Vacuum pump concept and selection methods

Vacuum pump concept and selection methods

Vacuum pumping action of the vacuum chamber is , in addition to gas molecules , to reduce the gas pressure in the vacuum chamber , so as to achieve the required degree of vacuum .

Vacuum pumping action of the vacuum chamber is , in addition to gas molecules , to reduce the gas pressure in the vacuum chamber , so as to achieve the required degree of vacuum . Generally speaking from the atmosphere to a high vacuum has a great range , so far there is not a vacuum system to cover this range. Therefore, in order to achieve process indicators for different products , work efficiency and equipment working life requirements, different needs of different sections of the vacuum vacuum system configuration. For optimal configuration, the selection of vacuum systems should consider the following points :

First, was pumping gas type and amount of exhaust

Check to make sure the type and amount of exhaust extraction process requirements . Because if the pump is pumping liquid gas species react pump system will be contaminated . Must also be considered when determining the appropriate amount of exhaust gas extraction time and generated during .

Second, the vacuum

Is to decide what kind of product structure , there is a degree of vacuum gauge and absolute pressure of these two readings. Represents the absolute value of the absolute pressure reading is that the closer reading of '0 ', the higher the degree of vacuum . In contrast to gauge , closer 760mmHɡ means that the higher the degree of vacuum , if you are asking for absolute pressure ( vacuum limit ) is close to '0 ', then only the vacuum pump in order to meet this demand, but if the demand is close to 1bar ( ie atmospheric pressure ) , so they can choose the Roots blower or centrifugal fans to meet this demand .

Third, determine the scope of work of the vacuum

    First, you must check to determine the degree of vacuum required for each process . Because the vacuum of each process has its own range of adaptation , we must seriously study identified .

Fourth, check the vacuum volume

    Determine the time to reach the required vacuum level required , flow resistance and leak vacuum channel. After considering to meet the requirements of vacuum pumping rate needed to maintain the vacuum under certain conditions the process requirements .

Fifth, determine the maximum vacuum

In determining the base of the system to check the vacuum pump to the process requirements of the ultimate degree of vacuum , because the ultimate vacuum of the system determines the optimal operation of the system vacuum. In general, the ultimate vacuum of the system is 20% lower than the working vacuum system , 50% lower than the maximum vacuum before the pump .

Sixth, the vacuum pump is calculated

S = 2.303V/tLog (P1/P2)

Where: S is a vacuum pump rate (L / s)

V is the vacuum chamber volume (L)

t is the time required to achieve the required degree of vacuum (s)

P1 is the initial pressure (Torr)

P2 to require a degree of vacuum (Torr)

For example : V = 500L t = 30s P1 = 760Torr P2 = 50Torr

Then : S = 2.303V / t Log (P1/P2) = 2.303x500/30xLog (760/50) = 45.29L / s

Of course, the above formula is a theoretical calculation , there are a number of factors not taken into account variables such as pipe flow resistance , leakage, the flow resistance of the filter is pumped gas temperature. Actually a safety factor should be taken into account