API 653 Fitness-for-Service & Repair 4

Question 1

API 653 defines the 'critical zone' of a tank bottom as the area within what distance from the shell?

Accepted Answer

3 feet

Answer

API 653 defines the critical zone as the annular bottom plate area within 3 feet of the inside edge of the shell, where stresses are highest.

Question 2

When a tank inspector finds a roof-to-shell weld that is cracked, the FIRST action should be to:

Accepted Answer

Assess whether the crack affects structural integrity and containment

Answer

The first step is to assess the severity and extent of the crack to determine if the tank must be taken out of service or if temporary measures are adequate pending repair.

Question 3

Under API 653, which party must approve a fitness-for-service assessment for a tank with damage exceeding the code's simplified criteria?

Accepted Answer

An engineer experienced in storage tank design

Answer

API 653 requires that complex fitness-for-service assessments beyond the simplified level be reviewed and approved by an engineer experienced in storage tank design.

Question 4

What is the maximum allowable out-of-plumb (tilt) for a tank shell per API 653 before it becomes a fitness-for-service concern?

Accepted Answer

1/100 of the tank height

Answer

API 653 indicates that shell out-of-plumb exceeding 1% (1/100) of the tank height is a concern that may require engineering evaluation.

Question 5

For hot-tap repairs on tanks in service, API 653 requires that the minimum remaining shell thickness at the hot-tap location be:

Accepted Answer

Sufficient to prevent burn-through based on an engineering analysis

Answer

Hot-tap repairs require an engineering analysis to confirm sufficient remaining wall thickness to prevent burn-through during welding with the tank in service.

(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 4