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The reason why the vacuum cannot be pumped up is because the vacuum unit has insufficient pumping capacity or high leak rate; or both, it requires patience to observe and record, and find out the cause of the fault, for example, the pumping time is the same, and the vacuum is biased. Low, at this time, close the high pressure valve, such as the vacuum gauge pointer quickly drops, in most cases the vacuum chamber leaks, should first find the leak point. If the vacuum gauge pointer drops very slowly, in most cases, the vacuum unit has insufficient pumping capacity. At this time, the focus can be placed on finding the vacuum pump and the valve to see where the leak occurs or the diffusion pump oil is contaminated and oxidized. Wait; or the front pipeline is not well sealed, the pump oil is insufficient; or the pump has oil emulsification, shaft seal oil leakage, valve plate damage and other faults.
The most troublesome thing for users in vacuum equipment maintenance is the detection of leak rate problems. Leakage of internal leakage and external leakage; external leakage is better to detect, internal leakage is difficult to do. The leaking point with large external leakage can be treated by the flame method. The principle of using the airflow to deflect the flame is first vacuumed, and the candle or lighter is gradually searched near the suspicious point. It will be found that the flame is offset to the leak point, and the leak can be found. point. The internal leakage should be checked from different vacuum working areas. After the vacuum system reaches a certain pressure value, the winding and evaporation systems are respectively started to observe whether the reading of the vacuum gauge has climbed after a brief drop, and the direction of the inner leakage point can be initially determined. Most of the internal leakage occurred on the equipment with water cooling point. No doubts were found in the leakage, but the following phenomena existed: the pumping speed of the mechanical pump was obviously low, the vacuum gauge was low, the mechanical pump oil was quickly emulsified, and the vacuum The iron-based parts in the room are obviously rusted. If the above conditions are met, the inner leakage can be inferred. First clean the cavity, then pass the cooling water, and check the water supply pipe for the wet point. The wet place is the leak point.
Speaking of what is possible here, everyone feels that it is not so difficult to detect leaks. It is the most troublesome problem for us. In fact, the big leaks are not difficult to find. The most difficult ones are small leaks and slight leaks.
Method for solving small leakage and micro leakage
The ionization tube can be used to detect leaks under high vacuum conditions, such as acetone or ethanol, using a medical syringe to spray acetone or ethanol to a suspected place, combined with a pointer vacuum gauge, when spraying to a leak point, the ionization gauge The pointer will obviously swing. To use this method, it is necessary to have patience. Wait until the indication of the ionization meter is stable, that is, the pumping capacity and the leak rate of the vacuum unit are balanced, and then the injection is repeated several times to confirm. Missing point.
Maintenance must pay attention to several links, disassembly, cleaning, inspection, assembly. It is important that vacuum equipment is of precision mechanical equipment regardless of size. Disassembly should follow the principle of light handling, can not be very dry, must not use a sledgehammer to knock; cleaning parts should be clean and thorough, in order to find problems and identify hidden dangers; vacuum pump products and general mechanical products are quite different, Generally, the mechanical products are often chamfered, and the angle of the vacuum pump is clear, it is easy to hurt the hand, should be more careful, remember.
Checking for leaks is a meticulous work, and every detail should not be dropped, and there must be no luck. There are often manufacturers to ask for help, saying that everything is checked, that is, the vacuum does not go, it may be that a vacuum hose for gas supply is not checked, or a water joint. Problems often appear inadvertently.
Maintenance should be remembered not to be too hasty, if the fault is not clear, take it for granted, and the old disease will not be removed and new diseases will be added, complicating the simple problem.
Many manufacturers have asked that regular maintenance can be done step by step. Under emergency conditions, equipment fails, and production tasks are urgent. What should be done in this case? At this time, as long as the fault is judged to be accurate, all the materials available on hand, such as vacuum sealant, vacuum seal wax, 704 silica gel, vacuum chamber plate, etc., can be repaired if there is no conflict with the work in progress. The principle is to enable the equipment to be produced normally without damaging the equipment and without affecting the work in progress.