Pneumatic suction conveying of plastic pellets is used in plastic processing plants to move plastic granules in an automated, controlled manner that is integrated into the production cycle.
In this in-depth analysis, we examine how pneumatic conveying works, how it differs from other technologies, and the role of the so-called Venturi principle.
How pneumatic suction conveying of plastic pellets works
In pneumatic conveying of plastic granules by suction, the material is conveyed through the conveying pipes using a vacuum generated upstream of the system.
In other words, it is not the air that pushes the pellets, but the pressure difference that draws them from the storage point to the machinery used for processing.
General principle of vacuum operation
The operating cycle is based on three stages: vacuum generation, air-material transport and final separation. A pump or turbine creates a lower pressure zone: as a result, air enters the circuit and transports the pellets along the pipe.
In the receiver unit, special filters or separation systems allow the material to be discharged into the hopper while the air is expelled. This system guarantees:
- clean handling of the pellets, reducing dispersion and waste;
- centralised management of the feeding of multiple processing machines, thanks to vacuum units that manage multiple lines simultaneously;
- control of loading cycles, using automatic systems.
Each element of the system contributes to flow stability and production continuity.
Centralised vacuum conveying
Pneumatic conveying of plastic pellets, therefore, uses a controlled air flow to move the granules in a closed circuit. In the case of suction, the vacuum can be generated on board the machine or in a shared vacuum unit, depending on the plant configuration.
Many companies adopt a centralised solution for specific reasons:
- system efficiency, with the ability to feed multiple machines from a single central unit;
- reduced risk of leaks along the line, thanks to constant vacuum;
- greater order in the production layout, with storage containers and collection points organised in a structured manner.
The centralised configurations offered in many cases by Vismec allow for optimisation of space and material handling times. Our centralised transport systems integrate vacuum units, automatic switching systems and cycle supervision into a single coherent architecture that is scalable and adaptable to future plant expansions.
How do you size a pneumatic pellet conveying system?
A frequently asked question concerns the sizing of feeding systems. The correct configuration depends on several variables:
- distance between the collection point and the processing machine, which affects pressure drops and the power required to generate stable negative pressure along the line;
- required air flow rate, to be calibrated according to the quantity of material to be transferred and the cycle times of the user machine;
- number of machines connected, a determining factor in choosing between a decentralised or centralised vacuum solution;
- type of plastic material transported, because specific weight, pellet shape and sensitivity to abrasion influence air speed and pipe diameter.
The flow speed must keep the pellets in suspension, avoiding accumulation or excessive wear. The choice of filters also affects operational continuity, especially in contexts with intensive production cycles.
With this process in mind, Vismec pneumatic transport systems can be integrated with gravimetric or volumetric dosing systems and dryers for granules, to ensure excellent material quality for machine feeding and, consequently, to promote a good final result.
The decentralised Venturi suction system in granule conveying
The Venturi suction system, on the other hand, is a technical solution used in some pneumatic pellet conveying configurations, particularly in compact or decentralised systems.
What is a Venturi vacuum conveying system?
The Venturi principle exploits the variation in speed of a fluid in a duct with a reduced cross-section. When compressed air passes through the constriction, its speed increases and the static pressure decreases. This difference generates a zone of negative pressure that draws the pellets into the transport line.
In this context, the Venturi system is used when it is necessary to feed individual machines without resorting to a centralised system, in applications with:
- short transfer distances between the pickup point and the individual processing machine;
- moderate flow rates compatible with non-continuous production cycles or limited material requirements;
- need for quick and flexible installations, i.e. in departments subject to frequent reconfigurations.
Since the Venturi system uses compressed air, energy consumption must be evaluated in relation to the required productivity. In very dynamic environments, this solution still allows the creation of dedicated lines with limited intervention on the existing layout.
Vismec solutions for pneumatic pellet conveying
Designing a pneumatic granule conveying system requires a detailed analysis of the production layout, distances, volumes transported and the desired level of automation.
Vismec designs and supplies both modular and centralised systems for the conveying of plastic granules, which can be integrated with storage containers, dehumidifiers and dosing units. The available configurations may include, among other things:
- single-phase and three-phase receivers, sized according to flow rate;
- centralised vacuum units, to feed multiple machines;
- automatic control systems, with cycle management and supervision.
We configure each system according to the customer’s needs, with a focus on operational continuity, material quality, efficiency and scalability.
If you operate in injection moulding, extrusion or plastic blow moulding and want to improve your granule transport systems, contact Vismec. We will offer you a configuration tailored to your goals, your company’s production layout and the required levels of automation.