Every tonne of ore that enters a heap leach operation must eventually be placed on the leach pad. The quality of that placement influences heap geometry, lift development, material distribution and the efficiency of the stacking operation.
The Radial Stacker is normally the final placement machine within the stacking train. While the upstream conveyors transport ore across the heap leach facility, the Radial Stacker controls where the ore is deposited across the active stacking area.
Understanding how Radial Stackers work at a system level, and how coverage is evaluated, helps project teams compare stacking arrangements without confusing equipment reach with overall heap performance.
Quick answer: what does a Radial Stacker do?
A Radial Stacker is a mobile conveyor that receives ore from the upstream stacking system and places it across an active stacking area. The machine distributes material through a controlled working arc and forms the final link between continuous conveying and ore placement on the heap.
What is a Radial Stacker?
A Radial Stacker is a conveyor designed to distribute material across a wider footprint than a fixed discharge conveyor. In heap leach applications, it normally operates at the discharge end of the stacking train and performs the final placement of ore onto the pad.
The machine may combine slewing, boom movement, tracked mobility and a stinger or extendable discharge section, depending on the selected configuration. These functions allow the discharge point to serve a planned stacking area while remaining connected to the upstream material flow.
The Radial Stacker does not replace ore preparation, agglomeration or careful transfer design. It is the placement component within a larger system whose performance depends on the quality and consistency of the material delivered to it.
Where the Radial Stacker fits in a heap leach stacking train
A typical mobile heap leach stacking train may follow this sequence:
Ore source → Ramp Conveyor → Grasshopper Conveyors → Transverse Conveyor → Horizontal Index Conveyor → Radial Stacker → Ore placement
Each machine has a specific role. Ramp and Grasshopper Conveyors extend the conveying route. The Transverse Conveyor provides the handoff to the retreat-stacking portion of the system. The Horizontal Index Conveyor supplies a movable feed point. The Radial Stacker performs final placement.
Why ore placement matters
Heap leaching depends on chemistry, hydraulics and the physical arrangement of the ore. Ore placement does not determine recovery on its own, but it influences the conditions within which irrigation and leaching take place.
Placement can affect heap geometry, material distribution, segregation patterns and lift development. Excessive particle-size separation or inconsistent placement may create zones with different permeability and solution-flow behaviour. Controlled placement is therefore one part of a broader approach that includes crushing, agglomeration where required, transfer design, stacking and irrigation.
A Radial Stacker does not guarantee recovery improvement. Its value lies in providing a controlled and repeatable method of positioning ore across the active stacking area.
Coverage optimisation explained
Coverage optimisation is the process of configuring and using the stacking system so that the required operating area can be serviced efficiently while maintaining controlled ore placement. It is not simply an attempt to maximise the geometric reach of one machine.
Effective coverage depends on the relationship between the stacker, its feed point, the heap geometry and the stacking strategy. Project teams should consider how much of the active area can be served before the stacking train requires major repositioning, and whether the arrangement supports the planned lift and retreat strategy.
Potential benefits of an appropriately configured coverage arrangement include:
- A larger active placement footprint than a single fixed discharge point.
- Fewer major system repositioning events within a stacking cycle.
- Better utilisation of the stacker and upstream conveyor train.
- Greater flexibility as cells, lifts and pad areas develop.
- Support for planned retreat-stacking arrangements.
These benefits remain dependent on the selected equipment, operating plan, ore characteristics and pad layout.
Radial coverage compared with fixed discharge
A fixed discharge conveyor deposits material at one location. As the pile grows, the conveying system generally needs to be moved or the material must be redistributed by other equipment.
A Radial Stacker provides a controlled working arc and movable discharge position. This allows the stacking system to place material across a broader area before a major repositioning event is required.
The comparison is not simply radial versus fixed. Project teams must assess the complete material handling strategy, including throughput, heap geometry, relocation frequency, mobile equipment availability and the degree of placement control required.
Relationship between the Radial Stacker and Horizontal Index Conveyor
In many retreat-stacking systems, the Radial Stacker and Horizontal Index Conveyor operate as a coordinated pair. The Horizontal Index Conveyor supplies ore to the stacker and provides a mobile feed point. The Radial Stacker distributes that ore across the active placement area.
This relationship allows the final part of the stacking train to progress across the pad while remaining connected to the longer upstream conveyor route. It is one of the key differences between a conventional fixed discharge arrangement and an integrated retreat-stacking system.
Heap geometry and lift development
The stacking system must support the planned geometry of the heap throughout the life of the operation. Relevant design inputs include cell dimensions, lift height, stacking direction, retreat path, target profile and future expansion areas.
The Radial Stacker contributes to this plan by controlling the placement footprint at the active face. The equipment configuration must be considered alongside geotechnical, metallurgical and operational requirements rather than selected as an isolated conveyor.
Segregation and placement considerations
Material can segregate whenever particles with different sizes, shapes or densities are handled and discharged. Coarse particles may travel further than fine particles, while impact and excessive drop height may damage agglomerates or concentrate fines in specific zones.
