Important API-571 Exam Questions

Answer: D

Explanation:

From API RP 571 on Microbiologically Influenced Corrosion (MIC):

''MIC depends on the presence of water, nutrients, and specific microbial species such as SRB (sulfate-reducing bacteria).''

''While flow velocity may influence deposition and oxygen content, MIC can occur in both stagnant and flowing systems. Hence, it's not strongly dependent on velocity.''

Thus, option D is correct --- MIC is largely independent of flow velocity.

Answer: A

Explanation:

From API RP 571 Section 5.1.2.1 and RP 941:

''High strength low alloy steels (HSLA) are more susceptible to hydrogen embrittlement, especially during cold work, forming, or welding. These materials, due to their higher tensile strengths, are more prone to cracking when exposed to hydrogen, particularly during fabrication or post-weld heat treatment operations.''

Therefore, Option A (High Strength Low Alloys) is the correct answer due to their known susceptibility during manufacturing and processing.

Answer: D

Explanation:

According to API RP 571, under Naphthenic Acid Corrosion (NAC):

''The most severe corrosion is typically found in areas of high velocity and turbulence, such as at pump around nozzles, transfer lines, elbows, reducers, and orifices.''

''NAC is characterized by uniform thinning and can accelerate significantly where flow-induced erosion is present.''

(Reference: API RP 571, Section 4.3.4.1 -- Naphthenic Acid Corrosion)

This clearly establishes that high velocity and turbulence increase NAC severity, making option D correct.

Answer: B

Explanation:

Comprehensive and Detailed Explanation From Exact Extract:

Polythionic acid stress corrosion cracking (PASCC) occurs in austenitic stainless steels exposed to sulfur-containing environments during shutdowns, particularly when sulfide scales react with oxygen and moisture.

According to API RP 571:

Unstabilized stainless steels, such as Type 304, are most susceptible

Stabilized grades (e.g., Type 321, titanium-stabilized) are more resistant

Carbon steel and Monel are not susceptible to PASCC

Referenced Documents (Study Basis):

API RP 571 -- Section on Polythionic Acid SCC

Answer: B

Explanation:

Comprehensive and Detailed Explanation From Exact Extract:

According to API RP 571, hydrogen embrittlement (HE) of carbon steels is a low-temperature damage mechanism. It occurs when atomic hydrogen enters the steel lattice, reducing ductility and toughness and potentially causing cracking or delayed failure.

API RP 571 clearly differentiates HE from high-temperature hydrogen damage mechanisms (such as HTHA). Hydrogen embrittlement is most severe at ambient to moderately elevated temperatures, typically below about 200 F (93 C), where hydrogen mobility and trapping promote embrittlement.

At higher temperatures, hydrogen tends to diffuse out of the steel and embrittlement effects diminish.

Referenced Documents (Study Basis):

API RP 571 -- Section on Hydrogen Embrittlement