of the deficient welding, which of the following requirements apply? 

a) One additional spot shall be taken and at least 3” of weld shall be represented 

b) Two spots adjacent to the section shall be examined by radiography 

c) Two spots ten feet from each side of the original radiography shall be 

examined 

d) Two spots, chosen randomly by the purchaser’s inspector, shall be examined 

by radiography 

Reference API-650, Paragraph 6.1.6 ANS: B 


API650: 8.1.6 Determination of Limits of Defective Welding When a 

section of weld is shown by a radiograph to be unacceptable under the 

provisions of 8.1.5 or the limits of the deficient welding are not defined by the 

radiograph, two spots adjacent to the section shall be examined by 

radiography; however, if the original radiograph shows at least 75 mm (3 in.) 

of acceptable weld between the defect and any one edge of the film, an 

additional radiograph need not be taken of the weld on that side of the defect. 


Q14. After an aboveground storage tank is completed, what shall be done 

with the radiographs? 

a) They shall become the property of the insurance company 

b) They shall become the property of the manufacturer 

c) They shall become the property of the purchaser 

d) They shall become the property of the API 

Reference API-650, Paragraph 6.1.8.2 ANS: C 

Q15. According to API-650, magnetic particle examination shall be performed 

to a written procedure. The examiner shall have his/her vision checked and 

be able to read which of the following? 

a) The magnetic particle written procedure at a distance not less than 12 

inches 

b) A Jaeger Type 3 standard chart at a distance not less than 12 inches 

c) A Jaeger Type 1 standard chart at a distance not less than 12 inches 

d) A Jaeger Type 2 standard chart at a distance not less than 12 inches 

Reference API-650, Paragraph 6.2.2 and 6.2.3 (a) ANS: D 


Q16. Ultrasonic examination shall be performed in accordance with a written 

procedure. Examiners shall be qualified and certified by the manufacturer as 

meeting the requirements of certification as generally outlined in which of the 

following? 

a) Level II or Level III of ASNT SNAT-TC-1B 

b) Level II or Level III of ASNT SNT-TC-1B 

c) Level II or Level III of ASNT SNAT-TC-1A 

d) Level II or Level III of ASNT SNT-TC-1A 

Reference API-650, Paragraph 6.3.2 and 6.3.3 ANS: D 


Q17. Liquid penetrant examination shall be performed in accordance with a 

written procedure. The examiner shall have his/her vision checked and be 

able to read which of the following? 

a) The liquid penetrant written procedure at a distance not less than 12 inches 

b) A Jaeger Type 2 standard chart at a distance not less than 12 inches 

c) A Jaeger Type 1 standard chart at a distance not less than 12 inches 

d) A Jaeger Type 3 standard chart at a distance not less than 12 inches 

Reference API-650, Paragraph 6.4.2 and 6.4.3 (a) ANS: B 


Q18. Undercutting of welds attaching nozzles, manholes, cleanout openings, 

and permanent attachments shall not exceed which of the following? 

a) Undercutting shall not exceed 1/64th inch 

b) Undercutting shall not exceed 3/32nd inch 

c) Undercutting shall not exceed 1/32nd inch 

d) Undercutting shall not exceed 3/64th inch 

Reference API-650, Paragraph 6.5.1 (b) ANS: A 


Answers to API-Standard 650 Section 6, Methods of Inspecting Joints 


Section 7 – Welding Procedure and Welder Qualifications 

Q1. Who is responsible for preparing the welding procedure specification, 

performing the qualification tests, and preparing the procedure qualification 

record? 

a) The welding operator or welder 

b) The purchaser’s inspector 

c) The purchaser’s welding engineer 

d) The erection manufacturer or the fabrication manufacturer if other than the 

erection manufacturer 

Reference API-650, Paragraph 7.2.1.1 ANS: D 


Q2. The manufacturer has the approval of the purchaser to use a material 

listed in API-650 but not included in the applicable table of ASME Section IX. 

What Group number would this material be included in if the minimum tensile 

strength is specified at 73,000 psi? 

a) This material would be included in Group number 2 

b) This material would be included in Group number 1 

c) This material would be included in Group number 3 

d) This material can not be used in AST construction 

Reference API-650, Paragraph 7.2.1.3 ANS: A 


API650: 9.2.1.3 Material specifications listed in Section 4 of this standard but 

not included in Table QW-422 of Section IX of the ASME Code shall be 

considered as P-No. 1 material with group numbers assigned as follows 

according to the minimum tensile strength specified: 

a) less than 485 MPa (70 ksi)—Group 1; 

b) equal to or greater than 485 MPa (70 ksi) but less than 550 MPa (80 ksi)— 

Group 2; 

c) equal to or greater than 550 MPa (80 ksi)—Group 3. 

Separate welding procedures and performance qualifications shall be 

conducted for A841M/A841 material. 


