API 653 Fitness-for-Service & Repair 3

Question 1

Under API 653, what is the minimum shell plate thickness for a tank to remain in service if no other defects are present?

Accepted Answer

Calculated minimum thickness based on shell design formula

Answer

API 653 requires the measured thickness to meet or exceed the calculated minimum required thickness from the shell design equation, not a fixed universal value.

Question 2

Which of the following is classified as an alteration rather than a repair under API 653?

Accepted Answer

Adding a new nozzle to an existing shell

Answer

Adding a new nozzle changes the original design configuration and is classified as an alteration, which requires engineering review and potentially a hydrostatic test.

Question 3

API 653 requires that weld repairs on tank shells be performed by welders qualified per which standard?

Accepted Answer

ASME Section IX

Answer

API 653 mandates that welders and welding procedures for tank repairs be qualified in accordance with ASME Section IX.

Question 4

When using the API 653 settlement fitness-for-service criteria, what type of settlement is most damaging to tank shell-to-bottom welds?

Accepted Answer

Edge settlement causing differential tilt around the perimeter

Answer

Edge (perimeter) differential settlement causes bending stresses at the shell-to-bottom weld, which is the most structurally critical area for tank integrity.

Question 5

A lap-welded repair patch on a tank shell must have a minimum distance from any existing weld seam of:

Accepted Answer

6 inches

Answer

API 653 requires lap-welded repair patches to be located at least 6 inches from any existing weld seam to avoid heat-affected zone interactions.

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

API 653 Fitness-for-Service & Repair 3