Belt conveyors are used in every sector that handles bulk solids because they are among the most economical methods of moving materials into and out of a facility. They are a vital tool in almost every situation because of their versatile handling skills and adaptable design. However, the inability to regulate the material feed rate is a drawback of conveyors.
Read More: feeder belts
Achieving streamlined, efficient production requires controlling the flow of bulk materials; otherwise, bottlenecks, subpar products, shutdowns, and a variety of other production problems soon become the norm.
Belt feeders, which meter material into a process or piece of equipment, are therefore utilized in bulk solids handling and processing activities to appropriately manage material flow. In order to achieve a dependable, efficient feeding solution, belt feeders must be built with a few extra criteria in mind, even if the design of a belt feeder is based on many of the same features as those of a belt conveyor.
Applications of Belt Feeders
Belt feeders’ ability to handle bulk materials precisely makes them valuable in a variety of applications. Belt feeders, which can handle everything from sand to ore, are particularly important when dealing with bulk materials that have low flowability. They frequently occur in the following environments:
Paper and pulp mills
Plants that generate electricity
Operations related to mining and mineral processing
Plants that produce and combine fertilizer
Facilities for producing chemicals
Operations involving aggregate handling
The Operation of Belt Feeders
A hopper placed right above a belt conveyor makes up a belt feeder. While an adjustable vertical strike-off plate regulates the height of material permitted to advance as the belt advances—that is, the material profile on the belt—the belt conveyor “pulls” material out from beneath the hopper. The belt has material on the skirt boards.
Compared to standard troughed belt conveyors, belt feeders run at substantially slower rates; they normally run between 30 and 60 FPM and seldom go beyond 100 FPM.
Managing the Material Feed Rate using a Belt Feeder
Belt speed and strike-off plate height are the two factors that are adjusted to determine feed rate.
Height of the Strike-off Plate
The height above the conveyor that the strike-off plate is fixed to is known as the strike-off plate height. The substance being dispensed’s particle size largely determines the strike-off plate height; higher particle sizes necessitate higher height.
The strike-off plate height may be adjusted to enhance or reduce the flow rate since the higher the plate is positioned, the more material is discharged onto the belt.
Speed of the Belt
The pace at which the belt travels beneath the hopper, or conveyor belt speed, also serves as a feed rate control mechanism. Increasing belt speed also increases flow rate.
To strike the ideal balance between the required flow rate and the volume of material the conveyor belt can carry, strike-off plate height and belt speed are simultaneously adjusted.
Aspects to Take into Account When Designing Belt Feeders
Belt feeder dependability and operation are influenced by several factors:
The load on the head
The most crucial element in belt feeder design is head load. The force exerted by the weight of the material sitting on the belt directly behind the hopper opening is known as the head load. The bulk density of the material, along with the size and arrangement of the hopper, determines the head load.
The head load is utilized to establish the amount of horsepower needed to move the belt as well as the degree of structural support that is necessary. The engine and related parts must be bigger and have more horsepower as the head load increases.
The feeder would not operate if a conveyor was too small for the head load because the motor would over-amp and stall out. Although it may seem like a great idea to oversize a belt feeder, doing so is wasteful and uses more energy than is required.
It is frequently preferable to attempt to reduce the head load on the conveyor since a higher head load necessitates the use of more durable components, raising the capital expenditure.
There are several methods for lowering head load:
Include a structural component inside the hopper.
The head load can be decreased by adding a steel structural element, frequently referred to as a “top hat,” to the inside of the hopper to relieve part of the material weight on the belt.
Make use of an inclined hopper.
An angled hopper’s edges can help sustain the material load when a straight-edge hopper is replaced, lessening the weight strain on the belt conveyor.
Make use of a smaller hopper.
Since the dimensions of the hopper play a major role in determining the head load, lowering the hopper opening’s size (and/or height) likewise lowers the head load. The same capacity can then be attained by increasing the belt speed.
Lowering the head load allows for the use of lighter-duty components and less horsepower, which lowers the unit’s cost without sacrificing capacity.
Skirting
Although belt speed and sliding gate height are the main factors influencing feed rate, the feed rate capacity may be increased by using skirt boards or skirting.
By giving the material more structure to rest against, skirt boards help to keep the material on the belt contained. By doing this, operators may frequently “over fill” the conveyor and increase its capacity. The conveyor that follows the belt feeder is usually not skirted and will not be able to contain as much material, but the increased speed of this conveyor helps to make up for this. This must be done carefully, though, because the next conveyor must also be able to handle the load. Additionally, it is not cost-effective to fully skirt long conveyor spans.
VFDs
A variable frequency drive, or VFD, is a crucial part of the belt feeder as belt speed is the main element that affects feeder flow rate.
During startup or shutdown, the VFD enables operators to modify belt speed in response to variations in capacity or shifting particle size. Without a VFD, operators wouldn’t be able to manage the speed of the belt and would only be able to make adjustments to the strike-off plate, which is constrained by the maximum height modification that is permitted.
Scale of Belts
A belt scale is often used by the conveyor that comes after the belt feeder. To verify the intended feed rate, the material on the conveyor is weighed using a belt scale.
When a material is prone to flow issues like ratholing, belt scales are especially helpful since they may show when the feed rate has decreased.
In conclusion
In almost every operation that handles bulk solids, belt feeders provide precise control over the material feed rate. However, in order to create a long-lasting, effective feeder, some unique considerations must be made.