Belt conveyors, a fundamental component in material handling systems, have evolved significantly over the years. Their simplicity, reliability, and versatility make them indispensable in various industries. They facilitate the continuous and efficient transport of bulk materials.
- Basic Design and Components of Belt Conveyors: The core structure of a belt conveyor comprises two drum pulleys with a continuous loop conveyor belt. Troughing idlers support the carrying run, while return idlers facilitate the return run. The drive pulley, powered by an electrical motor, moves the belt forward, and the unpowered tail pulley marks the conveyor’s end. This robust design enables conveyance under adverse conditions. Fugitive material, escaping from the conveyor belt at unintended locations, is managed through cleaning systems. This prevents carry back and maintaining operational efficiency.
- Advantages of Belt Conveyors: Belt conveyors offer superiority, reliability, and versatility in material transportation. Their economic benefits, cost-efficiency, and virtually unlimited range of capacities contribute to their widespread use. They find applications in large-scale operations, often integrated with stackers and reclaimers for seamless material handling.
- Environmental Acceptability and Process Functions: The environmental acceptability of belt conveyors makes them a preferred choice over other means of transportation. They also play a vital role in process functions, particularly in sorting and hand-picking materials during transit.
- Applications in Various Industries: Belt conveyors exhibit adaptability in diverse industries, including mining, steel plants, bulk handling structures, port trusts, thermal power plants, cement plants, chemical plants, and fertilizer plants. Their flexibility in different terrains, gradients, and path variations makes them a major component in continuous material transportation.
- Material Handling Capabilities: Belt conveyors are very versatile by handling materials ranging from fine chemicals to lumpy ore and coal. They transport closely sized or friable materials with minimal degradation and successfully manage materials prone to sticking or packing. Hot materials like coke, sinter, iron ore pellets, and hot briquetted iron are efficiently conveyed.
- Future Developments and Automation Complexity: The increasing demand for higher capacities and longer conveying lengths has led to the development of more complex conveyor systems. Automation with advanced control features remains a focal point, addressing environmental challenges and improving overall system efficiency.
2. Components of Belt Conveyors
2.1 Belt (Belt Carcass)
The belt carcass stands as the fundamental reinforcement and pivotal structural component of the conveyor belt. It represents its core essence. It is tasked with withstanding the various stresses encountered during the conveyor belt’s operation. The following key characteristics are essential for an effective belt carcass:
- Adequate Tensile Strength: Must withstand the maximum operating tension of the belt. Empowers the belt to move a loaded load efficiently.
- Longitudinal Flexibility: Requires sufficient flexibility for smooth operation over pulleys.
- Transverse Flexibility: Necessary for proper troughing when the belt is running empty.
- Longitudinal and Transverse Stiffness: Vital for providing the required support to the belt as it moves on spaced idlers.
- Impact Absorption: Should absorb the impact of materials loaded onto the conveyor belt.
- Smooth Load Transport: Enables the smooth and spillage-free transport of the load.
- High-Temperature Operation: Capable of operating at temperatures exceeding 90°C.
- Low Self-Weight and Small Specific Elongation: Ensures minimal weight and elongation at the working tension.
- Tear and Rip Resistance: Possesses good resistance to tearing and ripping, ensuring durability.
- Mechanical Fastener Holding Ability: Should securely hold mechanical fasteners.
- Adhesion between Plies: Requires good adhesion between different layers of the carcass.
- Long Service Life: Minimizes moisture absorption and ensures a prolonged service life.
Photo 1 : Belt Carcass
The types of Conveyor Belts are;
a) Standard Rubber Belts:
Composition: Blend of natural and synthetic rubber.
Application: Suitable for handling most abrasive materials.
b) Cut-Resistant Belts:
Composition: High natural rubber content.
Application: Ideal for belts operating under challenging conditions prone to cutting and gouging.
Composition: Covers with styrene–butadiene.
Application: Recommended for materials with temperatures up to 1,200°C.
Composition: Chlorobutyl covers.
Application: Designed for materials with temperatures of up to 1,700°C.
Composition: Neoprene covers with multi-ply carcass.
Application: Manufactured to meet the highest safety standards in underground mines.
f)Wood Handling Belts:
Features: Non-staining, resistance to oil and resin.
Application: Tailored for the timber industry.
g)PVC Solid-Woven Belts:
Composition: Polyester and nylon with PVC coatings.
Features: Withstands impact, tear, and abrasion, meeting stringent flame-resistant standards.
Composition: Manufactured from non-toxic materials.
Features: Resistant to oils, fats, and staining, meeting hygiene requirements in the food processing industry.
i)Nitrile-Covered PVC Belts:
Features: Flame retardant, oil, abrasion, and heat resistance.
