Roots vacuum pump has a very important performance index, the maximum allowable pressure difference, which is a key index related to whether the pump can operate normally. Before starting the Roots pump, the fore pump must be used to pre-pump the vacuum system to a certain degree of vacuum, and when the pressure difference of the Roots pump exceeds the maximum allowable pressure difference during operation, the Roots pump must be turned off, otherwise the pump and the pump will be damaged. motor.
Magnetic coupling drive Roots pump
Magnetic pump consists of three parts: pump, magnetic coupling and drive motor. The left end of the pump shaft is provided with an impeller, the right end is provided with an inner magnetic rotor, and the pump shaft is supported by a sliding bearing. The bracket connects the pump and the motor and ensures the positional accuracy of the inner and outer magnetic rotors. When the motor drives the outer magnetic rotor to rotate, the magnetic field drives the inner magnetic rotor to rotate synchronously through the air gap and the isolation sleeve, thereby driving the impeller to rotate.
EVP ZJ/ZJP-CL Magnetic Coupling Roots Vacuum Pump
Magnetic Roots Pumps of Advantages:
1.The sealing problem of the pump shaft is solved, and its leakage rate can be reduced to < 1 × 10 ^-3 Pa·L /s, which is two orders of magnitude lower than that of ordinary radially sealed pumps
2.It is driven by the coupling into synchronous drag, and there is no contact and friction. The power consumption is small, the efficiency is high, and it has damping and vibration reduction effect, which reduces the influence of motor vibration on the pump and the influence on the motor when the pump has cavitation vibration.
3.The process gas has no cross-contamination to the atmosphere and no oil pollution to the environment.
Magnetic Roots Pumps of Disadvantages:
The magnetic drive Roots pump is the same as the conventional direct drive Roots pump, which is divided into two types without relief valve and with relief valve. Its working condition is similar to the two types of ordinary direct-connected Roots pumps. If it generates a lot of heat under high pressure difference, it is easy to cause the magnet to demagnetize at high temperature, thus limiting its operation under high pressure difference; There will be a natural demagnetization phenomenon after work.
The hydraulic drive type Roots pump brings great benefits to the starting process, operation, pumping performance and overload protection of the Roots pump.
Hydraulic drive mainly relies on the change of the pressure energy of the working fluid to transmit energy. Hydraulic transmission mainly relies on the change of working hydraulic energy to transmit energy. Its liquid components are called hydraulic components, including various types of hydraulic couplings and hydraulic torque converters.
ZJL-CL Series Hydraulic drive Roots pump
Hydraulic transmission type Roots pump of Characteristics
The hydraulic drive type Roots pump using the torque-limiting hydraulic coupling has the following advantages:
(1) Due to the hydraulic transmission between the motor and the pump, it can absorb vibration, reduce impact, and start smoothly. The noise and vibration that may be produced by ordinary couplings are avoided.
(2) The hydraulic coupling improves the start-up performance of the motor, so that the motor can be started with no load, and it can quickly enter into normal operation after starting. The current in the starting stage of the pump is small, only 2.2 to 2.5 times the rated current of the motor. The motor is directly connected to the Roots pump, and when hydraulic transmission is not used, the starting current can reach 6.5 times the rated current of the motor.
(3) It has the characteristics of automatic stepless transmission. The motor starts with no load and quickly enters normal operation. At the same time, the Roots pump also starts, and as the pressure difference of the Roots pump decreases, the speed gradually rises and enters normal operation. During operation, as the load changes, the Roots pump will automatically shift.
(4) The pumping speed of the Roots pump under low vacuum is improved, and under the same conditions, the pumping time can be reduced by 50%. The structure is simple, the installation is convenient, and there is no need to bypass the pre-pumping pipeline, pipeline valve and pressure sensor.
(5) The roots pump and the backing pump can be started at atmospheric pressure at the same time, and run continuously in the entire pressure range of 0 ~ 10^5 Pa to avoid motor overload. Even in case of accidental leakage, it has a certain self-protection effect.
(6) Even if the Roots pump fails and gets stuck (the turbine stops rotating), the motor will still drive the pump wheel to rotate, and the motor will not be overloaded or burned due to heat.
Shaft Seal
Roots pump is an oil-free pump, and there is no requirement for oil lubrication and oil sealing in the vacuum chamber in contact with the process gas. But the rotors are supported by bearings and precisely meshed with each other with gears that need to be lubricated and can be a source of contamination for oil-free cleaning systems. Conversely, when extracting gases that are prone to react with oil, it may also be harmful to lubricating oils. In order to prevent the oil in the coupling cavity and the gearbox cavity from being transferred into the vacuum cavity, the relevant parts of the pump must be effectively sealed.
The shaft seal system of the hydraulic transmission Roots pump is composed of the following parts. The high-speed rotating oil slinger throws out all the oil attached to it through centrifugal force, and makes it flow back to the oil tank. A spiral labyrinth seal seals any incoming oil and returns it to the tank. Dry shaft seals made of polytetrafluoroethylene (PTFE) effectively prevent mutual intrusion between process gas and lubricating oil without the need for lubrication. The high-quality fine-felt bushing prevents dust particles from the process gas from entering the shaft seal system from the vacuum chamber, thereby preventing abnormal wear of the shaft seal. The shaft seal system composed of the above components can effectively prevent cross-contamination between process gas, oil and atmosphere.
EVP VACUUM has these two type: ZJ/ZJP-CL magnetic coupling and ZJL-CL Hydraulic drive Roots pump. For more details, please contact Shanghai EVP Vacuum freely.
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