API 653 EXAM QUESTIONS AND ANSWERS
API publications necessarily address problems of what type? - Answers - Problems of a
general nature. (Special notes section)
API Standard 653 covers in service steel tanks built to what standards? - Answers - 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? -
Answers - 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? - Answers - This
standard employs the principles of API 650. (1.1.3)
What is the definition of a "repair" to a tank? - Answers - 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? - Answers - 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? - Answers - 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? - Answers - 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?
- Answers - Pitting (4.3.1.3)
When can widley scattered pits inside the tank shell be ignored? - Answers - 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? - Answers - E =
0.85. (Table 4.2)
What can foundation settlement cause to appear in the shell of an AST? - Answers -
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? - Answers - 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)
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? - Answers - The current edition of API 650 must be used.
(1.1.5)
Who has the ultimate responsability for complying with the provisions of API653? -
Answers - The owner/operator. (1.2)
The inspector agency of the jurisdiction in which the above ground is storage tank is
operated is called what? - Answers - 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? - Answers - Authorized inspector (3.4)
What is the total metal loss divided by the period of time over which the metal loss
occurred? - Answers - Corrosion rate (3.9)
An AST operating at 250F is evaluated for continuing service. The inspector checks the
tank records and finds that the tank was originally built of ASTM A516 gr60. What
allowable stress should the inspector use in evaluation the minimum thicknesses of the
tank's shell? - Answers - 32,000 * 0.80 = 25,600 (4.3.10.1.1a or Table 4.1)
A six year old storage tank is inspected. The tank has a diameter of 125 feet and its
maximum liquid level height is 40 feet. The tank was constructed of ASTM A283 gr C
steel. The product stored in the tank has a specific gravity of 0.85. What is the Tmin for
the lower shell course plate? - Answers - Tmin = (2.6*H*D*G)/(S*E)
= (2.6*40*125*0.85)/(23600*1)
= (11050)/(23600) = 0.468"
(4.3.3.1)
An AST that has a diameter of 121ft and a height of 40ft (five 8ft courses).Its bottom
shell course has a thickness of 0.55" and a corrosion allowance of 0.1". The tank is built
API publications necessarily address problems of what type? - Answers - Problems of a
general nature. (Special notes section)
API Standard 653 covers in service steel tanks built to what standards? - Answers - 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? -
Answers - 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? - Answers - This
standard employs the principles of API 650. (1.1.3)
What is the definition of a "repair" to a tank? - Answers - 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? - Answers - 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? - Answers - 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? - Answers - 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?
- Answers - Pitting (4.3.1.3)
When can widley scattered pits inside the tank shell be ignored? - Answers - 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? - Answers - E =
0.85. (Table 4.2)
What can foundation settlement cause to appear in the shell of an AST? - Answers -
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? - Answers - 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)
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? - Answers - The current edition of API 650 must be used.
(1.1.5)
Who has the ultimate responsability for complying with the provisions of API653? -
Answers - The owner/operator. (1.2)
The inspector agency of the jurisdiction in which the above ground is storage tank is
operated is called what? - Answers - 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? - Answers - Authorized inspector (3.4)
What is the total metal loss divided by the period of time over which the metal loss
occurred? - Answers - Corrosion rate (3.9)
An AST operating at 250F is evaluated for continuing service. The inspector checks the
tank records and finds that the tank was originally built of ASTM A516 gr60. What
allowable stress should the inspector use in evaluation the minimum thicknesses of the
tank's shell? - Answers - 32,000 * 0.80 = 25,600 (4.3.10.1.1a or Table 4.1)
A six year old storage tank is inspected. The tank has a diameter of 125 feet and its
maximum liquid level height is 40 feet. The tank was constructed of ASTM A283 gr C
steel. The product stored in the tank has a specific gravity of 0.85. What is the Tmin for
the lower shell course plate? - Answers - Tmin = (2.6*H*D*G)/(S*E)
= (2.6*40*125*0.85)/(23600*1)
= (11050)/(23600) = 0.468"
(4.3.3.1)
An AST that has a diameter of 121ft and a height of 40ft (five 8ft courses).Its bottom
shell course has a thickness of 0.55" and a corrosion allowance of 0.1". The tank is built
