# Need to know about the calculating formula of - vacuum pump industry

by：J&T     2020-05-27

before choice models, we must find out some basic concept of the vacuum pump. Thin gas under vacuum, vacuum degree, usually by vacuum. Read the value of the known as vacuum in vacuum gauge. Vacuum value refers to the actual system pressure below the atmospheric pressure value. Table the value, also known as shown on table, industry, also known as the limit relative pressure, vacuum = atmospheres - namely Absolute pressure ( Atmospheric pressure is 101325 mpa commonly, the limit of water ring vacuum pump absolute pressure of 3300 mpa; The limit of the rotary vane vacuum pump absolute pressure of about 10 pa) Limit relative pressure: relative pressure is a measure of how much internal pressure is lower than the atmospheric pressure. Said the system pressure of the actual value is lower than the atmospheric pressure. Because the container is pumping air, so the pressure inside the container is always below the pressure outside the container. Therefore, when using relative pressure or pressure table, must have a minus sign in front of the value, said the pressure inside the container below the external pressure. Absolute pressure limit: absolute pressure refers to the internal pressure than the 'theory of vacuum measurement ( Theory of vacuum pressure value is 0 pa) 'How much higher. It is the object of absolute vacuum pressure is theoretical condition.

due to process limitation, in any case we can get the internal pressure up to the absolute vacuum value 0 pa. Therefore, by the vacuum pump vacuum suction vacuum values higher than the theory value. Therefore, when expressed in absolute vacuum, its no minus sign in front. Pumping capacity: pumping ability is vacuum pump pumping speed measure factor. General unit with L/S and m/h h said. This is a make up for the parameters of the gas leakage rate. It is easy to understand why a large quantity of pumping vacuum pump can be easily out we need vacuum pump, and less pumping vacuum pump is very slow, can't even vacuum pump out what we want. Due to a pipe or container can't be absolutely airtight, the large amount of air inhaled can make up for air leak and cause the loss of the vacuum degree of the factors, so it is easy to reach ideal atmospheric vacuum volume value. Advice when calculating the pumping ability theory, try to choose pumping capacity of high vacuum pump. Pumpability of concrete calculation formula are described below.

in the understanding of basic parameters of the vacuum pump, absolute pressure and relative pressure, we can proceed to select vacuum pump.

1。 The vacuum degree necessary for the process

vacuum pump working pressure should meet the requirements of process work pressure, when the choice of the vacuum degree should be higher than the vacuum degree of vacuum equipment to half an order of magnitude. ( For example, vacuum degree of vacuum process requirements for 100 mpa ( Absolute pressure) , the vacuum degree of vacuum pump should be at least 50 mpa - 10 mpa) 。 In general, if demands absolute pressure higher than 3300 mpa, water ring vacuum water pump vacuum unit is preferred. If required absolute pressure is less than 3300 mpa, can not choose the water ring vacuum pumps, rotary vane vacuum pumps or higher vacuum degree of vacuum pump as vacuum acquisition device.

2, technology on extraction yield requirements ( Extraction yield)

vacuum pump need pumping rate ( The vacuum pump in its working pressure discharge of gas, liquid and solid) General unit for the m3 / h and L/S, m3 / min. Specific calculation method can refer to the following formula to calculate and choose the type. Of course, the choice of the vacuum pump is a comprehensive process, involving relevant experience and other factors.

S=( V / t) ×ln( P1/P2)

type: s for pumping speed of vacuum pump ( L/s)

v is a vacuum chamber volume ( l)

t is the time needed for the vacuum degree required

(P1 is the initial pressure Palmer)

P2 is the required pressure ( Palmer)

3。 To determine the composition of the to pumping objects

first of all, by pumping object is gas, liquid or particles. If you want to pump gas to water vapor, or a small amount of impurities, such as particles and dust, should be carefully selected rotary vane vacuum pump. If required high vacuum degree, before rotary vane vacuum pump used in vacuum to obtain equipment, should add a filter for filtering.

in the second place, it is necessary to know whether the object pumping corrode ( Acidic or alkaline, acid and alkali value is how much? ) If gas containing acid and alkali corrosion or organic

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