Q3. When impact tests of the heat-affected zone are required, how shall this 

requirement be treated? 

a) Heat treated condition of the base metal shall be a non-essential variable 

b) Heat treated condition of the base metal shall be an essential variable 

c) Heat treated condition of the base metal shall be a supplementary essential 

variable 

d) Heat treated condition of the base metal does not need to be addressed on 

the welding procedure specification 

Reference API-650, Paragraph 7.2.1.4ANS: C 


Q4. If a protective coating has been applied to weld edge preparations, how is 

this condition treated on the welding procedure specification? 

a) The coating shall be removed and does not affect the weld and therefore 

does not need to be addressed 

b) The coating shall be included as an essential variable 

c) The coating shall be included as a non-essential variable 

d) The coating shall be included as a supplementary essential variable 

Reference API-650, Paragraph 7.2.1.4 ANS: B 


Q5. Materials to be used at a design metal temperature below ____, the 

qualification of the welding procedure for vertical joints shall include impact 

tests of the weld metal. 

a) 50°F (10°C) 

b) 32°F 

c) 60°F 

d) 0°F 

Reference API-650, Paragraph 7.2.2.3 ANS: A 

Q6. Welder qualification tests conducted by one manufacturer shall not 

qualify a welder or welding operator to do work for another manufacturer. 

a) True 

b) False 

Reference API-650, Paragraph 7.3.1 ANS: A 


API650: 9.2.2.3 For all materials to be used at a design metal temperature 

below 10°C (50°F), the qualification of the welding procedure for vertical joints 

shall include impact tests of the weld metal. If vertical joints are to be made by 

a machine, automatic, or semiautomatic process, impact tests of the heataffected 

zone shall also be made. 


Q7. Traceability to a welder or welding operator, either by welder’s 

identification stamp or “weld map”, is required on all but which of the following? 

a) Shell horizontal weld joints 

b) Shell vertical weld joints 

c) Annular plate butt welds (when annular plates are required) 

d) Roof plate welds and flange-to-nozzle neck welds 

Reference API-650, Paragraph 7.4 ANS: D 


Answers to API-Standard 650 Section 7, Welding Procedure and Welder 

Qualifications 


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Section 8 - Marking 

Q1. A nameplate shall identify aboveground storage tanks made in 

accordance with API-650. Where must this nameplate be located on the 

completed tank? 

a) This nameplate shall be attached to the tank shell adjacent to a manhole 

or to a manhole reinforcing plate immediately to the right of the manhole 

b) This nameplate shall be attached to the tank shell adjacent to a vertical 

weld joint at least 48” above the shell-to-bottom weld joint 

c) This nameplate shall be attached to the tank shell adjacent to a manhole 

or to a manhole reinforcing plate immediately above the manhole 

d) This nameplate shall be attached to the tank shell adjacent to a manhole 

or to a manhole reinforcing plate immediately below the manhole 

Reference API-650, Paragraph 8.1.2 ANS: C 


Q2. The manufacturer of an AST is required to certify to the purchaser that 

the tank has been constructed in accordance with API-650. How is this 

certification accomplished? 

a) The manufacturer shall provide the purchaser with a U-1 Data Report form 

b) The manufacturer shall provide the purchaser with letter 

c) The manufacturer shall provide the purchaser with an ASME acceptable 

“Certificate of Compliance” 

d) The manufacturer shall provide the purchaser with a notarized certificate of 

compliance 

Reference API-650, Paragraph 8.3 ANS: B 

API650: 10.3 Certification The Manufacturer shall certify to the Purchaser, by a letter 

such as that shown in Figure 10.2, that the tank has been constructed in accordance 

with the applicable requirements of this standard. An as-built data sheet in accordance 

with Annex L shall be attached to the certification letter. NOTE At the Purchaser’s 

request or at the erection Manufacturer’s discretion, additional pertinent information 

may be shown on the nameplate, and the size of the nameplate may be increased 

proportionately. 


Answers to API-Standard 650 Section 8, Marking 


Appendix A – Optional Design Basis for Small Tanks 

Q1. What is the maximum shell thickness including corrosion allowance 

permitted for tanks that comply Appendix A of API-650? 

a) 7/8th inch b) 3/4th inch 

c) 5/8th inch d) 1/2 inch 

Reference API-650, Paragraph A.2.1ANS: D 

Q2. What is the maximum tensile strength, before the joint efficiency is 

applied, permitted in the design of small tanks in accordance with Appendix A 

of API-650? 

a) 21000 psi 

b) 21500 psi 

c) 21000 ksi 

d) 21500 ksi 

Reference API-650, Paragraph A.3.1 ANS:A 


Q3. When computing the tension in each ring (course) of a small tank 

designed in accordance with Appendix A of API-650, where is this tension 

computed? 

a) The tension shall be computed 12 inches above the centerline of the 

course in question 

b) The tension shall be computed 12 inches above the centerline of the lower 

horizontal joint of the course in question 

c) The tension shall be computed 12 inches above the centerline of the tank 

in question 

d) The tension shall be computed 12 inches below the centerline of the upper 

horizontal joint of the course in question 

Reference API-650, Paragraph A.3.3 ANS: B 

Q4. What joint efficiency factor shall be used in the design of small tanks 

designed in accordance with Appendix A of API-650 when spot 

radiographic examination is applied? 

a) 1.00 b) 0.90 c) 0.85 d) 0.70 

Reference API-650, Paragraph A.3.4 ANS: C 


5. What joint efficiency factor shall be used in the design of small tanks 

designed in accordance with Appendix A of API-650 when spot radiographic 

examination is omitted? 

a) 1.00 

b) 0.90 

c) 0.85 

d) 0.70 

Reference API-650, Paragraph A.3.4 ANS: D 


Answers to API-Standard 650 

Appendix A - Optional Design Basis for Small Tanks 


API 651- CATHODIC PROTECTION QUESTIONS 

Section 4 - Corrosion of Above Ground Steel Storage Tanks 

Q1. According to API Recommended Practice - 651, there are four 

components in each corrosion cell. Theses components are an anode and all 

but which of the following? 

