Pass the API ICP Programs API-571 Questions and answers with CertsForce

Comprehensive and Detailed Explanation From Exact Extract:

Per API RP 571, mechanical fatigue failures are identified by the presence of beach marks or clam shell patterns on the fracture surface.

These features:

Appear as concentric rings

Represent successive crack growth increments

Radiate outward from the crack initiation site

This “clam shell” or “beach mark” appearance is one of the most recognizable signatures of fatigue failure.

Referenced Documents (Study Basis):

API RP 571 – Section on Mechanical Fatigue

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According to API RP 571, in the section on Boiler Water Condensate Corrosion:

“The major contributors to condensate corrosion are dissolved CO₂ and O₂. Carbon dioxide forms carbonic acid in the presence of water, lowering pH and causing generalized corrosion.”

“Oxygen causes pitting and localized corrosion unless chemically treated.”

Thus, option B (Carbon dioxide and oxygen) is the primary root cause and the correct answer.

According to API RP 571, under High Temperature Hydrogen Attack (HTHA):

“HTHA occurs when hydrogen diffuses into steel at elevated temperatures and reacts with carbides in the steel matrix to form methane (CH₄).”

“The methane is unable to diffuse out of the steel and forms internal pressures, leading to fissuring, decarburization, and eventual failure.”

“HTHA typically affects carbon steels and low alloy steels exposed to high temperature hydrogen services, particularly above 400°F (204°C) depending on partial pressure of hydrogen.”

(Reference: API RP 571, Section 4.2.1.3 – High Temperature Hydrogen Attack)

Hence, option D is the correct and technically supported answer.

API RP 571 under Ammonium Chloride Corrosion details:

“The corrosion results from the deposition of ammonium chloride salts from high-temperature process streams as they cool.”

“This typically occurs in crude unit overheads or other systems where salts condense out as the stream temperature drops below their dew point.”

“Corrosion becomes especially aggressive when the salts are wetted by condensation.”

(Reference: API RP 571, Section 4.3.3.1 – Ammonium Chloride Corrosion)

Therefore, option A is technically accurate and supported.

Comprehensive and Detailed Explanation From Exact Extract:

Hydrochloric acid (HCl) corrosion, particularly in crude unit overhead systems, is aggressive toward carbon steel and stainless steels.

According to API RP 571, nickel-based alloys, such as Monel (Ni–Cu alloys), exhibit excellent resistance to hydrochloric acid corrosion and are commonly used for:

Overhead piping

Injection quills

High-risk corrosion zones

Why the other options are incorrect:

Duplex and 300 series stainless steels are highly susceptible to chloride corrosion and SCC.

Copper-based materials alone lack sufficient resistance and structural strength in refinery HCl environments.

Referenced Documents (Study Basis):

API RP 571 – Section on Hydrochloric Acid Corrosion

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API RP 571 on Oxidation indicates:

“Oxidation is a surface loss phenomenon that generally results in uniform thinning. Ultrasonic thickness measurements are typically used to monitor metal loss in oxidizing environments.”

“Metallography may be used to confirm oxide scale structure but is not necessary for routine evaluation.”

Hence, option B is the most appropriate standard method.

As per API RP 945 (4th Edition, 2022):

“Post-weld heat treatment (PWHT) is the most effective method for reducing residual stresses that contribute to amine SCC. PWHT minimizes the stress intensity required for crack initiation and growth.”

Lowering temperature helps but is not always feasible.

Water content and amine concentration affect SCC but are not as impactful as PWHT.

Thus, Option A (Post-weld heat treatment) is the most effective mitigation.

Comprehensive and Detailed Explanation From Exact Extract:

Naphthenic Acid Corrosion (NAC) occurs in high-temperature refinery streams (typically 450–750 °F / 230–400 °C) containing organic acids. According to API RP 571, NAC is particularly aggressive toward carbon steels and low-alloy steels, and resistance improves with increasing chromium and molybdenum content, but is best with titanium.

Titanium exhibits exceptional resistance to NAC due to the formation of a stable, protective oxide film that is not attacked by naphthenic acids. API RP 571 identifies titanium as one of the most resistant materials available for severe NAC environments.

Why the other options are less suitable:

Option B (9 Cr-1 Mo steel) has limited resistance and is still susceptible at higher TAN and velocities.

Option C (317 stainless steel) offers improved resistance but can still experience attack under severe NAC conditions.

Option D (321 stainless steel) has lower molybdenum content than 317 SS, making it less resistant.

API RP 571 explicitly notes that titanium provides superior resistance compared to stainless steels and Cr-Mo alloys in NAC service.

Referenced Documents (Study Basis):

API RP 571 – Section on Naphthenic Acid Corrosion

API Corrosion and Materials Selection Study Guide

According to API RP 941, and also noted in RP 571:

“Nickel significantly improves resistance to HTHA (High Temperature Hydrogen Attack) by stabilizing austenitic phases and reducing carbide decomposition.”

Hence, option C is correct.

API RP 571 on Naphthenic Acid Corrosion (NAC):

“NAC results in thinning, especially in areas of high velocity and turbulence. Standard UT or radiographic inspection followed by UT thickness monitoring is typically used to detect wall loss.”

“Advanced techniques like angle-beam or eddy current are not typically required.”

So, option A correctly reflects the most effective and widely used method.