Bridging, blocking and powder segregation are the traditional powder handling challenges.
Is your product quite sticky and poor flowing? Are you having trouble in getting it out of your containers? What methods are you deploying to free this powder?
Over the years we have seen facilities where product has got stuck in the outlet of the container or hopper. In order to free the material, we have seen operators use mallets to thump the outside of the bin or rods to try to unblock the obstruction. Hammering the side of the equipment both distorts it and only leads to problems further down the track. Not exactly good manufacturing practice either.
What has happened in the bin to cause this? There are commonly two such causes: rat-holing and bridging.
Rat-holing happens when flow only takes place directly above the outlet of the container. Product at the sides gets held up and can cake or agglomorate. Once the central core is discharged, flow stops and the rest of the material remains stuck to the sides. This is when the mallets are deployed, to help create vibration and free the material. The sloping hopper/bin walls are not steep enough or low enough in friction for material to move, so instead the particles cling to the sides and themselves. This core flow means that particles can have a tendency to segregate, which means the blend becomes demixed. Yield is also poor as product sticks to the sides of the container.
Bridging is when an arch-shaped block of powder forms above the outlet. It is caused when particles interlock and become cohesive. Initially product flows, but this quickly stops once the free material is discharged. At this point the container is usually opened from above and rodded. This of course can create a dusty environment and can sometimes be a very hazardous operation.
What can be done?
There are several options available to correct this problem. The first is to use the geometry and the material of the hopper to induce movement. Material flow is determined by a combination of the angle at the bottom of the hopper and the friction caused by the internal surface, so for instance a shallower angle could be used if the surface has low friction, or a rougher surface would need a steeper angle.
Alternatively, we would promote the use of our unique Cone Valve IBC system. As the cone rises during the discharge process, the vertical lifting action breaks any bridges in the powder material. At the top of the lift there is also a small vibrating action, which further loosens any sticky product. The annular gap (ring shaped gap) that is formed in the outlet of the IBC as the cone lifts creates mass-flow of the material. This means that powder flows across the whole cross-sectional area of the container, with all the particles moving downward at the same rate, with the product that entered the IBC first, being the first to be discharged, what is called ‘FIFO’ (first in, first out). This prevents material being left behind on the walls of the IBC.
By the nature of the way in which powder is discharged from a Matcon IBC, the particles don’t move against each other, so each dose out of the container should be the correct mix. Segregation or de-mixing is avoided, giving a consistency across the finished product and a quality product in the final consumer pack.
For more information on how our Cone Valve technology overcomes the traditional powder handling challenges download the article by clicking on the link below: