API 510 Material Evaluation and Selection 2 â Questions and Answers
Question 1: What does the P-number system in ASME Section IX primarily classify base metals by?
- Weldability characteristics including chemistry and mechanical properties (Correct answer)
- Minimum tensile strength at room temperature
- Allowable stress values at design temperature
- Required preheat temperatures for all thicknesses
Correct answer: Weldability characteristics including chemistry and mechanical properties
P-numbers group base metals with similar weldability so that a single welding procedure qualification covers all materials in the same group.
Question 2: Which document provides primary material traceability for ASME pressure vessel components?
- Inspector's field inspection report
- Manufacturer's design specification sheet
- Mill test report (MTR) linked to the material heat number (Correct answer)
- ASME Code case approval letter
Correct answer: Mill test report (MTR) linked to the material heat number
The MTR ties chemical and mechanical properties to a specific heat number, enabling direct traceability of material used in pressure-containing parts.
Question 3: Positive Material Identification (PMI) using X-ray fluorescence (XRF) is most effective for verifying which material property?
- Exact carbon content in carbon steel
- Alloy composition of chrome-moly or stainless steel components (Correct answer)
- Microstructural condition after heat treatment
- Tensile strength at the design temperature
Correct answer: Alloy composition of chrome-moly or stainless steel components
XRF reliably detects alloying elements such as chromium, molybdenum, and nickel, but has limited sensitivity for carbon due to its low atomic number.
Question 4: Carbon steel pressure vessel components are generally limited to service below which temperature to avoid graphitization damage?
- 650°F (343°C)
- 750°F (399°C)
- 900°F (482°C)
- 850°F (454°C) (Correct answer)
Correct answer: 850°F (454°C)
Graphitizationâthe transformation of iron carbides into graphite nodulesâbecomes a practical concern in carbon steel above approximately 850°F (454°C) during extended service.
Question 5: Where are the allowable stress values for ASME pressure vessel materials published?
- ASME Section VIII Division 1, Appendix 1
- API 510 design stress tables
- ASME Section II Part D (Correct answer)
- ASME Section IX welding qualifications
Correct answer: ASME Section II Part D
ASME Section II Part D contains the stress tables, physical property data, and other material information referenced by all ASME fabrication codes.
Question 6: The carbon equivalent (CE) formula is primarily used to evaluate a steel's susceptibility to what condition?
- Resistance to wet H2S corrosion in sour service
- Minimum design metal temperature without impact testing
- Required PWHT duration and temperature
- Hydrogen-induced cracking and cold cracking in the weld heat-affected zone (Correct answer)
Correct answer: Hydrogen-induced cracking and cold cracking in the weld heat-affected zone
Higher carbon equivalents indicate greater hardenability, increasing the risk of hard, brittle HAZ microstructures susceptible to hydrogen cracking during or after welding.
Question 7: When original material documentation is unavailable for an in-service pressure vessel, what is the recommended first step per API 510?
- Perform PMI testing to identify alloy content and assign an appropriate material grade (Correct answer)
- Assume carbon steel properties and apply the most conservative allowable stress
- Replace all undocumented components before the next scheduled inspection
- Apply a safety factor of 4 to the calculated MAWP pending documentation
Correct answer: Perform PMI testing to identify alloy content and assign an appropriate material grade
PMI verifies the material's actual composition, allowing the inspector to assign a code-recognized material specification and calculate a defensible MAWP.
API 510 Material Evaluation and Selection 2
What does the P-number system in ASME Section IX primarily classify base metals by?