Diffusion pump is currently one of the most widely used and most important tools for obtaining high vacuum, usually referred to as oil diffusion pump. Diffusion pump is a secondary pump. It needs mechanical pump as the front stage pump.
(1) If the diffuser pump pumping system does not leak and the limit pressure of the system has not reached the expected results, it may be unreasonable system design and low effective pumping speed; or the electrode bleeding of the vacuum gauge and the vacuum gauge itself are limited by photocurrent and can not measure the low pressure.
(2) If the pumping performance of diffusion pump or unit deteriorates gradually after long-term use, that is, the limit vacuum degree and pumping speed decrease, and other normal conditions, the diffusion pump oil is gradually oxidized and the quality deteriorates. At this time, new diffusion pump oil should be replaced. The oil change step is: first unload the diffusion pump, take out the pump core, according to the requirements of the pump core cleaning and drying after the correct assembly and adding new oil.
(3) When the diffusion pump suddenly leaks into the atmosphere due to special reasons, such as bursting of vacuum gauge tube, misopening of the vacuum vessel vent valve or not closing the high vacuum valve, the high vacuum valve should be closed immediately, the diffusion pump should be stopped heating and the oil pan should be forced to cool down. After the failure is eliminated, the pumping test should be performed and the pump oil should be replaced according to the result.
(4) After the diffusion pump is disassembled and assembled into the system, if the system is pumped strictly according to the aforementioned operating procedures, it should be able to reach the original limit pressure of the pump; if the gap between the nozzles is carefully adjusted repeatedly, the vacuum should also be increased. If the vacuum can not be pumped, first check whether the leakage rate of the pump system is over the allowable value; at the same time check whether the heater of the diffusion pump is burned out, whether the supply voltage is normal, whether the cooling of the pump is normal. If all the above aspects are normal, it can be considered as a pump core assembly problems, such as the installation of misalignment, nozzle clearance is not correct, the pump core is not cleaned before assembly, organic solvents are not dried, pump oil is not enough or installed with poor quality pump oil and heating power adjustment is not correct.
(5) If the diffusion pump works normally all the time, and it does not move the system to make a leak somewhere, so that the unit’s pumping performance suddenly deteriorated, it may be the diffusion pump furnace wire broken or fuse broken, should be timely inspection and replacement.
(6) if the front pump is not working properly or the pumping capacity is not enough, the diffusion pump will not work properly.
(7) The operating conditions such as ambient temperature, humidity and cooling water temperature have great influence on the pumping performance of diffusion pump. For example, when the ambient temperature is too high (more than 35 degrees Celsius), the performance of the diffusion pump begins to decrease.
(8) the power of the diffusion pump is not adjusted properly, and the working state of the diffusion pump is also abnormal. When heating power is adjusted, it is best to find the appropriate temperature of the lowest oil return rate.
(9) Oil vapor reflux pollution system can also make the limit pressure of the system can not reach the expected results, which can be improved by referring to the vacuum technology network.
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