Although melt gear pumps possess numerous advantages in wire and cable manufacturing and other industrial applications, they also have some disadvantages or limitations. Below is a detailed analysis of the disadvantages or limitations of melt gear pumps:
Limited Rotational Speed
For polymer melts with high viscosity, the rotational speed of melt gear pumps may be limited. At high speeds, the shear force of the melt within the pump increases, potentially leading to material degradation or excessive heat generation. Therefore, to meet specific process requirements, the rotational speed may need to be reduced, thereby limiting the pump's flow output.
Gear Type Selection
In high-temperature melt gear pumps, the choice of gear type is a crucial factor. Different types of gears exhibit different performances and applicable ranges. For example, straight gears have greater strength but slightly higher pulsation compared to helical gears; helical gears have lower pulsation but inferior compression resistance compared to straight gears; herringbone gears combine the advantages of straight and helical gears but generate higher shear forces, which can easily cause thermal degradation of materials. Therefore, when selecting the gear type, it is necessary to weigh the material characteristics and process requirements.
Specific Material Requirements
Melt gear pumps have certain requirements for materials. For example, materials containing large particles, abrasive fillers, or reinforcing agents cannot be processed using extruders equipped with melt gear pumps, as the filler particles can easily form plugs that cannot pass through the gear tooth clearance of the melt gear pump. Plugging and abrasive wear on the teeth can quickly damage the melt gear pump. Additionally, finely dispersed mineral fillers may, when incompatible with plastics, fail to undergo shear in high-shear areas and gradually form plugs that can damage the melt gear pump.
High Maintenance Costs
The relatively complex structure of melt gear pumps results in higher manufacturing costs. Meanwhile, installation, maintenance, and repairs may also require a higher level of technical expertise and more time and effort. For instance, wear on gears, damage to bearings, and failure of seals can all lead to performance degradation or failure of the pump, necessitating regular maintenance and replacement.
Limited by Operating Environment
The performance of melt gear pumps may be affected by the operating environment. For example, high temperatures, high pressures, or corrosive environments can adversely impact the pump's performance. Therefore, when selecting and using melt gear pumps, it is necessary to consider the impact of the operating environment on the pump and take corresponding protective measures.
In summary, although melt gear pumps have many advantages, they also have some disadvantages or limitations. When selecting and using them, it is necessary to comprehensively consider specific process requirements, material characteristics, and the operating environment to ensure that the pump's performance and stability meet production needs.
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