Classification Basis and Requirements of Vacuum System

Vacuum system is an exhaust device used to obtain vacuum. It mainly consists of various vacuum pumps, vacuum gauges, vacuum valves and connecting pipes. Like power supply, ammeter, switch and wire in electronic circuit. Due to the different requirements for vacuum systems in various practical applications, there are many types of vacuum systems, which can be classified according to different situations.
Requirements for vacuum systems
Requirements for vacuum systems should depend on specific applications, and generally should meet the following points:
1. Make the vacuum chamber (or the device being pumped) obtain the required limit vacuum and working vacuum. Limit vacuum degree is the vacuum degree that can be achieved by vacuum chamber (or device) after long-term pumping of vacuum pump. Working vacuum degree is the vacuum degree that can be maintained by vacuum chamber (or device) during the exhaust process. In the process of exhaust, vacuum chambers (or pumped devices) often need some treatment (such as heating, electronic bombardment, etc.), which will produce a large amount of gas, so the working vacuum is generally lower than the limit vacuum. For example, the vacuum coating machine will emit a lot of gas when it starts vapor coating. At this time, the vacuum degree in the vacuum chamber (bell cover) is called working vacuum degree. For example, during the heating process of vacuum annealing furnace, the vacuum degree at this time is called working vacuum because of the large amount of exhaust of parts. For example, the vacuum degree of vacuum electronic devices in the process of baking and exhaust is also called working vacuum degree. When the baking is over, the vacuum in the device remains basically unchanged, which is called the ultimate vacuum.
In order to satisfy the working vacuum degree and the limit vacuum degree, the corresponding vacuum pump should be selected. Generally, the limit vacuum degree of the vacuum pump selected is higher than that of the vacuum chamber (or the device being pumped).
2. Make the vacuum chamber (or the device being pumped) obtain the required pumping speed. The pumping speed determines the time needed to reach the working vacuum and the ultimate vacuum. Increasing the pumping speed can shorten the exhaust time and improve the production efficiency. The size of the pumping speed can also be determined by the volume of the container being pumped and the size of the exhaust (leakage). For large vacuum chambers such as aerospace simulators, atomic energy experimental devices, and small but serious ventilation and leakage devices, large pumping speed pumps should be used.
3. There are suitable residual gas components in the vacuum chamber (or studio). Simply guaranteeing the working vacuum and the ultimate vacuum can only reflect the total pressure of the system, and can not fully guarantee some special requirements, but also have certain requirements for residual gas composition.
4. Vacuum system has simple and firm structure, convenient operation and maintenance, less power and water consumption, low noise, no pollution, low price and so on.
In order to meet the above requirements, we must proceed from the practical point of view and consider various factors comprehensively, and reasonably select vacuum pumps, vacuum gauges, vacuum valves and vacuum pipes. If some of the pumped containers have oil pollution sources, it is not necessary to choose oil-free vacuum pumps when selecting vacuum pumps. For example, some vacuum electronic devices only need 10-4 Pa of high vacuum, so as long as oil diffusion vacuum pump or Qinsheng vacuum pump is chosen as the main pump, ordinary ionization vacuum gauge is used as the measurement vacuum, if sputtering ion pump and ultra-high vacuum ionization gauge are selected, it will be overstaffed. Conversely, if we need ultra-high vacuum system, and choose pumps and vacuum gauges that can only obtain high vacuum, then we will not be able to.
In addition, in some industrial production, in order to improve labor productivity, it is necessary to choose a vacuum pump with large pumping rate, but the price of the vacuum pump with large pumping speed is more expensive, and the consumption of water and electricity is large. It may also improve labor productivity, while the cost of unit product is increased, which may lead to the decrease of economic efficiency. Therefore, many aspects should be considered.

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