Uniform design of vacuum pumps is not alwaysallows you to solve tasks that require high performance. The increase in performance due to the build-up of the element base also rarely justifies itself, it affects the reduction of the durability of the structure and the stability of the operation of its units. The solution of the problem was the fore-vacuum pump, which provides an autonomous discharge function. As a result, the main equipment is able to work with optimal pressure indicators.
Vacuum pumping units work withseveral levels of pressure, moving from one state to another as the work actions are carried out. Forvacuum works under conditions of a preliminary level of vacuum, which must be created with the help of special plunger, mercury or steam oil apparatus. The process of transition from one level of rarefaction to another involves the use of appropriate methods of pumping out the working medium, as well as measuring the pressure. The most effective means of implementing this task is the fore-vacuum pump. The principle of operation of such devices is based on obtaining a preliminary or higher level of vacuum discharge.
The simplest model for implementing this functiondemonstrates the plate-stator pump. In this arrangement, rotation of the cylindrical rotor is provided. The rotor with the plate divides the cavity into two parts: the first one compresses the working medium, and the second - the expansion. During operation, the for-vacuum pump corrects the pressure parameters, which is reflected in the main installation to which the pre-vacuum system is connected.
Like all other pumps, forevacuum units are characterized by the flow rate of the working medium and pressure indicators. As for performance, it varies on average from 0.6 to 3000 m.3/ h.The pumping speed is determined by the volume of the vacuum chamber and the time it takes to maintain it. Actually, this will be an indicator of productivity. The compression pressure of the working medium is also taken into account. A standard for-vacuum pump provides about 500 mbar. The working pressure range in the part of the minimum values is limited by the ultimate vacuum, which, in principle, is possible for a particular type of equipment. The upper limit is limited by the maximum pressure on the exhaust, at which point the pump provides a vacuum at the inlet. In particular, oil-rotational models have a limiting vacuum in the spectrum of 10-3 Torr.
Применяется несколько подходов к классификации such aggregates. The most common is the separation according to the principle of action - mechanical and physicochemical models. An example of a mechanical rotary pump has already been considered, and now it is possible to refer to examples of installations operating with gas. Thus, for example, plants that provide vacuum by changing the position of the chamber and periodically varying the volumes of the gas content by the valve are isolated. An alternative to such devices is the sorption modification, which does not pump the gas in batches, but binds it in the system. In this case, both physicochemical and traditional oil-free fore-vacuum pumps differ in the levels of working pressure. Thus, the models that work with low-, medium- and super-vacuum systems are distinguished.
In the segment there are different companies thatwork both on a household niche, and on maintenance of needs of the large industrial enterprises. For example, the Japanese company Anest Iwata offers forvacuum models with a range of performance indicators from 100 to 500 l / min. Also model rulers of dry pumps of this type are offered by the developers of Kashiyama. This company specializes in the production of high-performance spiral and screw type equipment that provides feed in volumes up to 3500 m3/ h. In this case, you can find in the family less powerful and inexpensive units with a capacity of about 5 m3/ h.Famous for the quality and English forvacuum pumps Edwards, in which the latest technology of pumping liquids. The equipment of this brand has proved itself in highly specialized areas. For example, Edwards pumps are used in instrument making, chemical production, in factories manufacturing lighting lamps, etc.
Initially, the concept of fore-vacuum pumpssuggested the possibility of disposing of conventional pumping structures from instability in work. Modern optimized systems, supplemented by such devices, are estimated as a single installation for several indicators. Most positive feedback refers to the high performance of equipment, the minimum level of noise and vibration. Accordingly, the service life of the main vacuum increases. On the other hand, forecoupling pumps are often criticized for introducing contaminants into the main pumping system. But this applies to oil structures, which gradually leave the market.
The principle of work of forecoucum is also consideredobsolete. Addition of the construction of pumping equipment by another unit contradicts the idea of optimizing the size of technology, which is sought by modern manufacturers. Nevertheless, today there is no alternative pressure regulator, which could replace the fore-vacuum pump. The price of such units, amounting to 5-10 thousand rubles. in the middle segment, also does not contribute to their spread. However, given the initial exact calculations of system performance, many enterprises manage to effectively use forvacuum. Another thing is that in the future it is necessary to provide for the maintenance costs of this installation, in addition to the main pump.
