API 510 Pressure Vessel Design & Fabrication Standards 3 — Questions and Answers
Question 1: In ASME Section VIII Div. 1, what is the maximum allowable working pressure (MAWP) stamped on a vessel's nameplate based on?
- The design pressure specified by the owner
- The weakest element of the completed vessel at the designated temperature (Correct answer)
- The pressure determined from the thickest component
- The relief valve set pressure minus 10%
Correct answer: The weakest element of the completed vessel at the designated temperature
Per UG-98, the MAWP stamped on the nameplate is the maximum pressure permissible at the top of the vessel based on the weakest component.
Question 2: Which ASME Code category of welded joints includes circumferential seams connecting shells to heads?
- Category A
- Category B (Correct answer)
- Category C
- Category D
Correct answer: Category B
Category B per UW-3 includes circumferential welded joints in the main shell, including head-to-shell seams.
Question 3: A vessel fabricated to ASME Section VIII Div. 1 requires post-weld heat treatment (PWHT). Per UCS-56, what is the standard holding temperature range for P-No. 1 carbon steel?
- 1050°F to 1150°F (566°C to 621°C)
- 1100°F to 1200°F (593°C to 649°C) (Correct answer)
- 900°F to 1000°F (482°C to 538°C)
- 1200°F to 1350°F (649°C to 732°C)
Correct answer: 1100°F to 1200°F (593°C to 649°C)
UCS-56 specifies a PWHT holding temperature of 1100°F to 1200°F (593°C to 649°C) for P-No. 1 carbon steel.
Question 4: Under ASME VIII-1 UG-84, what is the purpose of a Charpy impact test for pressure vessel materials?
- Verify ultimate tensile strength at elevated temperature
- Determine resistance to brittle fracture at low temperatures (Correct answer)
- Confirm weld hardness is within limits
- Measure corrosion resistance of the base metal
Correct answer: Determine resistance to brittle fracture at low temperatures
Charpy V-notch impact tests per UG-84 assess a material's notch toughness to prevent brittle fracture, especially at low minimum design metal temperatures (MDMT).
Question 5: What is the minimum required preheat temperature for welding P-No. 1 Group 2 carbon steel greater than 1.5 in. thick per ASME Section VIII Div. 1 (UCS-56 and applicable WPS requirements)?
- 50°F (10°C)
- 150°F (66°C) (Correct answer)
- 200°F (93°C)
- 300°F (149°C)
Correct answer: 150°F (66°C)
ASME Section I/VIII and WPS requirements generally require 150°F (66°C) preheat for P-No. 1 carbon steel over 1.5 in. thick to prevent hydrogen cracking.
Question 6: Per ASME Section VIII Div. 1, what hydrostatic test pressure is required for a completed vessel with an MAWP of 250 psi?
- 250 psi
- 312.5 psi
- 375 psi (Correct answer)
- 500 psi
Correct answer: 375 psi
UG-99(b) requires the hydrostatic test pressure to be at least 1.3 times the MAWP (adjusted for temperature), so 250 × 1.3 = 325 psi minimum; at ambient, stress ratio may push this to 375 psi for the standard 1.5× factor — per UG-99 the multiplier is 1.3.
Question 7: Which ASME Section VIII Div. 1 paragraph sets requirements for the minimum design metal temperature (MDMT) and the impact test exemption curves?
- UCS-66 (Correct answer)
- UG-84
- UCS-56
- UHT-5
Correct answer: UCS-66
UCS-66 provides the impact test exemption curves (A through D) for carbon and low alloy steels and establishes MDMT requirements.
API 510 Pressure Vessel Design & Fabrication Standards 3
In ASME Section VIII Div. 1, what is the maximum allowable working pressure (MAWP) stamped on a vessel's nameplate based on?