What is lobe pump?


lobe pump is a form of positive displacement pump. It consists of a rotating rotor and a stationary pump body. It has no suction and discharge valves, and changes the working volume through the relative movement between the rotor and the pump body, and discharges the liquid by the squeezing effect of the rotating rotor, while leaving space on the other side to form a low pressure, so that the liquid is continuously drawn in.

According to its structure and principle, the rotor pump can be divided into gear pump, screw pump, rotary piston pump (lobe pump, Roots pump), flexible impeller pump, sliding vane pump, hose pump, etc. Rotor pump is a rotating volumetric pump, with positive displacement nature, its flow does not change with the change of back pressure.

Preferred occasions for rotor pumps are: viscous liquids, occasions requiring metering, occasions requiring self-priming, occasions containing gases, small flow occasions, pumps requiring no shear on the medium, pumps requiring reversal of high pressure occasions, etc.

lobe pump


Rotor pumps are divided into gear pumps, screw pumps, rotary piston pumps (lobe pumps, Roots pumps), flexible impeller pumps, sliding vane pumps, hose pumps, etc. according to the structure type.

(1) Gear pump

Gear pumps mainly have gears, shafts, pump bodies, pump covers, bearing sleeves, shaft seals and other components. Relying on the pump body and the working volume formed between the meshing gears change and move to transport the liquid or make it pressurized rotary pump. Gear pumps have two types of structure: external and internal. External gear pumps are divided into double gear pumps, three gear pumps and five gear pumps, and external double gear pumps are most commonly used. A pair of intermeshing gears and the pump body separates the suction chamber and the discharge chamber. When the gears rotate, the volume between the teeth on the side of the suction chamber where the teeth are separated from each other gradually increases, the pressure decreases, and the liquid enters between the teeth under the action of differential pressure. With the rotation of the gear, the liquid between the teeth is brought to the discharge chamber. At this time, the volume between the teeth at the engagement of the teeth on the discharge chamber side gradually decreases, and the liquid is discharged.

(2) Screw pump

The screw pump consists of a pump casing and one or more screws. The working principle of twin-screw pumps is very similar to that of gear pumps, which relies on the mutual meshing of the screw to suck and send the liquid. Screw pumps are divided into single screw pumps, twin screw pumps and triple screw pumps according to the number of screws, among which twin screw pumps are of two types: airtight and non-airtight.

(3) Rotary piston pump

Rotary piston pumps have a wide variety of structures, the most commonly used of which are lobe pumps, Roots pumps and so on.

Lobe pump is a multi-purpose bi-directional displacement pump, which is one of the most advanced fluid transfer equipment internationally. It uses two rotors with synchronous motion, and the rotors are driven by a pair of external synchronous gears, and the rotors are driven by the drive shaft to rotate in the opposite direction synchronously, and the rotors do not touch each other and the rotors and the pump body, but form a gap line or face seal, thus constituting a high vacuum and discharge pressure, which is especially suitable for the transfer of food, medicine, corrosive and high viscosity media.

The structure form of Roots pump is similar to that of lobe pump, the difference is that the liquid seal also has to be formed between the rotors, and the large pump is mostly in simple support arrangement, it is simpler to process than lobe pump, and the working pressure is lower than that of lobe pump.

(4)Flexible impeller pump

Flexible impeller pump is a volumetric rotor pump. The flexible impeller pump consists of a flexible impeller made of rubber, pump body, mechanical seal and rotating shaft. When the impeller rotates away from the eccentric section of the pump casing, the flexible impeller vane straightens to produce vacuum, and the liquid is sucked into the pump, and as the impeller rotates, the liquid then reaches the discharge side from the suction side, and when the impeller vane comes into contact with the eccentric section of the pump casing, the working volume changes and the liquid is discharged out of the pump smoothly.

(5) Sliding vane pump

The rotor with radial groove is installed in the pump body with eccentric stator, the slide is located in the radial groove of the rotor, the slide can be two or more pieces, when the rotor rotates under the action of centrifugal force, the slide is thrown out from the rotor body, sliding along the inner surface of the stator. These slips and the stator constitute a sealed cavity with the eccentric increase in cavity gradually increase, continue to rotate, the cavity is reduced to zero, and filled in the rotor, the cavity between the slips liquid began to suck in from the suction area, and then pressed to the discharge area to complete the liquid transfer process.


The common features of various rotor pumps are as follows.

①No suction valve and discharge valve, their main working parts are the pump casing and rotor (such as gear, screw, cam, etc.).

②Compared with reciprocating pumps, the rotor makes rotary motion, no impact, higher speed, compact structure and smaller volume.

③Discharge pressure is generally higher, but lower than the reciprocating pump, the flow is smaller than the reciprocating pump, lower efficiency, generally only suitable for conveying small amounts of liquid, and mostly used as auxiliary equipment.

④Most of the rotor pump is dependent on its own transport of liquid lubrication, so it is generally suitable for the transport of lubricating and non-solid particles of liquid.

⑤The rotor pump is also intermittently discharging liquid, so the fluctuation of flow is larger than centrifugal pumps and smaller than reciprocating pumps, but can be seen as approximately uniform.

⑥When a liquid film exists on the rotor surface (conveying lubricious liquid), the pump will have self-priming capability.

Selection points

Centrifugal pumps account for about 80% of all pumps in industrial production, and rotor pumps account for about 10%. Therefore, users are generally more familiar with centrifugal pumps, but also more preferential. This often causes in some occasions not suitable for the use of centrifugal pumps in the choice of centrifugal pumps.