Application: Developed for mines with fire hazards.
j)Steel Cord Belts:
Composition: Steel wire inserted within high-quality rubber.
Features: Exceptional traction load and high impact material handling for long-distance conveyors.
Composition: Easily washable linings in nitrile, neoprene, or synthetic rubber.
Application: Ideal for handling materials containing vegetable oils and minerals.
l)Anti-Static Conveyor Belts:
Features: Cover rubber mixed to prevent static electricity.
Application: Vital for transporting fabrics prone to static or electronic products sensitive to electrification.
Understanding the distinct characteristics of each conveyor belt type empowers designers to make informed decisions which eventually ensures optimal performance in diverse applications.
2.2 Conveyor Idlers
Conveyor systems play a pivotal role in efficiently transporting bulk materials over long distances, and one of the key components contributing to their smooth operation is the belt conveyor idlers. These cylindrical rollers, strategically positioned between two pulleys at each end of the belt conveyor. They provide crucial support and facilitate the linear movement of the belt without sliding.
Photo 2 : Rollers (Idlers)
The conveyor idler, often referred to as an idler set, comprises rollers and a mounting frame. While the belt imparts rotary motion to the rollers, the idlers ensure the belt’s linear movement, forming an integral part of the conveyor system.
a)Functions of Conveyor Idlers
Conveyor idlers are indispensable elements in a conveyor system, ranking first in terms of quantity and second only to the belt in terms of cost. Despite the various idler types available, their fundamental functions remain consistent:
- Providing Trough Shape: Idlers play a crucial role in shaping the belt into a trough to contain the transported material effectively.
- Offering Support with Minimal Resistance: The primary function of idlers is to support the belt with the least amount of resistance, ensuring smooth belt motion.
- Minimizing Power Requirements: Conveyor idlers contribute to minimizing the power needed for material transport, enhancing overall energy efficiency.
Traditionally considered non-powered rotating mechanisms, idlers were labeled as such due to their lack of direct power transmission to the belt. However, contemporary perspectives recognize the critical role of idlers in ensuring the reliability and operational efficiency of the conveyor. Factors such as maintenance costs, power requirements, belt performance, and replacement are intricately tied to idler functionality, making them a powerful and indispensable component for boosting overall productivity.
In summary, conveyor idlers are not merely passive elements but active contributors to the performance and longevity of conveyor systems.
b) Parts of the Conveyor Rollers
The outer shell or tube forms the external layer of the roller which provides structural integrity and its shape. This component serves as the surface that comes into direct contact with the materials being conveyed.
- Central Axle, Spindle, or Shaft
The central axle, spindle, or shaft serves as the core internal component, offering a rotational axis around which the roller revolves. This central element is pivotal for the roller’s movement and alignment.
- Pair of Identical Bearings
Critical to the smooth rotation of the roller, a pair of identical bearings is positioned on either side of the central axle. These bearings minimize friction and facilitate the rotational motion of the roller.
To house and secure the bearings, suitable housings are incorporated into the roller’s design. These housings provide stability and protection to the bearings.
Rollers often operate in challenging environments. In such cases, to safeguard the internal components from contaminants, a sealing arrangement is implemented. This arrangement prevents the ingress of dust, moisture, or other detrimental substances.
Internal parts within the roller, such as bearings and shafts, require secure locking arrangements to maintain stability during operation. These locking mechanisms prevent unintended disassembly and ensure the longevity of the roller.
- Fixing Arrangement to Frames
For integration into larger systems, rollers are equipped with fixing arrangements that facilitate their attachment to frames or supporting structures. This ensures proper alignment and functionality within the overall system.
In a belt conveyor system, pulleys play a crucial role by altering the direction of the belt in a vertical plane. They create a continuous loop for uninterrupted operation. The pulley, also referred to as a drum, and its accompanying shaft combine to create a unified structure. Their operational features are interdependent.
The evolution of conveyor pulley construction has advanced from fabricated wood to cast iron and, currently, steel fabrication. Pulleys are produced in various sizes, with the standard steel pulley being the most widely employed in conveyor systems.
Photo 3: Pulleys
The parts of Pulleys are:
- Drum or Shell: The drum or shell is fabricated either from a rolled sheet of steel or from hollow steel tubing. This shell of the pulley is in direct contact with the belt. Hence, the diameter and face width of the shell depend on the rating and width of the belt used.
- Diaphragm Plates: The diaphragm or end plates of a pulley are circular discs welded to both the sides of the shell to strengthen the shell. These are fabricated from thick steel plate and are bored in their centre to accommodate the pulley shaft.
