Test method using helium gas

How to select helium test method

Feature of each test methods

Helium gas mixer and helium gas recycle machine are available to reduce the running cost.
Please ask your nearest Cosmo office, if you are interested. We will provide the best solution, depending on the initial cost and running cost.

●Vacuum method

Test Method	Detection Accuracy	Entire Part Test	Locating Leaks	Automation	Initial Cost	Running Cost	Maintenance Cost	Applicable Product
Vacuum Spray Method	1E-09Pa･m3/sec or higher	×	○	△	○	△	△	LDS3000 L300i
Vacuum Hood Method	1E-09Pa･m3/sec or higher	○	×	○	△	△	△

●Pressurization method

Test Method	Detection Accuracy	Entire Part Test	Locating Leaks	Automation	Initial Cost	Running Cost	Maintenance Cost	Applicable Product
Vacuum Chamber Method	1E-07Pa･m3/sec or higher	○	×	○	×	×	×	LDS3000 L300i
Bombing Method	1E-09Pa･m3/sec or higher	○	×	○	○	×	×
Sniffer Method	1E-06Pa･m3/sec or higher	×	○	△	○	×	△	P3000(XL)
Pressure Accumulation Method	1E-05Pa･m3/sec or higher	○	×	○	△	×	△	T-Guard

Details of Test Methods

Vacuum method

●Vacuum Spray method

Inside of the tested part is vacuum-evacuated and helium gas is sprayed from outside of the tested part by a spray gun.
Helium that leaks into the tested part is detected.

●Vacuum Hood method

Inside of the tested part which is covered by a hood is vacuum-evacuated.
Inside of the hood is pressurized with helium, and helium leaks into the tested part is detected.

Pressurization method

●Sniffer method

Inside of the tested part is vacuum-evacuated and pressurized with helium.
Helium that leaks to the outside of the tested part is detected by the sniffer probe.

●Vacuum Chamber method

Tested part is placed in a chamber. Inside of the tested part is vacuum-evacuated and then pressurized with helium.
Inside of the chamber is also vacuum-evacuated and helium that leaks into the chamber is detected.

● Pressure Accumulation method

Tested part is placed in a hood and inside of the tested part is vacuum-evacuated.
Then, the inside of it is pressurized with helium.
The helium that leaks into the hood is accumulated for a certain period to detect the helium (concentration)

● Bombing method

Tested part is placed in a bombing tank which is vacuum-evacuated for a certain period.
Tested part is bombed with helium for a certain period and then removed from the tank and placed in the chamber which is vacuum-evacuated.
Helium that leaks into the chamber from the tested part is detected.

Leak Test Machine of Pressure Accumulation Method(G-FINE)

Cosmo recommends the pressure accumulation method for easy helium leak test at low cost

Circuit Configuration

Helium Detector T-GUARD Circuit Configuration

Unlike the commonly used helium detector, T-Guard is capable of carrying out the automated measurements of background helium measurement and helium leak measurement.

T-Guard Test Procedure 1. Gross leak measurement 1 2. Fine leak measurement 1 (Measurement of helium amount in the chamber) 3. Accumulation 4. Gross leak measurement 2 5. Fine leak measurement 2 6. Purge (Detector cleaning)

Helium Detection Sensor Principle

Unlike the commonly used helium detector of magnetic deflection mass spectrometer type, T-Guard detects helium based on the system specialized in the measurement at atmospheric pressure.

Quartz film allows the permeation of only helium.
When helium enters a cell regulated to 25 kPa/abs, helium is the only one can permeates through the quarts film, increasing the pressure inside of the cell which evacuated to high vacuum.
The value of the electric current generated by the operation of vacuum pump when the pressure rises is detected as a leak.

Leak Test Machine of Vacuum Chamber Method

Cosmo also covers commonly used Vacuum Chamber method for helium leak test.

Circuit Configuration

Helium Detector LDS3000 Circuit Configuration

Helium enters LDS3000 reaches the spectrometer tube by back-diffusion phenomenon by a turbo-molecular pump, and helium leak rate is measured.
Leak detector with valves to automatically select a port according to the pressure to be applied are available.
Feel free to contact Cosmo for more detailed information.

Helium Gas Detection Principle

180° Magnetic deflection mass spectrometer tube

1. The molecular reaches the spectrometer tube are converted into positive ions by electrons of a filament, and are accelerated in the magnetic field and move.

2. The positive ions separate into their orbits according to the mass of the gas (helium) when it passes through the magnetic field.

3. Only the positive ions reach the ion collector are converted into voltage signal and amplified for helium measurement.