API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 41:

  A vacuum tower operating at 740?F is being entered to inspect. Several sets of Type 410 SS trays are bent at various angles. The trays are removed in order to straighten them. When an attempt is made to straighten them cracks form at the bends. What type of damage mechanism would cause the cracks to form?

  A. Hydrogen embrittlement
  B. Sulfide stress corrosion cracking
  C. 885?F embrittlement
  D. High temperature corrosion
  C. 885?F embrittlement

• Question 42:

  Soil corrosion of carbon steel can be minimized through the use of special backfill, coatings and _______.

  A. Cathodic protection
  B. Resistivity
  C. Temperature
  D. None of the above
  A. Cathodic protection

• Question 43:

  Titanium should not be used in known hydriding services such as _____ or ______.

  A. Caustic, amine
  B. Amine, sour water
  C. Sour water, Alkylation
  D. All of the above
  B. Amine, sour water

• Question 44:

  Hydrogen blisters may form as surface bulges on the ID, the OD on within the wall thickness of a pipe or pressure vessel. Blistering occurs from hydrogen generated by ______, not hydrogen gas from the process stream.

  A. H睸
  B. Corrosion
  C. Hydriding
  D. Sulfur
  B. Corrosion

• Question 45:

  Blistering, HIC, SOHIC and SSC damage can occur wherever there is a ____________ environment.

  A. Wet H睸
  B. Hydrogen
  C. Sulfur
  D. Aqueous
  A. Wet H睸

• Question 46:

  Metal dusting usually occurs in the operating temperature range of:

  A. 600癋-1200癋 (315癈-650癈)
  B. 900癋-1500癋 (480癈-815癈)
  C. 1200癋-1800癋 (650癈-980癈)
  D. 1500癋-2100癋 (815癈-1150癈)
  A. 600癋-1200癋 (315癈-650癈)

  ---

  As per API RP 571 Section 5.1.4.2 (Metal Dusting):

  "Metal dusting is a type of carburization attack that typically occurs in high carbon activity environments, with temperatures generally between 900癋 and 1200癋 (480癈 to 650癈), although damage has been reported as low as 600癋 (315癈)."

  Therefore, the commonly accepted operational range is best described by Option A: 600癋-1200癋 (315癈-650癈).

• Question 47:

  Increased corrosion rates have been observed in equipment and piping in HF acid service at what minimum threshold temperature?

  A. 100 癋 (38 癈)
  B. 150 癋 (65 癈)
  C. 212 癋 (100 癈)
  D. 250 癋 (121 癈)
  B. 150 癋 (65 癈)

  ---

  Comprehensive and Detailed From Exact Extract:

  According to,

  API RP 571 hydrofluoric (HF) acid corrosion rates increase significantly once operating temperatures exceed approximately 150 癋 (65 癈).

  Key points noted in API RP 571:

  Below ~150 癋, corrosion rates are relatively low due to formation of protective iron fluoride films.

  Above 150 癋, these films become unstable.

  Corrosion rates increase rapidly with temperature, especially under high velocity and water

  contamination conditions.

  Why the other options are incorrect:

  Option A (100 癋) is below the threshold for accelerated corrosion.

  Option C and D are well above the onset temperature but are not the minimum threshold. API RP 571 explicitly identifies 150 癋 (65 癈) as the critical temperature where corrosion acceleration begins.

  Referenced Documents (Study Basis):

  API RP 571 - Section on Hydrofluoric Acid Corrosion

  API Alkylation Unit Corrosion Study Guide

• Question 48:

  With Cl SCC, ________ levels of chloride ________ the likelihood of cracking.

  A. Decreasing, Increases
  B. Increasing, Decreases
  C. Increasing, Increases
  D. Increasing, Eliminates
  C. Increasing, Increases

• Question 49:

  The potential for galvanic corrosion will increase when:

  A. insulating dissimilar metals with different electro-chemical potentials.
  B. using a relatively large volume of anodic material.
  C. applying a coating to both metals.
  D. different metals are in contact with presence of electrolyte.
  D. different metals are in contact with presence of electrolyte.

  ---

  From API RP 571 Section 4.2.3 (Galvanic Corrosion): "Galvanic corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte. The more anodic metal corrodes preferentially."

  Contact without insulation and in presence of an electrolyte (like water or brine) is key to galvanic

  action.

  Insulating or coating prevents electrical connection or electrolyte contact, reducing corrosion risk.

  Hence, Option D correctly describes the condition that increases galvanic corrosion potential.

• Question 50:

  Amine cracking is ________ likely to occur in lean MEA and DEA services than in MDEA and DIPA services.

  A. More
  B. Less
  C. As
  D. None of the above
  A. More