- Shaft: The shaft is a central cylindrical steel rod of the pulley designed to accommodate all the applied forces from the belt and the drive unit with minimum deflection. It is locked to the hubs of the end discs by means of locking elements. In the case of a shaft of drive pulley, the shafts are often stepped to accommodate different diameters of bearings and the drive attachment to the same shaft.
- Locking Elements: Locking elements, which are high-precision items, when fitted over the shaft and into the pulley hubs, attach the pulley firmly to the shaft concentrically by tightening the screws around the locking element.
- Hubs: The hubs, fabricated and machined housings, are welded into the end plates.
- Lagging: Lagging is covering the pulley surface with rubberized material by vulcanization. Lagging is necessary to improve the friction between the conveyor belt and the pulley in order to improve the torque that can be transmitted through a drive pulley. Improved traction over a pulley assists training of the belt. In the figure, lagging with herringbone grooves is shown.
- Bearing: Bearings used for conveyor pulleys are generally spherical roller bearings and self-aligning relative to their raceways. They are chosen for their radial and axial load supporting characteristics. The bearings are housed in plummer blocks that are bolted to sole plates. Sole plates are welded to the structure and incorporate jacking screws to enable the pulley to be correctly and relatively easily aligned.
The proper implementation of conveyor drive components, such as speed reduction, electric motors, controls, and safety devices, is essential for all belt conveyor installations. The optimal drive location is one that minimizes the maximum belt tension, typically at the discharge end for simple horizontal and inclined conveyors, and at the load end for decline conveyors. However, specific conditions may necessitate alternative drive locations. In certain instances, internal drives are employed in longer conveyors or inclined boom conveyors due to considerations of economy, accessibility, or maintenance.
Photo 4 : Belt Conveyor Drives
Typically, belt conveyor drive equipment comprises a motor, speed reducer, drive shaft, and machinery to transmit power between components. The most effective arrangement involves a simple configuration with the fewest components. Nevertheless, in some cases, specialized components may be required to adjust starting and stopping, incorporate holdback features, or vary belt speed.
2.5 Other Components
In addition to the fundamental components, various ancillary elements and considerations play a crucial role in optimizing the performance and functionality of belt conveyors. These supplementary components and design considerations are essential for ensuring efficient material handling, easy maintenance, and seamless operation. Below is an overview of the key ancillary components and design factors that contribute to a well-functioning belt conveyor system:
- Top Strand of the Belt: Constitutes the upper part of the belt loop, carrying the material.
- Bottom Strand of the Belt: Forms the lower part of the belt loop, completing the conveyor circuit.
- Carrying Troughing Idlers/Rollers: Supports the belt in the carrying run, ensuring a trough shape for effective material transport.
- Transition Idlers/Rollers: Facilitates the smooth transition of the belt between troughed and flat shapes.
- Impact Idlers/Rollers: Absorbs shock from falling material, minimizing damage to the belt.
- Carrying Training Idlers/Rollers: Ensures the belt stays centered within the conveyor structure, reacting to any mistracking.
- Return Idlers/Rollers: Supports the flat return strand of the belt on its return path.
- Return Training Idlers/Rollers: Similar to carrying training idlers, but for the return path, adjusting mistracking.
- Drive or Head Pulley: A powered pulley driving the belt forward, playing a pivotal role in material transport.
- Tail Pulleys: Unpowered pulleys at the conveyor’s dead end, guiding the return run of the belt.
- Snub Pulleys: Increases belt contact, enhancing tension transmission and traction.
- Bend Pulleys: Alters the belt’s direction, especially in systems with a vertical take-up arrangement.
- Take-Up Pulleys: Equipped with counterweights to remove slack from the belt during operation.
- Drive Motor: Typically an electric motor with reduction gears, providing power to drive the conveyor.
- Counterweights: Attached to take-up pulleys, ensuring proper tension and tracking of the belt.
- Vertical Take-Up Arrangement: Adjusts the height of the take-up pulley to maintain belt tension.
- Feed Chute: Allows controlled feeding of materials onto the conveyor belt.
- Skirt Plates for Guiding the Material: Vertical plates guiding conveyed material, preventing spillage.
- Belt Cleaners for the Carrying Side of the Belt: Removes material adhering to the carrying side, maintaining cleanliness.
- Belt Cleaner (Plough Type) for the Bottom Side of the Belt: Cleans the bottom side of the belt on the return run, preventing material build up.
- Pulley Cleaner: Removes material adhering to pulleys, ensuring smooth operation.
- Discharge Chute: Guides material discharge from the conveyor, directing it to the desired location.
- Dribble Chute: An angled chute positioned under the head end to catch any material falling off the return side and redirect it into the discharge stream.
Novelty Structures supplies various components for belt conveyors.