What Is a Conveyor Pulley?
A conveyor pulley is a disc-shaped component used in belt conveyors to transmit power from the belt.
In a belt conveyor system, the conveyor belt operates as the drive pulley, which functions like a pulley to move the conveyor belt. There are various types of pulleys that play different roles, such as changing the direction of the belt or pulling it, and the belt conveyor operates through multiple pulleys positioned at key points of the belt conveyor system.
Uses of Conveyor Pulleys
Conveyor pulleys are primarily used in belt conveyor operations. Industries where conveyor pulleys are commonly used include:
- Steel and Coke
- Quarrying (Crushing Stones)
- Cement and Ready-Mix Concrete
- Asphalt
- Civil Engineering
- Thermal Power Plants
- Recycling
- Water Treatment
- Logistics
- Paper and Pulp
Additionally, pulleys themselves are used in various devices beyond belt conveyors, such as car engines, agricultural machinery, compressors, pumps, and office automation equipment.
Principle of Conveyor Pulleys
Overview
The main components of a conveyor pulley include the shaft, bearing, end disc (side plate), hub, and shell (outer ring).
The shell makes contact with the belt, while the end discs support it on both sides. The shaft rotates, transmitting power to the hub and end discs, causing the outer ring to rotate and move the conveyor belt. The bearing supports the shaft, ensuring it remains in the correct position.
Shell Processing
During belt conveyor operation, the conveyor belt and pulley can become misaligned. To prevent such occurrences, the pulley shell may undergo crown processing, where the diameter of the central part of the outer ring is made larger than that of the ends. Additionally, the surface may be coated with rubber (lining processing).
Types of lining processing include:
- Horizontal Grooves
- Double Helical Type (grooves angled toward the center)
- Diamond Type
The double helical type is highly effective in increasing friction with the belt and preventing foreign matter from entering. The diamond type features a larger rubber surface area in contact with the belt, enhancing friction and bearing larger surface pressure. Unlike the double helical type, it also easily accommodates bidirectional operation.
Types of Conveyor Pulleys
Overview
Conveyor pulleys primarily include:
- Drive Pulley (Head Pulley): Drives the belt conveyor
- Snub Pulley: Increases the wrap angle of the belt around the pulley
- Tail Pulley: Located at the tail of the conveyor
- Tension Pulley: Pulls the belt
- Bend Pulley: Changes the direction of the belt
Each type has its role, and selecting the appropriate one depends on factors such as the length of the conveyor and the type of material being transported.
Head Pulley / Tail Pulley
Belt conveyors have a head (drive side) and a tail. The pulley at the head is called the head pulley, while the one at the tail is called the tail pulley.
The pulley that drives the conveyor is known as the drive pulley, and it is generally the head pulley. However, in some cases, the head pulley and drive pulley are separate in belt conveyors.
Tension Pulley, Bend Pulley, and Snub Pulley
The tension pulley maintains the tension of the conveyor belt, preventing deviation or skewing. The bend pulley changes the direction of the conveyor belt. The snub pulley increases the wrap angle of the conveyor belt around the pulley, preventing the belt from slipping or sagging.
Selecting Pulley Size
The appropriate size of the pulley is closely related to the selection of the conveyor belt. For example, rubber conveyor belts typically require pulleys with larger diameters compared to resin conveyor belts. Additionally, the greater the tension on the conveyor belt, the larger the pulley diameter required.
A smaller pulley diameter causes the conveyor belt to bend more sharply. The sharper the belt bends, the greater the stress on the belt, increasing the likelihood of belt joints coming apart or detaching. If the pulley diameter is smaller than required, the belt may slip at the pulley. Larger pulley diameters reduce the bending degree of the conveyor belt, thereby minimizing stress and extending belt life. However, larger diameters generally increase the manufacturing cost of the pulley.