（1）Oil change standard of lyophilizer:
1.According to the service time; The duration of each use can be counted and a reference oil change time standard can be obtained, which will be used in the future;
2.Listen to the noise level during the operation of the vacuum pump and whether the operation sound is abnormal;
3.Intuitively, observe the color of the oil in the pump through the window at the rear of the vacuum pump. If it becomes turbid with color, it is necessary to replace the pump oil in time.
（2）Replacement steps:
1. Unplug the power cord connecting the pump and the lyophilizer host from the rear of the host;
2. Loosen and remove the clamp (like handcuffs) at one end of the large thick pipe (which should be the vacuum pipe) connected between the pump and the lyophilizer, and carefully pick up the interface washer under it from the pump port and put it aside;
3. Lift the pump onto the stool and prepare the washbasin, mineral water bottle, raw tape, hexagonal tool bag with mid infrared band, military knife, funnel and pump oil;
4. Unscrew the screw of the oil drain hole counterclockwise and catch the old oil with a bottle to prevent the screw from rushing into the bottle;
5. Pour out the old oil in the pump, clean the screw of the oil drain hole, wrap it with new raw tape, and then screw it on again with the hexagon socket screw. Because of the sliding wire, it can be screwed tightly;
6. Unscrew the screw of the oil filling hole on the upper surface of the pump, fill with an appropriate amount of new oil, and pay attention to observe whether there is oil leakage at the oil drain hole. If there is no leakage, continue to fill oil until it reaches the middle of the two sign lines of the window;
7. Screw on the oil filling hole screw, lift the pump to the original position, reconnect the air extraction pipe with the pump, and pay attention to put the washer first.
8. Connect the power cord with the host of the freeze dryer;
9. Turn on the host, enter the vacuum pumping interface, click the vacuum pump button on the interface, and then turn on the pump power switch;
10. In the initial few minutes of vacuum pumping, the sound of the pump is relatively loud. Soon, after a large amount of gas is pumped out, the sound will become smaller. Under the condition of good oil quality, the vacuum pump has little noise. During operation, pay attention to observe whether there is oil leakage at the rear of the pump.
