Raw Material Preparation Systems for Cable Compound Production

The quality of PVC compounds used in cable production depends directly on the stability of the dry blend preparation process. PVC resin, calcite or other mineral fillers, stabilizers, oils, and micro-additives must be incorporated into the process in the correct ratios and in the correct order to achieve a homogeneous mixture and feed it into the extrusion lines in a controlled manner. VOLDE develops engineering solutions covering the entire process chain — from raw material intake to the mixer line and extruder feeding — for PVC dry blend production facilities serving the cable industry. High-capacity, repeatable compound production is achieved through silos, pneumatic conveying lines, batch dosing systems, micro-additive dosing, hot/cold mixer feeding systems, and SCADA-controlled automation infrastructure

| Bringing PVC Resin, Calcite, and Recycled Raw Materials into the Process

The main raw materials used in cable compound facilities generally arrive at the plant in different packaging and forms. PVC resin is mostly stored in silos, while calcite and mineral fillers can be supplied as big bags or in bulk. Recycled materials are often incorporated into the system in ground or crushed form.

VOLDE raw material intake systems combine these different feeding methods within a single integrated process.

Main equipment:

• PVC resin silos
• Calcite and mineral filler silos
• Big-bag discharge stations
• Filtered bag dumping systems
• Recycled material bins

Raw materials are generally conveyed to upper elevations along the process line via vacuum pneumatic conveying systems. Special line designs that prevent line blockage and segregation are applied for conveying fine PVC powders.

| Dosing of PVC, Calcite, and Regrind

The accuracy of the recipe in dry blend production depends on the precise weighing of the main raw materials. In PVC compound production, dosing PVC resin, calcite, and recycled materials in the correct ratios in particular directly affects product performance.

VOLDE batch dosing systems, with SCADA-controlled recipe management, ensure that raw materials are automatically weighed.

The system structure is generally configured as follows:

• PVC resin weighing line
• Calcite / mineral filler weighing line
• Regrind or recycled material weighing line
• Weighed vacuum cyclone or weighing bins

Once weighing is complete, the raw materials are transferred to the mixer feed bin via the pneumatic conveying system.

Thanks to the SCADA system:

• Recipe management is carried out centrally
• Production data is recorded
• Operator errors are minimized
• Product repeatability is ensured

| Automatic Micro-Dosing of Stabilizers, Oils, and Additives

The additive materials used in cable compound formulations are generally materials that must be dosed in low quantities but with high precision.

• Heat stabilizers
• Stearates
• Pigments
• Process oils and plasticizers
• Flow regulators

VOLDE micro-dosing systems ensure that these additives are weighed automatically and with high precision.

• Filtered bag dumping bins
• Automatic micro-dosing modules
• Local filtration for dust control
• High speed and precision via a dual-weighing principle

For oil and liquid additives, the system can operate integrated with weighed liquid dosing units. This way, powder and liquid additives are incorporated into the process in the correct order at the mixer feeding point.

| Hot/Cold Mixer Lines and Transfer of the Mixture to Intermediate Silos

In PVC compound production, raw materials are first mixed in a high-speed hot mixer. At this stage, oils and additives are absorbed onto the surface of the PVC particles. The mixture is then stabilized in the cold mixer by lowering its temperature.

VOLDE mixer feeding systems operate integrated with:

• Automatic mixer filling
• Mixer feed bins
• Recipe-controlled loading
• Process automation.

The dry blend mixture from the mixer outlet is generally transferred to intermediate silos via a dense-phase pneumatic conveying system.

This method provides, particularly in cable compound facilities:

• Reliable transfer over long distances
• Prevention of segregation
• The advantages of an enclosed, clean process

| Feeding Material from Dry Blend Silos to Extruder Lines

The dry blend mixture is generally held in intermediate storage silos and fed from there to the cable compound extruders.

VOLDE extruder feeding systems offer different solutions:

• Vacuum conveyor systems
• Screw conveyors
• Gravimetric extruder feeders

Especially for fine PVC powders and cable compound facilities requiring high capacity, VOLDE's pneumatic conveying solutions provide stable, uninterrupted material transfer over long distances. The gravimetric feeders used at the extruder inlet continuously measure process flow rate, ensuring stable feeding in cable compound production.