Plastic Storage Solution

Table of Contents:

• Plastic storage: the first step in the process
• Anticipating the Technical and Environmental Challenges of Plastic Storage
• The Risks Associated with Improperly Organized Plastic Storage
• Toward an Integrated Approach to Plastic Storage
• TIM Solutions for Integrated Plastic Storage
• From plastic storage to comprehensive process architecture

Plastic storage: the first step in the process

Before being dried, metered, mixed, or injected, the material must be stored under conditions compatible with its physical characteristics. Virgin pellets, in-house regrind, mineral fillers, and moisture-sensitive additives do not all require the same treatment.

Improperly sized storage can lead to compaction, internal segregation, or variations in moisture content. These issues often remain undetected until the material is removed. It is only then that discrepancies become apparent—sometimes in the mix, and sometimes directly at the press.

Viewing plastic storage as an active part of the process helps prevent these delayed effects.

Anticipating the Technical and Environmental Challenges of Plastic Storage

An efficient plastic storage system involves more than just storage capacity in cubic meters. It must take into account the actual behavior of the products, environmental conditions, and the site’s safety requirements. These factors require both technical expertise in managing the flow of materials and a structured QHSE approach.

Adapt storage to the physical characteristics of the materials

Plastic resins and fillers differ in terms of their stability in silos or hoppers. Some granular materials flow easily, while fine powders or irregularly shaped particles may compact or segregate.

The stability of the storage depends in part on the bulk density, which determines the pressure on the walls and the rate of extraction. Particle size influences segregation between fine and coarse fractions.

The silo or hopper is designed based on the product’s behavior. The geometry, the angle of the walls, and the discharge method determine the consistency of the downstream flow.

Controlling Dust Emissions and Associated Risks

Storing fine powders or mineral fillers generates particles during filling and emptying. This dust compromises workshop cleanliness and can increase the risk of explosions.

Closed, airtight systems limit these emissions. Filters or filter bags integrated into silos and hoppers capture airborne particles. When necessary, ATEX-certified equipment is integrated into silos and hoppers for zones classified as 20 (continuous dusty indoor environment), 21 (occasional dust), and 22 (rare and non-persistent dust). These devices reduce the risk of ignition of explosive atmospheres formed by combustible dusts derived from mineral powders, ground granules, or filled formulations.

Monitor humidity and room temperature

Certain resins, particularly polyamides and some polyesters, are especially sensitive to moisture. After drying, moisture absorption can impair their mechanical properties or the surface quality of the injection-molded parts.

The warehouse must therefore minimize these re-picks by:

• an appropriate enclosure that protects the material from the ambient air;
• control of incoming air through dehumidification when necessary;
• Careful management of holding times for products that have already been dried.

Ambient temperature is also a parameter that must be monitored. Exposure to heat sources or significant temperature fluctuations can cause condensation or alter the product’s behavior during extraction.

Reducing physical strain and improving workplace ergonomics

Beyond the technical aspects, the storage of plastic directly affects working conditions. Repeated handling of bags or containers increases physical strain and the risk of musculoskeletal disorders.

Prioritizing bulk storage solutions that are suited to the site’s material-handling capabilities helps minimize these handling operations. An ergonomic workstation design that facilitates loading and unloading operations helps ensure safety and improve the quality of life at work.

Overall, this approach to storage goes beyond simple volume management. It aims to ensure stability, security, and compliance, while supporting the overall performance of the process.

The Risks Associated with Improperly Organized Plastic Storage

Improperly sized storage does not always cause an immediate failure. It introduces gradual imbalances that affect the process. Irregularities in extraction, variations in composition, and losses in traceability accumulate.

Arches, bridges, and partial flows

When material compacts under its own weight or exhibits high internal cohesion, it can form a arch above the outlet of the silo or hopper. This causes the flow to become irregular or even to temporarily stop. The result is an increase in micro-stops caused by bridging and repeated operator interventions.

In other cases, a flow channel forms: only a central column flows downward, while the areas on the sides remain stationary. Inventory turnover is no longer uniform, and traceability is compromised when batches are not clearly identified or when old residues remain in certain areas.

Segregation and Imbalances in Composition

In the case of mixtures of granules and powders, or products with different densities, storage can exacerbate segregation. Fine particles migrate to certain areas, while heavier particles settle to the bottom. The extracted flow no longer exactly matches the original formulation.

This imbalance can result in variations in color, discrepancies in mechanical properties, or instability in downstream processing. The presses and extruders then operate with material whose actual composition fluctuates slightly from one cycle to the next. The operator compensates, adjusts, and corrects—without always realizing that the root of the problem lies upstream, in the storage process.

Unstable production rates and downstream disruptions

In an industrial setting, consistent flow is critical to performance. When the flow from storage fluctuates erratically, the transfer becomes unstable. The metering devices receive an irregular flow. Downstream equipment must accommodate these fluctuations.

An occasional shortage of material can cause the machine to slow down. A sudden overload can disrupt the metering process or cause pressure fluctuations. These repeated fluctuations compromise the stability of the machine cycles and reduce the synthetic yield over time.

