According to the market survey and BODENFLO miniature pump sales analysis, micro vacuum pump in the miniature pump market occupies an extremely important position, as a power device, widely used in gas sampling, gas circulation, vacuum adsorption, accelerated filtration, automotive vacuum assistance and other occasions, in the medical, health, scientific research, environmental protection and other fields have also been widely used.

This article systematically summarizes the expertise of miniature vacuum pumps, hoping to help customers better understand and purchase micro vacuum pumps.

What is a micro vacuum pump and miniature air pump?

micro vacuum pump, in the simplest explanation, is an instrument with one inlet and one outlet suction nozzle and one exhaust nozzle, and it can continuously form a vacuum or negative pressure at the inlet; form a slight positive pressure at the exhaust nozzle; the working medium is mainly gas, and it is small in size.

For example, a closed container (at the beginning, the internal pressure is normal 100KPa) is connected to a micro vacuum pump to pump it continuously, and finally the gas pressure inside the closed container will be lower than atmospheric pressure, reaching an absolute pressure of 60KPa.

Not only that, after special technical improvement, in addition to the single pumping micro vacuum pump, it can also form a dual-use micro vacuum pump for suction and inflating (i.e. the exhaust end can produce a relatively large positive pressure), which can be used for pressurizing, inflating, overcoming the system resistance and so on, as well as the very unique water and gas dual-use micro vacuum pump, which can be used for long time idling, dry rotation and so on, unlike the general pump idling, or dry rotation will The pump is not damaged by idling or dry running.

Because the pressure difference between the suction port or the exhaust port and the outside atmosphere can be formed, unlike large vacuum pumps that need lubricating oil and vacuum pump oil, it will not pollute the working medium, and has the advantages of compact size, low noise, maintenance-free, and can run continuously for 24 hours.

2 important parameters of miniature vacuum pump

A vacuum is a state of gas in which the pressure is lower than 101325 Pa in a given space. In vacuum, the thinness of the gas is usually expressed by the pressure value of the gas, and obviously, the smaller the pressure value is, the thinner the gas is.

There are various kinds of vacuum pumps in the industry, and there are specified test methods to check the performance of each pump, the main parameters are：

• Limit vacuum (usually called vacuum degree): connect the vacuum pump with the test container, put in the gas to be tested and pump continuously for a long time, when the gas pressure in the container no longer drops and maintains a certain value, this pressure is called the limit vacuum of the pump. The smaller the value is, the closer it is to the theoretical vacuum.

• Flow rate: the volume of gas flowing through the suction port of vacuum pump in unit time. The volume of traditional industrial vacuum pump is generally very large, and the work of the pump needs special vacuum pump oil and lubricating oil, and the medium gas will contain a lot of oil mist. With the development of instrumentation industry and people’s requirements for environmental protection, miniature oil-free vacuum pumps in various countries have come into being, and generally have the following rules: the price of the pump and the vacuum index are closely related. The vacuum degree index is the main index that the producers of each country try to pursue, it reflects the overall strength of the corresponding mechanical processing, sealing technology, material science and other fields, and it is also an important means for the producers to gain profit. To improve the vacuum index, it is necessary to have higher sealing conditions, so it is necessary to use more accurate size and better material performance of the parts, so the production cost has increased significantly. And the price increase is much bigger than the increase of the vacuum index. Of course, the increase of pumping rate will also cause the price to rise, but the increase is not big.
• Therefore, when choosing a miniature vacuum pump, you need to carefully consider the vacuum index, pumping rate index, your own use, etc., so that you can take into account the performance and cost. The high vacuum degree miniature pump has higher requirements on the clean condition of working environment, temperature parameter, medium composition, etc. because it uses very precise sealing parts. Vibration and noise. The higher the flow rate and vacuum level, the higher the vibration and noise.

What is the basic principle of mini vacuum pump?

Simple summary: the circular motion of the motor makes the diaphragm inside the pump reciprocate through the mechanical device, thus compressing and stretching the air in the fixed volume of the pump cavity to form a vacuum (negative pressure), which generates a pressure difference with the outside atmosphere at the pump pumping port, and under the action of the pressure difference, the gas is pressed (sucked) into the pump cavity and then discharged from the exhaust port.

Although the principle is relatively simple, it is very difficult to achieve industrial grade stability and reliability. For example, in order to maintain a stable vacuum level, there are high requirements for the gas tightness of the pump, etc. With the guarantee of special technology and high-tech technology, the gas tightness of our miniature vacuum pump is relatively high, which can meet some customers’ applications with high requirements for gas tightness: such as analysis, inspection, circulation of rare gases in laboratory, etc.

Accordingly, every little increase of vacuum degree requires much higher material and technology level, so the cost is also increased significantly.

It can be seen that miniature vacuum pumps are actually very precise instruments, very different from ordinary civilian fish tank oxygen enrichment pumps, which are not comparable at all, and it is very normal that the price is slightly higher than them. Even with the sphygmomanometer on the common micro air pump than, but also a lot of high-grade. Sphygmomanometer commonly used on the micro air pump, the surface looks, the parameters are relatively close, but there is a considerable gap in reliability and life. Its life is generally in a few hundred hours, while the life of our micro vacuum pump is generally up to thousands of hours (full load, 24-hour uninterrupted test), if it is used intermittently, the life is much longer.

Micro vacuum pump: explanation of vacuum degree unit

There are two ways to identify the vacuum degree, one is with absolute pressure (i.e. absolute vacuum degree) and the other is with relative pressure (i.e. relative vacuum degree).

