Screw vacuum pump is a positive displacement vacuum pump in the emerging members, appeared in the 1990s, the development of later. However, as an ideal dry pump, screw vacuum pump has gained rapid development after its debut. Now follow Xiaobian to understand the basic knowledge of it!
First, screw vacuum pump characteristics
Screw vacuum pump is derived from screw compressor and screw liquid conveying pump. It is an ideal dry vacuum pump in positive displacement vacuum pump. It can provide a clean vacuum environment without oil, and the corrosive gas and condensable vapor, dust and particle gas has strong adaptability, so in the electronic semiconductor, pharmaceutical, petrochemical, etc. Some strict in clean vacuum environment, industry field of gas composition complex, screw vacuum pump's favour, gradually become the replacement of the traditional oil seal mechanical pump, liquid ring pump.
Screw vacuum pump through a pair of asymmetrical screw rotors in the opposite movement to periodically change the volume between the teeth to achieve gas transmission, to achieve the purpose of pumping. It has the following characteristics:
1. Clean and oil-free, multi-phase mixed transportation, wide adaptability. There is a strict gap between the rotor of screw vacuum pump, no oil in the pump cavity, can remove corrosive gas, toxic and containing dust, condensable vapor and other complex gases.
2. Simple structure, good dynamic balance and high reliability. Screw vacuum pump has few parts, no wearing parts in the core parts, and no balanced inertial force, reliable operation and long life.
3, because of the simple structure, few parts, so the operation, maintenance and maintenance is simple.
4, forced gas transmission, can ensure a large pumping speed in a wide pressure range, the exhaust volume is almost not affected by the exhaust pressure.
Two, screw vacuum pump structure
Screw vacuum pump is generally a twin-screw structure. Screw vacuum pump is through a pair of asymmetrical screw rotor, in the pump cavity for synchronous, high-speed reverse operation, periodical change between the volume of suction and exhaust produced by the suction equipment.
Its main structure includes screw rotor, bearing, pump body, seal and so on. Screw rotor by fine dynamic balance correction, supported by bearings, installed in the pump chamber, between the screw and the screw to maintain a strict certain clearance. When the pump works, there is no friction between each other, the operation is stable, the noise is low, the cavity does not need lubricating oil. Therefore, screw vacuum pump can remove a lot of water vapor and a small amount of dust gas occasions, high limit vacuum, low power consumption, energy saving, maintenance free and other advantages.
Screw vacuum pump main structure
As can be seen in the figure above, the screw vacuum pump is relatively simple in structure. Formally, screw vacuum pump has horizontal and vertical points; According to the different screw rotor profile can be divided into single-head screw vacuum pump and multi-head screw vacuum pump; Single-head screw vacuum pump according to the different pitch of the rotor, can be divided into equal pitch screw vacuum pump and variable pitch screw vacuum pump, variable pitch can be subdivided into one stage, two stage, three stage and so on.
Long lines within a lead which can complete suction, compression, exhaust process, less lead, which can effectively reduce the volume and weight of the pump, apply to the field of large pumping speed, but its complex type line, need special props and special machine tools, processing is expensive, and because of leakage triangle factors, vacuum degree is not high, so does not see more in the market.
Single-head type line is suitable for small and medium-sized screw vacuum pump, the market is also mostly single-head screw vacuum pump. There is no compression in the cavity of the same pitch screw vacuum pump, which can easily discharge solid particles and condensable gas, but its exhaust temperature and energy consumption are high; Variable pitch screw vacuum pump cavity has compression, low exhaust temperature and low energy consumption, but the tolerance to dust particles and condensable gas is not as good as equal pitch.
Three, screw vacuum pump working principle
Because it is derived from a screw compressor, the screw vacuum pump works similarly to the screw compressor. Let's illustrate it with a similar polycephalic line:
1. Inspiring process
A. Inspiration process is about to begin
B. During the inhalation process
C. End of suction process
2. Compression process
A. Compression process begins
B. In the process of compression
C. Compression process ends and exhaust starts
3. Exhaust process
A. During the exhaust process
B. End of exhaust process
Exhaust process of screw vacuum pump. When the intertooth volume is connected with the exhaust port, the exhaust process begins. With the continuous reduction of the volume between teeth, the gas with exhaust pressure is gradually discharged through the exhaust orifice.
Four, screw vacuum pump application
Sscrew vacuum pump is not only widely adaptable, can be pumped under harsh conditions, at the same time can achieve a higher vacuum (0.1 ~ 1Pa). Therefore, with the rapid development of semiconductor and petrochemical industry, screw vacuum pump as an ideal dry pump also began to be widely used in electronic semiconductor, pharmaceutical and chemical industry, such as semiconductor industry vapor deposition, etching, pharmaceutical and chemical industry distillation and drying, intermediates, solvent recovery, oil and gas recovery, etc.
Although due to cost of the type line technology and processing screw vacuum pump to purchase more expensive, but in the long run, the characteristics of its wide adaptability, high efficiency and energy saving environmental protection and low failure rate, maintenance can bring in running cycle higher comprehensive benefit and the social environment benefit, using the more extensive is the trend of the future.
