API-571 시험 - ICP실제시험문제와 답 - 149문항

Question No : 1

Damage from oxidation is usually determined by:

A.Metallographic examination
B.Ultrasonic thickness measurements
C.Hardness testing
D.Hammer testing

정답:
Explanation:
API RP 571 on Oxidation indicates:
“Oxidation is a surface loss phenomenon that generally results in uniform thinning. Ultrasonic thickness measurements are typically used to monitor metal loss in oxidizing environments.”
“Metallography may be used to confirm oxide scale structure but is not necessary for routine evaluation.”
Hence, option B is the most appropriate standard method.

Question No : 2

Which damage mechanism will not benefit much from PWHT mitigation?

A.Carbonate stress corrosion cracking
B.Sulfide stress cracking
C.Hydrogen-induced cracking
D.Amine stress corrosion cracking

정답:
Explanation:
API RP 571 discusses Hydrogen-Induced Cracking (HIC) and Blistering:
“Postweld heat treatment (PWHT) does not significantly reduce susceptibility to HIC, as the mechanism is primarily driven by hydrogen charging in wet H ₂ S environments and steel cleanliness, not residual stresses.”
“PWHT is more effective for SSC, SOHIC, and other stress-driven mechanisms.” Thus, HIC will not benefit much from PWHT, making option C correct.

Question No : 3

At what minimum level of nickel content does an alloy become nearly immune to chloride stress corrosion cracking?

A.12%
B.20%
C.35%
D.45%

정답:
Explanation:
API RP 571 states under Chloride Stress Corrosion Cracking (Cl-SCC):
“Nickel contents above approximately 35% provide significant resistance to chloride stress corrosion cracking. Alloys such as Alloy 625 and Alloy 825 exhibit excellent resistance.”
“Austenitic stainless steels with lower nickel contents, such as 304 and 316, are more susceptible to Cl-SCC.”
Hence, option C (35%) is correct.

Question No : 4

Which of the following generally manifests itself as a subsurface damage mechanism?

A.Sulfide Stress Corrosion Cracking (SCC)
B.Amine Stress Corrosion Cracking
C.Caustic Cracking
D.Stress-Oriented Hydrogen-Induced Cracking (SOHIC)

정답:
Explanation:
As defined in API RP 571, under Hydrogen Blistering and HIC/SOHIC:
“SOHIC typically manifests as subsurface stepwise cracking, generally oriented perpendicular to the direction of stress.”
“This mechanism initiates below the surface, typically in weld heat-affected zones, and requires metallographic or advanced ultrasonic methods to detect.”
By contrast, SSC, caustic cracking, and amine SCC are primarily surface-initiated, stress-related cracking mechanisms.
Thus, SOHIC is the subsurface mechanism in this list, making option D correct.

Question No : 5

Boiler water condensate corrosion is caused primarily by:

A.Sodium sulfites or hydrazines
B.Carbon dioxide and oxygen
C.High pH from water treatment problems
D.Dissolved iron oxides

정답:
Explanation:
According to API RP 571, in the section on Boiler Water Condensate Corrosion:
“The major contributors to condensate corrosion are dissolved CO ₂ and O ₂ . Carbon dioxide forms carbonic acid in the presence of water, lowering pH and causing generalized corrosion.”
“Oxygen causes pitting and localized corrosion unless chemically treated.”
Thus, option B (Carbon dioxide and oxygen) is the primary root cause and the correct answer.

Question No : 6

Hydrogen permeation or diffusion rates associated with wet H ₂ S damage of carbon steel and low-alloy steels have been found to be minimal at a pH of:

A.3
B.5
C.7
D.9

정답:
Explanation:
API RP 571 discusses this under Wet H ₂ S Damage C Hydrogen Blistering, HIC, SOHIC:
“Hydrogen generation is reduced as pH increases. At pH 9 and above, the corrosion potential is less favorable for hydrogen charging and thus permeation into the steel is minimal.”
“Most wet H ₂ S cracking damage mechanisms are accelerated under acidic conditions (pH < 7).”
Hence, high pH (around 9) environments offer the most protection against hydrogen damage, making option D the correct choice.

Question No : 7

Decarburization damage is normally verified by:

A.Impact testing
B.Tensile testing
C.Bend testing
D.Metallographic testing

정답:
Explanation:
According to API RP 571, under the section on High Temperature Hydrogen Attack (HTHA) and
Decarburization:
“Decarburization is typically confirmed by metallographic examination. This method reveals carbon loss and microstructural changes such as spheroidization or softening of pearlite.”
“Tensile or impact testing may not reveal early-stage decarburization, especially in partial layers.”
Therefore, metallographic testing is the standard and most direct method to confirm decarburization damage, making option D correct.

Question No : 8

Which of the following statements is most accurate with regard to thermal fatigue?

A.Thermal fatigue cracks generally initiate on the interior of a component due to high thermal stress
B.Because of their ductility, carbon steels have lower resistance to thermal fatigue
C.Visual examination is an ineffective method of monitoring thermal fatigue
D.Controlled rates of heating and cooling during startup and shutdown can lower stresses

정답:
Explanation:
API RP 571 on Thermal Fatigue emphasizes:
“Thermal fatigue results from cyclic thermal stresses during startup, shutdown, or transient operations.”
“The best mitigation strategy is to control heating and cooling rates to reduce temperature differentials and resulting stress.”
(Reference: API RP 571, Section 4.2.1.5 C Thermal Fatigue)
Hence, option D correctly identifies the preventive action.

