Types of Helium Leak Testing
Sniffer Method
The test component is filled with Helium Gas. In Case of Leak the Helium gas escapes through the leakage and detected by the sniffer probe
To pinpoint the location of the leak(s) (but not measure the total leakage), the likely potential leak sites of the part are
scanned using a Sniffer Probe connected to the inlet of the leak detector.
Hard Vacuum Method :
Typically the leak detector is connected by means of a "tee" connected in between the foreline of the high vacuum pump and the inlet of its backing pump. A system should be capable of maintaining a foreline pressure low enough to operate the leak detector at this location. Helium is
pressurized into the Test Piece kept inside the vacuum chamber. If a leak exists, helium will enter the chamber and rapidly diffuse through it. The leak detector should respond within several seconds or less.
Note that leak detector sensitivity will be diminished in systems with large backing pumps. A dynamic level system calibration captures this diminishing helium and factor in as Machine factor to calculate the actual leak rate of the test part.
Accumulation Testing Method :
This method can both locate and quantify leaks. Some type of shroud or hood is placed in such a manner as to envelop a
potential leak site. A certain amount of time is given to allow leaking helium to accumulate in the shrouded area, increasing
the helium concentration. The leak detector is then valved-in to the shrouded volume. If many potential leak sites exist in a
manifold or if many parts are to be tested at the same time, they can be sequentially valved-in to determine which site is leaking.
