Types of Powder Handling Problems and Effective Solutions

Bridging is more likely to occur when the hopper outlet is relatively small. Care should be taken when dealing with this type of blockage, as applying vibration may inadvertently impact the material further, making the blockage stronger and more difficult to clear.

Special attention is required when handling high-moisture sand, coarse aggregates (including ores), hygroscopic materials such as iron oxide, flour, and lime, as well as deliquescent materials such as salt, urea, and ammonium sulfate. These materials tend to cake and consolidate under high-humidity conditions or condensation, which can lead to bridging conditions.

Blasters, including Direct Blaster and Mini Blaster, as well as fluidizer, are commonly used to eliminate bridging.Vibration devices, such as vibrators and knockers, may not be suitable as a solution in all cases, depending on the characteristics of the material and the hopper design.

Arching is more likely to occur when handling high-moisture materials, cohesive powders and granular materials (including soybeans, fish meal, foundry sand, crushed sand, and clay), as well as ores and crushed aggregates.

Recommended solutions vary depending on hopper sizes.

• Small hoppers (up to 1 m diameter): Ball Vibrators, Vibrator Motors, and Knockers
• Medium-sized hoppers (1 to 3 m diameter): Vibrator Motors, Knockers, and Blasters
• Large hoppers (over 3 m diameter): EVSI 15 Series Vibrator Motors and Blasters

For arching caused by long fibrous materials or porous bulk solids, such as sawdust and rice bran, large-capacity Blasters are especially effective.

Ratholing is likely to occur when the hopper cone angle is greater than the angle of repose of the bulk material. It is particularly common when handling high-moisture materials, cohesive powders and granular materials, as well as low-density fine powders with relatively high bulk volume, such as carbon black, PVC, calcium carbonate, and talc. It can also occur when crushed sand, including materials containing lime dust, is stored in flat-bottom silos such as corrugated silos.

Blasters are generally recommended as the most effective solution to ratholing. In small hoppers, vibrator motors and knockers may also be effective in promoting material flow and reducing stagnation.

Wall build-up commonly occurs when cohesive materials or highly hygroscopic powders and granular materials, such as lime, foundry sand, clay, and pulverized coal are stored in a hopper.

Knockers are generally the most effective solution for removing material adhered to hopper walls. As a preventive measure, combining a Blaster with a Knocker is highly effective in reducing wall build-up before significant material adhesion occurs.