Question No : 9

Generally, to minimize corrosion of carbon steel in hydrofluoric acid service, residual elements (Cr,
Ni, Cu) should be less than:

A.0.15 wt.%
B.0.18 wt.%
C.0.25 wt.%
D.0.35 wt.%

정답:
Explanation:
API RP 751, which governs HF alkylation units, specifies:
“The total residuals of chromium, nickel, and copper in carbon steel used in HF service should be less than 0.15 wt.% to minimize corrosion risk.”
“Higher residuals increase the reactivity and corrosion rate of carbon steel in the presence of HF acid.”
(Reference: API RP 751, Section 5.3 C Materials Specification for HF Units)
Therefore, option A is the correct choice.

Question No : 10

During inspection of a process unit where sulfidation from high-temperature hydrogen exists in H ₂ S streams, the inspector should:

A.Use ultrasonic testing or radiographic testing thickness readings to monitor for loss of wall thickness
B.Use penetrant testing and magnetic-particle testing to look for surface-breaking cracks
C.Use angle beam ultrasonic testing to look for cracking at the mid-wall
D.Take boat samples and send them to the lab for metallographic analysis

정답:
Explanation:
API RP 571 under Sulfidation (High Temperature Sulfidic Corrosion) recommends:
“Thickness monitoring using ultrasonic testing (UT) or radiographic testing (RT) is the most common method for detection of wall loss due to sulfidation.”
“Sulfidation results in uniform thinning, especially in low Cr steels in hydrogen/H ₂ S environments.”
(Reference: API RP 571, Section 4.2.1.1 C Sulfidation)
Thus, option A is the most appropriate and effective inspection method.

Question No : 11

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

정답:
Explanation:
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 ₂ O ₃ ) layer.”
“Nickel may aid in high-temperature strength but does not directly improve oxidation resistance like chromium does.”
(Reference: API RP 571, Section 5.1.1 C Oxidation)
Hence, option A is correct.

Question No : 12

Which of the following can increase the corrosion rate of carbon steel via hydrofluoric (HF) acid corrosion?

A.High nitrogen content in process
B.Oxygen contamination
C.HF acid concentration above 98%
D.Weld hardness above 200 BHN

정답:
Explanation:
According to API RP 571 and API RP 751:
“In HF alkylation units, carbon steel can be used if weld hardness is controlled to ≤ 200 Brinell (BHN). Exceeding this can significantly increase the corrosion rate and susceptibility to cracking.”
“Hard welds act as preferential corrosion sites due to microstructural inhomogeneity and stress concentration.”
(Reference: API RP 571, Section 4.3.3.4 C Hydrofluoric Acid Corrosion; API RP 751, Section 5.3 C Materials of Construction)
Thus, option D is correct.

Question No : 13

The stream from a crude atmospheric overhead goes to the tube side of a shell-and-tube condenser with a temperature of 300°F (149°C) and a pressure of 10 psig (69 kPa). As the stream begins to condense water, its hydrochloric acid content lowers the water pH to about 4.0.
Which of the following would be the best alloy selection for the tubes with cooling water on the shell side?

A.410 Stainless Steel
B.Titanium
C.9 Cr-1 Mo Steel
D.316 Stainless Steel

정답:
Explanation:
API RP 571 notes in the context of Hydrochloric Acid Corrosion in overhead condensers:
“Titanium is highly resistant to low pH acidic aqueous phases, including hydrochloric acid formed during condensation in overhead systems.”
“Stainless steels like 316 and 410 are not suitable in the presence of free chlorides at low pH and elevated temperatures.”
(Reference: API RP 571, Section 4.3.3.3 C Hydrochloric Acid Corrosion)
Thus, Titanium is the preferred alloy under the described acidic and high-temperature conditions, making option B correct.

Question No : 14

Both sulfide stress corrosion cracking and stress-oriented hydrogen-induced cracking are most often found in:

A.Areas where there is significant hydrogen blistering.
B.Steel weldments.
C.Hardened steels.
D.Areas with temperatures above 300°F (149°C).

정답:
Explanation:
API RP 571 explains that both Sulfide Stress Cracking (SSC) and SOHIC are:
“Strongly influenced by material hardness. Carbon and low alloy steels with hardness exceeding 22 HRC (248 Brinell) are most susceptible.”
“They occur in hardened steels under tensile stress, in the presence of wet H ₂ S environments.” (Reference: API RP 571, Sections 4.2.2.1 and 4.2.2.7 C SSC and SOHIC)
Therefore, hardened steels are the common factor for both mechanisms, making option C the correct choice.

Question No : 15

Polythionic acid stress corrosion cracking is:

A.Identified by transgranular cracking on the process side of equipment and piping.
B.Found only in low carbon grades of austenitic stainless steel.
C.Typically localized and may not be evident until a leak appears.
D.Rarely found in process furnaces.

정답:
Explanation:
API RP 571 under Polythionic Acid Stress Corrosion Cracking (PTA SCC) specifies:
“Cracking is usually intergranular, and often localized, especially in sensitized austenitic stainless steels exposed to sulfur-containing environments during shutdown or cleaning.”
“It is not always visible on inspection and may only become evident when a leak occurs.” (Reference: API RP 571, Section 4.2.2.5 C PTA SCC)
Hence, option C is correct as it best describes the detection difficulty and behavior of PTA SCC.

ICP API-571 시험