API 510 Corrosion Mechanisms & Damage Assessment 3

Question 1

What is the primary concern with high-temperature hydrogen attack (HTHA) in pressure vessels?

Accepted Answer

Decarburization and fissuring that weaken the steel permanently

Answer

HTHA causes decarburization and internal fissuring as atomic hydrogen reacts with carbides in the steel, permanently reducing strength and ductility.

Question 2

An inspector observes a vessel operating in wet H₂S service. Which damage mechanism should be the primary concern?

Accepted Answer

Sulfide stress cracking (SSC)

Answer

Wet H₂S service promotes sulfide stress cracking, especially in high-strength or hardened steels, and is a critical concern per API 510 and NACE standards.

Question 3

What is the significance of the 'corrosion allowance' in pressure vessel design and inspection?

Accepted Answer

It is extra metal thickness added to account for expected corrosion over the vessel's service life

Answer

Corrosion allowance is the additional thickness beyond the calculated minimum to accommodate anticipated metal loss during the design service life.

Question 4

In API 510, what calculation determines the remaining corrosion allowance for an in-service vessel?

Accepted Answer

Actual measured thickness minus required minimum thickness

Answer

Remaining corrosion allowance equals the actual measured thickness minus the required minimum thickness (t_minimum), indicating how much additional metal loss is acceptable.

Question 5

Galvanic corrosion between two dissimilar metals is most likely to occur when:

Accepted Answer

The metals are in electrical contact in the presence of an electrolyte

Answer

Galvanic corrosion requires electrical contact between dissimilar metals and an electrolyte (conductive liquid) to complete the electrochemical cell.

(API 510) API 510 Inspector Certification Practice Test

(API 510) API 510 Inspector Certification Practice Test

API 510 Corrosion Mechanisms & Damage Assessment 3