There are many different types of rotor pumps, for example: rotary lobe pumps, gear pumps, screw pumps, rotary piston pumps, sliding vane pumps and Roots pumps are the most common types of lobe pumps. The following is a detailed introduction.
The rotary lobe pump is a self-priming volumetric pump in which two rotors mounted on two shafts are driven by synchronous gears to rotate against each other. The typical configuration of the rotary lobe pump is a double-supported lobe pump with its own reduction gear, but depending on the actual working conditions a single-supported lobe pump is also available. The rotor is a highly efficient three-lobe spiral rotor with a metal core, which can be covered with different rubber properties depending on the material, such as NBR, EPDM, Viton, SBR, etc.
Rotary lobe pumps have the advantages of strong self-priming capacity, good corrosion resistance, high standardisation and versatility. It can be widely used in the fields of oil and chemical industry, environmental protection, slurry transport, etc., urban flooding and drainage, drought relief, emergency rescue and drainage and other municipal drainage solutions.
II. Gear pumps
There is a pair of meshed gears in the gear pump casing, one of which is the active gear and the other is the driven gear, driven by the engagement of the active gear to rotate. A small gap is left between the gears and the pump casing. When the gears rotate in a certain direction, in the left side of the suction cavity where the gear teeth are gradually disengaged, the closed volume between the teeth increases, forming a local vacuum, and the liquid is sucked into the suction chamber under the action of differential pressure, and as the gears rotate, the liquid is pushed forward by the gears in two ways between the gears and the pump casing, and sent to the right side of the discharge cavity, where the two gears gradually engage, the volume decreases, and the liquid between the gears is squeezed to the discharge port.
Gear pumps generally come with their own safety valve, which opens when the discharge pressure is too high and returns the high pressure liquid to the suction port. Gear pumps are stable and structurally reliable, the disadvantage is that the teeth of the wheels are easily worn.
Gear pumps are often used for conveying non-corrosive viscous media such as oil, but not for conveying liquids containing solid particles and liquids with high volatility and low flash point.
III. Screw pumps
The screw pump is also a type of volumetric lobe pump. During operation, the screw rotates and engages at the same time, so that the liquid is driven by the spiral groove on one or several screws and discharged in the axial direction.
The main advantages of the screw pump are its compact structure, the basic lack of pulsation in flow and pressure, smooth operation, long life, high efficiency and a wide range of liquid types and viscosities. The disadvantages are the high manufacturing and processing requirements and the sensitivity of the operating characteristics to changes in viscosity.
IV. Rotary piston pumps
The curved rotor wings of a rotary piston pump rotate in a circular flow path inside the pump casing. The volume of the pump chamber increases at the inlet, creating a vacuum that draws the liquid into the pump; the liquid is conveyed to the outlet by rotating the rotor wings; at the outlet the rotor engages, the volume of the pump chamber decreases and the liquid is discharged.
Rotating piston pumps with non-abrasive rotors for smaller gaps and higher efficiency; high self-priming capacity; low shear; high outlet pressure; can handle high solids content; easy to dismantle for cleaning; some have CIP (Cleaning In Line) capability.
V. Sliding vane pumps
The rotor of a sliding vane pump is cylindrical and has a radial groove in which the sliding vane is placed, the sliding vane is generally 6 or more pieces and the sliding vane can slide freely in the groove.
The pump rotor is mounted eccentrically in the pump casing, with the rotor surface forming a crescent-shaped space with the inner surface of the pump casing. When the rotor is rotating, the sliding discs are pressed against the inner cavity of the pump by centrifugal force or spring force (the spring is placed at the bottom of the groove). In the first half turn of the rotor, the space surrounded by two adjacent slips gradually increases, forming a vacuum and drawing in the liquid, while in the second half turn of the rotor, this space gradually decreases, squeezing the liquid into the discharge pipe.
VI. Roots pumps
The Roots pump is also a positive displacement lobe pump. Two figure-of-eight rotors rotate in reverse synchronisation by means of a gear transmission, thereby discharging the liquid between them and the pump body. Roots pumps can be divided into two-lobe Roots pumps and multi-lobe Roots pumps. There is no contact between the rotors and between the rotor and the pump body, with a clearance of 0.1-1 mm depending on the size of the pump, which allows the pump to run smoothly at high speeds.