a) DC current supplied by batteries 

b) A cathode 

c) A metallic path connecting the anode and cathode 

d) An electrolyte 

Reference: API-651 Paragraph 4.1.1 ANS: A 


Q2. The base metal goes into solution (corrodes) by releasing electrons and 

forming positive metal ions. This statement describes what takes place at 

what component of a corrosion cell? 

a) The cathode 

b) The electrolyte 

c) The metallic connection between the cathode and the anode 

d) The anode 

Reference: API-651 Paragraph 4.1.1(a) ANS: D 

Q3. Which of the following is the most correct statement regarding the 

cathode? 

a) Moderate corrosion takes place at the cathode 

b) No corrosion takes place at the cathode 

c) All corrosion takes place at the cathode 

d) A chemical reaction takes place using electrons released at the electrolyte 

Reference: API-651 Paragraph 4.1.1(b) ANS: B 


Q4. The electrolyte contains ions and conducts positive current from the 

anode to the cathode. The most common electrolyte for external tank bottom 

surfaces is ____, while the most common for internal surfaces is ____. 

a) Water, sludge and moist soil 

b) Moist soil, water and sludge 

c) Acidic soil, water and sludge 

d) Moist soil, product and sludge 

Reference: API-651 Paragraph 4.1.1(d) ANS: B 

Q5. The two most common types of corrosion to tank bottoms are ______ 

and ______. 

a) Stress corrosion and galvanic 

b) Erosion and erosion/corrosion 

c) General and pitting 

d) Stray current and bimetallic 

Reference: API-651 Paragraph 4.1.2 ANS: C 


Q6. Which type of corrosion results in relatively uniform metal loss? 

a) Erosion and erosion/corrosion 

b) Stray current 

c) General 

d) Pitting 


Q7. Which type of corrosion may only affect relatively small areas, while 

substantial areas of the surface are unaffected by corrosion? 

a) Galvanic 

b) General 

c) Brittle 

d) Pitting 

Reference: API-651 Paragraph 4.1.2 ANS: D 


Q8. Composition of the metal is a factor in determining which areas become 

anodes and which become cathodes. What else can cause corrosion? 

a) Differences between weld metal, heat affected zone, and parent metal 

b) Differences in thickness between adjacent plates 

c) Improper fit-up of the welded joint 

d) Slag inclusion in the weld metal 



Q9. Which of the following is a correct statement regarding oxygen 

concentration of the electrolyte. 

a) Oxygen concentration in the electrolyte has no impact on the corrosion cell 

b) Areas of lower oxygen concentrations become anodic and areas of higher 

concentrations become cathodic. 

c) Areas of lower oxygen concentrations become cathodic and areas of 

higher concentrations become anodic 

d) Areas of lower oxygen concentrations become acidic and areas of higher 

concentrations become alkaline 

Reference: API-651 Paragraph 4.1.4 ANS: B 


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Oxygen Concentration Corrosion 

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Fe → Fe 2+ + 2e - 

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Oxygen Concentration Corrosion 

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Fe → Fe 2+ + 2e - 

Fe 2+ + 2OH - → Fe(OH) 2 

2e - + 2H + + ½ O2 → H 2 O 

2H + 

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Q10. Soil characteristics substantially affect what? 

a) What type of product may be stored in the tank 

b) What the maximum fill height of the tank is 

c) The type and rate of corrosion on a structure in contact with soil 

d) Perk rate for dissipation of small leaks from the tank bottom 


Q11. What is another term used for "stray currents"? 

a) Short circuits 

b) Positive currents 

c) Impressed currents 

d) Interference currents 



Q12. The most common and potentially the most damaging stray currents are: 

a) Direct currents 

b) Alternating currents 

c) Intermittent currents 

d) Close proximity alternating currents 


Q13. Which of the following is not likely to be a source of stray currents? 

a) Static electricity 

b) Welding machines 

c) Impressed current cathodic protection systems 

d) Railroads 



Q14. Two metals with different compositions connected in an electrolyte is a 

general description of: 

a) A battery 

b) A current suppressor 

c) A short circuit 

d) Galvanic corrosion 


Q15. All but one of the following is listed as major factors which influence the 

severity of internal corrosion. Which is not a factor? 

a) The pH level of the fluid in contact with the steel bottom 

b) The amount of nitrogen in the fluid in contact with the steel bottom 

c) Suspended solids in the fluid in contact with the steel bottom 

d) Conductivity of the fluid in contact with the steel bottom 

Reference: API-651 Paragraph 4.2.3 ANS: B 


Q16. Three major types of internal corrosion to be considered are general 

corrosion, pitting corrosion, and to a lesser extent in tanks, environmental 

cracking. 

a) True 

b) False 



Answers to API-651 Section 4, corrosion of Aboveground Steel Storage 

Tanks 


Section 5 - Determination of Need for Cathodic Protection 

Q1. API Recommended Practice 651 states that the need for cathodic 

protection must be determined for all storage facilities. Decisions governing 

the need for cathodic protection should be based on all but which of the 

following? 

a) Data from corrosion surveys and operating records 

b) National Board and ASME recommendations 

c) Prior test results with similar systems in similar environments 

d) National, state, and local code requirements and the recommendations in 

API-651 

Reference: API RP 651, Paragraph 5.1 ANS: B 


Q2. When should corrosion control by cathodic protection for new ASTs be 

provided? 

