API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 151:

  Metallic components form a surface __________ when exposed to sulfur compounds. This may react with air (oxygen) and moisture to form sulfur acids (polythionic acid).

  A. Oxide
  B. Sulfide scale
  C. Sulfate scale
  D. Caustic scale
  B. Sulfide scale

• Question 152:

  Areas of vulnerability in sulfuric acid Alkylation units include reactor effluent lines, reboilers, deisobutanizer, overhead systems and the _________ treating system.

  A. Caustic
  B. Sulfuric acid
  C. Catalyst
  D. H睸
  A. Caustic

• Question 153:

  The "L" grade of stainless steels will sensitize if exposed more than several hours above _______ or long term above _____.

  A. 1200?F, 800?F
  B. 1000?F, 600?F
  C. 1000?F, 750?F
  D. 1100?F, 800?F
  C. 1000?F, 750?F

• Question 154:

  The best method for finding damage from sigma phase embrittlement is:

  A. Hardness testing
  B. Ductility testing
  C. Magnetic particle testing
  D. Metallographic testing
  D. Metallographic testing

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  As per API RP 571 on Sigma Phase Embrittlement:

  "Sigma phase embrittlement occurs in stainless steels and nickel-based alloys due to the formation of a brittle intermetallic phase in the temperature range of 1050癋 to 1650癋 (565癈 to 900癈)."

  "This damage mechanism is not easily detected through surface or hardness testing and typically requires metallographic examination to confirm the presence of sigma phase in the microstructure."

  Metallographic testing allows clear identification of sigma phase particles and is thus the most reliable method, making option D correct.

• Question 155:

  Which of the following is not a method used to prevent brittle fracture?

  A. Thorough inspections
  B. Strict controls on selecting construction materials
  C. Post weld heat treatment
  D. Controlling minimum operating temperatures
  A. Thorough inspections

• Question 156:

  Amine stress corrosion cracking is a term applied to the cracking of steels under the combined actions of ________ and __________ in aqueous alkanolamine systems used to remove/absorb H睸 and/or CO?and their mixtures from various gas and liquid hydrocarbon streams.

  A. Temperature, pressure
  B. Pressure, stress
  C. Temperature, corrosion
  D. Tensile stress, corrosion
  D. Tensile stress, corrosion

• Question 157:

  In an RBI assessment, sulfidation was identified as a credible damage mechanism and assigned a corrosion rate of 8 mpy (0.20 mm/yr). Which of the following are critical factors in sulfidation?

  A. Concentration of sulfur species and operating temperature
  B. Operating temperature and corrosion rate
  C. Concentration of sulfur species, operating temperature, and metallurgy
  D. Corrosion rate and concentration of sulfur species
  C. Concentration of sulfur species, operating temperature, and metallurgy

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  Comprehensive and Detailed From Exact Extract:

  API RP 571 sulfidation corrosion is controlled by three primary variables:

  Sulfur species concentration (e.g., H#S, sulfur compounds)

  Operating temperature

  Metallurgy, especially chromium content

  Chromium significantly improves sulfidation resistance by forming protective sulfide scales. All three factors must be considered in RBI assessments.

  Referenced Documents (Study Basis):

  API RP 571 - Section on Sulfidation Corrosion

• Question 158:

  (Which of the following is the most important factor in determining carbon steel susceptibility to ethanol stress corrosion cracking in storage tanks?)

  A. Ethanol percentage
  B. Amount of aeration
  C. Moisture content
  D. Grade of steel
  C. Moisture content

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  Comprehensive and Detailed From Exact Extract:

  Ethanol stress corrosion cracking (SCC) of carbon steel is strongly dependent on the presence of water.

  Per, is the primary controlling factor, because:

  API RP 571 moisture content

  Water enables formation of corrosive species

  Dry or very low-water ethanol does not cause SCC

  Even small amounts of water significantly increase cracking risk Other factors influence severity, but without moisture, ethanol SCC does not occur. Referenced Documents (Study Basis): API RP 571 - Section on Ethanol Stress Corrosion Cracking

• Question 159:

  (Which of the following is the most effective inspection method when ammonium bisulfide corrosion may be present?)

  A. Penetrant testing or magnetic-particle testing for surface-breaking cracks
  B. Digital straight-beam spot ultrasonic testing for thickness on a grid
  C. Field metallographic testing for fissures in the heat-affected zone
  D. Ultrasonic scanning and/or profile radiography in areas of high and low flow velocity
  D. Ultrasonic scanning and/or profile radiography in areas of high and low flow velocity

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  Comprehensive and Detailed From Exact Extract: According to, high-velocity, wet API RP 571 ammonium bisulfide (NH#HS) corrosion typically occurs in sour service, such as hydroprocessing reactor effluent systems. The damage is characterized by localized wall thinning, often with highly irregular corrosion profiles that vary with flow regime. API RP 571 emphasizes that the most effective inspection techniques for NH#HS corrosion are those capable of: Detecting localized thinning Identifying corrosion patterns related to flow velocity Covering large areas efficiently Ultrasonic scanning (C-scan) and profile radiography are specifically recommended because they: Reveal localized and preferential metal loss Allow comparison between high- and low-velocity zones Are far superior to spot UT, which may miss localized attack Referenced Documents (Study Basis): API RP 571 - Section on Ammonium Bisulfide Corrosion

• Question 160:

  In general, the resistance of iron and nickel based alloys to sulfidation is determined by the ________ content of the material.

  A. Chromium
  B. Carbon
  C. Molybdenum
  D. Alloying
  A. Chromium