The reality is that most materials can be conveyed using multiple methods. For instance, it’s not always true that positive pressure pneumatic conveying is ideal for high-temperature materials, or that a tubular cable conveyor is the only solution for fragile materials. Choosing the right system requires balancing the advantages and disadvantages of each technology against the specific requirements of the application. Below are some guidelines to help determine the best conveying method for various bulk solid materials.
The First Rule: Consult the Experts
The most important rule is to seek guidance from specialists. While conveying technology has advanced significantly, there remains an element of expertise in selecting and designing the best system for a specific application. This process involves a deep understanding of the material and the operation, matched to the capabilities and limitations of each conveying method. Ideally, consult with a neutral expert who is not limited to selling one type of equipment. Such professionals can evaluate all parameters and recommend an optimal solution tailored to the needs of the operation.
The Corollary: Test Before You Buy
Testing is crucial to ensure that the selected system can reliably convey the material over the required distance without causing damage or unwanted changes to its properties. State-of-the-art testing facilities can simulate real-world conditions using full-size systems, flexible configurations, and a range of equipment. Comprehensive testing can verify system performance and help avoid costly mistakes during system fabrication and installation.
Comparison of Conveying Systems
Flexible Screw Conveyors
Flexible screw conveyors, also called spiral conveyors or helical conveyors, consist of a flexible or rigid tube housing a rotating screw, which is powered by an electric motor. The materials used for construction vary depending on the application, with screws made of carbon or stainless steel and outer tubes crafted from plastic or steel.
This relatively simple and economical system offers high reliability, efficient operation, and low capital and maintenance costs. Properly designed and tested, flexible screw conveyors can perform well in diverse applications, including handling materials prone to packing, caking, smearing, or fluidizing. Specialized systems can also manage fragile or brittle materials with minimal breakage.
Pneumatic Conveyors
Pneumatic conveyors are custom-engineered systems that use a gas stream (typically air, though sometimes inert gases) to transport bulk materials. The system can operate under positive pressure or vacuum, depending on the application. At the discharge point, materials are separated from the gas stream using cyclone separators, filter receivers, or process vessels.
Positive-pressure pneumatic systems are ideal for transporting materials from a single source to multiple destinations over longer distances and with higher capacity. Vacuum pneumatic systems, on the other hand, are better for applications that involve picking up materials from open containers using wands or transferring from multiple sources to a single or multiple destinations.
Tubular Cable Conveyors
Tubular cable conveyors, also known as drag or disc conveyors, use polymer discs attached to a steel cable to move materials through an enclosed steel tubing circuit. Driven by a wheel, the system gently moves bulk solids at slow speeds, ensuring minimal damage to the material. These modular systems can feature multiple inlets and outlets, which can be added or repositioned as needed.
Their compact design, with outer diameters as small as 4 inches (10 cm), allows them to navigate through tight spaces and accommodate a variety of layouts, including horizontal, vertical, or angled pathways.
By considering these guidelines and comparing the pros and cons of each technology, businesses can select a conveying system that aligns with their specific needs and operational goals.