Jamil Bundalli In Solutions To Common Problems

Ship Unloader Metering Bin

This is an example of a ship unloading hopper designed specifically to handle difficult flowing cohesive materials such as gypsum and bauxite.

Why Conventional Ship Unloading Hoppers Suffer from Chronic Bridging and Inconsistent Discharge

Standard ship unloading hoppers use a pyramid hopper that converge to a small opening that use a slide gate or clamshell to control discharge.

In summary, a pyramid hopper with a small opening is a poor choice of bin shape for handling difficult flowing cohesive materials such as gypsum or bauxite. First, the bin shape promotes a funnel flow discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with large bins with large discharge outlets. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

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Kamengo’s Solution

The solution to a reliable ship unloading hopper that is capable of handling difficult flowing cohesive materials has two parts. The first half of the solution is to use a plane flow hopper shape with a wide and long discharge opening. A plane flow hopper only converges in one plane at a time, and is vertical in the opposite plane. The plane flow hopper is the most conservative hopper shape. The purpose of using a conservative bin shape with a long and wide discharge outlet is to employ a geometry where if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern.

The second half of the solution is to pair the plane flow hopper with a Kamengo Feeder. The value of the Kamengo Feeder is that it withdraws material evenly from its entire opening, which by definition is necessary to actually achieve a mass flow discharge pattern in the hopper, which is necessary when handling a difficult flowing, cohesive bulk solid.

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To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please visit KamengoU.

Jamil Bundalli In Solutions To Common Problems

ROM Ore Railcar Unloading Bin

This is an example of a series of rail car unloading hoppers designed to handle large particle as well as difficult flowing cohesive materials.

Conventional Unloading Bins and Why they Suffer from Chronic Plugging and Inconsistent Discharge

A standard railcar unloader uses a series of pyramid hoppers that converge to a small opening that use any of slide gates, basket gates, vibrators or clamshells to control discharge.

In summary, a pyramid hopper with a small opening is a terrible choice of bin shape for handling difficult flowing cohesive materials. The bin shape promotes a funnel flow discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with large bins with large discharge outlets. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

Further, Feeders that operate partially open to control the flow of discharge and do not withdraw material from the full discharge outlet of the hopper all the time are dangerous, because this behavior further promotes a funnel flow discharge pattern and the formation of stable arches and ratholes. A reliable Feeder is “fully effective”, where it withdraws material evenly from the full discharge outlet of the storage above it.

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Kamengo’s Solution

The solution to a reliable railcar unloading hopper that is capable of handling both large particles as well as difficult flowing cohesive materials has two parts. The first half of the solution is to use a plane flow hopper shape with a wide and long discharge opening. A plane flow hopper only converges in one plane at a time, and is vertical in the opposite plane. The plane flow hopper is the most conservative hopper shape. The purpose of using a conservative bin shape with a long and wide discharge outlet is to employ a geometry where if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern.

The second half of the solution is to pair the plane flow hoppers with a Kamengo Feeder. The value of the Kamengo Feeder is that it withdraws material evenly from its entire opening, which by definition is necessary to actually achieve a mass flow discharge pattern in the hopper, which is necessary when handling a difficult flowing bulk solid. A further advantage of the Kamengo Feeder is its low profile, which helps to save height and related civil costs.

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To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please download our white paper entitled: The Design of Reliable Storage Bins and Feeders for the Mining Industry.

Jamil Bundalli In Solutions To Common Problems

Wet Phosphate Rock Receiving Hopper

This is an example of a series of wet phosphate rock receiving bins that are suffering from chronic bridging and rat-holing. It is a good example of poor bin geometry combined with uneven discharge that is resulting in inconsistent discharge.

The Existing Hopper and Why it is Suffering from Chronic Plugging and Inconsistent Discharge

The existing bins consists of a pyramid hopper stacked on top of a plane flow hopper that is stacked on top of a second small pyramid hopper. Wet phosphate rock is withdrawn from the hopper via a belt feeder, which is preferentially withdrawing material from the rear of the bin outlet.

The combination of the small openings and pyramid shape at the discharge combined with the behaviour of the belt feeder is resulting in a funnel flow or first-in, last-out discharge. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with large bins with large discharge outlets. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

The alternative to funnel flow is mass flow, which is a first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. The tell-tale sign that you have mass flow is that material is sliding down the bin walls.

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Kamengo’s Solution

The solution to fixing this problem storage and feed system has two parts. The first half of the solution is to replace the lower pyramid hopper with a plane flow hopper with a wide and long opening. The wide and long discharge opening is required to overcome the bridging dimension of wet phosphate rock. Overcoming the bridging dimension is necessary to ensure that the material cannot bridge over the feeder. Changing the bin geometry will promote a mass flow discharge. Mass flow is a first-in, first-out discharge pattern.

The second half of the solution is to pair the new plane flow hoppers with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. Again, by definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.

A great example of a fully-effective feeder is the Kamengo Feeder. In addition to being fully-effective, the Feeder offers consistent metering, and can be made as wide as needed and as long as wanted. As a result, the Kamengo Feeder offers valuable advantages when designing for a difficult flowing material.

