Oil diffusion pump is a vacuum pump using low pressure, high speed and directional flow of oil vapor jet. The limit vacuum of this pump is 10-4-10-5 Pa, the working pressure range is 10-1-10-4 Pa, the pumping speed range is several hundred thousand liters/sec (1 liter = 10-3 m 3). Oil diffusion pump is the main equipment to obtain high vacuum. It is widely used in vacuum smelting, vacuum coating, space simulation test and some vacuum systems insensitive to oil pollution.
The operation of the oil diffusion pump includes two operations: opening the pump and stopping the pump.
1. Turn on the cooling water of the diffusion pump, pre-vacuum with the mechanical pump, after the pressure of the diffusion pump is lower than 10-1Pa, turn on the power supply of the diffusion pump to heat the electric furnace and heat the diffusion pump.
2. For small pumps below K-400, the pump can work normally after 45 minutes of heating, and for large pumps between K-500 and K-1200, it needs 45-65 minutes of heating before it can work normally. Therefore, when using the diffusion pump vacuum system, we should pay attention to arranging the start-up time of the diffusion pump.
3. open the diffusion pump population valve, the pump can work normally.
1. close the power supply of the diffusion pump population high vacuum valve and vacuum gauge.
2. cut off the heating power of the diffusion pump, and the mechanical pump will continue to work.
3. After another 30 minutes (small pump) to 2 hours (large pump), close the valve between the diffusion pump and the mechanical pump, stop the mechanical pump work, and put air into the mechanical pump (if the mechanical pump inlet is equipped with electromagnetic bleeding valve, after cutting off the power supply of the mechanical pump, it will automatically bleed because of electrical interlock).
4. when the temperature of the oil pan is close to 50~60 degrees, the cooling water of the diffusion pump is closed.
5. in order to speed up the cooling of the diffusion pump, the electric furnace can be discharged and the spray water will be used for cooling. Modern large-scale diffusion pumps are equipped with quench water pipes (or sleeves) on the outer wall of oil pans. When the pump works normally, the water is not flowing. When the power supply is cut off, the water is flowing through and quenched.
1. When the oil temperature in the diffusion pump is high, it is not allowed to release the air, in order to prevent the oil from oxidizing and deteriorating, and affect the normal work. When the pump is stopped, the pump should be kept in vacuum.
2. when the pump is stopped for a long time, the cooling water in the water cooling pipe (sleeve) should be exhausted and dried with compressed air.
3. the mechanical pump stops working and bleed from the pump inlet, so as to avoid the mechanical pump oil flowing into the diffusion pump. The modern diffusion pump unit is designed with an electromagnetic discharge valve and automatically deflated when the pump is stopped.
4. After the diffusion pump works normally, it can open the population high vacuum valve, shut down the high vacuum valve when the pump stops, in order to reduce reflux pump oil and avoid contamination of the pumped container.
5. we should confirm that the cooling water is unblocked and the vacuum in the pump is greater than 1Pa before heating the diffusion pump. Regular inspection of pump oil, timely filling or replacement of oil.