API 571 Stress Corrosion Cracking 2

Question 1

Wet H2S damage in API 571 encompasses which specific damage forms?

Accepted Answer

HIC, SOHIC, SSC, and stepwise cracking (SWC)

Answer

API 571 groups hydrogen-induced cracking (HIC), stress-oriented HIC (SOHIC), sulfide stress cracking (SSC), and stepwise cracking (SWC) under the wet H2S damage category.

Question 2

Hydrogen-induced cracking (HIC) preferentially initiates at which microstructural features?

Accepted Answer

Non-metallic inclusions and laminations within the steel plate

Answer

HIC blisters and planar cracks initiate at MnS inclusions and laminations where atomic hydrogen recombines into molecular hydrogen, building up internal pressure.

Question 3

How does SOHIC (Stress-Oriented HIC) differ from standard HIC?

Accepted Answer

SOHIC cracks align perpendicular to applied stress and can link to form through-wall cracks

Answer

SOHIC involves HIC cracks that orient with applied or residual stress, potentially linking through the vessel wall thickness to create a serious through-thickness crack path.

Question 4

Sulfide stress cracking (SSC) most preferentially affects which type of steel?

Accepted Answer

High-strength steels with hardness exceeding HRC 22

Answer

SSC preferentially attacks high-strength, high-hardness steels because hardness directly correlates with susceptibility to hydrogen embrittlement in H2S environments.

Question 5

NACE MR0175/ISO 15156 provides requirements for which application?

Accepted Answer

Material selection for equipment in H2S-containing sour service

Answer

NACE MR0175 specifies material requirements, hardness limits, and heat treatment requirements for equipment exposed to H2S-containing environments to prevent SSC.

API 571 - API 571 Corrosion and Materials Practice Test

API 571 - API 571 Corrosion and Materials Practice Test

API 571 Stress Corrosion Cracking 2