Vacuum system maintenance method: pressure leak detection method in the bubble leak detection method
Bubble leak detection method is to fill the leakage gas with a certain pressure in the tested part, and then put it into the liquid. If there is a leak hole, the gas will enter the surrounding liquid through the leak hole to form bubbles, so as to determine the location of the leak hole. At the same time, according to the pressure of filling gas, bubble formation rate (number of bubbles formed per second), size (bubble diameter), combined with the properties of gas and liquid to roughly estimate the leakage rate of the hole. The bubble leak detection method is simple, intuitive and economical, but it is suitable for the air tightness inspection of the tested parts which can withstand positive pressure because of the need to fill the gas into the tested parts.
No matter which kind of bubble leak detection method is adopted in vacuum system maintenance and leak detection, attention should be paid in the application:
1. The type and pressure of leakage gas will affect the detection sensitivity.
2. The pressure of filling gas should also consider the mechanical strength of the inspected part.
3. The inspected parts should be cleaned thoroughly before being tested, and put into liquid after being inflated to prevent the leakage hole from being blocked.
4. Distinguish false leakage from true leakage. When the inspected part is put into the liquid, the adsorbed gas on its surface may form bubbles.
5. Sufficient light should be ensured during observation, and the liquid should be clear and transparent (in the soap film method, the thin consistency of the soap should be paid special attention to, too thin and easy to flow and drip, leading to missed detection, too thick and easy to block poor transparency or forming bubbles, leading to false detection), and the observation background should be dark; At the same time, the inspected parts should be stable, close to the water surface, and ensure that the water surface is calm.
In the process of vacuum system maintenance and leak detection, the leak holes shall be marked in time, and the welding shall be carried out for confirmation. If hydrogen is used as leak gas, special attention shall be paid to safety.
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