Introduction

Drums are rotating components found in belt conveyors that have the function of transmitting movement, diverting direction or even stretching the belt. This equipment is made up of four main structural components: the shaft, the hub, the disk and the cylinder. Figure 1 shows the distribution of these elements in a drum.

Figure 1: Drum components - SOURCE: https://www.exctmach.com/products/spare-parts/conveyor-pulley.html

The drums are also made up of the expansion rings, which are commonly used to couple the shaft to the hub, and the bearing housings and bearings, which will be responsible for allowing the drums to rotate. For this reason, the bearing is initially selected and, based on this definition, the bearing housing is selected, since each bearing requires a specific bearing housing. Bearings and plummer block housings are selected on the basis of minimum fatigue life requirements and according to the limit loads of the bearings.

Types of drums

Drums have different functions in a belt conveyor, depending on the position in which they are placed, such as providing deviations and bends in the belt. With this in mind, we can define some of the classifications for the component:

1. Return: located at the opposite end to the discharge terminal, its function is to return the belt to its initial position, and it can also act to tension the belt;
2. Stretcher: responsible for maintaining the ideal tension for the conveyor to function properly;
3. Drive: responsible for transmitting torque. This type of drum can be located at the discharge, center or return of the conveyor;
4. Deflection: its function is to deflect the belt's travel;
5. Backrest: its function is to increase the angle at which the belt grips the drive drum;

Design and applications

When sizing this type of equipment, the most important information is the width and tension of the belt, as well as the type of construction. As shown in Figure 2, the discs can be manufactured integrally and welded to the cylinder, or they can be welded to the hub and cylinder. The drum must be dimensioned taking into account the positions and types of weld, as well as the stresses required in each position.

Figure 2: Types of drum construction - SOURCE: Kot Collection.

This equipment is generally made of steel and, as already mentioned, one of its main functions is to drive the belt so that the expected operation of the conveyor is achieved. In this case, the drum to be used is the drive drum, which is coupled to the drive assembly, made up of motors and gearboxes. In some cases where necessary, a brake disk can also be attached to the drum shaft to be used in conjunction with a conveyor braking system.

For operations where high belt tensions are required, different drive configurations can be used. Among them, the use of a drive assembly on more than one drum can be considered, as well as the use of a double drive on the same drum.

Figure 3 below shows the braking system on a belt conveyor, as well as a double-drive drum.

Figure 3: Braking system on conveyor with double drive drum - SOURCE: https://www.mining-technology.com/contractors/crushers/johnson-industries/.

Due to the various applications of this equipment in belt conveyors, which in turn use a variety of loads, its calculation and sizing in projects is done according to the load capacity of each conveyor. Its manufacture also follows the technical standards and norms applicable to this type of equipment.

Another fundamental component in the use of drums is the coating, the purpose of which is to protect the equipment from wear and tear and also to increase its traction capacity. Given the various design variations, many factors must be analyzed when choosing a drum for your conveyor belt, such as the cost of the equipment, the environment in which it will be installed, the ease and cost of maintenance, as well as, of course, the parameters of use of the belt conveyor, such as tension, clamping angle, number of start and stop cycles, belt speed, among others. Figure 4 shows some lining models, which will be selected according to the purpose for which they are to be used.

Figure 4: Types of cladding - SOURCE: https://www.bocril.com.br/index.php?id=servicos2&cod=43

Market advantages

With the market constantly growing, new opportunities arise for the design and application of this component in environments that require greater capacity, efficiency or even safety. This results in the continuous development of technologies, with new coatings, dimensions and geometries, increasingly specific to the needs of their application.

One of the main advantages of using drums is when transporting materials over long distances, as the use of conveyor belts leads to significant cost savings. This is achieved by reducing the number of trucks used to transport materials, thus reducing the overall workload. In addition, it is also possible to reduce the direct interaction of employees with the material transportation process and with the material itself, which leads to greater operational safety. Another benefit of using conveyor belts is better control of particulate matter emissions. Some methods applied to conveyor belts for this purpose are presented below:

1. Enclosure of conveyor belts: prevents dust being drawn in during material transfers;
2.  Application of dust suppressant: this product forms a film around the material, reducing dust emissions;
3. Dedusting system: responsible for filtering the air before particles are released into the atmosphere;

Another factor to pay attention to is the conformity of the drums with the conveyors on which they will be used. It is essential to check that the drums and belts are compatible, thus avoiding subsequent adjustments to the initial design, or even rework to adapt the components.

Conclusion

Drums are rotating components that are subjected to high cycling and high loads from belt tensions. In addition, welding processes are inherent in the construction of this equipment, and it is also known that these processes lead to the emergence of regions where crack nucleation is favored. For this reason, it is essential that the design of drums is highly reliable, taking into account the correct manufacturing and sizing procedures, based on the applicable standards, thus avoiding fatigue failures of both the structure and its components, increasing the useful life and productivity of the equipment.

Following these considerations, the importance of drums in the use of belt conveyors is clear. Special attention must be paid to the maintenance and management of these components, avoiding production interruptions and always striving for operational efficiency and safety. The drum assembly encompasses different parts, so failures in individual components, such as the bearing or expansion ring, can compromise the entire functioning of the system. For this reason, carrying out structural inspections and assessments ensures greater equipment reliability, providing greater productivity and predictability for the maintenance of these assets.

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References

1. THE FUNCTION AND MECHANISM OF CONVEYOR PULLEY DRUMS - Terry J King Pr. Eng.
2. Faço Continuous Conveyor Manual, Ed. Faço, 1996.
3. CEMA Manual (Conveying Equipment Manufacturers Association), version 93.
4. Conveying Machines, Spivakovisky and Diaachkov, Editorial Mir, 1989.
5. Transportation and Elevation, P. Alexandrov, Ed. Mir, 1994.