Leak testing methods

What is NDT? 

Leak testing is also sometimes included in NDT and the methods used vary from simple bubble testing by visual examination, to very sensitive methods using radioactive gases.

The main methods are:
hydrostaticwater; dye
air pressure
soap solution - visual
 sound - ultrasonic detector
hydrogen - Pirani gauge; mass spectrometer
 halogen gas - electron capture gauge
helium - mass spectrometer
 radioactive gas - pulse counter

The mass spectrometer method with helium and the radioactive gas (Krypton-85) method are the most sensitive, but the latter requires special safety precautions.

Leak testing is widely used on pressure vessels and vacuum systems in situ, or a specimen can be placed inside a gas-filled enclosure and then tested for inward leaks.