Practice Test Geeks(API 510) Certified Pressure Vessel Inspector Practice Test
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Material Evaluation and Selection Flashcards

7 cards from real API 510 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. The Nelson curves published in API RP 941 define safe operating limits to prevent which damage mechanism?

    Answer: High-temperature hydrogen attack (HTHA) in carbon and alloy steels

    API RP 941 provides temperature versus hydrogen partial pressure curves that define the boundary above which HTHA becomes a risk for carbon and low-alloy steels.

  2. Sigma phase embrittlement in 316 stainless steel typically develops after extended exposure in which temperature range?

    Answer: Between 1000°F and 1700°F (538°C and 927°C) during service

    Sigma phase, an intermetallic compound that severely reduces toughness, precipitates from the ferrite phase of austenitic and duplex stainless steels within this temperature band.

  3. Which metallurgical damage mechanism reduces the impact toughness of 2.25Cr-1Mo steel after long-term service in the 650–1070°F (343–577°C) range?

    Answer: Temper embrittlement due to tramp element grain-boundary segregation

    Temper embrittlement results from grain-boundary segregation of tramp elements (P, Sn, As, Sb), raising the ductile-to-brittle transition temperature of the alloy steel.

  4. API RP 571 recommends which measure as the primary mitigation for alkaline stress corrosion cracking (caustic SCC) in carbon steel pressure vessels?

    Answer: Applying PWHT to all carbon steel welds above caustic SCC threshold conditions

    PWHT reduces residual welding stresses that, combined with caustic concentration and temperature, are the driving force for stress corrosion cracking in carbon steel.

  5. In wet H2S service, what is the maximum hardness specified for carbon steel weld heat-affected zones per NACE MR0175/ISO 15156 to prevent sulfide stress cracking?

    Answer: HBW 237 (HRC 22)

    NACE MR0175/ISO 15156 limits carbon and low-alloy steel hardness to HRC 22 (approximately HBW 237) to prevent sulfide stress cracking in sour service.

  6. Amine stress corrosion cracking (amine SCC) in pressure vessels most commonly affects which material-condition combination?

    Answer: Carbon steel with high residual welding stresses and inadequate PWHT

    Amine SCC initiates in residual stress fields at and near welds in carbon steel vessels, and is effectively prevented by full PWHT per API 945.

  7. Above which approximate temperature does creep become a significant design consideration for carbon steel pressure vessel components?

    Answer: 750°F (399°C)

    Carbon steel enters the creep range above approximately 700–750°F (371–399°C), where time-dependent plastic deformation must be considered in design and fitness-for-service evaluations.