When companies transport bulk material, the primary dilemma often revolves around deciding between pneumatic systems (also known as industrial air systems) and mechanical conveying systems. Both technologies are tailored for the same purpose – transferring materials from one location to another.
However, selecting the most appropriate method necessitates thoroughly considering various factors related to the specific application, including the nature of the materials to be conveyed, the distance and pathway involved, and the overall system design. This discussion will delve into the fundamental distinctions between these two conveying methods, beginning with pneumatic systems, and highlight their respective strengths and weaknesses.
OVERVIEW OF PNEUMATIC SYSTEMS
Pneumatic systems represent an optimal choice for transferring dry bulk materials. By utilizing enclosed pipelines, these systems employ industrial air mechanisms such as positive pressure, vacuum, dilute phase, and dense phase systems to transport materials. The materials are propelled through the system using air or inert gas, although the methods for generating and directing airflow vary among systems.
In a positive pressure system, transporting materials from point A to point B typically necessitates a positive pressure blower assembly, a rotary airlock, a cyclone receiver (occasionally equipped with an airlock valve), and a tubing system complete with elbows, sight glasses, and couplings. The exhaust air from the cyclone receiver must be vented to a secondary filter, or scrubber, or released into the atmosphere. A notable advantage of this system is its capability to add pickup points and deliver to multiple destinations by incorporating inline diverter valves into the conveying line. Various discharge methods are available for delivery to multiple locations.
In contrast, a vacuum system pulls materials through the pipeline rather than pushing them with air, making it a more hygienic method for moving bulk materials.
The dilute phase system is designed for lighter materials, such as powders, using a blower to suspend them in the airstream. This system employs pressurized air to propel materials at high speeds.
On the other hand, the dense phase system is utilized for conveying heavier materials that are not in powdered form, like plastic pellets. Since these materials are not suspended in air, this system pushes the product through in waves and operates at higher pressures and lower conveying velocities compared to dilute phase systems.
OVERVIEW OF MECHANICAL CONVEYING SYSTEMS
Mechanical conveying systems are employed for transporting substantial bulk materials. While pneumatic conveying systems cater primarily to powders and pelletized products, mechanical conveying systems are ideally suited for materials such as crushed rock, gravel, and other large, abrasive items that cannot be easily conveyed through an airstream. Furthermore, they are the preferred choice for products with high moisture, oil, or fat content.
The design of the control system in mechanical conveying relies on traditional machinery rather than air. Key components utilized in the conveying process encompass belts, chains, drive motors, buckets, rollers, and sprockets. There exists a diverse array of mechanical conveying systems.
Belt conveyors excel in moving vast quantities of material over extensive distances. They feature a broad belt positioned atop rollers, facilitating swift transportation.
Bucket elevators are utilized to elevate products to considerable heights within a factory or plant setting, employing buckets for this purpose.
Screw conveyors are tailored for transporting wet materials horizontally across short distances, typically not exceeding 24 feet.
Drag chain conveyors, featuring a chain and paddle design, are optimal for conveying dry products over long distances.
Vibrating feeders, equipped with vibrating trays that provide continuous motion, are ideal for products susceptible to clumping or sticking when left stationary.
THE ADVANTAGES OF PNEUMATIC SYSTEMS FOR CONVEYING MATERIALS
Pneumatic conveying systems offer numerous advantages when applied to various applications. The foremost benefits include:
1. Flexibility in Routing: These systems can be designed to run both horizontally and vertically, allowing them to be seamlessly integrated around existing equipment within your plant or facility. This versatility makes them a highly adaptable solution for transporting bulk products.
2. Contamination Protection: Since the product is enclosed within the ducts and piping of the pneumatic conveying system, it is effectively shielded from external contaminants, ensuring its integrity and quality.
3. Cost-Effectiveness and Maintenance Simplicity: Compared to mechanical conveying systems, pneumatic conveying systems are more economically viable and significantly easier to maintain. The absence of moving parts reduces maintenance requirements and overall costs, while also minimizing floor space utilization.
4. Multi-Point Convenience: The systems offer the convenience of multiple points where products can be introduced or discharged, enhancing operational efficiency and flexibility.