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Jamil Bundalli In Solutions To Common Problems

Metallurgical Coal Railcar Load-Out

This is an example of a met coal railcar loadout bin that is suffering from chronic bridging and rat-holing. It is a good example of poor bin geometry combined with uneven discharge that is resulting in inconsistent discharge.

The Existing Storage and Feed Arrangement and Why it is Suffering from Chronic Plugging and Inconsistent Discharge

The existing bin consists of of twin funnel flow (first-in, last-out) pyramid hoppers leading to small square discharge openings. One discharge opening is metered with a screw feeder and the other is metered using a clamshell gate.

The combination of the small openings and multiple shallow walls as well as the behavior of the feeders results in a hopper that cannot reliably discharged with only gravity. Because the discharge openings are small one would expect a tendency for stable rat-holes to form over the openings, and for the bins to suffer from erratic discharge. Finally, a consequence of having a first-in, last-out discharge is that stagnant material is left along the silo walls. Stagnant material will gain strength over time, further creating the conditions for plugging and erratic discharge.

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Kamengo’s Solution

The solution to fixing this problem storage and feed system has two parts. The first half of the solution is to reconfigure the hopper to include steep sloped walls, and move away from pyramid style hoppers to more conservative plane flow hoppers with a wide and long discharge opening. The wide and long discharge opening is required to overcome the bridging dimension of met coal. Overcoming the bridging dimension is necessary to ensure that the material cannot bridge over the feeder.

Changing the bin geometry will promote a mass flow discharge. Mass flow is a first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). The tell-tale sign that you have mass flow is that material is sliding down the bin walls. To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. This requirement leads to the second half of the solution.

The second half of the solution is to pair each plane flow hopper with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. Again, by definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.

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Jamil Bundalli In Solutions To Common Problems

Limestone Surge Bin Retrofit

This is an example of a limestone bin that is suffering from chronic bridging. It is a good example of an instance where the behavior of the Feeder is inducing rat-holing and bridging despite the fact that the bin is constructed with correct geometry.

The Existing Storage and Feed Arrangement and Why it is Suffering from Chronic Plugging and Inconsistent Discharge

The existing bin consists of several stacked chisel hoppers, and is discharged using a slide gate that opens from the middle outwards. To control the discharge onto the conveyor below, the slide gate opening is incrementally adjusted. Unfortunately, the system suffers from chronic rat-holing and bridging.

In summary, the bin is suffering from chronic plugging because when the slide gate is only partially open it induces a funnel flow discharge pattern despite the fact that the geometry of the storage bin is correct, where if the slide gate were removed, the bin would self-empty in a mass flow or first-in, first-out discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with a large discharge outlet. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

As noted, the storage bin is designed to discharge in a mass flow, or first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. The tell-tale sign that you have mass flow is that material is sliding down the bin walls. In contrast, with funnel flow, material is stagnant along the hopper walls. When the slide gate is only partially open, then material is not permitted to withdraw evenly from the entire discharge outlet of the storage bin because the slide gate has limited the “live” opening. The result is stagnant material along the bin walls and a funnel flow discharge pattern.

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Kamengo’s Solution

The solution to fixing this problem bin is simple. Given that the bin geometry is correct, such that if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern, only the behavior of the Feeder needs to be fixed. In this case, the feeder must be fully effective, which means that it must withdraw material evenly from its entire opening. The attached solution pairs the bin with a Kamengo Feeder. The reason for doing so is that the Kamengo Feeder withdraws material evenly from its entire opening, which by definition is necessary to actually achieve a mass flow discharge pattern in the bin.

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To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please visit KamengoU.

Jamil Bundalli In Solutions To Common Problems

Fine Ore Pile Reclaim (Copper Mine)

This is an example of a large fine ore storage reclaim that is suffering from chronic bridging.

Why the Existing Reclaim System is Suffering From Chronic Bridging and Inconsistent Discharge

The existing storage and feed arrangement consists of a storage building that has a flat floor and is being reclaimed from below through a series of long slots. Material is metered by a belt feeder below each slot. This case study is an example of making funnel flow work when handling a fine material.

In summary, because the storage facility has no sloping walls, but is instead reclaiming the pile through a series of long slots in the floor, the pile is expected to empty in a funnel flow or first-in, last-out discharge pattern. Funnel flow can certainly be made to work when the “effective” discharge outlet is wide and long. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

In the case of this facility, below each slot is a tapered chute and a belt feeder. The purpose the tapered chute is to try to even out the discharge by the belt feeder, because it has a propensity to withdraw material selectively from the rear of the slot. However, tapered chutes are only effective over short distances, and the slot is over 44-ft long. In summary, the tapered chute is having little effect, as a result the belt feeder is primarily pulling material from only a short section of the slot. As a result, despite the fact that the slot in the floor is long, effective opening through which material is being discharged (from the perspective of gravity) is small. And when the opening is small, rat-holing can be expected.

