Based on question and clarification requests, we note that this gentlemen has a packaging application / installation, handling a 1 – 2 mm ‘rubber crumb’, which is being stored in a 59 inch diameter x 55 inch straight wall height x 78 degree hopper angle. He states that the discharge outlet or opening is 31-½ inches diameter. The bulk density of this material is stated to be 28 PCF, no required flow rate.

Any material handling application is made up of at least two components: Storage/discharge and metering or rate regulation.

Rubber crumb is a Class 5 material, meaning it will physically interlock, absorb vibration, and will not flow easily due to gravitational effects.

What is puzzling is the stated discharge problem. The bin-hopper is not considered to be very ‘large’ with significant head loading. Considering a repose angle in excess of 50 degrees, a working hopper capacity would be less than 1400 lbs. With this configuration [31 ½ inch discharge opening!!] the rubber crumb should flow, unless it is being restricted in some manner not identified.

The gentlemen should locate and identify this bottleneck. Due to the Class 5 properties, and his existing bin-hopper, which he does not want to replace, we do not believe brute force / vibration applied to the hopper or straight wall is a solution. We would suspect the rubber crumb is forming a stable arch or bridge between the hopper outlet and downstream device, stated to be a bag filler.

Once the bottleneck has been located corrective mechanical measures may be required, such as an active flow promotion device like a mechanical stirrer to break up the bridge at the bottleneck. We would also look at contact materials, which will lower the wall friction in the hopper and straight wall. [Teflon perhaps?]. In some cases the lower portion of the cylindrical hopper is replaced with a series of large diameter, slowly rotating screws, or a mechanical Bin Activator [60 inch diameter in this case] for flow promotion.

He should also review the design and operation of the bag filler to see how the filler components relate to a Class 5 material operation. REMEMBER: Storage/Discharge and Regulation must be correctly integrated!