As we all know, the sensitivity and accuracy of helium mass spectrometer leak detector are very high. It is detected by using helium as the medium. Of course, this kind of helium is colorless, tasteless and harmless gas, but excessive inhalation of human body will cause harm. The use of helium detection requires the treatment of the gas before it can be discharged.

For products with particularly high requirements, helium mass spectrometer leak detector is generally used for detection. The following describes and explains the helium mass spectrometer leak detector in detail for the commonly used leak point type and leak rate type detection methods:

1、 Measuring leakage type

Determining the leakage point type is to determine the specific leakage point or leakage hole position of the component to be inspected,Common in large or large assemblies,Such as satellite, missile body, warhead, gas transmission pipeline, gas tank, oil tank, boiler, etc.

1. helium injection method

This is the most commonly used method,It is generally used to detect components with relatively small volume,Connect the tested device with the instrument,After vacuuming,Where there may be a leak in the tested device(Such as sealing joint,Weld, etc) Spray helium with a spray gun,If there is a leak somewhere in the tested device,When helium is sprayed on the leak,Helium is immediately sucked into the vacuum system,So as to diffuse into the mass spectrometry chamber,The output of the helium mass spectrometer leak detector will respond immediately,Attention should be paid to using this method:Helium is a lighter inert gas,It will rise automatically after spraying,In order to accurately spray helium at the leak position,When helium is sprayed from bottom to top,From near to far(Relative leak detector position) ,This is because helium may be sucked into the upper leakage hole when spraying below,It is difficult to determine the location of the leak;Moreover, the distance between the leak hole and the mass spectrometry chamber and the reaction time of the leak detector are also different,Therefore, helium injection should be carried out from near to far from the side close to the leak detector.

When testing large parts, vacuum pre pumping shall be carried out with the help of mechanical pump,The leak detection efficiency and time can be improved,Helium injection method is used to check those with complex structures,When there are many sealing openings and welds and they are crowded together,Because helium will spread quickly after being ejected,It is often difficult to accurately determine the location of the leakage gap,It is necessary to spray helium from different angles,Carefully observe the difference in reaction time and temporarily seal the found leakage with vacuum sealing mud,You can detect the leaks one by one.

2. helium absorption method

Helium absorption method is mainly used to inspect some large sealed containers. Such as missile body, warhead, gas tank, oil tank, etc,Vacuum the container first,Then fill the container with helium(In order to save the amount of helium,Low concentration helium can be used) ,Connect a rubber tube at the inlet flange of the helium mass spectrometer leak detector,The front end of the rubber tube has a capillary tube with a small diameter,Make the capillary move at the weld and sealing joint of the outer wall of the tested container filled with helium,If the container has a leak,Helium seeping through the leak will be sucked into the capillary tube,The leak detector will respond.

2、 Leakage rate type

The leakage rate measurement type is mainly used to detect the parts with strict sealing requirements,Such as spaceship, rocket liquid fuel storage tank, satellite, electronic components, etc. This method can only test the leakage rate of the test piece,The location and number of leaks cannot be determined.

1. helium filling method

Helium filling method is also called negative pressure method ,A closed gas chamber connects the vacuum pump and helium tank,Install the inspected parts into an air chamber,Start closing the valve of helium tank,The mechanical pump vacuumizes the air chamber first,Then close the vacuum pump valve,Open the valve of helium tank and fill the gas chamber with helium,And let it stand for a period of time. If there is a leak on a small device surrounded by helium,Helium slowly fills the inside of the small device. Then open the air chamber,Take out the tested device,Blow off the helium that may be adsorbed on its outer surface with compressed air.

Then put these devices one by one(Or group) Ground into a container connected to the air inlet flange of the leak detector,After evacuating the container, open the throttle valve,At this time, the helium originally entering the tested device will be released through the leak,The leak detector will give the leakage rate response.

This method can be used for the overall leak detection of satellites,Put the satellite into a large ring mold chamber,The vacuum system of the ring mold equipment is used to vacuum the ring mold,First, use the auxiliary pump for rough pumping and pre pumping,During leak detection, vacuum the satellite and inflation pipeline through mechanical pump,Fill the satellite with helium,Keep the pressure consistent with the pressure of satellite operation,Finally, turn on the helium mass spectrometer leak detector and calibrate the instrument with a standard leak,We can directly measure the leakage rate of the satellite.

2. bell jar method

Connect the helium mass spectrometer leak detector with the test piece with a vacuum rubber tube,Cover the test piece with a closed container,Fill the container with helium,The leak detector starts leak detection,If there is a leak in the test piece,The instrument can display its leakage rate;This method can measure the leakage rate of missile liquid storage tank,Plastic film is used for the outer cover of the tank and the helium cover,Rough pumping and pre pumping of tank body,In use standard leak proofing leak detector,Fill the helium cover with helium,The leakage rate of the tank can be measured。

Helium mass spectrometry leak detection technology is an indispensable technology in the field of vacuum leak detection,This technique has high leak detection efficiency,Easy to operate,The instrument is sensitive,High precision,Not easily disturbed by other gases,The methods listed above are often used in the field of leak detection technology,It includes leak detection from small parts to large parts,From leak detection to leak rate detection,Various leak detection methods are listed comprehensively,It is believed that it has a good reference value in practical engineering application.