When the material and conveying requirements are determined, selecting or designing the conveying system to achieve optimal conveying performance is crucial. A common misconception is that greater gas flow results in higher material flow. In reality, there is an optimal point between material flow and gas flow where conveying efficiency is highest. This optimal point can be determined through theoretical calculations and appropriate testing.

Not all materials are suitable for automatic feeding systems. The conveyability of a material can be assessed by measuring and analyzing its characteristic parameters. Key parameters for automatic feeders include:

Angle of repose

Bulk density

Particle factors

Electrostatic constant

Moisture sensitivity

Explosion risk

Toxicity and corrosiveness

(1) Angle of Repose
When assessing the conveyability of a material, flowability is one of the most important parameters. It is typically represented by the angle of repose, which is the angle formed between the sloped surface of a material cone poured from a certain height and the horizontal plane. A smaller angle indicates better flowability, and vice versa. However, for certain special materials, the angle of repose may not accurately reflect flowability.

(2) Bulk Density
Bulk density refers to the weight per unit volume of a material in a loose state. Since particles or powders contain both material and air, bulk density can vary depending on the stacking method. Therefore, the bulk density under actual conditions must be measured.

(3) Particle Factors
The weight, particle size distribution, shape, and hardness of particles are key factors influencing material flowability and the design of the conveying system.

(4) Moisture Sensitivity
All materials have hygroscopic properties. Materials sensitive to moisture may clump or agglomerate when they absorb moisture, altering their flowability. In severe cases, they may adhere to pipe walls or filter surfaces, leading to pipe blockages or filter clogging.

(5) Explosion Risk
When fine particles mix with air and reach a critical concentration, the presence of a spark can potentially cause an explosion. Dust explosions require several conditions: oxygen, critical concentration, and a spark. While material concentration during conveying is difficult to control, oxygen and sparks can be managed. Using inert gas to isolate oxygen and eliminating static electricity to prevent sparks can help mitigate explosion risks.