Analysis of the Overall Structure and Structural Characteristics of Polymer Melt Gear Pumps

The structural characteristics of polymer melt gear pumps primarily encompass the following aspects:

I. Overall Structure

Compact Design: It is designed to integrate the main working components within a small space, occupying minimal area and facilitating installation and layout. It can be flexibly applied in various production environments, such as being directly installed underneath reactors or within pipelines.

Modular Design: It comprises multiple modules, including the pump body, drive system, sealing devices, etc. These modules cooperate while remaining relatively independent, facilitating manufacturing, assembly, maintenance, and replacement of components, which reduces maintenance costs and time.

II. Gears and Bearings

High-Precision Gears: Often employing involute helical gears or herringbone gears. Helical gears increase the contact ratio of meshing, providing continuous and smooth extrusion of materials, reducing pressure fluctuations. Their self-cleaning action during rotation keeps the tooth roots clean, preventing material deposition and decomposition. However, the helix angle should not be too large to avoid generating significant axial forces. Herringbone gears, on the other hand, offer smooth extrusion and balance axial forces, but they can cause material retention at the tooth roots and have higher processing costs.

High-Quality Bearings: Mostly utilizing "d"-type sliding bearings, which feature a simple structure, easy installation, low operational noise, and good impact resistance. The polymer itself can serve as a lubricant, forming a good dynamic lubricating film to withstand high loads on the gear shafts.

Integrated Gears and Shafts: Manufacturing gears and shafts as a single unit enhances rigidity and reliability, ensuring stable operation during the transport of materials at high temperatures, pressures, and viscosities.

III. Pump Body and Flow Channels

Optimized Flow Channel Design: The internal flow channels are smooth and devoid of dead spots, reducing resistance during melt transport, minimizing shear degradation of polymer melts, improving product quality, and preventing material residue, thereby ensuring material purity and quality.

Large Suction Port Design: For gear pumps transporting high-viscosity materials, the suction port diameter is generally larger. Sometimes, a diffused suction port is used to expand the volume of the low-pressure zone, reducing the inlet liquid velocity and suction resistance of the pump, which in turn decreases the radial force acting on the shaft neck and bearings, extending their lifespan.

IV. Sealing Devices

Combination of Sealing Methods: Common sealing methods include mechanical seals, gland packing seals, spiral seals, etc. Often, combined seals, such as melt dynamic seals + gland packing seals or mechanical seals + gland packing seals, are used to effectively prevent leakage and ensure sealing performance under high temperatures, pressures, and viscosities.

Self-Lubricating Seal Structure: Some melt gear pumps utilize special self-lubricating structures for shaft seals, such as processing spiral flow channels on the non-load-bearing surface of the bearing inner wall. Leveraging the spiral action and pressure difference between the bearing ends, some melt lubricates and cools the shaft neck and bearing, forming a circulation system, reducing wear on the bush and shaft, and extending equipment lifespan.

V. Drive and Regulation Systems

Reliable Drive System: Generally comprising a motor, reducer, and universal joint coupling, it provides stable power to the gear pump, ensuring its normal operation under harsh conditions such as high temperatures and pressures.

Strong Adjustability: As a volumetric forced delivery pump, it can adjust the output flow by altering the pump's rotational speed. Variable frequency speed regulation is recommended, enabling near-linear flow output of the gear pump, better meeting the needs of different production processes.

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