Comparison between Roller Screen and Banana Screen

Overview

Screening equipment is a key device that achieves separation through the difference in material particle size and is widely used in multiple fields such as mining, chemical engineering, and building materials. Roller screens and banana screens are two highly used screening devices in industrial production, but they have significant differences in working principles and applications.

Working Principles

Roller Screen Working Principle

The roller screen uses multi-axis rotation to push the material forward and simultaneously perform screening. Its working mechanism consists of rows of screen shafts. Each screen shaft rotates in the same direction, causing the material to move forward along the screen surface while stirring the material. Particles smaller than the screen hole size fall off the screen holes under the action of their own weight and the rotational force of the screen shafts, while particles larger than the screen hole size remain on the screen surface and continue to move forward before entering the crusher for crushing.

Banana Screen Working Principle

The banana screen has a large sloping screen surface at the feeding end until the discharge port. The sloping screen surface at the feeding end enables more materials to pass through the screen surface at a higher screening speed and allows thinner materials to stratify. During the screening process, materials with randomly distributed particle sizes are produced by the particle factory and fall into the screen box under the action of gravity, colliding with the simply harmonic vibrating screen surface. Under the combined action of the screen surface force, gravity and the intergranular force, the material undergoes stratification during the conveying process. Some small-sized particles pass through the screen and become underscreen materials, while the remaining material is discharged from the discharge end and becomes overscreen materials.

Structural design

Structural design of roller screen

Roller Screen Each sieve shaft has a set of drive devices to drive the sieve shafts. A screen plate cleaner is installed at the lower part of the screen shaft to keep the screen plates clean. The Screen plates of the Roller Screen are all cast from manganese steel. The control circuit of the roller motor is equipped with an air switch overload protection device. When the screen shaft is blocked, it can automatically alarm and cut off the motor. The screen shaft and the reducer are equipped with nylon shearing pins. When there is a sudden large torque, the shearing pins can be used to cut off, protecting the motor.

The Roller Screen screen shaft is equipped with an overload protection device. In the middle of the coupling, a nylon sleeve pin is used. When the screen shaft is jammed, the nylon sleeve pin will break due to excessive shear force to achieve overload protection.

When the current coal volume is large and far exceeds the working capacity of the roller screen, coal will clog the interior of the machine box. When the pressure exerted by the coal on the box reaches a certain time and pressure, the pressure sensor will respond, and the electric push rod will act, keeping the baffle in a vertical position, allowing the screened coal to fall directly to protect the roller screen. And it is easy to maintain.

Structural design of banana screen

The banana screen is composed of a sieve box, a sieve surface, an exciter, a transmission device, a supporting device, etc.

The screen box is composed of side plates, drive beams, crossbeams, reinforcing beams and discharging end beams. It is the main working component of the banana screen and has functions such as transmitting the excitation force, supporting the exciter, withstanding the impact of materials and screening and conveying materials.

The banana screen is used to handle sticky and wet materials. Therefore, in the design of the sieve plate, the impact resistance should be taken into account, while ensuring a high opening rate of the sieve surface and the passability of the materials. The feeding section is a two-span heavy-duty sieve plate, which is welded by light rail according to the screening requirements. Moreover, it is designed with a structure that is wider at the front and narrower at the back along the direction of material movement to facilitate the rapid classification of materials.

The exciter adopts an external eccentric block structure, featuring light weight, compact structure, centralized lubrication of moving parts, high overall precision, good relaxation performance and high safety.

The transmission device adopts the motor – bearing housing – universal drive shaft transmission mode. The device is fixed on a motor bracket. After the motor decelerates through the V-belt, the power is transmitted to the vibrator through a pair of paired bearing housings fixed on the motor frame. The universal drive shaft compensates for the radial runout caused by the vibration process of the banana screen and the resonance when it starts and stops.

Performance characteristics

The performance characteristics of roller screens

1. The shape of therollerscreen plate is a hexagonal parabolic shape and rounded to eliminate sharp corners, which reduces the rotational resistance and enables the throwing of lumps in the material to the upper part, making it more conducive for small-sized materials to fall to the bottom of the screen.
2. The bearing housing of each screen shaft is a flexible base. Once the screen shaft gets stuck, the base will slightly move, thereby breaking the triangular force causing the jam and eliminating it instantly.
3. The drive reducer adopts a vertical hollow shaft reducer, eliminating the coupling, which occupies less space and has a simpler transmission structure.
4. Each screen shaft is equipped with a wear-resistant cleaning device, which is not prone to clogging.
5. All screen shafts are independently driven, and single-shaft maintenance does not affect the operation of the entire machine.
6. Inspection holes are installed on both the upper and rear parts for convenient inspection and maintenance.
7. The screen shaft and the box body adopt an impeller seal, which is more effective in preventing dust from spreading out.

The performance characteristics of banana screen

1. The banana screen frame and each component (rectangular support crossbeam) are reasonably arranged and evenly stressed, featuring high reliability and a long service life. It is aesthetically pleasing in shape, simple in structure, easy to maintain and occupies relatively little space.
2. The side plate structure is unique, all connected by cold riveting. The reinforcing ribs are distributed according to the stress points, with no welds, no stress concentration, no deformation or tearing, greater strength and higher reliability.
3. Advanced vibration parameters, stable performance, smooth operation, and low noise.
4. The exciter adopts a new type of “eccentric block external integral box type” structure exciter, with helical gear transmission, which is safe and reliable, has excellent lubrication and sealing, and is convenient for maintenance, replacement and amplitude adjustment.
5. Both the feeding box and the discharge port are equipped with wear-resistant and replaceable liners to protect the beams in the blind hole area from impact and wear.
6. The blind plate of the feeding box forms two angles with the banana screen surface of the rear section to buffer the impact of large pieces of materials on the screen surface, slow down the material speed, and also play a role in dispersing the materials of the feeder.