API 653 Corrosion Assessment 3

Question 1

In API 653, what is the maximum allowable corrosion rate used to project the retirement thickness when two inspection data points are available?

Accepted Answer

The long-term corrosion rate or short-term corrosion rate, whichever is greater

Answer

API 653 requires using the greater of the long-term or short-term corrosion rate to conservatively project remaining life.

Question 2

Which type of soil condition is generally considered most corrosive to unprotected tank bottoms?

Accepted Answer

Clay-rich, wet soil with low electrical resistivity

Answer

Clay-rich, wet soils with low electrical resistivity provide an excellent electrolyte path, promoting corrosion of unprotected steel tank bottoms.

Question 3

What is the API 653 definition of a 'critical zone' on a tank shell for corrosion assessment purposes?

Accepted Answer

The area within 12 inches above the tank bottom

Answer

API 653 defines the critical zone as the shell plate area within approximately 12 inches above the tank bottom, where corrosion is typically most severe.

Question 4

When assessing pitting corrosion in a tank shell, API 653 allows evaluation using which standard?

Accepted Answer

API 579-1/ASME FFS-1

Answer

API 579-1/ASME FFS-1 provides fitness-for-service assessment methods for pitting corrosion that are referenced by API 653.

Question 5

Which NDE method is specifically recommended by API 653 for locating weld seam corrosion on tank floors?

Accepted Answer

Vacuum box testing

Answer

Vacuum box testing is used to check weld seams on tank floors for leaks and is commonly used during internal inspection to identify corrosion-related failures at welds.

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

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

API 653 Corrosion Assessment 3