API 510 Pressure Vessel Design & Fabrication Standards 4 — Questions and Answers
Question 1: A torispherical (flanged and dished) head is being designed per ASME VIII-1 UG-32(e). What is the crown radius (L) used in the minimum thickness formula?
- Equal to the inside diameter of the shell (Correct answer)
- Not greater than the outside diameter of the skirt
- Equal to twice the inside shell radius
- Equal to the knuckle radius
Correct answer: Equal to the inside diameter of the shell
Per UG-32(e), for a standard torispherical head, the crown radius L shall not be greater than the outside diameter of the skirt, and for a standard head equals the shell inside diameter.
Question 2: Per ASME Section VIII Div. 1, what is the minimum shell thickness (excluding corrosion allowance) allowed for pressure vessels under internal pressure?
- 1/16 in. (1.6 mm) (Correct answer)
- 3/32 in. (2.4 mm)
- 1/8 in. (3.2 mm)
- No minimum specified beyond the design formula requirement
Correct answer: 1/16 in. (1.6 mm)
UG-16(b) specifies that, except for certain heat exchanger tubes, no shell or head shall be less than 1/16 in. (1.6 mm) thick after forming.
Question 3: In ASME Section VIII Div. 1 fabrication, what is the maximum allowable out-of-roundness (peaking/banding) for a cylindrical shell per UG-80?
- 1% of the nominal outside diameter
- 0.5% of the nominal inside diameter
- 2% of the nominal outside diameter
- The difference between max and min diameters shall not exceed 1% of nominal diameter (Correct answer)
Correct answer: The difference between max and min diameters shall not exceed 1% of nominal diameter
UG-80 requires that the difference between maximum and minimum inside diameters at any cross-section shall not exceed 1% of the nominal inside diameter.
Question 4: Which ASME Section VIII Div. 1 table provides the allowable stress values (S) for carbon and low alloy steel materials used in vessel design calculations?
- Table UCS-23 (Correct answer)
- Table UG-23
- Table UG-27
- Table UCS-56
Correct answer: Table UCS-23
Table UCS-23 (Section II Part D) lists the maximum allowable stress values for carbon and low alloy steel materials used in VIII-1 pressure vessel design.
Question 5: A nozzle reinforcement calculation per ASME VIII-1 UG-37 is required to show that the area removed by the opening is replaced within a defined reinforcement zone. What width defines the reinforcement zone on each side of the nozzle centerline?
- The nozzle outside diameter
- The larger of d or (t_n + t + d/2)
- The inside diameter of the opening (d) (Correct answer)
- Two times the shell thickness
Correct answer: The inside diameter of the opening (d)
Per UG-40, the reinforcement zone width on each side of the nozzle axis equals the larger of the nozzle inside diameter (d) or (Rn + tn + t) but the basic zone half-width is d, the finished inside diameter of the opening.
Question 6: According to ASME Section VIII Div. 1, which Code paragraph governs the use of pneumatic testing as an alternative to hydrostatic testing?
- UG-99
- UG-100 (Correct answer)
- UG-101
- UG-102
Correct answer: UG-100
UG-100 permits pneumatic testing when hydrostatic testing is not practical, requiring a test pressure of at least 1.1 times the MAWP with added safety precautions.
Question 7: What does the 'U' stamp on a pressure vessel signify under ASME Section VIII Div. 1?
- The vessel was fabricated under a Quality Control system certified by ASME (Correct answer)
- The vessel meets Div. 2 alternative rules
- The vessel is rated for unfired steam service only
- The vessel underwent ultrasonic examination only
Correct answer: The vessel was fabricated under a Quality Control system certified by ASME
The ASME 'U' stamp certifies that the pressure vessel was designed and fabricated in accordance with ASME Section VIII Div. 1 under an authorized quality control system.
API 510 Pressure Vessel Design & Fabrication Standards 4
A torispherical (flanged and dished) head is being designed per ASME VIII-1 UG-32(e).
What is the crown radius (L) used in the minimum thickness formula?