API 510 Material Evaluation 3

Question 1

An austenitic stainless steel vessel used in a chloride-containing service environment develops cracking that follows grain boundaries. What is the most likely damage mechanism?

Accepted Answer

Intergranular stress corrosion cracking (IGSCC)

Answer

Intergranular SCC in austenitic stainless steels occurs when sensitization depletes chromium at grain boundaries, and chloride stress corrosion follows these weakened zones.

Question 2

During material evaluation, an inspector finds hardness readings of 250 HB on a weld heat-affected zone in wet H2S service. What is the significance of this finding?

Accepted Answer

Concerning; hardness exceeds 248 HB limit per NACE MR0103/ISO 15156

Answer

NACE MR0103/ISO 15156 limits hardness to 248 HB (22 HRC) for carbon and low-alloy steels in wet H2S service to prevent sulfide stress cracking.

Question 3

A material evaluation reveals a carbon steel vessel component has experienced graphitization. Which condition is most likely responsible?

Accepted Answer

Extended service at temperatures between 650°F and 875°F (343-468°C)

Answer

Graphitization occurs in carbon steels typically between 650-875°F over extended periods, where iron carbide decomposes to form graphite nodules, reducing toughness.

Question 4

When evaluating duplex stainless steel for fitness-for-service, which microstructural condition most severely degrades toughness and must be confirmed absent?

Accepted Answer

Sigma phase formation from extended exposure between 600-1700°F

Answer

Sigma phase forms in duplex stainless steels exposed to 600-1700°F and causes severe embrittlement by consuming the ferrite phase.

Question 5

An inspector is evaluating a vessel that previously contained a caustic solution. Cracking is found in welds and heat-affected zones. What is the required assessment approach per API 579-1/ASME FFS-1?

Accepted Answer

Environment-assisted cracking assessment per Part 9 of API 579

Answer

Caustic SCC is an environment-assisted cracking mechanism evaluated under Part 9 of API 579-1/ASME FFS-1 for stress corrosion cracking fitness-for-service.

(API 510) API 510 Inspector Certification Practice Test

(API 510) API 510 Inspector Certification Practice Test

API 510 Material Evaluation 3