a) After final welding and before hydrostatic testing 

b) After all stress relief has been carried out 

c) In the initial design 

d) After the tank is in service for 6 months 

Reference: API RP 651, Paragraph 5.1.1ANS: C 

Q3. Generally tanks in petroleum service use ______ on the internal surfaces 

to control internal corrosion. 

a) AC Current instead of DC current cathodic protection systems 

b) Coatings 

c) Cathodic protection in conjunction with coatings 

d) Since pure hydrocarbon fluids are usually not corrosive experience shows 

that internal corrosion will never occur therefore, corrosion control is not 

necessary 

Reference: API RP 651, Paragraph 5.1.3 ANS: B 


Q4. Cathodic protection is an effective means of corrosion control only if it is 

possible to pass electrical current between what two components? 

a) Anode and cathode 

b) Tank shell and roof support system 

c) Roof to bottom through roof support structures 

d) Tank shell and tank bottom 

Reference: API RP 651, Paragraph 5.1.4ANS: A 

Q5. A full evaluation of tank history should be performed prior to _______. 

a) Filling the tank for the 25th time 

b) Painting the exterior surface of the tank 

c) Temporarily removing the tank from service 

d) Determining the need for cathodic protection 

Reference: API RP 651, Paragraph 5.2.1 ANS: D 


Q6. Such items as site plan, soil properties, previous repairs, existing 

cathodic protection of nearby structures, maintenance history, and expected 

life should be investigated and determined when conducting the 

____________. 

a) Evaluation of the location of a refinery 

b) Probability study of tank settlement 

c) Evaluation of tank design/construction history 

d) Evaluation of tank repairs and alterations 

Reference: API RP 651, Paragraph 5.2.1.1ANS: C 

Q7. Of the following items which is not an item that should be investigated 

and determined in the evaluation of types of service? 

a) Type of product stored 

b) Product temperature 

c) Ambient temperature 

d) Presence and depth f water bottoms 

Reference: API RP 651, Paragraph 5.2.1.2 ANS: C 


Q8. Such items as tank inspections per API Standard 653, corrosion rate 

records, stray current problems, design and performance of previous 

protection systems, and structure-to-soil potential surveys should be 

investigated and determined when conducting the ______. 

a) Evaluation of tank repair/alteration/construction history 

b) Evaluation of tank design/construction history 

c) Evaluation of types of service 

d) Evaluation of inspection/corrosion history 

Reference: API RP 651, Paragraph 5.2.1.3ANS: D 

Q9. The cushion material under the tank has a significant effect on external 

corrosion of the tank bottom. The material can also influence: 

a) The effectiveness and applicability of external cathodic protection 

b) The effectiveness and applicability of internal cathodic protection 

c) The decision to use or not use a rectifier or DC generator set to supply 

current 

d) The type of product that may be stored in the tank 

Reference: API RP 651, Paragraph 5.3.1.1 ANS: A 


Q10. What is an advantage of using fine particles for the cushion material? 

a) The fine particles should be uniform which makes it easier to transport 

b) Fine particles provide a more dense cushion to help reduce the influx and 

outflow of oxygen 

c) Fine particles will not permit the passage of product should a leak occur in 

the tank bottom 

d) Fine particles will hold moisture longer permitting it to stabilize and prevent 

acid from forming in the electrolyte 

Reference: API RP 651, Paragraph 5.3.1.1 ANS: B 

Q11. What is the main disadvantage in using large size particles in the soil 

cushion material? 

a) The large particles may puncture the tank bottom 

b) The large particles may trap moisture and allow general corrosion to form 

c) If large particles are used, differential aeration corrosion may result where 

the particles contact the tank bottom 

d) The large particles are more difficult to transport 

Reference: API RP 651, Paragraph 5.3.1.1ANS: C 


Q12. A soil resistivity of about 1250 OHM-CM would indicate the soil is 

probably ____. 

a) Mildly corrosive 2000-10000 

b) Very corrosive 10000 less corrosive 

Q13. The results of soil resistivity surveys can be used to determine 

________. 

a) When it is time to replace the cushion material under the tank bottom 

b) The need for cathodic protection 

c) The amount of compression of the cushion material under the tank 

d) The best place to install a corrosion test bed 



Table 1—General Classification of Resistivity 


Q14. A properly designed concrete tank cushion constructed on stable, 

properly prepared subsoil may be effective in all but which of the following? 

a) Cracks in the tank bottom weld seams 

b) Intrusion of groundwater 

c) Soil-side corrosion 

d) The need for cathodic protection 

Reference: API RP 651, Paragraph 5.3.2.1ANS: A 

Q15. Cracks through the concrete cushion may permit water and 

contaminants to permeate to the steel tank bottom and provide a path for 

proper electrical current flow. 

a) True 

b) False 



Q16. Corrosion of the steel tank bottom installed on a concrete cushion may 

result from moisture accumulation caused by all but which of the following? 

a) Condensation 

b) Blowing snow or rain 

c) Humidity in the air surrounding the tank 

d) Flooding 

Reference: API RP 651, Paragraph 5.3.2.2 ANS: C 


Q17. Why would it be more important to provide proper support under 

cushions of new asphalt than for concrete? 

