Pneumatic Conveying Systems

Pneumatic conveying systems are widely used across the bulk material handling industry to transport dry bulk materials throughout a facility. These systems move materials through pipelines, typically using air as the conveying medium.

Choosing between pressure and vacuum conveying is a key consideration for facility owners transporting dry bulk materials via pneumatic systems. Depending on the operational requirements, a hybrid approach using both systems may prove to be the most effective.

To ensure optimal system design and performance, Polimak experts will assess the available resources, evaluate system feasibility, and recommend the conveying method that best suits the material and application.

The design, production, and installation of pneumatic conveying systems for bulk materials require extensive know-how and many years of experience. Simple installation, low maintenance requirements, long-term, problem-free operation, and durability in harsh environments are key features of high-quality pneumatic conveying systems.

Polimak provides pneumatic conveying solutions and expertise to a variety of industries, including chemicals, food, plastics, and cement. A well-designed pneumatic conveying system is a practical and cost-effective method for transporting dry bulk materials from one point to another.

Types of Pneumatic Conveying Systems

There are several methods for pneumatically transporting dry bulk materials, with the key difference between them being the conveying phase. Conveying phases refer to the manner in which dry bulk materials are moved through a conveying pipeline. Pneumatic conveying phases can be categorized into two main types:

1. Dilute Phase Conveying

2. Dense phase Conveying

1. Dilute Phase Pneumatic Conveying

In dilute phase pneumatic conveying systems—also known as lean phase systems—dry bulk materials are conveyed at velocities exceeding the saltation velocity (the minimum air velocity required to keep particles suspended in the airstream without settling at the bottom of the pipe). These systems generally function with air entry pressures less than 1 bar, enabling the movement of dry bulk materials through pipelines at relatively high speeds.

In dilute phase systems, the bulk material particulates are entirely kept in suspension by the airstream as they travel through the conveying pipe. The system operates with low pressure and high velocity for material transfer – hence the term "low pressure systems."

Particle velocity play a critical role in these systems as it determines the material’s end product. Very low velocity may cause the material to settle at the bottom of the pipe, while excessive velocity can lead to particle-to-particle and particle-to-wall collisions, resulting in bulk material degradation.

The two methods that can be used are:

• Dilute phase pressure conveying

• Dilute phase vacuum conveying

Dilute phase conveying systems are the most widely used pneumatic conveying systems across various bulk material handling industries for transporting bulk solids. These systems are ideal for transporting non-abrasive bulk materials, products with low bulk density, and materials that are difficult to break. Examples of dry bulk materials that can be processed using dilute phase pneumatic conveying systems include sugar, flour, pellets, chemicals, polymers (resins and compounds), calcium carbonate, cement, and coal dust.

2. Dense Phase Pneumatic Conveying

Dense phase conveying systems are pneumatic conveying systems that utilize relatively low velocity gas and rely on a high-pressure differential, either positive or negative, to transport dry bulk materials in pipelines. These systems typically operate at velocities beneath the saltation threshold.

Dense phase pneumatic conveying systems are also known as high-pressure conveying systems. These systems work with low velocities to ensure a gentle and efficient transfer of bulk materials. In this configuration, dry bulk materials move with less wear and impact inside the conveying pipeline, and their flow (dense phase transfer form) generally takes the form of two types: plug flow or dune (wave) flow. The dense phase transfer form is largely determined by both the properties of the bulk material as well as the plant configuration.

This type of pneumatic transport system is suitable for various abrasive, friable, fragile, and mixed-batch dry bulk materials. The two available methods for dense phase conveying are pressure conveying and vacuum conveying.
Pneumatic conveying systems transport bulk materials without exposing them to fast-moving mechanical components, unlike conventional equipment such as belt, screw, vibrating, drag conveyors, or bucket elevators. This helps minimize the risk of contamination or physical damage to the materials.

Some of the dry bulk solids transported with pneumatic conveyors include sugar, spices, salt, flour, maize (corn), popcorn, coffee beans, sand, limestone, cement, coal, gypsum, plastic pellets, plastic powders, calcium carbonate, and many more.

Advantages of Pneumatic Conveying Systems

Pneumatic conveying systems offer numerous benefits to users, including the following:

• Pneumatic conveying systems can transport materials over long distances, with conveying pipes installed both vertically and horizontally.

• Materials are conveyed through a closed pipeline, keeping the materials clean and preventing dust from escaping into the atmosphere.

• The compact design of pneumatic conveying systems allows for easy integration with current equipment, making them more adaptable than mechanical systems.

