Considerations For An Optimal Conveyor Transfer Chute Design
Conveyor transfer chute problems are often expensive. Close attention in the design phase can prevent or at least minimize them.
Consider for example a chute that keeps blocking. Each time it happens material handling operations come to a halt and product spills. There is disruption and waste, both of which could be avoided with a better design.
Here’s some guidance on how to go about optimizing transfer chute design.
Transfer Chute Overview
For anyone not versed in these material handling units, a primer is in order. Conveyor transfer chutes deposit material onto a belt conveyor. This material might be delivered by truck and dropped into a hopper above the chute, but most are used for belt-to-belt transfers.
A belt-to-belt transfer chute is fed material from the upper conveyor. Typically, material waterfalls off the belt into the head chute compartment. From here it falls under gravity with baffles or plates in the drop and loading chutes directing it onto the lower conveyor.
Conveyor transfer chutes should not be confused with chute conveyors, despite their similar names. Although still gravity-assisted, chute conveyors provide a slope that packages slide down.
4 Considerations For Transfer Chute Design
The starting point is to understand the application and performance requirements. After that, points to address are:
- Throughput required
- Material characteristics
- Conveyor directions/angles
The transfer chute will act as a funnel, constraining the maximum throughput of the conveyor system, and must be sized accordingly. Consider both weight and volume per hour and ensure there’s ample capacity. Once constructed and installed there’s no easy way to increase the volume a transfer chute can handle.
Delivery and discharge velocity are other aspects of throughput to consider. On the input or top side, conveyor speed determines the material descent path. At the bottom, the chute should be sized and shaped to deliver material onto the discharge belt at close to belt speed. This avoids differentials that will accelerate belt wear and increase motor loads.
2. Material characteristics
Density and particle size distribution will influence how material drops through the chute and the likelihood of blockages. The material will also wear the chute interior as it falls, so abrasiveness is a third point to consider. Transfer chutes are usually fitted with liners that provide abrasion-resistance and so extend chute life. Liner material should be chosen with regard to the material being handled.
Also under the heading of material characteristics, consider the propensity of the material to break up, segregate and release dust. Besides being an appreciable source of product loss, dust creates environmental problems and needs periodic clean-up.
Dust is created by material impacts inside the chute. It can be managed by incorporating a settling zone and fitting seals or skirts around the lower conveyor.
The drop distance in a conveyor transfer chute is a determining factor in the horizontal exit speed. This distance should be set so the material is discharged onto the lower conveyor at a velocity close to that of the belt. However, the further material falls within the transfer chute the more fragmentation occurs and the more dust is released.
Effective drop height can be reduced by adding intermediate ledges or steps within the chute. An additional benefit is that as material accumulates in these areas it absorbs the impact of falling material, which reduces wear within the chute.
Another factor to consider under the head of “drop” is how the rock box directs material flow onto the discharge conveyor. The rock box is the chute component that narrows the chute width and manages the flow rate. The drop box must be engineered and positioned to deposit material into the center of the lower conveyor. Off-center depositing will affect tracking and greatly accelerate belt wear.
4. Conveyor directions/angles
In-line conveyors are the most straightforward layout to handle. Here, the input and discharge conveyors are in the same orientation and there’s no need to change material direction. However, transfer chutes are often used to move material onto conveyors moving in a different direction.
When designing for such setups the main point to consider is how the material will waterfall off the upper conveyor. This dictates the horizontal spacing needed for the chute. It’s often advisable to make the discharge belt appreciably wider than the input belt to minimize spill.
Discuss Your Transfer Chute Design Requirements
The transfer chute is a critical piece of equipment in many mining, quarrying, and other material handling operations. Poorly designed transfer chutes create downtime throughout the conveyor system and can have a major impact on output and productivity.
Careful attention to the properties of the material being conveyed, along with an understanding of how it moves through the transfer chute, will guide decision-making at the design stage. Considering these factors up-front will result in a transfer chute design that aids rather than restricts production.
West River Conveyors are specialists in material handling solutions for mining and other bulk material handling industries. We design and manufacture a range of terminal equipment that increases productivity and improves operations. Transfer chutes are just some of the many conveyor system components we produce.