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Roots vacuum pump how to choose and configure dynamic working principle - _ roots vacuum pump

by:J&T     2020-05-22

let's grasp the dynamic principle and characteristics of the roots vacuum pump, look forward to everyone in the aspect of model selection and application of the pump has the certain help.

principles: the principle of the roots vacuum pump and roots blower. Because of motor rotor continues to turn, be smoked gas from the air inlet into the middle of the motor rotor and the pump body within the interior space where v0, then through the outlet line. Because after breathing where v0 interior space is fully enclosed, therefore, in the pump cavity gas without narrowing and peng. But when the top of the motor rotor turning the outlet edge, where v0 interior space and the exhaust side each other, because of the exhaust gas pressure is higher, is part of the gas to return through interior space where v0, gas gas pressure increase suddenly. When the motor rotor rotation again, gas discharged outside the pump.

roots vacuum pump has the following features:

in a wider category of gas pressure inside the large pumping speed;

start fast, can immediately work;

in the gas is pumped with dust and water vapor is not sensitive;

the motor rotor without RunHua, no oil in the pump cavity;

little vibration, dynamic balance equipment standard is good, there is no automatic exhaust valve;

drive small output power, mechanical friction damage of equipment;

compact structure, covers an area of small;

run maintenance fee is low.

therefore, roots vacuum pump in metallurgical industry, petroleum chemical industry equipment, papermaking, food, electronics industries, departments widespread use.

roots vacuum pump can not separate application, general conditions are all applied in conjunction with backing pump, application level before the mechanical pump is in order to reduce the pressure from the roots vacuum pump, because the roots vacuum pump compression ratio is limited, so choose the level before the mechanical pump pumping speed is critical.

roots vacuum pump of the larger compression ratio is over discharged pressure change, under the high pressure from larger compression ratio most of 3:1, but the maximum compression ratio is in the middle of the discharged pressure for 1 to 10 mbar ( 1mbar=0. 75Torr) Around 50:1, and even higher. Choose the backing pump pumping speed, therefore, should be based on the roots vacuum water pump considering the long-term work pressure category.

such as a system software with the roots vacuum pump vacuum generator sets, and provisions in 1 mbar channel pressure pumping speed 600 liters per second, and long-term work, ask how many pumping speed should be selected before the pump?

hypothesis with 30 liters per second before the first stage pump, compression ratio K = 600:30 = 20 to calculate K = 20 larger when discharged pressure for 30 mbar.

thus calculated and selected by the level of 30 liters per second before the pump, the channel pressure is less than 1. 5 mbar in the following work is practicable, but higher than 1. 5 mbar channel work pressure when they adopt some backing pump.

in this case, the work of vacuum value 1 mbar is less than 1. 5 mbar, therefore before 30 liters per second stage pump can consider described the ultrafiltration device of vacuum.

Q1 should take into account the rules in the process of the squeeze time

if everything is far better than the normal working hours long time, can choose smaller backing pump; If the vacuum chamber is a large, rapid drainage and regulation, but also with a lot of backing pump, sometimes in order to give full play to the machinery and equipment of high efficiency, stronger generating set is equipped with large drainage pump, in normal work after stop using it, and use smaller backing pump keep, did that in order to save the output power.

Q2 you should think about the roots vacuum pump to the provisions of the generating set limit pressure

is picking up a backing pump, be sure to consider the high limit vacuum value ( 1 x10 - 3 ~ 1 x10 - 2 pa pressure) Generally adopt a bipolar spin built-in skeleton seal mechanical pump or bipolar electro-hydraulic directional control valve mechanical pump as the backing pump. Ultimate vacuum requirement in ( 1 x10 - 2 x10 - pa ~ 1 1Pa) Can choose between a single stage oil seal mechanical pump as the backing pump, ultimate vacuum requirements between 133 ~ 1333 pa can choose reciprocating vacuum pump or liquid ring vacuum pump as the backing pump.

was elected with a reciprocating or thick liquid ring type vacuum pump is regarded as the backing pump of the roots vacuum pump, pumping speed of pump before 1/2 - general for roots vacuum pump 1/4, cannot too big, otherwise will make the compression ratio is too big, cause the roots vacuum pump exhaust temperature is high and can't work normally.

Q3 should also consider is whether the corrosive medium in the smoke gas, whether they contain non-condensable gas, is large or small amounts of

if containing corrosive gas, will not be able to choose oil seal mechanical pump, oil seal mechanical pump is not suitable for sexual steam ejector contains a lot of condensable gas, otherwise will soon the sealing liquid emulsification, ejector contains trace of condensable vapor gas, also must have a device with a gas ballast oil seal mechanical pump as the backing pump.

in order to obtain the low inlet pressure ( 1~100pa) High extraction rate, can use a roots vacuum pump as another roots vacuum pump former level 3 or 4 sets of pump, pumping speed ratio between the roots vacuum pump at this time in between 2 ~ 5.


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