a) Asphalt is inherently alkaline and therefore does not have the potential of 

preventing corrosion 

b) Asphalt is not inherently alkaline and therefore does not have the potential 

of preventing corrosion 

c) Asphalt may degrade and become a corrosive substance 

d) Asphalt may crack allowing moisture to reach the tank bottom where it will 

react violently with the asphalt and the steel tank bottom 

Reference: API RP 651, Paragraph 5.3.3.1ANS: B 


API651: 5.3.6 Continuous Asphalt Pad 

A pad of new asphalt may provide many of the same advantages and 

disadvantages as a concrete pad for reducing corrosion and eliminating the 

need for cathodic protection. Proper support to prevent cracks and to prevent 

accumulation of water between the pad and the tank bottom is an important 

consideration. Asphalt degrades with time and can provide a path for water 

and dissolved contaminants to come into contact with the steel tank bottom, 

allowing corrosion to occur. Cathodic protection, if applied, may or may not 

aid in stopping corrosion when the asphalt becomes deteriorated. In fact, 

deteriorated asphalt may shield cathodic protection current in a manner 

similar to a disbonded coating on a pipeline. The condition of the external 

surface of the tank bottom as well as the asphalt can be determined if 

coupons are cut from the tank bottom. For new tank construction, use of 

asphalt pads is discouraged. 


API651: 5.3.4 Crushed Limestone or Clam Shell Pad 

In certain locations, the tank pad could consist of a layer of crushed limestone 

or clam shells. Such tank pads without the use of cathodic protection have 

produced mixed results. The tank pad should be fine and uniform, since 

differential aeration corrosion cells will cause pitting at contact areas between 

the large particles and the metal. The intrusion of water from rain or 

groundwater makes the environment under the tank alkaline, which may 

reduce corrosion. If contaminants are present in the pad, or with time infiltrate 

the pad, corrosion may accelerate. Thus, the use of crushed limestone or 

clam shells does not clearly eliminate the need for cathodic protection. 


Q18. How can the condition of the external surface of tank bottom and the 

asphalt cushion be determined? 

a) Raise the entire tank and inspect the tank bottom and the asphalt 

b) Take a core sample from the asphalt for testing. This test will reveal the 

amount of steel that has gone into solution and been trapped in the asphalt 

c) Conduct a soil resistivity survey around the periphery of the tank 

containment 

d) By cutting coupons from the tank bottom 

Reference: API RP 651, Paragraph 5.3.3.2 ANS: D 

Q19. A soil analysis reveals the pH of a native soil cushion to be 6.25. This 

soil is considered to be: 

a) Moderately corrosive 

b) Mildly corrosive (the least of the multiple choice) 

c) Corrosive 

d) Very corrosive 

Reference: API RP 651, Paragraph 5.3.4.1 and Table 2 ANS: B 


API651: 5.3.2.1 Sand Pad Material 

The following are issues to sand pad material. 

g) Measuring pH indicates the hydrogen ion content of a soil. 

• Corrosion of steel is fairly independent of pH when it is in the range of 5.0 

to 8.0. 

• The rate of corrosion increases appreciably when pH is < 5.0 and 

• decreases when pH is > 8.0. 

pH may be determined in accordance with ASTM G51 or equivalent. 


Q20. A soil analysis reveals the sulfates level of a native soil cushion to be 

5525ppm. This soil is considered to be 

a) Moderately corrosive 

b) Mildly corrosive 

c) Corrosive 

d) Very corrosive 

Reference: API RP 651, Paragraph 5.3.4.1 and Table 2ANS: D 

Q21. What is the most common material used as a cushion beneath storage 

tank bottoms? 

a) Clean concrete 

b) Clean sand 

c) Clean Asphalt 

d) Clean modified aggregate 



Q22. The use of oiled sand beneath tank bottoms does not eliminate the need 

for cathodic protection and in fact may cause cathodic protection to be less 

effective because: 

a) The oiled sand has higher resistivity (outcome) 

b) The sand is unable to conduct electrical current 

c) The oil acts as an insulator and blocks all current flow (root cause) 

d) The oil creates a vapor bearer entrapping water and contaminants next to 

the tank bottom 

Reference: API RP 651, Paragraph 5.3.5 ANS: A 

5.3.5 Oiled Sand Pad 

Historically, in some cases oil has been added to the sand for 

various reasons, including compaction and corrosion control. 

However, if cathodic protection is applied, the higher resistivity 

of oiled sand may prevent it from being effective. For new tank 

construction, use of oiled sand is discouraged. 


Q23. There are several ways the tank cushion can become contaminated. 

Three of the following are methods of cushion contamination, which one is 

not? 

a) In coastal areas salt spay may be washed down the side of the tank 

b) Fertilizer from spraying operations in rural areas 

c) Airborne chemicals from industrial operations 

d) Residual build-up of electrons in the sand cushion 

Reference: API RP 651, Paragraph 5.3.6.1 ANS: D 


Q24. Leakage of product from the tank bottom can cause accelerated 

corrosion by creating ____. 

a) Stray current corrosion 

b) Corrosion cells where none existed before 

c) More positively charged electrons 

d) A film that would block electrical current flow 


Q25. When a layer of crushed-limestone or clam-shell is used for the tank 

cushion, why is it important to ensure the particles are fine and uniform? 

a) Large particles could puncture the tank bottom 

b) Differential aeration corrosion cells will cause pitting at contact areas 

between the large particles and the metal 

c) Large particles may allow the formation of dissolved gas pockets which 

could become a hazard if hot tap work is performed on the tank bottom 

d) Large particle will eventually fracture and create voids in the tank cushion 



Q26. What is an advantage of using crushed-limestone or clam-shell under tank 

bottoms? 