• A pneumatic system can deliver a product to any location accessible by a pipeline.

• These systems require minimal space, allowing for compact installation and helping maximize available floor space in industrial environments.

• Pneumatic conveying systems are composed of only a few main components—typically a pump or blower, a pipeline, and a feeding device—making them straightforward and easy to maintain, as each part can be repaired independently.

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These valves are typically actuated by pneumatic actuators and are used to automatically open and close the product flow to discharge material to downstream equipment.
Installed below silos or hoppers, these valves are used for maintenance operations of equipment such as rotary valves, screw feeders, etc., that are positioned below the butterfly valve.
These valves are typically actuated by pneumatic actuators and are used to automatically open and close the product flow to discharge material to downstream equipment.
In this design, the butterfly valve is sandwiched between two flanges. Rubber sealing at both faces of the valve provides a tight seal between the flanges and the wafer butterfly valve.
One side of the valve has a bolted flange connection, while the other side features a built-in short pipe designed for fixing a flexible sleeve.
These valves have bolted flange connections on both sides, making them suitable for installation on silos, hoppers, screw feeders, and similar applications.
Bulk tanker trucks or open trucks can be filled with powdered materials delivered within FIBC bags. These systems generally consist of bulk bag discharging station, mechanical or pneumatic conveyor and loading bellow. Big bag discharge station transfers the bulk solid from big bag to conveying system. Conveying system transfers it to truck loading area. And loading bellow is used to fill tanker truck without any dust emission. Since truck loading operations are done within limited time, high capacity big bag discharge systems and bulk material conveying systems are used. For short distances, screw conveyors are preferred to transfer material from big bag discharge station to truck loading chute. For long conveying distances, pneumatic conveying systems provide better service. There may exist a storage hopper or silo above bulk truck loading bellow to compensate material flow between inlet and outlet. Bulk bag discharge and truck filling systems have automatic control system that monitors product level in truck and operates all equipment accordingly. Optional weighing system can be added to measure the amount of material that is filled to truck.
Big bag discharge systems can deliver dry bulk solids in powder and granular form to weighing and batching systems. The loading hopper of the weighing system should remain full during dosing and batching. Big bag discharge systems can monitor the product level in the loading hopper and maintain a constant level automatically. Depending on the dosing speed and conveying distance, mechanical conveying systems or pneumatic loading systems may be used. Dust collectors can be employed to prevent dust emissions during hopper loading, especially for materials with high dust content.
Dry bulk packaging systems are used to fill powdered or granular materials into bags, drums, jars, sacks, etc. Bulk materials delivered in big bags must be transferred to packaging machines without interruption. The loading hopper of the packaging system should remain full during the filling and packaging process. Big bag discharge systems can monitor the product level in the loading hopper and maintain a constant level automatically. Depending on the packaging speed, mechanical conveying systems or pneumatic loading systems can be selected. Dust collectors can be used to prevent dust emissions during hopper loading, especially for materials with high dust content.
Mixer automation systems are used to mix dry bulk solids according to specific recipes. Raw materials delivered in FIBC bags can be transferred to mixing units through a combination of conveying equipment and bulk bag discharge systems. Depending on the type of application, pneumatic conveying or mechanical feeding systems can be used to fill mixers. Big bag discharge stations can be manufactured with built-in dosing systems. The amount of raw material to be loaded into the mixer is automatically controlled with the help of a weighing and dosing system. Dust collectors can be used to prevent dust emissions during the mixer filling process.
Bulk material stored in big bags can be automatically filled into small bags. Big bag discharge systems come with optional built-in bag filling units. For low filling capacities, these units are installed below the big bag discharge hopper, providing a practical and cost-effective solution. Both big bag discharging and bag filling operations can be handled by a single, compact system. For higher bag filling needs, bag filling machines are installed near the bulk bag discharge stations. Pneumatic conveying systems or mechanical conveyors can be used to transfer bulk material from the FIBC bag discharge station to the bag or sack filling system.
Mechanical conveyors can be used for silo loading from big bag discharge stations. Screw feeders, bucket elevators, rotary valves, or chain conveyors are connected to big bag discharge stations to fill silos. The selection of conveying equipment directly depends on the conveying distance, height, transferred material, and capacity. Bucket elevators are preferred for high silos, while screw feeders are preferred for shorter silos and short distances. The big bag discharge system can be installed on top of the silo for faster filling. In this case, rotary valves or butterfly valves are better choices as they provide simple flow control. Dust collection systems may be required depending on the dust content of the bulk solid. During silo loading, air content in the silo escapes to the atmosphere and carries some dust along with it. Vacuum fans and jet filters in dust collectors prevent dust emissions into the environment. The collected dust is sent back to the silo, thus preventing product loss.
Pneumatic conveying systems installed after bulk bag discharge units transfer bulk material through conveying pipelines to fill silos. This configuration is useful in applications where high transfer rates and long conveying distances are needed. In production lines where raw materials are stored in warehouses far from storage silos, bulk bag discharge stations can be installed close to the warehouses, and pneumatic conveying systems are used to fill silos from long distances. This design reduces the need for forklifts and cranes for bulk material transfer on the production site and increases overall efficiency.

