Roots vacuum pump

- Nov 15, 2018-

Roots vacuum pump


Structural form


1. Overall structure of pump


The pump body layout of roots vacuum pump determines the overall structure of the pump. At present, there are three types of roots vacuum pumps:


1). Vertical structure of the intake and exhaust level setting, assembly and connection pipes are more convenient. But the pump's center of gravity is higher and the stability is poor when running at high speed, so this type is mostly used in small pumps.


2). The air inlet of horizontal pump is above and the air outlet is below. Sometimes, for easy connection of the vacuum system pipes, the vent can be connected from the horizontal direction, that is, the inlet and exhaust directions are perpendicular to each other. At this point, the vent can be opened from left or right in both directions, with one end of the exhaust pipe connected to the other end or to the bypass valve. This pump structure has low gravity and good stability when running at high speed. General large, medium - sized pump more use this structure.


3). Two rotor shafts of the pump are installed perpendicular to the horizontal plane. This kind of structure assembly gap is easy to control, rotor assembly is convenient, pump cover area is small. But the pump center of gravity is higher and gear disassembly is not easy, the lubrication mechanism is also relatively complex. Foreign products only.


2. The transmission mode of the pump


The roots vacuum pump's two rotors are operated in relative synchronization by a pair of high-precision gears. The driving shaft is connected to the motor through a coupling. There are mainly two kinds of transmission structure arrangement:


One is that the motor and gear are placed on the same side of the rotor as shown in the figure. The driven rotor is driven by the motor end gear directly. In this way, the torsional deformation of the active rotor shaft is small, so the gap between the two rotors will not be changed due to the large torsional deformation of the active shaft. Therefore, the gap between the rotors is even in the running process.


The biggest shortcoming of this transmission mode is: a. there are three bearings on the driving shaft, which increases the processing and assembly difficulty of the pump, and the disassembly and adjustment of gear are also inconvenient; B. The overall structure is uneven, and the pump's center of gravity is in the direction of the motor and the side of the gear box.


The other is the motor and transmission gear respectively installed on both sides of the rotor. This form makes the overall structure of the pump symmetrical, but the active shaft torsion deformation is larger. In order to ensure the rotor clearance is uniform during operation, the shaft should have sufficient rigidity, and the connection between shaft and rotor should be tightened (existing rotor and shaft welded or cast into an integral structure). This structure is widely used because it is easy to disassemble and assemble.


3. Feature


Its quick start, less power consumption, low operation protection cost, high pumping speed, high efficiency, not sensitive to the large amount of water vapor and dust contained in the pumped air, larger pumping rate in the pressure scale of 100-1 pa, able to quickly eliminate the suddenly released gas.


This pressure scale is beneficial to the oil seal mechanical vacuum pump and the dispersion pump. As a result, it is often connected in series between the dispersing pump and the oil-seal mechanical vacuum pump, used to improve the amount of pumping at both ends of the pressure scale. At this time it is also known as mechanical inflator.


1)  In the wider pressure scale, there is a larger pumping speed;

2) The rotor has good geometrical symmetry, so the vibration is small and the running is bumpy. There are gaps between the rotor and between the rotor and the shell. It is unnecessary to be smooth. The friction loss is small.

3) There is no need of oil seal and smooth in the pump chamber.

4) No contraction in pump chamber, no exhaust valve. The structure is simple, compact and insensitive to dust and water vapor in the exhaust gas;

5) The contractile contrast was low, and the effect on hydrogen gas extraction was poor.


4. Applications


Roots vacuum pump has been tested on petroleum, chemical industry, plastics, pesticide, turbine rotor dynamic balance, aerospace space simulation, etc., so it should be widely used in China.


At the same time, roots vacuum pump is widely used in the smelting, degassing, rolling, and vacuum distillation, vacuum concentration and vacuum drying in food and medicine industries. Vacuum pump accessories for vacuum pump noise control, vacuum pump silencer.


The outer surface of rotor is a rather large and complex curve cylinder. Roots pump has been developed rapidly in recent years both at home and abroad. It has been widely used in metallurgy, petrochemical, electrician and electronic industries.

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