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The Use of Inserts in Hoppers
Guest article by Lyn Bates of Ajax Equipment
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Why Fit Inserts ?
Hopper inserts are fitted for a wide variety of reasons, as Table 1. They form part of the tools available to the designer to optimise the performance of bulk solids storage containers.
The first stage of the design process is to determine a form of flow regime that is appropriate to the physical properties of the bulk material and the circumstances of the application. The shape of flow channel may be satisfied by a hopper of simple geometrical construction, such as a cone or wedge shape, but other considerations will influence the constructional method by which such a flow channel is secured. There will also remain cases where a more sophisticated approach is more viable. Some of these objectives overlap or are compounded.
| Table 1. Reasons for Fitting Hopper Inserts
Located in the Hopper Outlet Region
To aid the commencement of flow
To secure reliable flow through smaller outlets
To Increase solids flow rates
To improve the consistency of density of the discharged material
To secure mass flow at reduced wall inclinations
To expand the flow channel, secure higher part of 'live' storage
To improve the extraction pattern
To prevent 'flushing'
To reduce overpressures on feeders
To save headroom/ secure extra storage capacity
To counter or redress segregation
To blend the hopper contents on discharge
To improve counter current gas flow distribution
To prevent blocking by lumps and agglomerates
Positioned in the Body of the Hopper
To accelerate the de-aeration of dilated bulk material
To reduce overpressures/prevent threshold compaction levels
To alter the flow pattern for countering 'Arching' and 'Piping'
To Secure Mass Flow at lower wall angles
Fixed at the Hopper Inlet
To reduce segregation
To reduce particle attrition
To secure a higher fill level
To divert oversized product
To counter excessive wall wear
For personnel safety
Some features are independent, others inter-related. More than one objective may apply. |
This is clearly a vast and relatively un-exploited subject that is impossible to cover in a short article. Whereas there are many fabricators who manufacture bins the technology of bulk materials flow is a separate subject and expert information is less readily available. Some of these techniques are simple and obvious, whilst other demand an understanding of solids mechanics, powder testing techniques and flow regimes, and therefore remain in the domain of specialists. However, listing the objectives may stimulate attention to the prospects and allow users to contemplate the potential of improving performance by methods other than ‘brute force’.
A note of caution must however be added. This is not a field to be explored lightly. High loads and unusual stresses can be developed by fittings that intrude in a flow stream or cause eccentric flow patterns. However, supported by quantified measurements of relevant powder properties, these techniques offer great opportunities to overcome many types of storage and handling difficulties.
Lyn Bates, Ajax Equipment
Lbates@ajax.co.uk
Help others by posting your comments, suggestions and
experiences with bulk solids feeding or any other materials handling concerns you may have
on our On-Line Help Forum. For
past Ask Joe ! Articles, visit the Ask Joe! Archived Articles.
Guest articles for the Ask Joe! Column are always welcome,
for more information please contact Joe Marinelli directly at his email address:
joe@solidshandlingtech.com.
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