API 653 QUESTIONS AND ANSWERS
WITH SOLUTIONS 2024
API publications necessarily address problems of what type? - ANSWER Problems of a general nature.
(Special notes section)
API Standard 653 covers in service steel tanks built to what standards? - ANSWER This standard covers
steel storage tanks built to API 650 and its predecessor API 12C. (1.1.1)
What API Standard always governs for tanks that have been placed in service? - ANSWER In the case of
apparent conflicts between the requirements of this standard and API 650 or its predecessor API 12C,
API 653 shall govern for tanks that have been placed in service. (1.1.2)
API Standard 653 employs the design principles of what standard? - ANSWER This standard employs the
principles of API 650. (1.1.3)
When design and construction details are not given and are not available in the standard to which the in
service tank was originally constructed, then details that will provide a level of integrity equal to the level
provided by the current edition of which standard must be used? - ANSWER The current edition of API
650 must be used. (1.1.5)
Who has the ultimate responsability for complying with the provisions of API653? - ANSWER The
owner/operator. (1.2)
The inspector agency of the jurisdiction in which the above ground is storage tank is operated is called
what? - ANSWER Authorized inspection agency (3.3)
An employee of an authorized inspection agency certified as an AST inspector per API 653 Appendix D, is
known as what? - ANSWER Authorized inspector (3.4)
What is the total metal loss divided by the period of time over which the metal loss occurred? - ANSWER
Corrosion rate (3.9)
, What is the definition of a "repair" to a tank? - ANSWER Work necessary to maintain or restore a tank to
a condition suitable for safe operation. (3.24)
What must be done when the results of a tank inspection show that a change has occurred from the
original physical condition of that tank? - ANSWER An evaluation shall be made to determine its
suitability for continued use. (4.1.1)
What must be done when the cone roof tank roof plates corrode to an average thickness of less than
0.09" in any 100 in^2 area? - ANSWER Shall be repaired or replaced. (4.2.1.2)
What section of API 653 must be considered when changing the service of a tank to operation at
temperatures above 200F? - ANSWER All requirements of API 650, Appendix M. (4.2.4.3)
What form of corrosion does not normally represent a significant threat to the overall structural integrity
of the tank shell unless it is present in a severe and numerous form? - ANSWER Pitting (4.3.1.3)
When can widley scattered pits inside the tank shell be ignored? - ANSWER Provided that:
a) no pit depth results in the remaining shell thickness being less than one-half the minimum acceptable
tank shell
thickness exclusive of the corrosion allowance; and
b) the sum of their dimensions along any vertical line does not exceed 2 in. in an 8-in. length (see Figure
4.2). (4.3.2.2).
A tank of a single butt-weld with a back-up bar construction, built to an unknownstandard in 1940 is
inspected. Corrosion is general and an evaluation of the tank's minimum thickness is required. What
joint factor would you use? - ANSWER E = 0.85. (Table 4.2)
What can foundation settlement cause to appear in the shell of an AST? - ANSWER Shell distortions.
(4.3.5.2, 4.3.5.3)
Unless a stress analysis is performed what is the minimum bottom plate thickness in the critical zone of
the tank bottom? - ANSWER the smaller of one-half the original bottom plate thickness or 50 % of tmin
of the lower shell course, but not less than 0.1 in. (4.4.5.4)
WITH SOLUTIONS 2024
API publications necessarily address problems of what type? - ANSWER Problems of a general nature.
(Special notes section)
API Standard 653 covers in service steel tanks built to what standards? - ANSWER This standard covers
steel storage tanks built to API 650 and its predecessor API 12C. (1.1.1)
What API Standard always governs for tanks that have been placed in service? - ANSWER In the case of
apparent conflicts between the requirements of this standard and API 650 or its predecessor API 12C,
API 653 shall govern for tanks that have been placed in service. (1.1.2)
API Standard 653 employs the design principles of what standard? - ANSWER This standard employs the
principles of API 650. (1.1.3)
When design and construction details are not given and are not available in the standard to which the in
service tank was originally constructed, then details that will provide a level of integrity equal to the level
provided by the current edition of which standard must be used? - ANSWER The current edition of API
650 must be used. (1.1.5)
Who has the ultimate responsability for complying with the provisions of API653? - ANSWER The
owner/operator. (1.2)
The inspector agency of the jurisdiction in which the above ground is storage tank is operated is called
what? - ANSWER Authorized inspection agency (3.3)
An employee of an authorized inspection agency certified as an AST inspector per API 653 Appendix D, is
known as what? - ANSWER Authorized inspector (3.4)
What is the total metal loss divided by the period of time over which the metal loss occurred? - ANSWER
Corrosion rate (3.9)
, What is the definition of a "repair" to a tank? - ANSWER Work necessary to maintain or restore a tank to
a condition suitable for safe operation. (3.24)
What must be done when the results of a tank inspection show that a change has occurred from the
original physical condition of that tank? - ANSWER An evaluation shall be made to determine its
suitability for continued use. (4.1.1)
What must be done when the cone roof tank roof plates corrode to an average thickness of less than
0.09" in any 100 in^2 area? - ANSWER Shall be repaired or replaced. (4.2.1.2)
What section of API 653 must be considered when changing the service of a tank to operation at
temperatures above 200F? - ANSWER All requirements of API 650, Appendix M. (4.2.4.3)
What form of corrosion does not normally represent a significant threat to the overall structural integrity
of the tank shell unless it is present in a severe and numerous form? - ANSWER Pitting (4.3.1.3)
When can widley scattered pits inside the tank shell be ignored? - ANSWER Provided that:
a) no pit depth results in the remaining shell thickness being less than one-half the minimum acceptable
tank shell
thickness exclusive of the corrosion allowance; and
b) the sum of their dimensions along any vertical line does not exceed 2 in. in an 8-in. length (see Figure
4.2). (4.3.2.2).
A tank of a single butt-weld with a back-up bar construction, built to an unknownstandard in 1940 is
inspected. Corrosion is general and an evaluation of the tank's minimum thickness is required. What
joint factor would you use? - ANSWER E = 0.85. (Table 4.2)
What can foundation settlement cause to appear in the shell of an AST? - ANSWER Shell distortions.
(4.3.5.2, 4.3.5.3)
Unless a stress analysis is performed what is the minimum bottom plate thickness in the critical zone of
the tank bottom? - ANSWER the smaller of one-half the original bottom plate thickness or 50 % of tmin
of the lower shell course, but not less than 0.1 in. (4.4.5.4)
