How much do you know about the pumping speed of vacuum pump?
As one of the important parameters of vacuum equipment selection, the pumping speed of vacuum pump is often contacted. But do we really know the pumping speed of vacuum pump?
The pumping speed of the vacuum pump is called the pumping speed, also called the volume flow rate. According to the definition, it refers to the ratio of the gas flow through the test cover and the balance pressure measured at the specified position on the test cover when the pump is equipped with the standard test cover and operates according to the specified conditions. More generally speaking, the pumping speed of vacuum pump refers to the volume of gas flowing in unit time at the pump inlet, and the common unit is L / s.
But in practical application, the meaning of pumping speed we contact actually includes many kinds. Let the vacuum pump manufacturer take you to understand:
The first is nominal pumping speed.
The nominal pumping speed is the nameplate pumping speed of the vacuum pump, which is one of the equipment parameters given by the vacuum pump manufacturer when the equipment leaves the factory. The pumping speed we usually contact is actually the nominal pumping speed of the vacuum pump.
The second is the geometric pumping speed, that is, the theoretical pumping speed.
The geometric pumping speed is the geometric volume of the gas that can be discharged by the vacuum pump at a certain speed in unit time. It is related to the volume of the suction cavity, the rotating speed of the rotor, and the number of suction and discharge times of the rotor in one cycle. When the geometric dimension and revolution of the vacuum pump are fixed, its geometric pumping speed is also determined.
But in fact, there are backflow, leakage and resistance of intake passage in the use of vacuum pump, which will lead to efficiency loss. The geometric pumping speed of vacuum pump is only the theoretical pumping speed, but it is difficult to achieve. Therefore, it is larger 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 it can be understood as the volume of gas that the vacuum system can pump from the pumped container in unit time under the pressure at the outlet of the container. In different pressure range, the pumping efficiency of vacuum pump changes: when the inlet pressure of the pump exceeds a certain pressure, its actual pumping speed will start to decline; when the working pressure of the vacuum pump is close to its limit pressure, its actual pumping speed will approach zero. Therefore, the actual pumping speed must be less than the theoretical pumping speed, but it should be noted that in general, we will choose to work within the optimal pumping speed range of the vacuum pump, while in the stable pumping section, the actual pumping speed is greater than the nominal pumping speed.
At the same time, the flow conductivity of the vacuum system pipeline also limits the pumping speed of the vacuum pump.
Pumping curve 2
The 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. The given pumping rate only represents the pumping rate for a certain gas. If there is no special indication, it refers to air extraction.
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