Polypropylene Cable Extrusion Homogeneity
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Solution Overview
Problem
Existing processes for manufacturing high voltage energy cables with polypropylene matrix and dielectric fluid coatings face challenges in achieving intimate and homogeneous admixing, maintaining low contamination, and ensuring industrially acceptable extrusion rates, due to limitations in screw extruders and filter-induced pressure drops.
Innovation Solution
A continuous process and apparatus using a compounder to intimately mix polypropylene matrix and dielectric fluid, followed by a volumetric pump to raise pressure, and a filter to remove contaminants, allowing the mixture to be extruded at a high and consistent rate through an extrusion head, with a cooling tube maintaining the coating layer's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a screw extruder is used to mix polypropylene matrix and dielectric fluid, then the extrusion process can be performed, but the admixing is not intimate and homogeneous enough for high voltage applications
Solution Approach 1:
The patent divides the mixing function from the extrusion function into separate units: a compounder for intimate mixing and an extruder for shaping and extrusion. This segmentation allows each unit to be optimized for its specific function, achieving both homogeneous mixing and high extrusion rates.
Solution Approach 2:
The patent introduces an intermediary device (the compounder) between material preparation and extrusion. This compounder pre-mixes the polypropylene matrix and dielectric fluid to achieve intimate homogeneity before the mixture enters the extruder, ensuring high-quality mixing without compromising extrusion productivity.
2Reliability
If a filter is installed to remove contaminants and maintain dielectric strength, then cable safety is improved, but pressure drop reduces extrusion rate
Solution Approach 1:
The patent performs preliminary mixing in the compounder before filtration and extrusion. By achieving intimate homogeneity in advance, the mixture flows more smoothly through the filter, reducing pressure drop and maintaining higher extrusion rates while still ensuring contaminant removal.
Solution Approach 2:
The patent optimizes process parameters including temperature, pressure, and flow rate across different stages. By carefully controlling these parameters, the system maintains low viscosity and high flowability through the filter, minimizing pressure drop while ensuring effective contaminant removal for high dielectric strength.
3Reliability
If crosslinked polymers are used for polymeric layers, then mechanical and electrical properties under high temperature are improved, but a long degassing period is required increasing production time
Solution Approach 1:
The patent uses thermoplastic polypropylene-based materials instead of crosslinked polymers. These thermoplastic materials do not require degassing and can be quickly processed and reprocessed if needed, significantly reducing production time while still providing adequate performance for high voltage cable applications.
Solution Approach 2:
The patent changes the material class from crosslinked polymers to thermoplastic polymers with specific characteristics (polypropylene matrix with dielectric fluid). This parameter change eliminates the need for degassing while maintaining suitable mechanical and electrical properties through careful material formulation and processing parameter optimization.
4Ease of operation
If thermoplastic materials with low crystallinity are used to provide flexibility, then cable flexibility is improved, but mechanical properties and thermopressure resistance may be impaired
Solution Approach 1:
The patent uses a composite material system consisting of polypropylene matrix intimately admixed with dielectric fluid. This composite structure provides both flexibility (through the thermoplastic polypropylene with low crystallinity) and enhanced mechanical properties (through the composite formulation and intimate mixing), achieving a balance between flexibility and strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient and continuous production of high voltage cables with improved homogeneity and reduced contamination, achieving extrusion rates up to three times faster than conventional methods while maintaining the dielectric strength and mechanical properties required for high voltage applications.
Implementation Method 1
The pellets of insulation material are worked under heat and pressure in an extruder, such as a screw extruder
Implementation Method 2
a volumetric pump that pushes the mixture through a filter removing possible contaminants up to an extrusion head
Implementation Method 3
a filter removing possible contaminants up to an extrusion head
Implementation Method 4
the filtered insulation material is then received by a pump, such as a gear pump, which supplies the filtered insulation material to a mixer, such as a static mixer, from which the material exits into the cross-head of a conventional extruder which applies the material to the cable core
Implementation Method 5
The pellets of insulation material are worked under heat and pressure in an extruder
Implementation Method 6
with a cooling tube maintaining the coating layer's integrity
Data Source
Figure 1~2
Figure 3
AI summary
It is disclosed a process for manufacturing an energy cable comprising at least one conductor and at least one polymeric coating layer. The process comprises: compounding a polypropylene matrix and a dielectric fluid to obtain a polymeric mixture; raising flow pressure of the polymeric mixture; filtering the polymeric mixture; causing the polymeric mixture to flow through an extrusion head to produce the coating layer on the conductor; and cooling the cable.