Vacuum pump pumping speed and vacuum unit configuration! Absolutely practical.
Different vacuum systems require different degrees of vacuum. Therefore, it is often necessary to complete by a set of vacuum units, that is, by working in different pressure range of vacuum pumps connected together.
The vacuum pump on the high vacuum side can achieve the required vacuum degree of the system, while the vacuum pump on the low vacuum side is directly discharged into the atmosphere. Obviously the simplest vacuum unit is a vacuum pump that runs directly into the atmosphere. However, a high vacuum system generally requires a three-stage unit, and a middle vacuum system generally requires a two-stage unit.
It is difficult for a high vacuum pump and a low vacuum pump to form an effective high vacuum unit. There are several reasons for this. Continuity of flow is one of them. The high vacuum pump has the limitation of the pressure of the front stage, that is, the front stage is higher than a certain pressure, the pump can not work normally. When the current stage pump reaches this critical pressure, the pumping speed will often decrease, so that the exhaust flow of the former stage pump may be less than the exhaust flow of the main pump, the inconsistent flow destroyed the flow continuity requirements, will inevitably cause the vacuum unit can not work properly. But if the high and low vacuum pump is connected with a middle vacuum pump, it can play a connecting role, continuous flow, and each pump can work in the best state. Roots pump can work in the vacuum range, is the most suitable, so also known as roots booster pump, due to its compression ratio is not high, just can be connected to a few Pa to a few hundred Pa range. When the three-stage high-vacuum unit enters a higher vacuum degree, the exhaust flow of the main pump is obviously reduced, and at this time, only a smaller front-stage pump can maintain the continuity of air extraction, which is often used in practice, so as to reduce the energy consumption of the unit.
Another reason why a high vacuum unit often requires a three-stage unit is due to the limitation of the suction pressure of a high vacuum pump. All pumps have initial working pressure, and conventional high vacuum pumps are in the range of several Pa. Therefore, the pre-pump must be pre-pumped to the pressure of the main pump to start work. But straight line level before pumped to the pressure of the atmosphere often require a long time, because as the pressure to reduce the pumping speed of the pump in reducing, especially for the periodic vacuum suction unit, to meet the requirements of the vacuum degree of work time is, the longer you smoke, also the longer period of time in the vacuum degree of work, therefore, increase the taichung with low level before the vacuum pump, vacuum pump can achieve in a relatively short time main pump can work stress, so that we can make the system as soon as possible into the work pressure, guarantee the efficiency of the equipment.
Both roots pump and oil booster pump can be used as medium vacuum pump. Molecular booster pump has a very high compression ratio, which not only enables it to obtain clean vacuum, but also has excellent high vacuum performance. At the same time, it also has a super pumping capacity in the middle vacuum range. This makes the molecular booster pump is currently the only vacuum pump with medium and high vacuum performance, so only need to cooperate with the low vacuum pump can form a performance comparable to the three-stage high vacuum unit. Specifically, because the molecular booster pump high pressure, so can make the former pump easy to be in a high flow state; And the molecular booster pump suction high pressure, reduce the pre - pumping burden of the pump. Molecular booster pump can work in 100-50pa, the pressure from the atmosphere to the first stage of the pump, basically in accordance with the law of each time pressure down an order of magnitude, therefore, the unit can have a high extraction efficiency. Simplifying the high vacuum unit and canceling the roots pump is another advantage of the molecular booster pump. For larger high-vacuum application equipment, the pre-pumping capacity of the front-stage pump can be appropriately strengthened to further shorten the pumping time. Because the pre-pumping time is very short compared with the whole exhaust process, the use time of the front-stage pump is also very short, so it can double as the pre-pumping function of multiple sets of equipment, which is often very realistic. This makes the large-scale application of the vacuum unit has been greatly simplified.
In some medium vacuum applications, it is necessary to enter the range of 10-1pa, which is often difficult to realize for the secondary units of roots pump, and the use of secondary units connected together with roots pump can improve the vacuum degree by an order of magnitude and enter 10-1pa, so the application of vacuum is also commonly used in the tertiary units. Since the molecular booster pump can be fully pumped at 10-1pa, it can also replace the two-stage roots pump in the three-stage medium vacuum unit. In general, the long time working in the vacuum of the low pressure range of the roots pump, molecular booster pump can be completely replaced. And the long time working in the high vacuum pressure range of the roots pump should be relatively small, because this pressure range before the pump often has a strong pumping speed.
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