API 653 Code Requirements 5

Question 1

Per API 653, what is the maximum allowable out-of-plumbness (tilt) for an existing tank shell before corrective action is required?

Accepted Answer

1 inch per 10 feet of shell height, not to exceed 5 inches total

Answer

1% of the total shell height

Answer

1/100 of the shell height or 1 inch, whichever is greater

Answer

Any measurable tilt requires immediate shutdown

Question 2

Under API 653, which non-destructive examination (NDE) method is typically used for detecting bottom plate laminations?

Accepted Answer

Ultrasonic testing (UT)

Answer

Magnetic particle testing (MT)

Answer

Liquid penetrant testing (PT)

Answer

Radiographic testing (RT)

Question 3

According to API 653, when evaluating a tank for settlement, what type of settlement is most critical and likely to cause structural damage?

Accepted Answer

Differential settlement, particularly localized shell settlement

Answer

Uniform settlement across the entire foundation

Answer

Edge settlement occurring uniformly around the perimeter

Answer

Settlement of the center of the bottom relative to the shell

Question 4

Per API 653, what welding process qualification requirements apply to welders performing repairs on API 653 tanks?

Accepted Answer

Welders must be qualified under ASME Section IX or AWS D1.1

Answer

Any certified welder with 2 years of experience is automatically qualified

Answer

Only the owner's approval is needed, no formal qualification required

Answer

Welders must hold an API-specific welding certification

Question 5

What is the significance of the 'critical zone' at the tank bottom as defined in API 653?

Accepted Answer

The annular plate ring within 3 inches of the shell-to-bottom weld

Answer

The area around manway openings where stress concentrations are highest

Answer

The center bottom area most susceptible to internal corrosion

Answer

The top course of the shell near the roof-to-shell weld

Question 6

Under API 653, what is required before returning a tank to service after a change in service to a more severe product?

Accepted Answer

An engineering review and possible re-rating or re-inspection of the tank

Answer

A simple visual inspection by the owner is sufficient

Answer

Only regulatory notification is required

Answer

No action is needed if the new product is at the same pressure

Question 7

According to API 653, what is the primary purpose of cathodic protection (CP) systems on aboveground storage tank bottoms?

Accepted Answer

To protect the soil-side of the tank bottom from external corrosion

Answer

To detect leaks from the tank bottom

Answer

To prevent static electricity buildup during product transfers

Answer

To satisfy EPA secondary containment requirements