German WERUCON pump WERUCON model WERUCON price

WERUCON pumps are rotary pumps that rely on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquids or increase their pressure. They consist of two gears, a pump body, and front and rear covers, forming two enclosed spaces. When the gears rotate, the volume on the disengaging side increases from small to large, creating a vacuum that draws in liquid, while the volume on the meshing side decreases from large to small, forcing the liquid into the pipeline. The suction chamber and discharge chamber are separated by the meshing line of the two gears. The pressure at the discharge port of a gear pump depends entirely on the resistance at the pump outlet.

WERUCON pump operating principle

The concept of a gear pump is very simple. Its most basic form consists of two gears of identical size meshing and rotating within a closely fitted housing. The interior of this housing resembles a "8" shape, with the two gears installed inside; the outer diameter of the gears and their sides fit closely with the housing. Material from the extruder enters between the two gears at the suction inlet, filling this space. As the teeth rotate, the material moves along the housing and is finally discharged when the teeth mesh. Gear pumps are also known as positive displacement devices. Like a piston in a cylinder, when one tooth enters the fluid space of another, the liquid cannot occupy the same space as the tooth simultaneously because liquids are incompressible; thus, the liquid is mechanically squeezed out. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, providing a continuous discharge volume at the pump outlet. With each revolution of the pump, the discharged volume remains the same. As the drive shaft rotates uninterrupted, the pump discharges fluid without interruption. The pump's flow rate is directly related to its rotational speed. In practice, there is a small amount of fluid loss within the pump because this fluid is used to lubricate the bearings and the sides of the gears. Furthermore, the pump body cannot have a gap-free fit, so it is impossible for the fluid to exit the outlet 100%. Therefore, a small amount of fluid loss is inevitable, preventing the pump's operational efficiency from reaching 100%. However, the pump can still operate well, achieving an efficiency of 93% to 98% for most extruded materials. This type of pump is not significantly affected by changes in fluid viscosity or density during the process. If there is a damper, such as a filter screen or restrictor placed on the discharge side, the pump will push the fluid through them. If this damper changes during operation—for example, if the filter becomes dirty or clogged, or if the back pressure of the restrictor increases—the pump will maintain a constant flow rate until the mechanical limit of the weakest component in the system is reached (a torque limiter is usually installed). There is actually a limit to the rotational speed of a pump, which mainly depends on the process fluid. If oil is being transported, the pump can rotate at high speeds, but this limit increases significantly when the fluid is a high-viscosity polymer melt. It is crucial to fill the space between the two teeth on the suction inlet side with high-viscosity fluid; if this space is not fully filled, the pump cannot discharge an accurate flow rate. Therefore, the PV value (pressure × flow velocity) is another limiting factor and a process variable. Due to these limitations, gear pump manufacturers offer a range of products with different specifications and displacements (volume discharged per revolution). These pumps are matched to specific application processes to optimize system capacity and price.

