2. In the following situations, PHW600B or WAA series products should be used.
1. Use a micro pump to pump air or vacuum, but sometimes liquid water enters the pump cavity.
2. It is required that the micro pump can pump both air and water.
3. Mainly use micro pumps to pump water, but do not want to manually add "diversion" before pumping. (Some water pumps need to manually add some "diversion" before working, so that the pump can pump up the low water, otherwise the pump will not be able to pump water or even be damaged.) The strength of PHW600B or WAA series products is that they do not come into contact with water. Just draw a vacuum, after forming a vacuum, press the water up by air pressure, and then start pumping water.
4. Use a micro-pump to pump water, but sometimes the pump may have no water to pump and it is in a "dry running" state. Some traditional water pumps are afraid of "dry running", even fatal. The PHW600B or WAA series products are essentially a composite function pump, which integrates the functions of a vacuum pump and a water pump. Some people call it a "vacuum water pump". Therefore, when there is no water, it will vacuum, and when there is water, it will pump water. Regardless of whether it is pumped or pumped, it belongs to the scope of normal work, and there is no such thing as "dry running" damage.
3. The situation is slightly more complicated if the air is pumped with a micro pump.
(1) Judging the working condition of the suction side of the micro pump
The micro pumps used for pumping are divided into two categories: gas sampling pumps and micro vacuum pumps. Although they are usually simply referred to as miniature vacuum pumps without distinction, they are different from a technical point of view, and special attention should be paid to the selection.
In short, the gas sampling pump can only carry a small load (that is, the resistance of the pump suction side cannot be too large), but the price is cheap; in a strict sense, the miniature vacuum pump can carry a large load (the suction side allows large resistance, or even complete Blocked), but the price is slightly more expensive. The specific differences between the two can be found in the article "On the difference between micro vacuum pumps and gas sampling pumps", which will not be repeated.
Gas sampling pumps include: PM series (specific models such as: PM950.2, PM850.5, PM8001, PM7002, PM6503); miniature vacuum pumps include: 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 miniature vacuum pumps, such as VM7002, VAA6005, PC3025, etc.
The resistance of the suction end of the micropump can be measured with an instrument. Compare it with the Por value of the pump's technical parameter "Maximum Allowable Resistance at the Air Inlet" to know whether the selection is appropriate. It is usually determined by a simple method based on experience. For example, the following situations are all due to a large load (that is, the resistance of the pumping end of the pump is large), and can only be selected within the scope of the miniature vacuum pump:
① A very long pipe should be connected to the suction end of the pump, or the pipe has many bending points, severe bends or even blocked or closed, or the inner hole of the pipe is very small (for example, less than φ2 mm);
②There are throttle valve, solenoid valve, gas circuit switch, filter and other components in the pipeline;
③The pump suction port is connected with a closed container, or although the container is not closed, the air intake is small;
④ The pump suction port is connected with the suction cup, which is used to adsorb objects (such as integrated blocks, precision workpieces, etc.);
⑤The suction end of the pump is connected to the filter container, and a filter screen is placed at the mouth of the container to accelerate liquid filtration.
(2) Judging the working condition of the exhaust end of the micro pump
All of the above are discussing the resistance of the suction side of the micropump. According to these judgment conditions, the selection range has been narrowed, but the resistance of the exhaust side must also be considered, so that the selection range can be finally determined.
In practical applications, the exhaust conditions faced by miniature vacuum pumps are different: one is that the exhaust is very smooth and direct to the atmosphere; the other is that the exhaust resistance is relatively large, such as valves and small elbows in the exhaust pipe , Large damping sensor, non-dedicated muffler, exhaust below the liquid level, gas exhaust to a closed or semi-closed container, etc. In modern design and manufacturing, miniature vacuum pumps facing different exhaust conditions are treated differently. The parameter "maximum resistance Por value of the exhaust port" is to calibrate the pump's exhaust capacity, so that we can use strict technical means to determine whether the selection is appropriate.
Simply put, for systems with large exhaust resistance, our selection range is: FM series, FAA series, PCF series; for systems with low exhaust resistance, the selection range is: VM series, VAA series, PK series, PC series, VCA series, VCC series, VCH series, PH series. According to the above steps, we can already determine the selection range of the micro pump. Among the several optional series delineated, the specific model can be determined according to our requirements for flow and vacuum. For products of poor quality that are not included in this article, try not to use them. Pay attention to the parameter selection to leave a margin, especially the flow parameter. After the pump is connected to the pneumatic system, the flow will be attenuated due to pressure loss caused by the pneumatic components such as pipes and valves, so the flow rate obtained is less than the nominal flow rate of the pump.