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Kamengo’s Solution

The solution to fixing this problem is to replace the chute and belt feeder with a fully-effective feeder. A fully-effective feeder is one where the feeder withdraws material evenly from its entire infeed opening. With a fully effective feeder, the full length and width of the slot is “live”, and with a large effective discharge area, the pile can reliably be discharged in a funnel flow discharge pattern.

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Jamil Bundalli In Solutions To Common Problems

Dry-Stacked Tailings Filter Cake Truck Load-Out Bin

This is an example of a tall truck load-out bin designed specifically to handle difficult flowing cohesive, high-moisture content dry-stacked tailings filter cake.

Why Conventional Clam Shell Bins Suffer from Chronic Bridging and Inconsistent Discharge

Standard truck load-out bins use a clamshell or slide gates to meter discharge. Unfortunately, many of these systems suffer from chronic bridging and rat-holing.

In summary, these bins suffer from chronic plugging because when the clam shell or slide gate is only partially open it induces a funnel flow discharge pattern despite the fact that the geometry of the storage bin may be correct, where if the slide gate or clam shell were removed, the bin would self-empty in a mass flow or first-in, first-out discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with a very large discharge outlet. However, when the discharge outlet is constricted, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

Ideally, a cohesive bulk solid such as a high-moisture content filter cake should be discharged in mass flow, or a first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. The tell-tale sign that you have mass flow is that material is sliding down the bin walls. In contrast, with funnel flow, material is stagnant along the hopper walls. When the clam shell or slide gate is only partially open, then material is not permitted to withdraw evenly from the entire discharge outlet of the storage bin because the slide gate has limited the “live” opening, causing some sections of material in the storage bin to be stagnant during discharge. The result is a funnel flow discharge pattern.

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Kamengo’s Solution

The solution to a reliable truck load-out storage bin for handling cohesive materials such as high-moisture content filter cake is simple. First, ensure the geometry of the storage bin is correct, such that if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern. Typically, Kamengo would recommend a plane flow hopper with a long and wide discharge opening, as this is among the most conservative bin shapes. Second, pair the storage bin with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. By definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.

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Jamil Bundalli In Solutions To Common Problems

Hot Lime Silo Retrofit

This is an example of a hot lime silo that is suffering from chronic bridging. It is a good example of poor bin geometry combined with uneven discharge that is resulting in chronic bridging.

Why the Existing Storage and Feed Arrangement is Suffering from Chronic Plugging and Inconsistent Discharge

The existing bin consists of a 25-foot diameter silo and 55-deg cone that converges to a 2-foot diameter opening that is fitted with a basket gate.

In summary, the silo is suffering from chronic plugging because the shallow cone and the behavior of the basket gate are inducing a funnel flow discharge pattern. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with a large discharge outlet. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

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Kamengo’s Solution

The solution to fixing this problem storage and feed system has two parts. The first half of the solution is to replace the bottom half of the cone with a mass flow chisel hopper with a wide and long opening. The result is an expanded flow bin, with the lower half of the storage silo emptying in mass flow and upper portion emptying in funnel flow. As long as the funnel flow portion is emptied completely on a regular basis the storage bin geometry will be reliable.

Mass flow is a first-in, first-out discharge pattern. The definition of mass flow is that during discharge, the entire mass of stored material comes down as a single body (single mass). The tell-tale sign that you have mass flow is that material is sliding down the bin walls. To achieve this, material must discharge evenly from the entire discharge outlet of the storage bin. This requirement leads to the second half of the solution.

The second half of the solution is to pair the plane flow chisel hopper with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. Again, by definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.

Learn More

To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please visit KamengoU.

Jamil Bundalli In Solutions To Common Problems

Lime Silo Retrofit

This is an example of a solution to fix a lime bin that is suffering from chronic bridging.

Why the Existing Silo is Suffering From Chronic Plugging and Inconsistent Discharge

The existing bin is a silo with a steep cone that converges to a vibratory feeder. The vibratory feeder employs a shallow cone and a small outlet.

In summary, the silo is suffering from chronic plugging because the shallow cone of the vibratory feeder is inducing a funnel flow discharge pattern, while constricting the material discharge to too small an opening. Funnel flow (which is a first-in, last-out discharge pattern) can be made to work with a large discharge outlet. However, when the discharge outlet is small, gravity is insufficient to overcome the strength of the bulk solid at the discharge outlet, and hence chronic bridging and rat-holing is expected.

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Kamengo’s Solution

The solution to fixing this problem bin has two parts. The first half of the solution is to rip out the funnel flow cones, and replace them with a steeper mass flow cone and mass flow chisel hopper. Doing so fixes the geometry of the silo such that if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern. The second half of the solution is to pair the new cone and hopper with a Kamengo Feeder. The reason for doing so is that the Kamengo Feeder withdraws material evenly from its entire opening, which by definition is necessary to actually achieve a mass flow discharge pattern in the silo. If the Feeder instead withdrew material unevenly, a funnel flow discharge pattern would ensue (regardless of the bin geometry), and rat-holing would occur.

Learn More

To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please visit KamengoU.

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