API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 211:

  Corrosion rates associated with hydrofluoric (HF) acid would be expected to increase if:

  A. Copper-nickel alloy is used
  B. Temperature and water content increase
  C. Temperatures are below 150癋 (66癈) and there is less than 3% water
  D. HF acid concentration increases
  B. Temperature and water content increase

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  According to API RP 571 and API RP 751 (HF Alkylation Units): "HF acid corrosion rates increase with elevated temperature and higher water content. This is because water acts as an ionizing agent that facilitates the acid's attack on steel."

  "Corrosion is minimized when water content is strictly controlled, usually between 0.5-1.5%."

  "Contrary to some assumptions, increasing HF acid concentration actually decreases corrosivity."

  Hence, option B is correct.

• Question 212:

  __________ is usually found in aqueous environments or services where water is sometimes or always present, especially where stagnant or low-flow conditions allow the growth of microorganisms.

  A. MIC
  B. HIC
  C. SOHIC
  D. None of the above
  A. MIC

• Question 213:

  In what damage mechanism does hydrogen combine with carbides in steel to form bubbles or cavities of CH#?

  A. Hydrogen blistering
  B. Hydrogen embrittlement
  C. Hydrogen-induced cracking
  D. High temperature hydrogen attack
  D. High temperature hydrogen attack

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  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 (CH#)."

  "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癋 (204癈) depending on partial pressure of hydrogen."

  API RP 571, Section 4.2.1.3 - High Temperature Hydrogen Attack) Hence, option D is the correct and technically supported answer.

• Question 214:

  Soil to Air interface areas are usually more susceptible to corrosion than the rest of the structure because of ___________ and __________ availability.

  A. Moisture
  B. Bacteria
  C. Oxygen
  D. B and C
  E. A and C
  E. A and C

• Question 215:

  With sulfuric acid corrosion, alloys such as Alloy 20 resist dilute acid corrosion and form a protective ________ film on the surface.

  A. Sulfide
  B. Chloride
  C. Iron sulfate
  D. Iron oxide
  C. Iron sulfate

• Question 216:

  Carbonate SCC may easily be mistaken for SSC or SOHIC; however, the carbonate cracks are usually ________ the toe of the weld and have multiple parallel cracks.

  A. Further from
  B. Closer to
  C. Diagonal to
  D. Perpendicular to
  A. Further from

• Question 217:

  With cooling water corrosion, _________ oxygen content tends to ________ carbon steel corrosion rates.

  A. Increasing, increasing
  B. Decreasing, decreasing
  C. Decreasing, increasing
  D. Increasing, decreasing
  A. Increasing, increasing

• Question 218:

  One way to prevent oxide scale formation on alloy steel is to increase the:

  A. Chromium content of the steel
  B. Carbon equivalent of the alloy
  C. Molybdenum content of the steel to 6%
  D. Nickel content of the steel
  A. Chromium content of the steel

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  API RP 571 under Oxidation states:

  "Resistance to oxidation is improved significantly by increasing chromium content, as it promotes the formation of a protective chromium oxide (Cr#O#) layer." "Nickel may aid in high-temperature strength but does not directly improve oxidation resistance like chromium does."

  API RP 571, Section 5.1.1 - Oxidation)

  Hence, option A is correct.

• Question 219:

  Which of the following is the lowest threshold temperature at which creep damage is a concern in carbon steel with tensile strength > 60ksi (414 MPa)?

  A. 600癋 (316癈)
  B. 700癋 (371癈)
  C. 800癋 (427癈)
  D. 900癋 (482癈)
  B. 700癋 (371癈)

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  API RP 571 states in the section on Creep Damage:

  "Creep damage in carbon steels generally becomes a concern above 700癋 (371癈), especially for steels with higher tensile strength (greater than 60 ksi)." "For prolonged exposure above this temperature, time-dependent deformation can lead to material degradation and cracking, especially at weldments and stress concentrations." Thus, the lowest threshold for creep in high-strength carbon steels is 700癋 (371癈), making option B correct.

• Question 220:

  Carbonate cracking typically propagates _________ to the weld; the pattern of cracking observed on the surface is sometimes described as ________.

  A. Transverse, Eyebrow
  B. Parallel, Spider web
  C. Diagonal, Half moon
  D. Perpendicular, Stair step
  B. Parallel, Spider web