Flow stability, therefore, does not depend solely on active equipment. It begins with the way the material is stored and extracted.

The Economic Challenges of Plastic Storage

The cost of materials often accounts for the largest portion of the unit cost. Poorly organized inventory management can lead to indirect overconsumption. To compensate for a temporary shortage, safety margins are increased. To ensure quality, certain additives are used in slightly higher quantities than necessary.

Taken individually, these adjustments seem minor. But when accumulated over large volumes, they become significant. Variations in density or composition resulting from storage can skew material balances, create inconsistencies between theoretical and actual consumption, and complicate performance analysis.

Conversely, when storage is organized and well-managed, material flows become more predictable. Material balances become more reliable. Variances decrease. Profitability does not depend solely on production rate; it also depends on effective management of material flow from the moment it enters the shop floor.

Toward an Integrated Approach to Plastic Storage

Optimizing storage is not about increasing capacity or adding more silos. It involves analyzing the nature of the products, expected throughput rates, and the overall layout of the facility. The choice between a silo, a buffer hopper, or big-bag storage must be consistent with the target throughput and the frequency of material changes.

Technical integration requires:

• a balance between storage capacity and the machines' actual power consumption;
• compatibility between the extraction system and the downstream conveying system;
• a continuous flow all the way to the dosing or mixing stage without any sudden interruptions;
• Clear batch management to ensure traceability.

When this consistency is ensured, plastic storage is no longer viewed merely as a holding area. It becomes a key component of the process, ensuring consistency, safety, and performance.

If your facility is experiencing bridging, fluctuations in discharge flow rate, or repeated discrepancies between projected and actual consumption, it may be worthwhile to reassess the design of your plastic storage system. A targeted technical analysis can often identify concrete opportunities for improvement without requiring a complete overhaul of the production area.

TIM Solutions for Integrated Plastic Storage

Efficient plastic storage depends on more than just the capacity of a silo or hopper. It must be part of an overall system capable of ensuring consistent discharge, continuous flow, and compatibility with downstream equipment. TIM designs its solutions with this in mind, integrating storage at the heart of the material transfer and preparation process.

Plastic storage systems incorporate material extraction, continuous flow, and connections to downstream equipment. TIM designs these systems in conjunction with material transfer and preparation functions.

Storage capacity based on the actual behavior of materials

The design of a storage system begins with an analysis of the properties of the material being handled. Bulk density, particle size distribution, internal cohesion, sensitivity to moisture, and flowability determine the geometry of the silo or hopper, as well as the associated discharge devices.

A storage system designed for virgin pellets with good flowability differs from a system used for fine powders, elastomer compounds, or heterogeneous ground materials. The angle of the walls, the shape of the bottom, the type of discharge device, and the connections are determined based on the observed behavior of the product.

The storage facility has the required capacity and ensures a steady withdrawal rate consistent with the flow rate required by downstream equipment.

Mastering the Extraction of Hard-to-Flow Materials

Some materials have low flowability or high internal cohesion, which makes gravity flow difficult. Mineral powders, plasticized PVC, film shreds, and filled formulations require specialized equipment to minimize intermittent blockages.

Flat-bottom hoppers equipped with discharge systems featuring flexible or semi-rigid paddles ensure uniform material extraction. When combined with a flexible mechanical feeder, they stabilize the flow to injection molding machines or extruders, even when the material does not flow naturally.

These devices reduce bridging, micro-stops caused by manual interventions, and fluctuations in the machine's power supply.

Ensure consistency between storage and transfer

Plastic storage is linked to the transfer method. A hopper that is properly sized but poorly connected to the conveyor system causes fluctuations in flow rate.

The connection between the silo, buffer hopper, and conveyor system is based on a balance between the discharge capacity and the conveyor’s throughput. The diameter of the pipes, the motorization, and the equipment configuration are adapted to the actual mass flow rate expected during production. When flowability is poor, additional discharge devices are incorporated into the system.

The storage system then provides a flow that is compatible with the subsequent stages of the process.

Security and Compliance in Sensitive Environments

Plastic storage may take place in areas where dust poses a hazard. Transitube systems are ATEX-certified in both design and manufacturing, which allows them to be installed in classified indoor areas when required.

The equipment's airtight design reduces dust emissions and protects sensitive materials from ambient humidity, thereby preserving the physical properties of the stored product.

From plastic storage to comprehensive process architecture

Plastic storage is part of a process chain that includes transfer, mixing, dosing, grinding, and packaging. At TIM, it is part of a modular system that connects silos or hoppers to big-bag filling systems, multi-product dosing stations, or turnkey installations.

The engineering department examines material characteristics, expected production rates, and layout constraints to define a consistent layout for the entire line. This consistency minimizes the number of connection points and reduces the need for adjustments during production.

Storage thus ensures a steady and predictable supply for plastics processing equipment.

For more information:

Plastic Storage
Dry-blend transfer
Micronized transfer
Plastics processing feed system
Reuse of plastic sprues
Flexible screw transfer
Plastic waste transfer