The basic principle of miniature vacuum pump: the circumferential motion of the motor makes the diaphragm inside the pump reciprocating through the mechanical device, thus compresses and stretches the air in the fixed volume pump chamber to form a vacuum (negative pressure). Under the action of the pressure difference, the gas pressure (suction) is put into the pump chamber and then discharged from the exhaust outlet.
A sealed vessel (at the beginning, the internal pressure is 100 KPa) is connected with a miniature vacuum pump, which is continuously pumped. Finally, the gas pressure in the sealed vessel will be lower than the atmospheric pressure, reaching the absolute pressure of 60 KPa. Moreover, after special technical improvements, besides the single-suction miniature vacuum pump, it can also form a miniature vacuum pump (i.e., the exhaust end can produce relatively large positive pressure), which can be used for pressurization, inflation, overcoming system resistance and so on, as well as a very unique water-air dual-purpose miniature vacuum pump. It can be used in situations requiring long-term idling, dry rotation, etc., unlike other occasions. Normal pump idle, or dry turn will damage the pump.
Because the pressure difference between the suction port and the outside atmosphere can be formed, unlike the large vacuum pump, which needs lubricating oil and vacuum pump oil, does not pollute the working medium, and has the advantages of compact size, low noise, maintenance-free and continuous 24-hour operation, the micro vacuum pump is widely used as a power device for gas sampling, gas circulation and vacuum. Adsorption, accelerated filtration, automotive vacuum boost and other occasions have been widely used in medical, health, scientific research, environmental protection and other fields.
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With the vigorous development of instrumentation industry, compact, oil-free and environmentally friendly micro-vacuum pumps and micro-air pumps are more and more widely used. How can we choose the most appropriate product among the micropumps with various specifications?
First of all, the use of micro-pumps should be clarified. We discuss them one by one in three categories.
Fold input compressed air
1. If only compressed air is output by a miniature air pump.
Simply put, it is only used to inflate and inflate air, and the pump's suction port is basically not used.
Folding pumping or suction
Second, if the following circumstances, you should choose PHW600B or WAA series products.
1. Pumping air or vacuum with a micro-pump, but sometimes liquid water enters the pump chamber.
2. It is required that the micro-pump can pump both air and water.
3. Mainly use micro-pump to pump water, but do not want to add manual "water diversion" before pumping. (Some pumps need to add some manual "water diversion" before work, so that the pump can pump up the low water, otherwise the pump can not pump or even damage. ) The advantage of PHW600B or WAA series products is that when it does not touch water, it vacuum, and then pressure water up by air pressure, and then start pumping.
4. Pumping with micro-pumps, but sometimes there may be no water to pump, in a "dry" state. Some traditional pumps are afraid of "running dry" or even deadly. PHW600B or WAA series products are essentially a kind of compound function pump, which integrates the functions of vacuum pump and water pump. Some people call it "vacuum pump". Therefore, in the absence of water, it will vacuum, when there is water, it will pump. Whether it is pumping or pumping, it belongs to the normal working category, so there is no so-called "dry rotation" injury.
Third, if it is pumped by micro-pump, the situation is slightly more complicated.
(1) Judging the working condition of the pumping end of a micro-pump
There are two kinds of micro-pumps for air pumping: gas sampling pump and micro-vacuum pump. Although they are usually referred to as miniature vacuum pumps indiscriminately, they are different from each other from a technical point of view, and special attention should be paid to their selection.
In short, the gas sampling pump can only carry a small load (i.e., the resistance at the pump end can not be too large), but the price is cheap; strictly speaking, the micro vacuum pump can carry a large load (the pump end allows large resistance, or even completely blocked), but the price is slightly expensive. The specific difference between the two can be seen in the article "On the difference between micro vacuum pumps and gas sampling pumps", which will not be repeated.
Gas sampling pumps are PM series (such as PM950.2, PM850.5, PM8001, PM7002, PM6503); micro vacuum pumps are: VM series, VAA series, PK series, PC series, VCA series, VCC series, VCH series, PH series, FM series, FAA series, PCF series, all specifications under these series are real micro vacuum pumps, such as VM7002, VAA6005, PC3025, etc.
The resistance of the pump end can be measured by an instrument, and it can be compared with the Por value of the technical parameter of the pump, which is the maximum allowable resistance of the intake port. Usually, according to experience, a simple method is used to determine, for example, the following situations belong to the larger load (i.e., the greater resistance of the pumping end of the pump), which can only be selected within the scope of the miniature vacuum pump: 1) long pipeline should be connected at the pumping end of the pump, or the pipeline has many bending points, severe bending and even blockage and closure, or the inner hole of the pipeline is very small (e.g., less than 2 mm); 2) throttle valves, throttle valves, throttle val Solenoid valves, air circuit switches, filters and other components; (3) the pump suction port is connected with the closed container, or the container is not closed but the intake volume is small; (4) the pump suction port is connected with the suction cup for adsorbing objects (such as integrated blocks, precision workpieces, etc.); (5) the pump suction end is connected with the filter container, and the container port is placed with a filter for accelerating liquid filtration.