a) This material is plentiful and relatively inexpensive 

b) Contamination is easier to detect because of discoloration 

c) Water from rain or groundwater makes the environment under the tank alkaline, 

which may reduce corrosion 

d) The use of this material eliminates the need for cathodic protection 

Reference: API RP 651, Paragraph 5.3.7 ANS: C 

Q27. Heated tanks or tanks storing hot product can cause: 

a) Increased water intrusion due to causing snow to melt and run down the tank 

sides 

b) Excessive drying out of concrete foundations resulting in premature 

deterioration and failure 

c) Accelerated corrosion on the internal surface especially in tanks with water 

bottoms 

d) Accelerated corrosion on the external surface due to elevated temperature is 

the area is wet 

Reference: API RP 651, Paragraph 5.4.1 ANS: D 


API651: 5.4 Other Factors Affecting Cathodic Protection 

5.4.1 Contents of Tank 

Aboveground storage tank temperature can influence corrosion on tank bottoms. 

Accelerated corrosion can occur on the external surface of the bottom of heated 

tanks due to elevated temperatures if the area is wet. 

NOTE The corrosion rate of steel may double with every 18 °F (10 °C) increase 

in temperature above 77 °F (25 °C). 

Aboveground storage tanks containing products above ambient temperature may 

require an increase in cathodic protection design current density to achieve 

adequate protection on the external surface of the bottom. Conversely, sufficient 

heat could dry out a well-drained tank pad, thus, increasing its resistivity and 

reducing performance of cathodic protection. However, tank operators should be 

aware that if water penetrates the previously dried out tank pad (such as: flooding, 

condensation, blowing rain or snow, poor drainage, rooftop water), the resistivity 

of the tank pad can decrease, developing a more corrosive condition. For this 

situation, the installation of a cathodic protection system should be installed. 


Q29. During the installation of a new steel bottom over an existing steel bottom, 

which has been repaired, if water or other electrolyte intrudes into the annulus, 

what can happen? 

a) A galvanic cell may form which will cause the new steel tank bottom to 

corrode at an accelerated rate 

b) An electrochemical reaction may take place creating hazardous gasses 

c) A galvanic cell may form which will cause the old tank bottom to corrode at an 

accelerated rate 

d) A galvanic cell may form which will turn the old tank bottom into an anode 

Reference: API RP 651, Paragraph 5.4.3.2 ANS: A 

Q30. With the installation of _____ in a diked area prior to new tank construction, 

most cathodic protection systems are rendered ineffective. 

a) A secondary containment system utilizing a perforated impervious membrane 

b) A secondary containment system utilizing an impervious membrane 

c) A secondary containment system utilizing a metallic impregnated screen 

membrane 

d) A secondary containment system utilizing a non-impervious membrane 



Answers to API-651 Section 5, Determination of Need for Cathodic 

Protection 


Section 6- Methods of Cathodic Protection for Corrosion 

Control 

Q1. What is the basic principle that makes cathodic protection effective. 

a) Cathodic protection is a technique for preventing corrosion by making the 

entire surface of the metal to be protected act as the rectifier 

b) Cathodic protection is a technique for preventing corrosion by making the 

entire surface of the metal to be protected act as the corrosion cell 

c) Cathodic protection is a technique for preventing corrosion by making the 

entire surface of the metal to be protected act as the cathode 

d) Cathodic protection is a technique for preventing corrosion by making the 

entire surface of the metal to be protected act as the anode 

Reference: API-651, Paragraph 6.1 ANS: C 


Q2. What are the two systems of cathodic protection? 

a) Galvanic and repressed current 

b) Galvanic and impressed current 

c) Galvanic and reversed current 

d) Galvanic and induced current 

Reference: API-651, Paragraph 6.1 ANS: B 

Q3. Galvanic cathodic protection systems use a metal, that is more active 

than the structure to be protected, to supply the current required to stop 

corrosion. What is another term(s) used to describe this material? 

a) Anode, commonly referred to as a galvanic or sacrificial anode 

b) Cathode, commonly referred to as a galvanic or sacrificial cathode 

c) Ribbon cathode, commonly referred to as a sacrificial ribbon cathode 

d) Impressed current anode, commonly referred to as the impressed anode 



Q4. Where on the galvanic series is clean and shiny mild steel? 

a) Clean and shiny mild steel has a value of –1.1 volts 

b) Clean and shiny mild steel has a value of –1.0 volts 

c) Clean and shiny mild steel has a value of –0.8 volts 

d) Clean and shiny mild steel has a value of –0.5 to -0.8 volts (v.s CSE) 

Reference: API-651, Paragraph 6.2.1 and Table 3 ANS:D 

Q5. The most common metals used as galvanic anodes in soil are: 

a) Lead and copper 

b) Aluminum alloy (5% zinc) and Mild steel (clean and shiny) 

c) Magnesium and zinc 

d) Mild steel in concrete and cast iron 



Q6. Of the following, which is not an advantage of galvanic cathodic 

protection systems? 

a) No external power is needed 

b) Capital investment is low for small-diameter tanks 

c) Method is limited to use in low-resistivity soils 

d) Interference problems (stray currents) are rare 


Q7. Impressed current cathodic protection systems use: 

a) Alternating current 

b) Direct current usually provided by a rectifier 

c) Direct current usually provided by a dry cell battery 

d) Either direct current or alternating current depending upon which is 

available 



Q8. Of the following, which is not a disadvantage of impressed current 

cathodic protection systems? 