The “absolute pressure” means that the vacuum pump is connected with the testing vessel, and after enough time of continuous pumping, the pressure in the vessel will not continue to fall and maintain a certain value, then the gas pressure value in the vessel is the absolute pressure of the pump. If there is absolutely no gas in the container, then the absolute pressure is zero, which is the theoretical vacuum state. In practice, the absolute pressure of vacuum pump is between 0 and 101.325KPa. The absolute pressure is measured with an absolute pressure gauge, which has an initial value of 101.325KPa at 20°C and altitude = 0. In short, the air pressure identified by the reference to the “theoretical vacuum” is called: “absolute pressure” or “absolute vacuum”.

The “relative vacuum” is the difference between the pressure of the measured object and the atmospheric pressure at the place of measurement. It is measured with a common vacuum gauge. In the absence of vacuum, the initial value of the gauge is 0. When the vacuum is measured, its value is between 0 and -101.325KPa (usually expressed as a negative number). For example, if the measured value is -30KPa, it means that the pump can pump to a vacuum state 30KPa lower than the atmospheric pressure at the measurement location. The relative pressure value of the same pump may be different in different locations, because the atmospheric pressure of different measurement locations is different, which is caused by different objective conditions such as altitude and temperature. In short, the air pressure, which is identified by the reference to the “atmospheric pressure of the measuring place”, is called “relative pressure” or “relative vacuum”.

The most scientific and common “vacuum” in international vacuum industry is the absolute pressure; it means “ultimate vacuum, absolute vacuum, absolute pressure”, but “relative vacuum “(relative pressure, gauge pressure, negative pressure) is also widely used (BODENFLO chooses “relative vacuum”) because of the easy measurement method, very common measuring instruments, easy to buy and cheap price.

Relative vacuum = ultimate vacuum (absolute pressure) – atmospheric pressure at the measuring place

For example, the ultimate vacuum degree of a miniature vacuum pump is 35KPa, then its relative vacuum degree is about 35-100=-65Kpa, which is shown as -0.065Mpa on the common relative vacuum table (because it is related to the local atmospheric pressure), that’s why some customers buy the pump and measure it with the vacuum table, but misunderstand that the manufacturer’s parameter is not reached, which is far from the reason. BODENFLO miniature vacuum pumps use the relative vacuum mark, that is, use the relative vacuum gauge test, customers can rest assured that the purchase.

What is a negative pressure pump, positive pressure pump, the two links and differences?

Generally “L” type micro pumps have two inlet and exhaust ports, the inlet port can produce lower than atmospheric pressure (i.e. atmospheric pressure) air pressure called “negative pressure“; in the exhaust port can produce higher than atmospheric pressure called “positive pressure “;
for example, often said that the vacuum pump is a negative pressure pump, booster pump is a positive pressure pump.

Difference：

Positive pressure pumps and negative pressure pumps are very different. For example, the gas flow, negative pressure pump is the external gas is sucked into the pumping nozzle; positive pressure is sprayed out from the exhaust nozzle; such as the level of air pressure, etc. In fact, “negative pressure pump”, “positive pressure pump” is mainly from the function and the main use to artificially distinguish. “Negative pressure pump” is mainly used in the vacuum (negative pressure) requirements of the occasion, such as: pumping, gas analysis, gas circulation, gas sampling, vacuum adsorption, indirect suction, etc.; and “positive pressure pump” is mainly used in the need for pump as a power, gas transfer, to The two are commonly used in medical, scientific research, environmental protection, instruments, control and so on.

Contact： jean@bodenpump.com

The two are not absolutely different from each other.

The exhaust side of “negative pressure pump” also has positive pressure, but it is micro positive pressure, which is much smaller than the output pressure of “positive pressure pump”, such as micro vacuum pump BD-01V, BD-02VB, BD-03VB, BD-04VB, BD-07VB, BD-08VB and so on. V series such as BD-01V, BD-02VB, BD-03VB, BD-04VB, BD-07VB, BD-08VB, etc. are “negative pressure pumps” and “suction pumps”.
The pumping end of the “positive pressure pump” is also slightly negative pressure in order to complete the role of pumping. Of course, many times, both the pump pumping end can provide a high negative pressure, but also need the exhaust side of the output of a large positive pressure, mini pumping, pumping dual-use pump BD-04AB, BD-07AB, BD-08AB, etc. can be very good to complete this requirement.

Like BD-04VB this model, it can provide -80Kpa negative pressure and >350Kpa positive pressure at the same time, the volume is small, the pumping and exhaust side can be added to the valve, blocking can also work normally, to achieve both multi-functional, but also reduce the cost of the purpose.

About the difference between micro vacuum pump and gas sampling pump

1. Usually we call all small volume pumps which can produce negative pressure as micro vacuum pumps, but we should strictly distinguish them when selecting products.
2. The real sense of micro vacuum pump (such as BD-03, BD-03, BD-04, BD-07, BD-08 series, etc.) is a pump that can pump vacuum to the closed container for a long time, and it can drive a larger load. The pressure difference between inside and outside the pump chamber is small when the gas sampling pump is working, so the load it carries is very small. It is because of the different requirements on the carrying capacity that the spare parts chosen by the mini vacuum pump and gas sampling pump are very different.
3. Micro vacuum pump has high requirements for both diaphragm and motor. For these two main parts, fatigue strength, reliability, life expectancy and other technical indicators are required to meet the standards under load, unlike the gas sampling pump, which is only required to meet the standards under a very light load (tests have proved that the gas sampling pump is easily damaged by a slightly larger load). Therefore, the cost difference between the two types of miniature pumps is very large.
4. In summary, if the micro vacuum pump is used for gas sampling, it is bound to get high reliability and longer life, but the cost is high; if the gas sampling pump is used in the occasion of slightly larger load, the reliability and life will be greatly reduced, and even cannot work properly, although it has a greater advantage in cost. When selecting the model, it is good to consult clearly with the technical department in order to take into account the cost and performance.

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