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ZJP Roots Vacuum Pump Series


Roots vacuum pump

  • Product description
  • Advantage
  • Features
  • benefit
  • Technical data

    A mechanical booster pump is a mechanical vacuum pump with a pair of double-lobed rotors that rotate synchronously at a high speed. It uses two figure-eight rotors to rotate in the pump casing to produce suction and exhaust. The principle is similar to that of a Roots blower. Because it works in the low pressure range, the free path of gas molecules is large, and the resistance for gas to leak through tiny gaps is great, so it can obtain a higher compression ratio and can be used as a booster pump; but it cannot directly discharge gas to In the atmosphere, it needs to be used in series with the foreline vacuum pump.


    Working principle:

    1. The working principle of the pump

    When working, the pumped gas enters between the rotor and the pump body from the air inlet. At this time, a rotor and the pump body separate the gas from the air inlet. The separated gas is continuously rotated by the rotor. Send to the exhaust port. The VO space is in a closed state. Therefore, there is no compression and expansion. But when the peak of the rotor turns to the edge of the exhaust port, the pressure from the VO part is lower than the pressure at the exhaust port. In order to make the pressure in the connected volume uniform, the gas diffuses from the exhaust port to the VO from the exhaust gas and compresses it to the exhaust port to remove it. At this time, the other side of the rotor is connected with the air inlet to suck in gas. When the rotor continuously rotates, repeat the above-mentioned pumping process to continuously exhaust the gas that has slipped in. This kind of working process is equivalent to increasing the rotor space from a certain minimum value to the maximum value, and then reducing it from the maximum value to the minimum value. This is the volume working principle of this pump.

    The pump works under very low inlet pressure. Due to the high rotation speed of the rotor (2860 rpm), the linear velocity on the surface of the rotor is close to the thermal movement speed of the molecules. At this time, the gas molecules that collide on the rotor are carried by the rotor to the exhaust port with higher pressure, and then by the front stage. Pre-vacuum pump excluded. This is the principle of molecular action of this type of pump.

    Under the combined effect of these two principles, this type of pump promotes this type of pump to have a high pumping speed and a stable pumping speed curve in the interval (1.3×103~1.3 Pa).


    2. Principle of bypass valve

    The bypass line between the outlet and inlet of the ZJP series mechanical booster pump is equipped with a bypass valve. This bypass valve controls the pressure difference between the inlet and outlet of the pump not to exceed the rated value (2666 Pa). When the rated value is exceeded, the valve opens automatically, and the inlet and outlet of the pump are connected. At this time, the pump is almost working under the load of the normal pressure difference. . When the pressure difference is lower than the rated value, the valve automatically closes.

    According to the characteristics of this type of pump, you can freely choose different backing pumps according to different conditions of use, especially when the vacuum degree is not high, and it is required to extract a large amount of water vapor or a small amount of dust and weak corrosive gases, etc. It can be used with two-stage water ring vacuum pump and valve vacuum pump. Of course the ultimate vacuum that can be reached is lower, and the power ratio is also different.

  • Features of ZJP pump:


    1. There is a gap between the rotor and the pump cavity, and there is no contact between the rotor and the rotor, and no lubricating oil is required.


    2. The rotor has good geometric symmetry, no friction, low power consumption, stable operation, low noise, high speed of direct drive, small size, light weight, and high pumping speed.


    3. There is no compression phenomenon like mechanical vacuum pump in the pump cavity. Therefore, it does not require an exhaust valve. Therefore, suspicious vapor can be removed.


    4. Quick start, can reach the ultimate vacuum in a short time, low power, low operation and maintenance cost.


    5. The pump is equipped with a bypass valve to make the pump run safely and reliably.


    6. The pump has a large pumping speed in a wide pressure range (1.3×103~1.3 Pa), which can quickly discharge the suddenly released gas.


    It makes up for the shortcomings of the diffusion pump and the oil-sealed mechanical pump that the pumping speed is very small at 1.3×103~1.3 Torr. This pump is widely used in vacuum degassing and vacuum smelting in the vacuum metallurgical industry, vacuum treatment of molten steel, heat treatment, etc., and can also be used in industries such as chemical industry, food, medicine, and motor manufacturing. In particular, it needs to be pointed out that when its front stage adopts a two-stage water ring pump, it can pump out gas containing a large amount of water vapor, so it is also suitable for distillation, evaporation, freezing, drying and other life processes









    The pumping rate (L/S) is between 5×







    Ultimate vacuum Torr


    Ultimate vacuum Pa


    Long-term maximum pressure difference Torr







    Bypass valve pressure difference pa



    Ultimate vacuum less noise
    in dB (A)







    Maximum pump temperature


    Equipped with motor power (kw)







    Speed ​​(rpm)


    Flange diameter (import * export)







    Lubricant brand

    1#Mechanical vacuum pump oil

    Recommended fore pump







    Weight (kg)







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    Installation Notes

    1. Before installation, check whether each part of the pump is damaged, and check whether the order contract is consistent with the product. 

    2. The pump must be installed in a place where the environment is clean, there is no dust or there is little dust and it is not easy to contaminate the medium. The suction port of the pump should be based on usage. (For example, when the foreline pump adopts oil-sealed mechanical pump), dustproof device can be installed. 

    3. The working environment temperature of the pump is 5~40℃. The maximum temperature rise of the pump is not more than 100°C.

