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Leak Testing Techniques Flashcards

7 cards from real NDT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which leak testing method is BEST suited for detecting leaks in underground pipelines without excavation?

    Answer: Acoustic emission or acoustic leak detection

    Acoustic emission and acoustic leak detection methods can locate leak sources in buried pipelines by detecting the sound generated by escaping fluid.

  2. In a vacuum bell jar leak test using a helium mass spectrometer, what is the test configuration?

    Answer: The part is placed in a vacuum chamber; helium is applied outside, and the detector monitors inside

    In the vacuum bell jar method, the part interior is evacuated and connected to the detector, and helium applied outside permeates through leaks to be detected.

  3. What is the significance of the 'leak rate' unit 'Pa·m³/s' (or atm·cc/s) in leak testing?

    Answer: It quantifies the volumetric flow of gas through a leak at a given pressure differential

    Leak rate units like Pa·m³/s express the volume of gas passing through a leak per unit time at a specified pressure, quantifying how much gas is lost.

  4. What condition must be met before performing a pneumatic pressure leak test on a pressure vessel?

    Answer: A risk assessment must confirm pneumatic testing is safe, as compressed gas stores more energy than liquid

    Because compressed gas stores significantly more energy than liquid, a pneumatic test requires a safety risk assessment before proceeding.

  5. A refrigerant system leak is most commonly detected using which instrument?

    Answer: Electronic halogen (refrigerant) leak detector

    Electronic halogen or refrigerant-specific detectors sense refrigerant molecules escaping from a leak and are standard tools in HVAC/R leak testing.

  6. Which factor most significantly affects the sensitivity of a bubble leak test?

    Answer: The surface tension and viscosity of the bubble solution

    Lower surface tension solutions produce smaller, more visible bubbles from tiny leaks, directly affecting the sensitivity of the test.

  7. What is the purpose of a 'soak time' or 'stabilization time' in a pressure decay leak test?

    Answer: To allow temperature and elastic effects to stabilize so pressure changes reflect only actual leaks

    Soak time allows thermal equilibration and elastic expansion of the test part to stabilize, so subsequent pressure decay is attributable to leakage rather than these effects.