API 653 Tank Inspection, NDE & Testing 4

Question 1

According to API 653, when is an internal inspection required after a tank has undergone a major repair to its shell?

Accepted Answer

Before the tank is returned to service following the repair

Answer

API 653 requires that the adequacy of major repairs be verified by inspection before the tank is returned to service, ensuring the repair meets all applicable requirements.

Question 2

What does a 'tee-pee' or 'cone' deformation pattern in a tank floor plate most likely indicate?

Accepted Answer

Differential settlement causing upward buckling of floor plates

Answer

A cone or tee-pee deformation in tank floor plates is typically caused by differential foundation settlement, which creates localized upward buckling.

Question 3

During tank floor inspection using MFL, a 'C-scan' display showing widespread low-amplitude signals across the entire floor most likely indicates:

Accepted Answer

General uniform corrosion or mill scale throughout the floor

Answer

Widespread low-amplitude MFL signals distributed across the floor are consistent with general uniform corrosion or surface mill scale rather than isolated pitting.

Question 4

API 653 requires that all welded repairs on a tank shell in HF (hydrofluoric acid) service must be subject to what additional NDE requirement?

Accepted Answer

Post-weld heat treatment (PWHT) followed by hardness verification

Answer

HF service imposes strict hardness limitations to prevent stress corrosion cracking; PWHT is required and hardness must be verified to confirm compliance.

Question 5

When calculating the maximum allowable fill height (MAFH) for a tank with an identified corroded shell course, which variable directly determines the controlling calculation?

Accepted Answer

The minimum measured thickness within the corroded area

Answer

The MAFH calculation uses the minimum measured thickness of the corroded shell to determine the maximum liquid head the shell can safely sustain.

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

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

API 653 Tank Inspection, NDE & Testing 4