a) High current output 

b) High maintenance costs 

c) High operating costs 

d) High capital cost for small installations 


Q9. A cathodic protection rectifier has two major components; what are they? 

a) A step-down transformer to reduce the AC supply voltage and rectifying 

elements to convert DC to AC output 

b) A step-down transformer to reduce the AC supply voltage and rectifying 

elements to convert AC to DC output 

c) A step-down transformer to reduce the DC supply voltage and rectifying 

elements to convert DC to AC output 

d) A step-down transformer to reduce the AC supply voltage and rectifying 

elements to regulate the AC output 



Q10. Impressed current anodes used in soil are not made of: 

a) Graphite 

b) High silicon cast iron 

c) Zinc 

d) Mixed metal oxides on titanium 


Q11. Impressed current anodes may be installed underneath the tank. 

a) True 

b) False 



Answers to API-651 Section 6, Methods of Cathodic Protection for 

Corrosion Control 


Section 8 – Criteria for Cathodic Protection 

Q1. API-651 provides criteria for determining the adequacy of cathodic 

protection of aboveground storage tanks. What document is referenced for a 

more detailed description? 

a) ASME Section V, Nondestructive Examination 

b) API-Standard 650, Welded Steel Tanks for Oil Storage 

c) API-Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction 

d) NACE RP-01-69 


8.2 Protection Criteria 

8.2.1 There are several criteria used to determine if adequate cathodic 

protection has been achieved on aboveground storage tanks. For a more 

detailed description, refer to the latest edition of NACE RP0193. 


NACE RP0193-2001 Standard Recommended Practice - External Cathodic 

Protection of On-Grade Metallic Storage Tank Bottoms. 

NACE RP0169-2002 Control of External Corrosion on Underground or 

Submerged Metallic Piping Systems. 


Q2. In determining if adequate cathodic protection is being achieved, which of 

the following would be correct? 

a) A negative (cathodic) potential of at least 850 mV with cathodic current 

applied 

b) A positive (cathodic) potential of at least 850 mV with cathodic current 

applied 

c) A negative (cathodic) potential of at least 85.0 mV with cathodic current 

applied 

d) A positive (cathodic) potential of at least 85.0 mV with cathodic current 

applied 



Q3. How must the required negative potential be measured? 

a) This potential shall be measured with respect to a saturated copper/copper 

sulfate reference electrode (CSE) contacting the metal tank bottom 

b) This potential shall be measured with respect to a saturated copper/copper 

sulfate reference electrode (CSE) contacting the electrolyte 

c) This potential shall be measured with respect to a saturated copper/copper 

sulfate reference electrode (CSE) contacting the metal casing of the 

rectifier 

d) This potential shall be measured with respect to a saturated copper/copper 

sulfate reference electrode (CSE) contacting the positive terminal of the 

power source 





a) Negative polarized potential of at least 8.50 mV relative to a CSE 

b) Negative polarized potential of at least 85.0 mV relative to a CSE 

c) Negative polarized potential of at least 850 mV relative to a CSE 

d) Negative polarized potential of at least .850 mV relative to a CSE 


Q5. Name a common method of measuring polarized potential. 

a) Measuring the distance between the tank bottom and the anode 

b) Measuring the AC current relative to the DC current 

c) Using the “instant on” method 

d) Using the “instant off” method 





a) A minimum of 1000 mV of cathodic polarization measured between the 

tank bottom metallic surface and a standard reference electrode 

contacting the electrolyte 

b) A minimum of 850 mV of cathodic polarization measured between the tank 

bottom metallic surface and a standard reference electrode contacting the 

electrolyte 

c) A minimum of 100 mV of cathodic polarization measured between the tank 

bottom metallic surface and a standard reference electrode contacting the 

electrolyte 

d) A minimum of -0.85 mV of cathodic polarization measured between the 

tank bottom metallic surface and a standard reference electrode 

contacting the electrolyte 



Q7. The standard method of determining the effectiveness of cathodic 

protection on a tank bottom is the __________ measurement 

a) Resistivity 

b) DC current 

c) Tank-to-soil 

d) Interference current 



Q8. How is the tank-to-soil potential measurement performed? 

a) This measurement is performed using a low-impedance voltmeter and a 

stable, reproducible reference electrode contacting the electrolyte 

b) This measurement is performed using a high-impedance voltmeter and a 

stable, regenerative reference electrode contacting the electrolyte 

c) This measurement is performed using a high-impedance voltmeter and a 

stable, reproducible reference electrode contacting the electrolyte 

d) This measurement is performed using a high-impedance voltmeter and an 

unstable, non-reproducible reference electrode contacting the electrolyte 



Q9. Tank-to-soil potential measurements are typically taken with current 

applied; however, corrections for ______ in the soil must be made. 

a) IW drop(s) 

b) IR drop(s) 

c) ER drop(s) 

d) IE drop(s) 


Q10. Correction for IR drop in the soil is often necessary for measurements 

made at the tank perimeter even if the reference electrode is placed 

immediately adjacent to the tank. This is especially true if ______ is/are close 

to the tank. 

a) Distributed anodes 

b) The cathodic protection power supply rectifier 

c) The sacrificial anode 

d) The DC power supply (battery) 



Q11. Monitoring the actual structure-to-soil potential under the tank should be 

considered. How can this be accomplished? 

