Mass Spectrometer

Helium leak mass spectrometer testing is a way to detect very small leaks across a pressure boundary. The test is conducted with the use of a mass spectrometer, which is calibrated to detect the presence of helium molecules. Helium molecules are very small, so using helium as a tracer gas will find very small leaks that other leak tests may not find. This can be conducted in one of 3 ways: - Detector-probe technique - Tracer-probe technique - Hood technique The detector-probe test is conducted by pressurising a component with helium gas, and then scanning the component “sniffing” for the presence of helium with the detector probe. The mass spectrometer is monitored to verify the presence of helium leakage. The tracer-probe test is conducted by placing the component under a vacuum and connecting it to the mass spectrometer. The tracer probe is then used to “spray” helium around the component under test. If a leak is present, the helium will be drawn into the part due to the differential pressure. The mass spectrometer is monitored to verify the presence of helium leakage. The hood test is conducted by placing the component under a vacuum and connected to the mass spectrometer. A “hood” or “envelope” is then established around a portion of the component under test, such as the tube-sheet bundle of a heat exchanger. The hood, which is normally made of a plastic material or bag, is then filled with helium to test a large area at one time. If a leak is present, the helium will be drawn into the part due to the differential pressure. The mass spectrometer is monitored to verify the presence of helium leakage.