SPED Pressure Testing & Commissioning 2 — Questions and Answers
Question 1: During a hydrostatic pressure test, at what minimum hold time must the test pressure be maintained to verify integrity per ASME B31.3?
- 10 minutes (Correct answer)
- 30 minutes
- 1 hour
- 4 hours
Correct answer: 10 minutes
ASME B31.3 requires a minimum hold time of 10 minutes at test pressure for hydrostatic tests, though the examiner may require longer.
Question 2: Which fluid is preferred for hydrostatic testing of piping systems that will operate at cryogenic temperatures?
- Kerosene
- Water (Correct answer)
- Nitrogen gas
- Methanol
Correct answer: Water
Water is the preferred hydrostatic test medium even for cryogenic service because it is safe, incompressible, and readily available.
Question 3: What is the primary hazard associated with pneumatic pressure testing compared to hydrostatic testing?
- Corrosion of pipe internals
- Greater stored energy leading to more violent failure (Correct answer)
- Higher test pressures required
- Difficulty detecting leaks
Correct answer: Greater stored energy leading to more violent failure
Compressed gases store significantly more energy than liquids at the same pressure, making pneumatic test failures far more violent and hazardous.
Question 4: A piping system is pneumatically tested at 110 psig. What is the minimum preliminary test pressure used to check for leaks before full pressurization per ASME B31.3?
- 25 psig
- 110 psig
- 55 psig
- 10 psig (Correct answer)
Correct answer: 10 psig
ASME B31.3 requires a preliminary pneumatic test at no more than 10 psig before ramping to full test pressure to check for obvious leaks.
Question 5: When flushing a new piping system during commissioning, which criterion typically determines adequate flushing completion?
- Flush duration exceeds 2 hours
- Outlet flow velocity equals inlet velocity
- Flush fluid cleanliness meets system cleanliness class (e.g., NAS or ISO 4406) (Correct answer)
- Differential pressure across the system stabilizes
Correct answer: Flush fluid cleanliness meets system cleanliness class (e.g., NAS or ISO 4406)
Flushing is complete when the circulating flush fluid achieves the target cleanliness class, typically measured by particle count per ISO 4406 or NAS 1638.
Question 6: Which document is issued after all pre-commissioning checks are satisfied and authorizes introduction of process fluids into a piping system?
- P&ID redline markup
- Mechanical Completion Certificate (Correct answer)
- Pressure Test Record
- Punch List A-item log
Correct answer: Mechanical Completion Certificate
A Mechanical Completion Certificate (MCC) formally confirms all construction and pre-commissioning activities are complete, authorizing process fluid introduction.
Question 7: What action must be taken on spring-loaded safety valves during a hydrostatic pressure test of the connected piping?
- Set them to lift at 1.5× operating pressure
- Remove or block them to prevent premature opening (Correct answer)
- Leave them in-line with no modification
- Replace them with blind flanges permanently
Correct answer: Remove or block them to prevent premature opening
Safety/relief valves must be removed or isolated during hydrostatic tests to prevent them from opening at their set pressure, which is below the test pressure.
SPED Pressure Testing & Commissioning 2
During a hydrostatic pressure test, at what minimum hold time must the test pressure be maintained to verify integrity per ASME B31.3?