Rotoflo

What are silos and silo discharge systems?

Silos are generally used for the storage and discharge of powdered or granular bulk solids; a silo discharge system is designed to aid in the discharge of materials quickly and efficiently, thereby eliminating the risk of powder bridging, ratholing or blockage.

Rotoflo silo discharge units can be built-in or retrofitted to existing vessels and, as such, will allow materials to be safely and efficiently discharged from a silo or hopper. With multiple configurable outlets, a Rotoflo silo discharge unit can both reduce the risk of material flow problems within a vessel and provide a controlled rate of discharge to multiple downstream processes.

What causes powder flow problems in silos and hoppers?

There are a number of reasons why you might experience flow problems in bulk material silo storage. These range from moisture causing compaction/blockages, to poor silo design or unsuitability. The types of issues can be related to the silo itself, its shape and geometry, or the material, or both. However, poor equipment design is usually what causes the majority of issues.

Common causes of flow problems:

• Vessel geometry include angle of the hopper and outlet size
• Wall friction – friction between the material being stored and the vessel wall material.
• Internal friction – friction within the material being stored.
• Consolidation of the material within the vessel due to materials self-weight.
• Ratholing
• Powder bridging
• Segregation of particles in the materials
• Flooding or flushing of the flow
• Degradation of the particles
• Consolidation with time of the material within the vessel.
• Attraction of the material particles (electrostatic or Van-der-Waals forces)
• Liquid bridges due to moisture within the stored material or adsorbed from the atmosphere.

Two of the most common issues are Ratholing and Powder Bridging. So, let’s look at what they are and why they happen.