WERUCON pump drive unit

Gear pumps are driven by an independent motor, which effectively blocks upstream pressure pulsations and flow fluctuations. Pressure pulsations at the gear pump outlet can be controlled within 1%. Using a gear pump on an extrusion production line can increase the flow output speed and reduce shear and residence time of the material in the extruder. External meshing gear pumps are the most widely used type; generally, the term "gear pump" refers to external meshing gear pumps. Their structure is shown in Figure 5-14, mainly consisting of a driving gear, driven gear, pump body, pump cover, and safety valve. The sealed space formed by the pump body, pump cover, and gears constitutes the working chamber of the gear pump. The shafts of the two gears are mounted in bearing holes on the two pump covers. The driving gear shaft extends out of the pump body and is rotated by the motor. External meshing gear pumps feature a simple structure, light weight, low cost, reliable operation, and wide application range. During operation, the driving gear rotates with the motor and drives the driven gear to rotate. As the meshing teeth on the suction chamber side gradually separate, the volume of the suction chamber increases, pressure decreases, and liquid from the suction pipe is drawn into the pump. The sucked liquid is pushed by the gears in two paths within the tooth grooves to the discharge chamber. After entering the discharge chamber, the liquid is squeezed by the continuous meshing of the gear teeth and enters the discharge pipe. As the driving and driven gears rotate continuously, the pump continuously sucks in and discharges liquid. A safety valve is installed on the pump body. When the discharge pressure exceeds the specified pressure, the transported liquid automatically opens the safety valve, allowing high-pressure liquid to return to the suction pipe. Internal meshing gear pumps consist of a pair of mutually meshing internal gears, a crescent-shaped piece between them, and a pump shell. The crescent-shaped piece separates the suction chamber from the discharge chamber. When the driving gear rotates, a partial vacuum forms where the gears disengage, drawing liquid into the pump to fill the spaces between the teeth in the suction chamber. The liquid then enters the discharge chamber in two paths along the inner and outer sides of the crescent-shaped piece. Where the teeth enter meshing, the liquid existing between the teeth is squeezed and sent into the discharge pipe. In addition to features such as self-priming capability and flow rate independence from discharge pressure, gear pumps have no suction or discharge valves on the pump shell, offering simple structure, uniform flow, and reliable operation. However, they have low efficiency, high noise and vibration, and are prone to wear. They are mainly used to transport various non-corrosive, solid-particle-free oils with lubricating properties, typically at temperatures not exceeding 70 °C, such as lubricating oil and edible vegetable oil. The general flow range is 0.045 to 30ms/h, the pressure range is 0.7 to 20MPa, and the operating speed is 1200 to 4000r/min.

WERUCON pump maintenance

1) Maintenance after wear of the gear pump shaft: Shaft wear in gear pumps is mainly caused by friction between the ends of the shaft and the supporting needle rollers, resulting in a reduced shaft diameter. For slight wear, the shaft diameter can be increased by plating with hard chrome to repair it. If the shaft wear is severe, it should be remanufactured using 45 steel or 40cr steel. After rough and finish turning of the shaft blank, the bearing areas must undergo heat treatment to achieve a hardness of hrc60-65. Then, grinding is performed to ensure the surface roughness ra of the bearing fit area is no greater than 0.32μm; the permissible deviation for roundness and cylindricity of the shaft is 0.005mm; the gear fit area follows h7/h6, and the surface roughness ra should be no greater than 0.63μm. 2) Maintenance after wear of the gear pump body: Wear on the inner surface of the pump body occurs mainly on the arc-shaped working surface in the oil suction section. For slight wear, it can be repaired with an oil stone to remove burrs before use. The pump body is cast from iron. If severe wear occurs, the part should be replaced. If the end faces of the gears inside the pump are repaired by grinding, the width dimension of the pump body must also be adjusted to equal the amount removed from the gear ends. The re-machined end faces of the pump body must meet the technical requirements shown in Figure 3. 3) Maintenance after wear of the gear pump end covers: The end covers of gear pumps are made of cast iron. Slight wear can be ground flat on a surface plate, while severe wear should be ground flat on a surface grinding machine. The planar contact between the repaired end covers and the pump body connection surface should be no less than 85%. The permissible deviations for flatness, perpendicularity of the end face to the hole centerline, parallelism between the two end faces, and parallelism between the centerlines of the two shaft holes are all 0.01mm. The surface roughness ra after grinding should be no greater than 1 5μm. 4) Maintenance and replacement of needle roller bearings in gear pumps: After repairing pump components, the needle rollers in the bearings should be replaced. Requirements for needle rollers are: the dimensional error of the diameter of all needle rollers should not exceed 0.003mm, the length tolerance is 0.1mm, and the fit clearance with the shaft should be around 0.01mm. During assembly, the bearing housing must be filled with the required number of needle rollers, arranged parallel to each other.

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