A Radial Stacker provides greater control over the discharge location, but it does not eliminate segregation. Transfer geometry, feed consistency, discharge height, stockpile slope, ore condition and operating practice remain important.
Common design considerations
Throughput requirements
The conveyor, drive, belt width and transfer arrangement must suit the required duty. Capacity should be confirmed against representative material characteristics and the complete system, not selected from a nominal range alone.
Coverage area
The required placement footprint should be defined from the heap-development plan. Coverage depends on stacker geometry, working arc, discharge position and integration with the movable feed system.
Heap-development strategy
Advance stacking, retreat stacking, lift sequencing and future pad expansion influence the preferred equipment arrangement.
Ore characteristics
Particle-size distribution, moisture, bulk density, fines, clay content and agglomerate strength affect handling and placement behaviour.
Mobility and repositioning philosophy
The project should define how frequently the stacker and associated conveyors need to move, the prepared travel areas required and how repositioning fits into production planning. Detailed movement procedures remain part of controlled operating documentation, not public website content.
System integration
The Radial Stacker should be selected as part of the stacking train. Transfer heights, chute interfaces, power and control philosophy, structural compatibility and feed alignment need to function as one system.
What a Radial Stacker cannot solve on its own
- Poor crushing or uncontrolled particle-size distribution.
- Inadequate agglomeration where agglomeration is required.
- Weak transfer design or excessive material impact.
- Inconsistent feed rate or unsuitable material moisture.
- Irrigation, drainage or metallurgical problems elsewhere in the heap.
- A heap-development plan that has not defined the required placement area.
This is why the most useful equipment discussions begin with the overall process and stacking strategy rather than the machine in isolation.
Frequently asked questions
Here are some common questions we get asked at Carmaky.
What is a Radial Stacker?
A Radial Stacker is a mobile conveyor that places ore across the active stacking area of a heap leach pad. It is typically the final piece of equipment in the stacking train and is responsible for controlled ore placement and heap development.
What is the purpose of a Radial Stacker in heap leaching?
The primary purpose of a Radial Stacker is to distribute ore across the heap leach pad in a controlled manner. Effective placement helps support planned heap geometry, lift development and material distribution across the active stacking area.
How does a Radial Stacker differ from a Grasshopper Conveyor?
Grasshopper Conveyors primarily transport ore across the heap leach pad, while the Radial Stacker performs the final placement of ore. The Radial Stacker works at the discharge end of the stacking train and controls where material is deposited.
What is coverage optimisation?
Coverage optimisation is the process of maximising the active stacking area that can be serviced by the Radial Stacker while maintaining controlled ore placement. The objective is to achieve efficient heap development with minimal disruption to stacking operations.
Can a Radial Stacker be used for retreat stacking?
Yes. Radial Stackers are commonly used in retreat-stacking systems and are often paired with Horizontal Index Conveyors. Together they allow ore to be placed while the stacking train progressively retreats across the heap.
Why is ore placement important in heap leaching?
Ore placement can influence heap geometry, material distribution, permeability and solution movement through the ore body. Consistent placement helps support the conditions required for effective heap leaching.
Do Radial Stackers improve metal recovery?
A Radial Stacker does not directly recover metal. However, controlled ore placement may contribute to more consistent heap construction, which can support the overall conditions required for efficient leaching.
What equipment normally works with a Radial Stacker?
A typical heap leach stacking train may include Ramp Conveyors, Grasshopper Conveyors, Transverse Conveyors, Horizontal Index Conveyors and Radial Stackers. The exact configuration depends on the project requirements.
How large an area can a Radial Stacker cover?
Coverage depends on the stacker configuration, heap design, stacking strategy and operating requirements. The effective coverage area is generally influenced by the stacker’s working arc and integration with the wider stacking system.
What should be considered when selecting a Radial Stacker?
Key considerations may include throughput requirements, heap geometry, stacking strategy, mobility requirements, ore characteristics, planned lift heights and integration with the overall stacking train.
What is the relationship between a Radial Stacker and a Horizontal Index Conveyor?
The Horizontal Index Conveyor supplies ore to the Radial Stacker and allows the feed point to move with the stacking operation. The Radial Stacker then performs the final placement of ore across the heap.
Are Radial Stackers only used in heap leach applications?
No. Radial Stackers are used in a range of bulk material handling applications. However, they are particularly effective in heap leach operations where controlled placement and large-area coverage are required.
Conclusion
The Radial Stacker transforms continuous ore flow into controlled placement. Its commercial value comes from the ability to serve a planned stacking area while remaining integrated with the upstream conveyor train.
Coverage optimisation should be evaluated at system level. The required footprint, heap geometry, retreat strategy, ore condition and relationship with the Horizontal Index Conveyor all influence the final equipment configuration.
For mines and project teams, the most effective approach is to define the required stacking outcome first, then configure the Radial Stacker and wider material handling system around that requirement.
Related resources: heap leach stacking systems · Heap Leach Resource Centre
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