API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 461:

  Which of the following materials is not susceptible to high temperature hydrogen attack?

  A. 300 Series SS
  B. 5 Cr-1Mo
  C. 9Cr-1Mo
  D. All of the above
  D. All of the above

• Question 462:

  In a naphthenic acid corrosive (NAC) environment, what is the effect of sulfur?

  A. No effect
  B. Sulfide cracking
  C. Inhibition
  D. Corrosion accelerator
  C. Inhibition

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  According to API RP 571 Section 5.1.3.4 (Naphthenic Acid Corrosion - NAC): "Sulfur can act as an inhibitor to NAC. Where sulfur content in crude is high, a reduction in naphthenic acid corrosion is sometimes observed, especially in certain parts of vacuum and atmospheric units. However, this is not universally reliable, and corrosion can still occur based on local operating conditions and metal temperatures." Thus, Option C (Inhibition) is the correct choice, as sulfur can reduce NAC under some conditions.

• Question 463:

  Which of the following locations would be most susceptible to naphthenic acid corrosion (NAC)?

  A. Downstream from an injection point
  B. Deadlegs
  C. Under deposits
  D. Regions of high velocity and turbulence
  D. Regions of high velocity and turbulence

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  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."

  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.

• Question 464:

  Hydrogen stress cracking is normally found in:

  A. high strength low alloy steels and carbon steels.
  B. stainless steel internals such as trays.
  C. the presence of sulfuric acid.
  D. mild carbon steels at high temperatures and high hydrogen partial pressure.
  A. high strength low alloy steels and carbon steels.

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  Hydrogen Stress Cracking (HSC) is a subclass of environmental cracking that occurs in certain materials when hydrogen is present. According to API RP 571, HSC typically affects high-strength low alloy steels and carbon steels, particularly under tensile stress in a hydrogen-containing environment. This includes areas like weld-affected zones and hard spots in steels.

  From API RP 571 Section 5.1.2.1 (Hydrogen-Induced Cracking):

  "Hydrogen stress cracking (HSC) can occur in carbon steel and low alloy steels in environments containing hydrogen at ambient to moderately elevated temperatures (up to 200癋 or 93癈)... Hardness is a critical factor for HSC. High hardness in welds and heat affected zones (HAZ) are most susceptible." Additionally, API RP 939-C does not directly define HSC but reinforces the relationship between hydrogen exposure and metal integrity, particularly under conditions not exceeding 450 癋 (230 癈) for

  hydrogen services.

  Thus, option A is correct, as it directly reflects the metal types most susceptible to HSC in operational environments defined by API RP 571.

• Question 465:

  Thermal fatigue cracks usually:

  A. Initiate on the surface of the component.
  B. Initiate in the subsurface of the component.
  C. Grow very rapidly (at the speed of sound in the material).
  D. Are very tight and narrow.
  A. Initiate on the surface of the component.

• Question 466:

  Start-up and shutdown of equipment increase the susceptibility of thermal fatigue. There is no set limit on temperature swings; however, as a practical rule, cracking may be suspected if the temperature swing exceeds about _________.

  A. 150?F
  B. 200?F
  C. 250?F
  D. 300?F
  B. 200?F

• Question 467:

  The regenerator reboiler and the regenerator are areas where the temperature and __________ of the amine stream are the highest and can cause significant corrosion problems.

  A. Pressure
  B. Stress
  C. Turbulence
  D. Concentration
  C. Turbulence

• Question 468:

  Which of these materials exhibit an endurance limit below which fatigue cracking will not occur?

  A. Carbon steel
  B. 300 Series SS
  C. 400 Series SS
  D. None of the above
  A. Carbon steel

• Question 469:

  Proper application of ________ will control but not eliminate microbes that cause MIC so that continued treatment is necessary.

  A. Ozone
  B. Caustic
  C. Biocides
  D. None of the above
  C. Biocides

• Question 470:

  Caustic corrosion is most often associated with:

  A. Boilers and steam generating equipment
  B. Caustic treaters
  C. Caustic injections in crude units
  D. Caustic storage tanks (non-postweld heat treated)
  C. Caustic injections in crude units

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  API RP 571, under "Caustic Corrosion" (also referred to as Caustic Stress Corrosion Cracking or Caustic

  Cracking), notes that this form of damage is:

  "Most commonly associated with the injection points of caustic (e.g., NaOH) in crude units, particularly

  upstream of desalter vessels and heat exchanger circuits."

  "This damage occurs due to the combination of caustic environment and tensile stress, especially in carbon

  steel and low alloy steels."

  "Stress relief heat treatment of welds can mitigate susceptibility."

  API RP 571, 3rd Edition, Section 4.2.2.3)

  Thus, among the options, caustic injections in crude units are the most typical area of concern, making

  option C the correct answer.