NDT Leak Testing Techniques 5

Question 1

Which NDT leak testing method relies on detecting the ultrasonic frequencies generated by turbulent gas flow through a leak?

Accepted Answer

Ultrasonic leak detection

Answer

Gas escaping through a leak creates turbulence that generates ultrasonic frequencies (typically 35–45 kHz), which are detected by ultrasonic leak detectors.

Question 2

In mass spectrometer leak testing, what is the 'background' signal and why must it be managed?

Accepted Answer

It is the residual helium already present in the detector environment that can mask small leak signals

Answer

Background helium from prior testing or ambient sources raises the baseline signal, potentially masking small leaks and reducing sensitivity.

Question 3

What is the correct action when a leak is found in a pressure system during a hydrostatic test?

Accepted Answer

Depressurize the system completely before any repair is attempted

Answer

Safety requires full depressurization before any repair work, as working on pressurized systems poses severe injury risk.

Question 4

Which leak testing technique would be most appropriate for verifying the integrity of a spacecraft fuel tank before launch?

Accepted Answer

Helium mass spectrometer leak testing to detect micro-leaks

Answer

The extreme sensitivity of helium mass spectrometer testing makes it the preferred method for critical aerospace applications where micro-leaks could be catastrophic.

Question 5

What does a 'fine leak' test specification of 1×10⁻⁸ atm·cc/s indicate?

Accepted Answer

The maximum allowable leak rate is one hundred-millionth of an atmosphere-cc per second

Answer

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.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Leak Testing Techniques 5