Melt pumps and screw pumps exhibit significant differences in both structure and functionality. Below are the specific distinctions between the two:
I. Working Principle
Melt Pump: A melt pump is a positive displacement transfer device. Its working principle relies on the change in working volume caused by the intermeshing of the driving and driven gears to convey the melt. When the gears rotate in the prescribed direction, the melt enters the tooth spaces of the two gears in the feed area. As the gears rotate, the melt is carried into the conveying area, and then the gears mesh again, extruding the melt out of the discharge area and pressing it into the outlet piping.
Screw Pump: The working principle of a screw pump involves conveying liquid through the rotation of the screw. When the driving screw rotates, the enclosed volume of the screw pump increases in pressure under the compression of the screw threads and transfers axially. Since the screws rotate at the same speed, the flow rate of the liquid discharged is also uniform.
II. Structural Characteristics
Melt Pump: A melt pump primarily consists of a pump casing, driving gear, driven gear, sliding bearing, front and rear end plates, gland sealing, etc. Its structure is compact, with the tooth profiles of the gears, pump body, and side cover plates forming the feed area, conveying area, and discharge area of the pump.
Screw Pump: A screw pump, on the other hand, mainly consists of an outer rotor, inner rotor, and viscosity compensator (alternatively, the main components are the rotor and stator). Its structure is relatively complex, but it offers high sealing reliability, often employing a combination of piston sealing and mechanical sealing.
III. Performance and Applications
Melt Pump:
Melt pumps are primarily used for conveying, pressurizing, and metering high-temperature, high-viscosity polymer melts.
They feature stable flow rate, high pressure, precise control, and high efficiency.
They are widely used in the extrusion molding of plastics, resins, and rubber products, such as granulation, film, tubing, sheet, and plate industries.
Screw Pump:
Screw pumps also exhibit broad applicability, particularly suitable for conveying thick liquids, high-viscosity media, and media containing particles or fibers.
They have a wide range of flow rate variations and broad adaptability to temperature, viscosity, and pressure.
However, screw pumps are relatively large in size, require more space, and have higher costs.
IV. Maintenance and Servicing
Melt Pump: Melt pumps require regular maintenance, including checking the pump outlet pressure, tightening bolts, monitoring bearing and casing temperatures, shaft sealing conditions, and power supply.
Screw Pump: Screw pumps also require regular maintenance and servicing, but the specific maintenance content may vary depending on the pump type and working environment.
In summary, melt gear pumps and screw pumps exhibit significant differences in working principle, structural characteristics, performance and applications, as well as maintenance and servicing. When selecting and using them, comprehensive consideration should be given based on the specific working environment and requirements.
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