Vacuum pump is a kind of device or equipment that uses mechanical, physical, chemical or physicochemical methods to extract air from the container to obtain vacuum. Generally speaking, vacuum pump is a device which can improve, produce and maintain vacuum in a closed space by various methods.
According to the working principle of vacuum pump, vacuum pump can be basically divided into two types, namely gas capture pump and gas transfer pump. It is widely used in metallurgy, chemical industry, food, electronic coating and other industries.
Common vacuum pumps include dry screw vacuum pump, liquid ring vacuum pump, reciprocating pump, slide valve pump, rotary vane vacuum pump, roots vacuum pump and diffusion pump. These pumps are essential main pumps in the application of vacuum technology in various industries of national economy.
vacuum pump of system parameters:
Vacuum degree: the thinness degree of gas in vacuum state, usually expressed as vacuum degree. The value read from the vacuum gauge is called vacuum degree. The value of vacuum degree indicates that the actual value of the system pressure is lower than the atmospheric pressure. The value expressed from the table is also called the table pressure, which is also called the limit relative pressure in the industry, that is: vacuum degree = atmospheric pressure absolute pressure (generally 101325pa, the limit absolute pressure of water ring vacuum pump is 3300pa; the limit absolute pressure of rotary vane vacuum pump is about 10Pa).
Limit relative pressure: the relative pressure is how much lower the measured internal pressure is than “atmospheric pressure”. It shows that the actual value of system pressure is lower than that of atmospheric pressure. Because the air inside the container is pumped, the pressure inside is always lower than the pressure outside the container. Therefore, when expressed in terms of relative pressure or gauge pressure, the value must be preceded by a minus sign, indicating that the internal pressure of the container is lower than the external pressure.
Ultimate absolute pressure: the absolute pressure is how much higher the measured internal pressure is than the theoretical vacuum (the theoretical vacuum pressure value is 0Pa). The object of comparison is the absolute vacuum pressure value of theoretical state. Due to the limitation of technology, we can not pump the internal pressure to the absolute vacuum 0Pa, so the vacuum value of vacuum pump is higher than the theoretical vacuum value. So when we use absolute vacuum, there is no minus sign in front of the value.
Pumping capacity: pumping capacity is a measure of the pumping speed of a vacuum pump. General units are expressed in L / s and m3 / h. It is a parameter to make up the air leakage rate. It’s not hard to understand why it’s easy for a vacuum pump with a large amount of air to pump the same volume of container in theory, and why a vacuum pump with a small amount of air can’t pump the vacuum that we want? Because it’s impossible for a pipeline or container to never leak, and the large amount of air can make up for the factors that cause the vacuum drop caused by the leakage. It’s easy to get the ideal vacuum value of the atmosphere. It is suggested that, in the case of calculating the theoretical pumping capacity, we try to choose a vacuum pump with a higher pumping capacity. The specific calculation formula of air extraction will be introduced below.
After knowing the basic parameters of vacuum degree, absolute pressure and relative pressure, we can enter the formal selection of vacuum pump. When purchasing vacuum pump and vacuum equipment, priority should also be given to the quality of equipment, transportation, maintenance and repair costs, etc.