API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 111:

  A section of vacuum bottom outlet piping is being replaced because of naphthenic acid corrosion (NAC). Which of the following potential replacement materials would be most resistant to NAC?

  A. Titanium
  B. 9 Cr-1 Mo steel
  C. 317 stainless steel
  D. 321 stainless steel
  A. Titanium

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  Comprehensive and Detailed From Exact Extract:

  Naphthenic Acid Corrosion (NAC) occurs in high-temperature refinery streams (typically 450-750 癋 / 230-400 癈) 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

• Question 112:

  ________ is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor bubbles.

  A. Condensate corrosion
  B. Cavitation
  C. Dew-Point corrosion
  D. Atmospheric corrosion
  B. Cavitation

• Question 113:

  For 5Cr-0.5Mo, what is the threshold temperature for creep?

  A. 500?F
  B. 800?F
  C. 600?F
  D. 700?F
  B. 800?F

• Question 114:

  Welds joining dissimilar materials (ferritic and austenetic) may suffer __________ related damage at high temperatures due to differential thermal expansion stresses.

  A. Stress
  B. Creep
  C. Fatigue
  D. Thermal stress
  B. Creep

• Question 115:

  Corrosion rates of carbon steel pipe in sulfuric acid service increase significantly:

  A. At acid concentrations above 95%
  B. At acid concentrations below 65%
  C. In stagnant conditions
  D. At acid concentrations above 65%
  B. At acid concentrations below 65%

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  According to API RP 571, under Sulfuric Acid Corrosion:

  "The most aggressive corrosion typically occurs below 65% H#SO#, particularly between 20% to 50%

  concentration range."

  "Above 95% concentration, sulfuric acid becomes less corrosive to carbon steel due to its dehydrating nature."

  "Dilute sulfuric acid is highly ionized and conducts electricity well, increasing corrosion rates."

  API RP 571, Section 4.3.3.2 - Sulfuric Acid Corrosion)

  Hence, the most severe corrosion occurs below 65% concentration, making option B the accurate answer.

• Question 116:

  Hydrochloric acid corrosion is a general and localized corrosion and is very aggressive to most common materials of construction. Damage in refineries is often associated with dew point corrosion in which vapors containing _______ and hydrogen chloride condense from the overhead stream of a distillation, fractionation, or stripping tower.

  A. O?
  B. O
  C. H睴
  D. CO?
  C. H睴

• Question 117:

  ___________ cracking has been a major problem in coke drum shells.

  A. Stress
  B. Carburization
  C. Thermal fatigue
  D. Sulfide
  C. Thermal fatigue

• Question 118:

  Cracking susceptibility increases with __________ pH and carbonate concentration.

  A. Increasing
  B. Decreasing
  C. Low
  D. High
  A. Increasing

• Question 119:

  Susceptibility to hydrogen stress cracking __________ with __________ hardness.

  A. Increases, increasing
  B. Decreases, increasing
  C. Decreases, Decreasing
  D. Both A and C
  D. Both A and C

• Question 120:

  Amine cracking is most often associated with which services?

  A. Lean amine
  B. Rich amine
  C. Amine solutions below 140 癋 (60 癈)
  D. High concentration amines
  B. Rich amine

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  Comprehensive and Detailed From Exact Extract:

  Amine stress corrosion cracking is most frequently associated with rich amine services, where:

  Acid gas loading (H#S / CO#) is high

  Corrosive contaminants and degradation products are present

  Higher operating temperatures and stresses exist

  Per API RP 571, cracking is far more common in rich amine systems than in lean amine circuits.

  Why the other options are incorrect: Lean amine has lower acid gas content and reduced SCC risk SCC is not limited to low temperatures Concentration alone is not the dominant factor

  Referenced Documents (Study Basis): API RP 571 - Section on Amine Stress Corrosion Cracking