Addtime： 2020-07-16 Browse times： 2559
Dry vacuum pump is mainly used in semiconductor industry, chemical industry and film industry. The foreign dry pump market is in a booming stage. For example, in Japan, the semiconductor industry has replaced the oil sealed mechanical pump with dry vacuum pump, while more than 45% of the European and American semiconductor industry have replaced the oil sealed mechanical pump with dry vacuum pump, which greatly improves the performance and quality of products. In order to meet the requirements of different application fields and working conditions, there are screw vacuum pump, multi-stage Roots vacuum pump, multi-stage claw vacuum pump, reciprocating piston vacuum pump, scroll vacuum pump and turbine oil-free vacuum pump. The limit pressure of dry pump is from 10 Pa to 10-2 PA, and the pumping speed is from 20 m3 / h to 500 m3 / h.
1. Introduction and principle of dry vacuum pump
This is a vertical twin-screw dry vacuum pump. The principle of suction and exhaust is the same as most of them. It uses a pair of screws to make synchronous high-speed reverse rotation in the pump shell to produce suction and exhaust effect.
When dry vacuum pump works, there is no friction between each other, the operation is stable, the noise is low, and the working chamber does not need lubricating oil. Therefore, the dry screw pump can remove a large amount of water vapor and a small amount of dust. Compared with the constant pitch structure, the screw has the advantages of higher limit vacuum, lower power consumption, energy saving and maintenance free. It is an updated product of oil sealed vacuum pump.
The spare parts for two years are standard O-rings. The top-down conveying mode can reliably handle the moisture and dust entrained with liquid, and no filter is needed. The optimized screw shape design can reduce the power consumption to the minimum, and the simple design can make the pump cavity completely disassembled in 1 hour, which is easy to clean and maintain.
2. Unique cooling method
Many pump rotors are stuck because of inhalation of dust and crystalline substances, high-temperature polymerization of substances, sublimation of heat sensitive substances, resulting in the gap between rotors is blocked. Another reason is that due to long-term operation, the rotor will deform due to thermal expansion and cold contraction, resulting in pump seizure.
Cooling mode of dry vacuum pump:
At present, jacket cooling water is often used to cool the rotor of dry pump on the market.
The cooling system of some vertical screw vacuum pumps is more unique. For example, the internal coolant cooling and direct gas cooling are added in the pump to maintain the temperature of the internal surface well. The temperature is not too high or too low. It is always maintained at a suitable temperature to prevent the decomposition of heat sensitive substances and high temperature polymerizable substances, such as HCN and MMA manufacturers Together.
3. How to remove flammable, explosive and corrosive media?
It is well known that corrosion is caused by the reaction of acid ions and basic ions in solution with metals. The higher the temperature, the faster the corrosion rate. General vacuum pumps use some anticorrosive materials or do some anticorrosive coating on the rotor to slow down the corrosion rate.
However, due to the harsh thermal conditions in the operation of dry vacuum pump, it is not suitable to use the above-mentioned corrosion-resistant materials to deal with corrosive media.
In addition, the use of iron metal high nickel coating material, once the appearance of fine cracks will lead to rapid electrochemical corrosion of the material. So, as long as the specially designed equipment can control the temperature reliably and keep the corrosive medium in the gas phase, if there is no ionic form, will there be no corrosion? The answer is yes. With its own advanced cooling system, the temperature in the pump chamber and rotor can be adjusted to avoid corrosion. Therefore, the rotor of the screw dry vacuum pump is made of stainless steel without any coating, which reduces the cost and increases the safety performance.
There are two indexes to evaluate explosion: flash point and ignition point of combustible materials. Because the two screws in the screw dry vacuum pump have no friction in the pump body, so there will be no electric spark and no fire source. In addition, it reduces the temperature in the pump through its own cooling system, which makes it difficult to reach the ignition point of the pumped material, so as to put an end to explosion!
4. Sealing of dry vacuum pump
There is no shaft seal between the pump and the outside, and there is no seal between the pump chamber and the cooling circulating water circuit, so the toxic and harmful medium can be removed.
Most of the faults of the pump are caused by the wear of the shaft seal. There is only one non-contact seal on each shaft of the pump. There is no shutdown caused by the damage of the shaft seal, and the oil in the gearbox is pumped into the pump due to the leakage of the shaft seal, resulting in the vacuum environment and exhaust port pollution.
5. Composition of control system
The dry vacuum system also has the best control system, with independent workstation and bus, which can solve the problems of temperature, pressure, speed, motor synchronization, start-up and shutdown, valve switch and pump self-cleaning control, etc., and temperature measurement points are added to the places where there may be temperature rise, thus enhancing the safety of the system. The dry pump system can adapt to the most severe environment in chemical and pharmaceutical industry.
It is mainly composed of the following three parts: built-in basic drive module; data bus control cabinet; coolant pump control and explosion-proof motor control center.
6. Characteristics of dry vacuum pump
Some vacuum pumps are driven by two motors synchronously to ensure full speed and torque control while maintaining no component contact during pump operation; no sealing design ensures no leakage;
By controlling the inner surface temperature, the requirements of the new ATEX explosion-proof regulations can be met. Because it can maintain the minimum internal temperature, it can control the condensation of pumping gas and the damage effect caused by corrosion; it can easily transport corrosive medium and safely transport flammable and explosive gas.
1) Clean and environmental protection; 2) high vacuum degree; 3) anti-corrosion design (patented technology); 4) extractable condensable gas and a small amount of dust gas (patented technology); 5) special shaft seal design to prevent mutual pollution between pumped medium and lubrication system; 6) anti overload design; 7) stable operation; 8) high standard configuration; 9) complete accessories; 10) high quality and sound spare parts supply.
7. Summary
Dry vacuum pump is the development trend of the industry in the future. Although it is not used much now, in addition to the high price, there are also users who do not have a good understanding of the dry vacuum pump and can not see the future economic benefits to the enterprise. However, the dry vacuum pump makes the working volume oil-free, so it brings many benefits.
Some vertical screw vacuum pumps meet the requirements of the new ATEX explosion-proof regulations by controlling the inner surface temperature. Because it can maintain the minimum internal temperature, it can control the condensation of pumping gas and the damage effect caused by corrosion; it can easily transport corrosive medium and safely transport flammable and explosive gas.
It is suitable for treating medium containing solid particles and does not need to add a filter.
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