1. Most of the internal leakage occurred on the equipment with water-cooled jacket. No doubt was found through checking the external leakage, but there were the following phenomena: the pumping speed of the mechanical pump was obviously low, the indication value of the vacuum gauge was low, the mechanical pump oil was quickly emulsified, and the iron-based parts in the vacuum chamber were obviously rusted. If the above conditions are met, internal leakage can be basically determined. Clean the inner wall first, and then pass cooling water to see if there is any wet point. The wet point is the leakage point.
2. Small leakage and micro leakage are difficult to check. The commonly used method is to use the ionization tube sensitive to some gases in high vacuum state to detect leakage, such as acetone or ethanol. Use a medical syringe to spray acetone or ethanol to the suspicious place. When it is sprayed to the leakage point, the pointer of the ionization meter will swing obviously. In this way, it is necessary to be patient and wait until the indicator value of the ionization meter is stable - that is, the pumping capacity and leakage rate of the vacuum unit are balanced, and then spray. It is better to repeat several times to confirm the leakage point.
3. For larger leakage point, flame method can be used. Based on the principle that air flow can make the flame deviate, vacuum first. For example, use candle or lighter to gradually search around the suspicious point, and it will be found that the flame deviates to the leakage point, then the leakage point can be found.
4. The stainless steel water ring vacuum pump can be selected. It has strong corrosion resistance and will not be used properly!
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