API 510 Pressure Vessel Design & Fabrication Standards 5 — Questions and Answers
Question 1: Per ASME Section VIII Div. 1 UW-11, when is spot (10%) radiographic examination required rather than full radiography for Category B and C butt welds?
- When the vessel operates above 150 psi
- When the designer selects spot RT for the joint efficiency credit of 0.85 (Correct answer)
- When the vessel wall exceeds 1.25 in. thickness
- Whenever the vessel is in lethal service
Correct answer: When the designer selects spot RT for the joint efficiency credit of 0.85
Spot RT per UW-11(b) is selected at the designer's option to obtain a joint efficiency of 0.85, rather than full RT (E=1.00) or no RT (E=0.70).
Question 2: What is the primary purpose of the Manufacturer's Data Report (Form U-1) required by ASME Section VIII Div. 1?
- To document the hydrostatic test procedure in detail
- To certify that the vessel was designed, fabricated, and inspected in accordance with the Code (Correct answer)
- To record the NDE technician qualifications
- To list all approved materials used in construction
Correct answer: To certify that the vessel was designed, fabricated, and inspected in accordance with the Code
The U-1 form is the Manufacturer's Data Report certifying that the pressure vessel was designed, fabricated, and inspected in full conformance with ASME Section VIII Div. 1.
Question 3: When calculating the required shell thickness for a horizontal vessel, which load combination per ASME VIII-1 UG-22 must the designer consider in addition to design pressure?
- Wind loads only
- Weight of vessel contents, weight of vessel itself, and wind or seismic loads (Correct answer)
- Seismic loads only at installations above 2,500 ft elevation
- Only thermal expansion loads at elevated temperatures
Correct answer: Weight of vessel contents, weight of vessel itself, and wind or seismic loads
UG-22 requires consideration of internal/external pressure plus weight (vessel, contents, attachments), wind, seismic, and other applicable loadings when determining required thickness.
Question 4: A weld joint between a nozzle neck and a shell is classified under ASME VIII-1 as which weld joint category?
- Category A
- Category B
- Category C
- Category D (Correct answer)
Correct answer: Category D
Category D per UW-3 covers welds connecting nozzles, communicating chambers, or other connections to the main shell, head, or side plates.
Question 5: In ASME Section VIII Div. 1, what is the minimum thickness (t_min) for a flat unstayed circular head attached by welding per UG-34?
- t = d × sqrt(CP / SE) (Correct answer)
- t = P × d / (2SE)
- t = d × sqrt(P / 2S)
- t = P × R / (SE - 0.6P)
Correct answer: t = d × sqrt(CP / SE)
UG-34(c) gives the formula t = d × sqrt(CP/SE) for flat circular heads, where C is a coefficient based on attachment method.
Question 6: What does ASME Section VIII Div. 1 UG-116 require to appear on the pressure vessel nameplate?
- Only the MAWP and design temperature
- MAWP, design temperature, MDMT, Code year of construction, U symbol, and serial number among other items (Correct answer)
- Only the U stamp, serial number, and MAWP
- The hydrostatic test pressure and Inspector's signature
Correct answer: MAWP, design temperature, MDMT, Code year of construction, U symbol, and serial number among other items
UG-116 specifies that the nameplate must include the U symbol, manufacturer's name, serial number, year built, MAWP, design temperature, MDMT, and other required markings.
Question 7: Per ASME Section VIII Div. 1 UCS-57, what NDE method is required for detecting laminations in plate material thicker than 2 in. (50 mm) used in pressure vessel shells?
- Magnetic particle testing (MT)
- Liquid penetrant testing (PT)
- Ultrasonic examination (UT) (Correct answer)
- Radiographic examination (RT)
Correct answer: Ultrasonic examination (UT)
UCS-57 requires ultrasonic examination of plate material over 2 in. thick to detect internal laminations or discontinuities that could compromise vessel integrity.
API 510 Pressure Vessel Design & Fabrication Standards 5
Per ASME Section VIII Div. 1 UW-11, when is spot (10%) radiographic examination required rather than full radiography for Category B and C butt welds?