Pneumatic conveying systems used for silo loading utilize blower pumps or compressors. Motor power, pipeline diameter, and equipment selection depend on the type of bulk material, transfer distance, silo height, and transfer capacity. Level sensors, jet filters, and other equipment are installed on storage silos to ensure the proper operation of the silo filling system.
Pneumatic conveying systems installed after bag dump units transfer bulk material through pipelines to fill silos. This configuration is ideal for applications requiring high transfer rates and long conveying distances. In production lines where raw materials are stored in warehouses far from storage silos, bag dump stations can be installed close to warehouses, allowing pneumatic conveying systems to transport materials over long distances. This design reduces the excessive use of forklifts and cranes for bulk material transfer within the production site, improving overall efficiency.

Pneumatic transfer systems used for silo loading utilize blower pumps or compressors. Motor power, pipeline diameter, and equipment selection depend on factors such as the type of bulk material, transfer distance, silo height, and transfer capacity. Level sensors, jet filters, and other equipment are installed on storage silos to ensure the proper operation of the silo filling system.
Mechanical conveyors can be used for silo loading from bag dump stations. In this configuration, screw feeders, bucket elevators, rotary valves, or chain conveyors are connected to bag dump stations to fill silos. The selection of conveying equipment depends on factors such as conveying distance, height, material properties, and capacity. Bucket elevators are preferred for high silos, while screw feeders are ideal for shorter silos and short distances. Bag dump systems can be installed on top of the silo for faster filling. In such cases, rotary valves or butterfly valves are better choices as they provide simple flow control.

Dust collection systems may be required depending on the dust content of the bulk solid. During silo loading, air inside the silo escapes to the atmosphere, carrying dust particles with it. Dust collectors equipped with a vacuum fan and jet filter capture airborne dust. The collected dust is returned to the silo, preventing product loss and ensuring a cleaner environment.
The inlet skirt is an optional feature designed to extend the lifespan of the flexible connector sleeve. Its upper portion is attached to the outlet port of the upstream equipment and extends down into the bin activator’s inlet port. The primary function of the inlet skirt is to serve as a protective shield, safeguarding the flexible connector seal from wear and damage.
A vibratory motor is externally mounted to the bin activator. When powered, the motor generates vibrations that facilitate a steady flow of dry bulk materials within the system. Depending on the application requirements, one or two vibratory motors can be installed externally.
To accommodate a bin activator, the cone of a silo must be shorter than usual, resulting in a wider outlet. A flange supplied with the bin activator is separately welded to the silo’s outlet, slightly above the opening, at the production site. Once installed, the vibrating bin discharger is securely bolted to the flange, ensuring a stable and reliable connection.
Special spring suspension links and an engineered polymer seal work together to create a flexible connection between a vibrating bin discharger and the equipment positioned above it.

The proper design and installation of the polyurethane seal prevent it from slipping off and ensure a secure seal, eliminating the risk of dry bulk material leakage. Additionally, the seal offers high stress resistance and long-term durability, withstanding stresses caused by motor vibrations, pressure conditions, and other operational factors.

Externally installed spring suspensions provide full resilience to the vibrations of the cone head. They ensure that the generated vibrations affect only the cone itself rather than the upstream equipment structure.
An internally tapered, conical-shaped baffle plate is positioned at the center of the bin activator’s diameter. The baffle is rigidly attached to the equipment body using structural steel components. It facilitates bulk material flow from upstream equipment by directly inducing vibrations into the material.

A secondary deflector plate reduces the weight of the bulk material in the lower portion of the bin activator by acting as a wedge beneath the material, directing it around the areas adjacent to the cone’s surface.

Polimak baffle plates are available in various configurations, including convex and cone plates, and in different angles (15°, 30°, 45°, or even 60°) depending on the flow characteristics of the handled bulk material and the specific application requirements.