The pumping speed of vacuum pump is one of the important parameters for the selection of vacuum equipment, which is often touched. But do we really know the pumping speed of vacuum pump?

The pumping speed of vacuum pump is called pumping rate, also known as volume flow rate. According to the definition, it refers to the ratio of the gas flow from the test cover to the balance pressure measured at the specified position on the test cover when the pump is equipped with a standard test cover and works under specified conditions. More generally speaking, the pumping speed of vacuum pump refers to the volume of gas flowing through the unit time at the inlet of the pump, and the commonly used unit is L / s.

However, in practical application, there are many meanings of pumping speed. Let the dry screw vacuum pump manufacturer give you a reason:

The first is nominal pumping speed.

The nominal pumping speed is the label pumping speed of vacuum pump, which is one of the equipment parameters given by the vacuum pump manufacturer when leaving the factory. The pumping speed we usually contact is actually the nominal pumping speed of vacuum pump.

The second is the geometric pumping speed, which is the theoretical pumping speed.

Geometric pumping speed is the geometric volume of gas that can be discharged per unit time by vacuum pump at a certain speed. It is related to the suction chamber volume of vacuum pump, rotor speed, and the number of suction and exhaust of rotor rotation cycle. When the geometric size and revolution of the vacuum pump are fixed, its geometric pumping speed is also determined.

But in fact, there are some problems in the use of vacuum pump, such as backflow, leakage and inlet channel resistance, which will lead to the loss of efficiency. The geometric pumping speed of vacuum pump is only theoretical pumping speed, which is difficult to realize. Therefore, it is greater than the nominal pumping speed of the product.

Third, the actual pumping speed.

The actual pumping speed is the actual effective pumping speed measured by the vacuum pump, or understood as the volume of gas that can be pumped out of the vacuum system per unit time under the pressure at the outlet of the container. In different pressure range, the pumping efficiency of vacuum pump is variable: when the inlet pressure of the pump exceeds a certain pressure, the actual pumping speed will start to decline; when the working pressure of the vacuum pump is close to its limit pressure, the actual pumping speed tends to zero. Therefore, the actual pumping speed is certainly less than the theoretical pumping speed, but it should be noted that in general, we will choose to work in the optimal pumping speed range of vacuum pump, and in the stable pumping speed section, the actual pumping speed is greater than the nominal pumping speed.

At the same time, the flow conductivity of vacuum system pipeline also limits the pumping speed of vacuum pump.

What kind of pumping speed do you know?

Nominal pumping speed, geometric pumping speed and actual pumping speed can be simply understood as: Geometric pumping speed > actual pumping speed > nominal pumping speed.

In addition, the pumping speed of vacuum pump is also related to the type of gas. Given the pumping rate, only represents the pumping rate for a certain gas. If there is no special indication, it refers to air extraction.