Bridging, in the context of powder handling or powder processing, refers to a phenomenon where powder particles interlock or form a bridge across an opening or gap, preventing the free flow of the powder.
Bridging can occur in various situations, such as when powders are stored in hoppers, discharged from bins or silos, or transferred through pipes or chutes. It happens when the cohesive forces between the powder particles are stronger than the gravitational or shear forces acting on them.
The powder forms a stable arch or bridge when bridging occurs, obstructing the powder flow underneath. This can lead to flow issues, uneven discharge, or even complete blockage of the powder flow.
The powder’s particle shape and size, moisture content, electrostatic charges, and surface characteristics are some of the variables that can cause bridging. Additionally, the design of the storage or handling equipment, such as the hopper angles, outlet sizes, and surface roughness, can also influence the likelihood of bridging.
There are several strategies that can be used to stop or prevent bridging. These include using mechanical devices like vibration or air fluidization to agitate the powder and disrupt the bridges, adjusting the hopper design to promote better flow, using flow aids or additives to reduce powder cohesion, or controlling the powder’s moisture content or electrostatic charge.
Understanding and addressing bridging issues are crucial in industries where powders are handled or processed, such as pharmaceuticals, food processing, chemical manufacturing, and powder metallurgy, to ensure smooth and efficient powder flow.