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Duplomatic pump is a rotary pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquid or increase its pressure. It consists 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 the 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 the gear pump depends entirely on the resistance at the pump outlet.

Duplomatic pump structural features

1) Simple structure and low cost; 2) Low operational requirements and wide application; 3) The end covers and the spaces between the gear teeth form many fixed sealed working chambers, so it can only be used as a positive displacement pump. The gears adopt the advanced technology of the nineteen nineties internationally--double circular arc sine curve tooth profile. Compared with involute gears, its most prominent advantage is that there is no relative sliding on the tooth flank during gear meshing, so there is no wear on the tooth surface, smooth operation, no fluid trapping, low noise, long service life and high efficiency. This pump breaks away from the constraints of traditional design, bringing gear pumps into a new realm in terms of design, production and use. The pump is equipped with a differential pressure safety valve for overload protection. The full return pressure of the safety valve is 1.5 times the rated discharge pressure of the pump. It can also be adjusted according to actual needs within the allowable discharge pressure range. However, this safety valve cannot be used as a pressure reducing valve for long-term operation; a pressure reducing valve can be installed separately if needed. The shaft end seal of this pump is designed in two forms: one is mechanical seal and the other is packing seal, which can be determined according to specific operating conditions and user requirements.

Duplomatic pump drive unit

The gear pump is driven by an independent motor, which can effectively block upstream pressure pulsations and flow fluctuations. The pressure pulsation 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 the shear and residence time of materials in the extruder. External meshing gear pumps are the most widely used type of gear pump; generally, when referring to gear pumps, it usually means external meshing gear pumps. Its structure is shown in Figure 5-14, mainly consisting of driving gear, driven gear, pump body, pump cover, and safety valve. The sealed space formed by the pump body, pump cover, and gears is the working chamber of the gear pump. The shafts of the two gears are respectively installed in the bearing holes on the two pump covers, with the driving gear shaft extending out of the pump body and rotated by the motor. External meshing gear pumps have simple structures, light weight, low cost, reliable operation, and wide applications. When the gear pump is working, the driving gear rotates with the motor and drives the driven gear to rotate. When the meshing teeth on the suction side gradually separate, the volume of the suction chamber increases, the pressure decreases, and the liquid in the suction pipe is drawn into the pump; the sucked liquid is pushed by the gears in the tooth slots into the discharge chamber in two paths. After entering the discharge chamber, due to the continuous meshing of the two gears, the liquid is squeezed and enters the discharge pipe from the discharge chamber. As the driving gear and driven gear continuously rotate, the pump can continuously suck in and discharge liquid. A safety valve is installed on the pump body; when the discharge pressure exceeds the specified pressure, the transported liquid can automatically push open 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 function of the crescent-shaped piece is to separate the suction chamber and the discharge chamber. When the driving gear rotates, a partial vacuum is formed where the gears disengage, drawing liquid into the pump to fill the spaces between the teeth in the suction chamber, then entering the discharge chamber along the inner and outer sides of the crescent-shaped piece in two paths. Where the teeth enter meshing, the liquid existing between the teeth is squeezed and sent into the discharge pipe. In addition to having self-priming capability and flow rate independent of discharge pressure, gear pumps have no suction or discharge valves on the pump shell, featuring simple structure, uniform flow, and reliable operation, but they have low efficiency, high noise and vibration, and are prone to wear. They are mainly used to transport various oils that are non-corrosive, free of solid particles, and have lubricating properties, with temperatures generally not exceeding 70 ℃, such as lubricating oil and edible vegetable oil. The general flow range is 0.045～30ms/h, pressure range is 0.7—20MPa, and operating speed is 1200—4000r/min.

Duplomatic pump trapped oil phenomenon

For stable operation of the gear pump, the overlap ratio of gear meshing must be greater than 1, meaning there are always two pairs of gears meshing simultaneously, trapping some oil between the closed volumes formed by these two pairs of teeth. This closed volume initially decreases gradually with the rotation of the gears and then increases. The reduction in the closed volume causes the trapped oil to be compressed, generating high pressure and squeezing out through gaps, leading to oil heating and additional load on components; meanwhile, the increase in closed volume creates a local vacuum, causing dissolved gases in the oil to separate and produce cavitation. These phenomena result in strong vibrations and noise, known as the trapped oil phenomenon in gear pumps. 1) Hazards: Large radial unbalanced forces can cause shaft bending, contact between tooth tips and the housing, accelerate bearing wear, and reduce bearing lifespan. 2) Elimination method: To eliminate trapped oil, relief grooves are typically opened on both side covers, allowing the closed volume to communicate with the pressure oil chamber via the left relief groove when decreasing, and with the suction oil chamber via the right relief groove when increasing.

Weidou Intelligent Technology specializes in selling German Duplomatic gear pumps, Duplomatic gear pumps, Duplomatic diaphragm pumps, Duplomatic centrifugal pumps, Duplomatic piston pumps, Duplomatic vacuum pumps, Duplomatic screw pumps, Duplomatic submersible pumps, Duplomatic peristaltic pumps, Duplomatic lubrication pumps, Duplomatic vane pumps, Duplomatic metering pumps, Duplomatic hand pumps, Duplomatic drum pumps, Duplomatic lobe pumps, Duplomatic booster pumps, Duplomatic liquid pumps, Duplomatic air pumps, all originally imported from Germany. Welcome customers to inquire and order.