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.
Read the first 7 Leak Testing Techniques flashcards as text
Which NDT leak testing method relies on detecting the ultrasonic frequencies generated by turbulent gas flow through a leak?
Answer: Ultrasonic leak detection
Gas escaping through a leak creates turbulence that generates ultrasonic frequencies (typically 35–45 kHz), which are detected by ultrasonic leak detectors.
In mass spectrometer leak testing, what is the 'background' signal and why must it be managed?
Answer: It is the residual helium already present in the detector environment that can mask small leak signals
Background helium from prior testing or ambient sources raises the baseline signal, potentially masking small leaks and reducing sensitivity.
What is the correct action when a leak is found in a pressure system during a hydrostatic test?
Answer: Depressurize the system completely before any repair is attempted
Safety requires full depressurization before any repair work, as working on pressurized systems poses severe injury risk.
Which leak testing technique would be most appropriate for verifying the integrity of a spacecraft fuel tank before launch?
Answer: Helium mass spectrometer leak testing to detect micro-leaks
The extreme sensitivity of helium mass spectrometer testing makes it the preferred method for critical aerospace applications where micro-leaks could be catastrophic.
What does a 'fine leak' test specification of 1×10⁻⁸ atm·cc/s indicate?
Answer: The maximum allowable leak rate is one hundred-millionth of an atmosphere-cc per second
1×10⁻⁸ atm·cc/s means the component must not leak more than one hundred-millionth of an atm·cc of gas per second — a very tight fine leak specification.
What is the main limitation of the soap bubble / liquid film leak test method?
Answer: It has low sensitivity and may miss very small leaks
Soap bubble tests are a gross leak method with limited sensitivity; very small leaks may not generate visible bubbles within the observation time.
In NDT leak testing documentation, why must the test pressure, test medium, hold time, and acceptance criteria all be recorded?
Answer: Complete records ensure traceability, repeatability, and compliance with quality and safety standards
Full test documentation provides traceability for quality assurance, supports repeat testing, and demonstrates compliance with applicable codes and standards.