The pumping speed of a vacuum pump is one of the important parameters for the selection of a vacuum device, and it is usually touched on a regular basis. But do we really understand the pumping speed of a vacuum pump?
The pumping speed of a vacuum pump is called the pumping rate, also called the volumetric flow rate. According to the definition, when the pump is equipped with a standard test mask and operates according to the specified conditions, the flow rate of gas flowing from the test mask and the specified position on the test mask are measured. The ratio of equilibrium pressure. More informally speaking, the pumping speed of a vacuum pump is the volume of gas flowing through the pump at the inlet of the pump per unit time. The common unit is liters/second (L/S).
However, in practical applications, the meaning of pumping speed that we come in contact with actually contains a variety of things. Let's take a look at these kinds of pumping speeds.
The first is nominal pumping speed
Nominal pumping speed is the pumping speed of the vacuum pump, which is one of the equipment parameters given by the vacuum pump manufacturer when the equipment is shipped. The pumping speed we normally touch is actually the nominal pumping speed of a vacuum pump.
The second is the geometric pumping speed, which is the theoretical speed
The geometric pumping speed is the geometric volume of gas that the vacuum pump can discharge at a certain speed. It is related to the suction chamber volume of the vacuum pump, the rotation speed of the rotor, and the number of times of suction and exhaust of the rotor one revolution. When the vacuum pump's geometry and revolutions are constant, its geometric pumping speed is also determined.
However, in reality, there are backflows, leaks, and intake passage resistances in the use of the vacuum pump, which can cause loss of efficiency. The geometric pumping speed of vacuum pump products is only the theoretical pumping speed, but it is actually difficult to achieve. Therefore, it is greater than the nominal pumping speed of the product.
Third, the actual speed
The actual pumping speed is the actual pumping speed actually measured by the vacuum pump, or the volume of gas that the vacuum system can extract from the pumped container per unit time under the pressure at the outlet of the container. In different pressure ranges, the pumping efficiency of the vacuum pump is changed: when the inlet pressure of the pump exceeds a certain pressure, the actual pumping speed will begin to drop; when the working pressure of the vacuum pump is close to its ultimate pressure, the actual pumping Speed is approaching zero. Therefore, the actual pumping speed is definitely less than the theoretical pumping speed, but it should be noted that under normal circumstances, we will choose to work within the optimal pumping speed range of the vacuum pump. In the stable pumping speed section, the actual pumping speed is greater than the nominal pumping speed. of.