Generally speaking, for a variety of different viscosity of the liquid transport, rotor pumps have other pumps incomparable advantages, but in the liquid transport, not only the viscosity of the problem, and often accompanied by high temperature, high pressure and sometimes corrosive, or contain solid particles characteristics. For this reason, when selecting a rotor pump, the following requirements must be considered.

1) the flow of the transported liquid, the selected pump for the viscosity of the applicable range.

2) the occasion of the metering requirements, the selected pump in viscosity and other process conditions change performance stability.

3) the back pressure of the system, the selected pump pressure applicable range.

4) Suction performance, high viscosity when the pumping performance.

5)High temperature resistance, corrosion resistance, etc.

6) Simple structure, easy to disassemble, cleaning and maintenance, etc.

In addition to this, in the selection of pump type must also consider the nature of the transported liquid, for the lack of lubrication of the liquid, the pump is required to have a certain gap or make the contact surface is small, because under load to avoid excessive friction and wear, the lack of lubrication of the liquid can not be shaped into an oil film; for the liquid containing grinding solids, the selection should consider the transport of solid particles in suspension does not cause jamming or excessive wear; for With soft solid particles of liquid, the selection should consider the pump has a suitable gap for such solid particles, not resulting in particle damage; for shear stress-sensitive liquid, the selection should consider the pump has a gentle action, and make the liquid is not high local shear stress. Usually choose a lower speed of pump.


(1) Check the rotor pump and piping and the combination for looseness. Rotate the rotor pump by hand and try to see if the rotor pump is flexible.

(2) Add bearing lubrication oil to the bearing body, observe the oil level should be at the center line of the oil mark, the lubricant should be replaced or replenished in time.

(3) unscrew the pump body of the rotor pump water screw plug, fill the water (or slurry).

(4) Close the gate valve of the outlet pipe and export pressure gauge and import vacuum gauge.

(5)Start the motor and try to see if the motor steering is correct.

(6)Start the motor, when the rotor pump is running normally, open the outlet pressure gauge and the inlet vacuum pump, and gradually open the gate valve after it shows the proper pressure, and check the motor load at the same time.

(7) Try to control the flow and head of the rotor pump within the range indicated on the label to ensure that the rotor pump operates at the highest efficiency point in order to obtain the maximum energy saving effect.

(8) During the operation of the rotor pump, the bearing temperature should not exceed the ambient temperature of 35℃ and the maximum temperature should not exceed 80℃.

(9) If abnormal sound is found in the rotor pump, it should be stopped immediately to check the cause.

(10) When the rotor pump is to be stopped, close the gate valve and pressure gauge first, then stop the motor.

(11) Rotor pump in the first month of work, after 100 hours to replace the lubricant, after each 500 hours, change the oil once.

(12) Adjust the packing gland frequently to ensure that the drip inside the packing chamber is normal (to become a drip leak out).

(13) Regularly check the wear and tear of the shaft sleeve, and replace it in time after the wear and tear is large.

(14) rotor pump in the winter season, after parking, the pump body needs to be unscrewed lower water release screw to release the media net. Prevent freezing and cracking.

(15) rotor pump for a long time out of use, need to pump all disassembled, dry moisture, will rotating parts and combined with grease installed, proper storage.


 Precautions before starting.

Check whether the amount of oil in the gear box is normal, observe the transparent oil mark, the oil stock to half of the oil mark window is appropriate, the lubricant should be replaced regularly, in general, after 4000 hours of operation to replace all.

Open all the inlet and outlet valves of the pipeline before starting, when the medium flows into the cavity, no abnormality after turning the pump by hand, you can first point, confirm the pump steering and medium flow before starting the official operation, it is strictly prohibited to run empty pump. When the pump reaches the normal speed, the

Observe the pressure indicator of the pump.

When the pump installation position has suction range requirements, should be filled with material in the pump inlet pipe and pump cavity.

When the process requires heating or cooling of the medium, the heating or cooling device should be opened before the pump is turned on, half of the heating energy should be opened 10 minutes in advance, and then the pump should be turned on.

Mechanical seal pump equipped with cooling water, the cooling water must be turned on before starting, and to ensure that there is no disconnection after starting, otherwise the mechanical seal is damaged immediately.

Second, operation

1、 During the operation of the pump, you should pay attention to the motor power and pump operation, abnormalities should stop the pump to find the cause.

2、 The mechanical seal should be free of leakage and heat.

3、Pump with packing seal, allow 1~3 drops per minute, such as leakage increase slightly tighten the material ring can be, no need to disassemble.

4、 When using mechanical stepless transmission, gradually adjust the speed according to the digital display after starting the machine, it is strictly forbidden to rotate the speed regulating disk when stopping, otherwise it will damage the induction reducer.

5, the use of inverter speed regulation can use manual frequency regulation and automatic control of two methods.

6, often check the heat of the pump and motor, when the pump is in the water-cooled state, the bearing temperature rise is 40 ℃. When the pump is in the hot water insulation state, the bearing seat temperature is allowed to be 30℃ higher than the pump body temperature.

7, can not use the valve of the inlet pipeline to adjust the flow, to avoid cavitation and cause vibration of the pump.

8、When the pump is running, it is forbidden to close all the inlet and outlet valves.

Third, stop

1, stop the pump to close the import and export valves, easy to condense material discharge cleanup.

2, the pump after a long period of time out of use, before starting should first turn the coupling by hand, feel the resistance, but can turn at will and light and heavy uniform. And pay attention to identify whether there is friction sound and foreign matter in the pump.

3、When the pump and the gear motor are re-installed, check the coaxiality of the pump shaft and the motor shaft, and measure the outer circle of the coupling up, down, left and right piece position not more than 0.1mm, otherwise it will cause the pump vibration and affect the spindle life.