Bins and hoppers are often used in conjunction with aeromechanical and flexible screw conveyors. These types of conveyors are often fed by material stored within a bin or hopper, and they may also discharge material into a bin or hopper. In such systems, achieving consistent material flow requires using bins and hoppers whose design is congruent with the needs of aeromechanical and flexible screw conveyors. This blog explains some of the factors that should be considered when selecting and using bins and hoppers for aeromechanical and flexible screw conveyors.
About storage bins and hoppers
Bins and hoppers are storage vessels for bulk materials that work through the principle of gravity-flow. As material enters or exits the bin or hopper, the force of gravity allows material to flow down the bin or hopper. Reliable gravity-flow depends in large part upon the friction angle between the flowing material and the bin or hopper wall. For this reason, good design is a prerequisite for achieving effective material flow from a bin or hopper.
Infeed bins or hoppers are designed to feed material into a conveyor, while discharge bins or hoppers are used to accept material discharged from a conveyor. Both types perform the same essential storage function and need to be capable, after filling, of releasing material at a reliable and consistent rate.
Selecting bins and hoppers for aeromechanical and flexible screw conveyors
When using bins or hoppers with aeromechanical or flexible screw conveyors, a number of factors should be evaluated to ensure the right design choice is made. These factors include the following:
- The size and configuration required to meet capacity and spatial constraints.
- The flow properties and characteristics of the materials that will be stored within the bin or hopper.
- The shape, angle and finishing of the internal walls and surfaces required to achieve a reliable material flow.
- The outlet sizing required to achieve effective material discharge from the bin or hopper at the required rate.
- Whether discharge from the bin or hopper requires regulation from a control device. As explained below, this is particularly important when using a bin or hopper to feed an aeromechanical conveyor, as this equipment type requires regulated feeding.
- Whether the bin or hopper is required to be easily mobile. If so, a movable design with lock-down casters can be selected.
Bins and hoppers for aeromechanical and flexible screw conveyors: design considerations
Proper design of a bin or hopper is essential for promoting good gravity-flow. Bin or hopper walls should be steep enough to overcome the force of friction between the material and the wall. Flow within the bin or hopper can be assisted by the use of flow aids such as a vibrator or agitator. The use of flow aids may be necessary for handling hard-to-handle materials, such as those that are sticky or which tend to clump or cake when stored.
Because the infeed section of an aeromechanical conveyor is a funnel, a regulated feed of material is required to achieve a consistent flow of material through the conveyor. For this reason, when feeding an aeromechanical conveyor from an infeed bin or hopper, it is necessary to use a flow regulator to ensure continuous material flow through the bin or hopper and into the conveyor infeed funnel.
Materials with small particle sizes or high moisture content may have a tendency to cohere and obstruct the flow out of a bin or hopper. High particle cohesion can give rise to bridging or rat-holing within the bin or hopper. Avoiding these types of flow obstruction requires giving due consideration to the design, as well as the size and length, of the bin or hopper outlet.
Infeed bins or hoppers which handle materials that tend to cake or pack should be designed with a steep-wall conical geometry which creates sufficient shear force to overcome the tendency of material to cohere and stick. In addition, the wall surfaces should be electro-polished to a mirror-like finish which promotes good material flow from the bin or hopper into the conveyor. In particularly challenging applications, flow promotion aids, such as feeders may need to be employed to overcome material packing and caking.
At UniTrak, we have extensive experience in supplying bins and hoppers, either as standalone items or as part of our equipment or systems. Infeed hoppers are standard equipment on our Powderflight aeromechanical and UniFlex flexible screw conveyors. Discharge hoppers are available upon request and we can work with you to design a storage bin or hopper for any bulk solids handling application.
UniTrak supplies bins and hoppers in a variety of designs and capacities, and we manufacture both stationary and mobile models. Applications we have serviced include those in the food, chemical, biomass, and other industries. To find out more about the bins and hoppers for aeromechanical and flexible screw conveyors which UniTrak can provide, please contact our sales team.