a) Permanently installed reference electrode or by burying reference 

electrode every 20 feet around the perimeter of the tank 

b) Inserting a reference electrode under the tank through a perforated tube or 

attaching a reference electrode to the tank shell 

c) Permanently installed reference electrode or by inserting a reference 

electrode under the tank through a perforated tube 

d) Permanently installed bare copper wire connected to the tank bottom or by 

inserting a reference electrode under the tank through a perforated tube 



Q12. Other standard reference electrodes may be substituted for the 

saturated copper/copper sulfate reference electrode. Which of the following is 

not a common substitute? 

a) Reference electrode ➪ Zinc, Voltage ➪ +0.25 

b) Reference electrode ➪ Saturated KCI calomel Voltage ➪ -0.78 

c) Reference electrode ➪ Silver/silver chloride Voltage ➪ -0.80 

d) Reference electrode ➪ Aluminum alloy (5% zinc) Voltage ➪ +0.08 

Reference: API-651, Paragraph 8.4 and Table 4 ANS: D 


Answers to API-651 Section 8, Criteria for Cathodic Protection 


Section 11 – Operation and Maintenance of Cathodic 

Protection Systems 

Q1. Why is it important to conduct potential surveys when there is an adequate 

liquid level in a tank? 

a) Bottom-to-electrolyte potential readings may indicate adequate protection for 

the portion of the tank in contact with the soil but when the tank is full and all 

of the bottom is in contact, protection may not be sufficient 

b) Bottom-to- anode potential readings may indicate adequate protection for the 

portion of the tank in contact with the soil but when the tank is full and all of 

the bottom is in contact, protection may not be sufficient 

c) Bottom-to-cathode potential readings may indicate adequate protection for the 

portion of the tank in contact with the soil but when the tank is full and all of 

the bottom is in contact, protection may not be sufficient 

d) Bottom-to-electrolyte potential readings may indicate adequate protection for 

the portion of the tank in contact with the soil but when the tank is full and all 

of the bottom is in contact, protection may be far more than necessary 



Q2. Measurements of the native structure-to-soil potential should be made 

___. 

a) Immediately after any cathodic protection system is energized (?) 

b) Within two days after any cathodic protection system is energized 

c) Within 6 months after any cathodic protection system is energized 

d) Prior to energizing a new cathodic protection system 


Q3. After a system has been energized, it may take _____ for polarization to 

a steady state to 

take place. 

a) Two and a half years 

b) One year 

c) Several months 

d) Fifteen minutes 



API651: 11.3 Cathodic Protection Surveys 

11.3.1 General 

11.3.1.1 Prior to energizing a new cathodic protection system, measurements 

of the native structure-to-soil potential should be made. Immediately after any 

cathodic protection system is energized or repaired, a survey should be 

conducted to determine that it operates properly. An initial survey to verify 

that it satisfies applicable criteria should be conducted after adequate 

polarization has occurred. (?) Polarization to a steady state may take several 

months after the system is energized. 

Keywords: 

■ after adequate polarization has occurred. 

■ Immediately after any cathodic protection system is energized or repaired, 


Q4. To ensure the effectiveness of cathodic protection, how often should 

cathodic protection surveys be taken? 

a) Every two years 

b) Annually 

c) Bi-annually 

d) Quarterly 


Q5. How often should all sources of impressed current be checked? 

a) At intervals not exceeding two years 

b) At intervals not exceeding one year 

c) At intervals not exceeding two months 

d) At intervals not exceeding two weeks 

Reference: API-651, Paragraph 11.3.3.1ANS: C 


11.3.2 Inspection, Testing, and Maintenance of Cathodic Protection 

Facilities 

11.3.2.1 Inspection and tests of cathodic protection facilities should be made 

to ensure their proper operation and maintenance. 

11.3.2.2 All sources of impressed current should be checked at intervals not 

exceeding two months unless specified otherwise by regulation. Evidence of 

proper function may be current output, normal power consumption, a signal 

indicating normal operation, or satisfactory electrical state of the protected 

structure. A satisfactory comparison between the rectifier operation on a 

bimonthly basis and the rectifier operation during the annual survey implies 

the protected status of affected structures is similar. This does not take into 

account possible effects of foreign current sources. 


Q6. Tank bottoms shall be examined for evidence of corrosion at least once 

each year by conducting an internal inspection and taking coupon cutouts. 

a) True 

b) False 


Q7. Records to demonstrate the need for corrosion control measures should 

be retained for 

a) 5 years 

b) 10 years 

c) 15 years 

d) As long as the facility remains in service 



Q8. Records related to the effectiveness of cathodic protection should be 

retained for a ______ period unless a shorter period is specifically 

permitted by regulation 

a) 5 years 

b) 10 years 

c) 15 years 

d) As long as the facility remains in service 


API651:11.4.7 

• Records sufficient to demonstrate the need for corrosion control measures 

should be retained as long as the facility involved remains in service. 

• Records related to the effectiveness of cathodic protection should be 

retained for a period of five years unless a shorter period is specifically 

allowed by regulation. 


API651:11.4.7 

• Records sufficient to demonstrate the need for corrosion control measures 

should be retained as long as the facility involved remains in service. 

• Records related to the effectiveness of cathodic protection should be 

retained for a period of five years unless a shorter period is specifically 

allowed by regulation. 


Answers to API-651 Section 11, 

Operation and Maintenance of Cathodic Protection Systems 



ANS: ANS: 


ANS: ANS: 




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Understanding API ICP653 Reading 9-Worksheet-04

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