    4. The pump foot installation can be installed on a cement foundation or a steel frame foundation according to the usage, but the level must be calibrated. Otherwise, the normal operation of the pump will be affected. 

    5. The intake and exhaust pipelines should be sealed, even a small leak will affect the vacuum. 

    6. In principle, the length of the pipeline should be as short as possible, and joints and elbows should be used sparingly. The diameter of the pipeline should not be smaller than the inlet diameter of the pump. 

    7. It is better to install a flexible hose, such as a metal bellows, in the middle of the connecting pipeline between this type of pump and the foreline pump. In order to connect and prevent damage to the pump due to the vibration of the backing pump.

    8. It is best to install a vacuum valve on the intake and exhaust pipes of the pump to keep the vacuum in the pump cavity after stopping.

    9. A valve should be installed on the cooling water inlet pipe to adjust the water volume. The temperature of the cooling water outlet should be between 20 and 40 ℃ during operation. Note that the water temperature should not exceed 40 ℃ to avoid scale deposits in the water jacket.

    10. The pump must have a pre-pump as its backing pump, it cannot be used alone. If equipped with an oil-sealed mechanical vacuum pump as the backing pump. The two are used in tandem. Therefore, it is also suitable for pumping out gas with high oxygen content, which is explosive, corrosive to ferrous metals, chemically reacts to vacuum oil and contains dust, otherwise it will affect the service life of the backing pump.


    Instructions for use

    Preparation before starting: 

    1. Check whether the cooling water pipe is unblocked.

    2. Check the lubricating oil in the gear box and the end cover. The oil level should reach the oil level line of the sight glass. The oil cup of the outer shaft seal is often filled with lubricating oil and must be kept clean at the same time. The oil should be changed after the new pump is used for 30-50 hours, and the oil can be changed according to the usage in the future.

    3. If there is dust or other metal powder in the inhaled gas. A dust-proof or filter device should be installed in front of the suction port. If the inhaled gas is corrosive, neutralization measures must be adopted. 4. Check whether each part is loose. Whether the rotation direction of the motor is the same as the direction of the arrow on the pump.



    1. Start the foreline pump.

    2. Open the intake valve of the pump type pump. 

    3. Start the pump and open the cooling water valve immediately after the pump is started. 

    4. The pump should be stable when running, and the rotor should not have impact sound. 

    5. No oil leakage is allowed at the shaft seal of the pump. 

    6. During the operation of the pump, if the local temperature rise is too large, the reading of the ammeter suddenly changes, or irregular noise or other abnormal phenomena occur, stop immediately and check the cause.



    1. Close the intake valve on the intake pipe first. 

    2. Stop the pump. (With closing the exhaust valve) 

    3. Stop the foreline pump.

    4. Close the cooling water inlet valve 

    5. If you stop using it for a long time, or you must drain the water in the cooling water jacket in a cold area, otherwise the water in the jacket will freeze and damage the pump castings.



    1. The environment in the pump room should always be kept clean and dry. 

    2. Always pay attention to the lubrication of each part. If insufficient, it should be supplemented in time. If it is found to be dirty, it should be replaced in time. And pay attention to the sealing of the screw plug when it is screwed in again.

    3. The working pressure difference of the pump should be controlled within the allowable pressure difference range of the bypass valve, otherwise the motor will burn out easily.

    4. Disassembly and assembly of the pump


    a. Loosen the screws and remove the end cover B 

    b. Use hydraulic device to remove gear

    c. Loosen the bolts to remove the bearing gland and bearing seat B (and bearing)

    d. Loosen the bolts, take out the pin and unload the side cover B 

    e. Loosen the bolts to remove the motor, remove the pump coupling, and remove the coupling seat

    f. Loosen the bolts to take out the pin and unload the end cap

    g. Remove the lock nuts and oil slinger on the main and driven shafts

    h. From the side cover B direction, remove the shaft and rotor together

    i. Remove the retaining ring bearing seat armour, side cover armour, sealing sleeve and ring. 

    5. Assembly: Check carefully all the disassembled pads. If the hair ring is damaged, replace the disassembled parts with a new pad of the same material thickness when installing the pump, clean it with gasoline, carbon tetrachloride or ether, and assemble it after drying. ; The sealing plane between the pump body and the side cover is sealed by resin, the assembly sequence is just the opposite of the disassembly sequence, and the end face gap is adjusted according to the figure. When installing the main and driven gears, the fasteners should be in contact with the end faces of the bearings, and then the bolts of the fastening device should be tightened.



    cause of issue

    Take measures


    The vacuum is not up to the requirement

    Leakage of the pumped container or connecting pipeline

    Eliminate air leakage from the pumped container or connecting pipeline

    The pump oil seal is damaged and leaking

    Replace the oil seal

    The screws of each part of the pump are loose

    Tighten the loose screw


    Abnormal sound

    Bearing fatigue damage

    Replace the bearing

    The rotor gap changes

    Remove the gear, clean it, reinstall it and
    adjust the gap between the rotors

    Coupling fatigue damage

    Replace the coupling

    Gear fatigue damage

    Change gear

    Motor burnt out

    Large foreign objects fall into the pump cavity

    Eliminate foreign objects

    The overflow valve is rusty

    Disassemble the overflow valve and reinstall it after cleaning