How to choose vacuum pump in vacuum drying

It is well known that vacuum drying oven must be equipped with a vacuum pump when it is used, but many users do not know how to select a matching vacuum pump. Most users know that no matter how large the vacuum oven is, the vacuum pump will be equipped with a larger vacuum pump, which will speed up the actual pumping speed. In practice, this is not the case, because the connection between the pump and the oven will be based on the The size of the box is used to design the thickness of the air extraction pipe, so as to control the vacuum degree stably. If the pump is equipped with too large air extraction pipe, because of the limitation of the air extraction pipe and the interface, the speed of vacuum extraction cannot be accelerated, but it is not good for the pump after a long time. Therefore, when purchasing a vacuum drying box, we need to communicate with the sales staff about how large the box should be equipped with how large the vacuum pump is the most reasonable state. In this way, it can be matched properly, so that the service life of the equipment will be extended.

Vacuum drying box can be divided into two types: horizontal type and up and down combination type. The box is made of carbon steel by stamping, the shell is electrostatic spray plastic, and the working room material is stainless steel. The box body is insulated with silica wool, and the high temperature resistant silicone rubber sealing ring is installed between the working room and the glass to ensure the sealing performance of the door and the working room and greatly improve the vacuum degree in the box. The temperature controller adopts the international advanced PID adaptive controller, without setting internal parameters, overshoot and temperature control. Temperature control device with timing and over temperature protection function, improve the safety of the equipment.

Vacuum pump can be generally divided into dry and non dry. Dry type is also called oil-free type. The oil-free type is characterized in that it does not rely on other components but on the components of the machine itself to achieve the required vacuum. There are many kinds of oil-free division. But in the laboratory, there are two kinds of oil-free piston type (mostly used for microbiological detection) and corrosion-resistant diaphragm type (mostly used for chemical laboratory). Piston type is generally used in combination with vacuum suction filtration, microbiological detection, waste liquid extraction, vacuum drying box and other equipment. Corrosion resistant diaphragm type is generally used together with rotary evaporator, vacuum drying oven, centrifugal concentration, etc. But the non dry type is different. It needs to use other components (such as water and oil) to achieve the ideal vacuum degree. Therefore, the non dry type generally refers to the oil pump and circulating water pump. The oil vane pump is often used in the laboratory. This is a relatively small type, which is generally used in combination with the freeze-drying machine and vacuum drying box.

Vacuum dryer is composed of refrigeration system, vacuum system, heating system, electrical instrument control system. The main components are drying box, condenser, refrigerating unit, vacuum pump, heating / cooling device, etc. The process of vacuum drying is to place the dried materials in a closed drying chamber, vacuum the dried materials with a vacuum system and heat them continuously, so that the water inside the materials diffuses to the surface through the pressure difference or concentration difference, and the water molecules obtain enough kinetic energy on the surface of the materials. After overcoming the mutual attraction between the molecules, they escape to the low-pressure space of the vacuum chamber, so as to be true. The process of pumping. Vacuum pump is the most important part of vacuum drying, so what are the precautions for the use of vacuum pump of vacuum dryer? Let’s understand together!

1. Generally, the vacuum pump of the vacuum dryer shall be overhauled after 2000 hours of operation, the aging degree of the rubber seal shall be checked, the exhaust valve piece shall be checked for cracking, and the dirt deposited on the valve piece and exhaust valve seat shall be cleaned. Clean the parts in the whole vacuum pump cavity, such as rotor, rotor, spring, etc. It is usually washed with gasoline and dried. Clean rubber parts and dry them with dry cloth. When cleaning and assembling, handle with care to avoid damage.

2. Clean the vacuum dryer pipe if possible to ensure that the pipe is unblocked.

3. Check whether the vacuum pump pipeline and joint of vacuum dryer are loose. Turn the vacuum pump by hand to see if it is flexible.

4. Check the oil level frequently. If it does not meet the requirements, adjust it to meet the requirements. When the vacuum pump is running, the oil level shall be up to the center of the oil mark.

5. Check the oil quality frequently. If the oil is deteriorated, replace it with new oil in time to ensure that the vacuum pump works normally. In the first month of operation, the vacuum pump of the vacuum dryer changes the lubricating oil after 100 hours, and then changes the oil once every 500 hours.

6. The oil change period shall be considered according to the actual use conditions and whether it can meet the performance requirements, etc., which shall be determined by the user at his discretion. General new vacuum pump, when pumping clean and dry gas, it is recommended to change oil once in about 100 hours. After no ferrous metal powder can be seen in the oil, the oil change period can be appropriately extended in the future.

7. Add bearing lubricating oil into the bearing, observe that the oil level should be at the center line of the oil mark, and replace or supplement the lubricating oil in time.

8. After reassembly, the test run shall be carried out. Generally, it is required to run for 2 hours without air and change the oil for two times. Because a certain amount of volatile substances will be left in the vacuum pump during cleaning, and it will be put into normal operation after normal operation.

9. Jog the motor, and try to see whether the rotation direction of the motor is correct.

10. Screw out the water plug of vacuum pump body of vacuum dryer, and fill the water (or slurry).

11. Close the gate valve, outlet pressure gauge and inlet vacuum gauge of the outlet pipe.

12. Start the motor. When the vacuum pump is in normal operation, open the outlet pressure gauge and the inlet vacuum pump. Gradually open the gate valve and check the motor load after the appropriate pressure is displayed.

13. Try to control the flow and head of the vacuum pump of the vacuum dryer within the range indicated on the label, so as to ensure that the vacuum pump operates at the highest efficiency point, so as to achieve the maximum energy saving effect.

14. During the operation of vacuum pump of vacuum dryer, the bearing temperature shall not exceed the ambient temperature of 35C, and the maximum temperature shall not exceed 80C.

15. In case of any abnormal sound of vacuum pump of vacuum dryer, stop the machine immediately to check the cause.

16. When the vacuum pump of vacuum dryer is to stop using, first close the gate valve and pressure gauge, and then stop the motor.

17. Frequently adjust the packing gland to ensure that the leakage in the packing chamber is normal (it is better to leak out in drops).

18. Periodically check the wear condition of the sleeve, and replace it in time after the wear is serious.

19. When the vacuum pump of the vacuum dryer is used in cold winter, it is necessary to unscrew the drain plug at the lower part of the pump body to discharge the medium completely after shutdown. Prevent frost cracking.

20. If the vacuum pump of vacuum dryer is out of service for a long time, it is necessary to disassemble the pump completely, dry the water, coat the rotating parts and joints with grease and install them, and keep them properly.

The above is the overall content of the precautions for the use of vacuum pump in the dryer, and it is necessary to use the vacuum machine correctly to maximize the benefits.

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