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Detecting systems-hellium detector

Detecting systems - hellium detector

The main component of the whole system is a helium detector using a mass spectrometer detecting molecules of helium.

This method of leak detection is initiated when a tracer gas, helium, is introduced to a test part that is connected to the MSLD system. The helium leaking from the test part diffuses through the system, its partial pressure is measured, and results are displayed on a meter.

The delay in response to helium is given by the ratio of functional residual volume of the chamber and effective pumping speed of the hellium detector.

Principle of mass spectrometer in helium leak detector

(MSLD = Mass Spectrometer Leak Detector)

MSDL operating principle consists of ionization of gases in a vacuum and accelerating of the various ions through a

voltage drop and a magnetic field. The helium ions are separated and collected, and the resulting ion current is amplified and indicated on the meter.

An MSLD consists of:

• a spectrometer tube, quantitatively sensitive to the presence of helium

• a vacuum system, to maintain adequately low operating pressure in the spectrometer tube

• vacuum gauge(s)

• mechanical pump(s), to evacuate the part to be tested

• valves, to transfer the connection of the evacuated part from the mechanical roughing system to the spectrometer vacuum system

• amplifier and readout instrumentation, to monitor the spectrometer tube output signal

• electrical power supplies and controls, for valve sequencing, protective circuits, etc.

• certified calibrated leak

• fixturing, for attachment to the part to be leak-tested