Any pump to be repaired, repaired or a new pump shall be tested for any fault, the form and position of the fault, the ultimate vacuum degree and the time that can be reached, and the pumping rate shall be identified if conditions permit.

The specific methods and steps of test sampling are as follows:

1. Clean all parts of the pump to remove oil and dirt. Take off the belt and use the reverse switch to test the positive and reverse rotation of the motor, so that its direction of rotation is consistent with the direction of the arrow marked on the pump wheel. If there is no mark on the pump wheel, press the air inlet of the pump with the palm of your hand and turn the pulley with the other hand. When you feel the inward suction, the rotation direction of the pulley is the correct direction, and mark it. Then install the belt and connect the test device at the air inlet of the pump before starting the pump. Usually, one end of the vacuum rubber tube is inserted into a thermocouple tube, and the other end is inserted into the air inlet of the pump to be tested. Before that, a little castor oil should be applied on the rubber pipe mouth to make it lubricated and easy to insert and remove. The rubber pipe is clamped with iron clip (if metal pipe is connected, it is connected to the pump port with flange plate, and the other end is sealed with metal glass to connect to the gauge pipe or gauge pipe joint, and there is a vent valve in the middle of the pipe). First turn the pulley by hand for several turns. If there is no big obstacle, the motor can be started intermittently. Make the pump run normally.

2. Check the operation of the pump: listen to the pump sound for noise and abnormal sound; see how the valve plate of the air port is beating; whether the oil reaches the center of the oil standard; whether there is oil leakage, air leakage and water leakage; check whether the surface of the pump cavity is deformed, and make records one by one.

3. Use high frequency spark leak detector and thermocouple vacuum gauge to check the change of vacuum degree. When the spark hits the neck of the gauge (not on the gauge), the vacuum can be judged by the glow color; normally, after the pump is turned on, the glow color will gradually change from dark purple and rose red to light blue, until the glow is very small, and only the fluorescence of glass can be seen. At this time, the vacuum degree is high. After the glow turns to light blue, a thermocouple vacuum gauge can be used to monitor the vacuum. At the beginning, it can also be measured by thermocouple vacuum gauge alone. But do not do both at the same time to avoid damaging the thermocouple gauge. If the spark detector moves back and forth on the glass tube during the inspection, no glow can be produced, and the spark can drill into the glass tube into a linear shape, indicating that the vacuum degree is very low (close to atmospheric pressure). If it is always purple, the vacuum degree of the pump is not high, should carefully check the various parts of the pump, to see whether there is leakage of rubber pipe joints and other places. If the thermocouple tube has certain indication when measuring the vacuum degree, it can clamp on the iron clamp or stop the pump suddenly for a short time to record the pressure change curve with time to judge whether it is caused by poor pump or air leakage. It is necessary to distinguish the different situations of leakage, deflation and pump damage, and make a careful judgment.

When using the thermocouple vacuum meter, we should pay attention to its test characteristics. The vacuum degree measured by it is the full pressure of gas including water and oil vapor. The reading depends on the type of gas. It is required to measure the partial pressure of the permanent gas with the compression type vacuum gauge when appraising the vacuum pump. Therefore, the vacuum degree of the pump should be compared with the original data. When the pump is connected to the vacuum system for use, the limit vacuum degree it can reach should also be measured in the test pumping test. For example, it is 2 × 10-2 Torr ((65 lattice) (1 Torr = 133 PA) measured by thermocouple vacuum gauge, and it may be 5 × 10-4 Torr measured by compression vacuum gauge, which is exactly consistent with the index on the pump label. When repairing the pump, if the vacuum degree measured by the thermocouple vacuum gauge is lower than 2 × 10-2 Torr, for example, only less than 40 lattices ((4 × 10-2 Torr), it can be considered that the vacuum degree of the pump is low, and it should be properly repaired and debugged. If the pump does not record the original data, it can be roughly considered that it should be repaired if it is lower than 50 grids. Naturally, whether the vacuum pump needs to be repaired mainly depends on the actual needs and possible conditions of production.