Roller Screen -
page title project1 roller screen
Roller ScreenA Certain Solution for Sticky & Brittle Material Screening in Pelletizing Plant
roller screen details
FMS Roller screen Overview
The main characteristic of roller screen is its smooth movement and integrity preservation of brittle particles. Roller screen also provides higher performance, slight sound and capability of separating high moisture sticky materials. Roller screens are mainly used in iron ore processing plants for concentrate scalping before HPGR and sizing pellets after the balling disc.
Considering the roller screen function, design parameters like inclination, roller coating type, and surface roughness, driving system and sealing system must be chosen accurately. FMS offers different kinds of roller screen to meet the range of needs of its clients:
- single and double deck roller screen for the balling department
- single and double deck roller feeder for the grate feeding station
- Tramp removal from concentrate
- Compact size & pilot roller screen
FMS Roller Screen Technology
1.Single deck roller screen for the balling department
Single deck roller screens are found in the balling department and are most often used to screen the undersize in the upper section of the screens, the good products in the second section and the oversize pellets, which fall at the discharge end of the screen. The rejected products (undersize and oversize pellets) fall on a conveyor underneath the screen and are returned to the balling disc. Good products are picked up by another conveyor, which will ultimately feed the roller feeder at the entrance of the furnace.
Both chain driven and multi-drive types can be used for pellet sizing. Easy and quic k maintenance Operations are main priority of multi-drive roller screens while chain driven type is more compact.
2. Roller feeder for the grate feeding station
The roller feeder is placed at the grate feeding station. Pellets coming from the balling department are discharged on it. One of its purposes is to remove the fines coming from the breakage of pellets on their way to the furnace. Its main function is to distribute evenly the good pellets on the indurations furnace grate. This equipment can be driven with a chain or with individual drives. The roll length can be provided up to6 meters upon feeding capacity.
3. Tramp removal from concentrate
The duty of this screen is scalping material before feeding them into the next equipment. This type of roller screen is usually used for ore concentrate with high humidity;while, vibratory screen can not perform properly for sticky material with humidity above %8. Usual roller gap is about 12 to 30 mm.
FMS utilizes special UHMW roller coating for tramp removal applications which results in high feed capacity and extra ordinary roller life time.
4. Compact size & pilot roller screen
Currently in different plants of worldwide, it is required to increase the capacity of pelletizing plants; while there is no space for addition of a proper roller screen. In such cases, FMS presents compact size roller screen as solution. Compact size roller screen can be designed regarding the available space under balling disks.
Removing tramps from concentrate iron ore in the plants with lack of space, has the same story. FMS designs compact roller screens regarding required capacity and available room in client plant.
Pilot Roller Screens are also available for experimental research activities.
Professional Design Procedure
In the case of roller diameter design, FMS attempts to select smaller diameter rolls. Smaller rolls provide more screening area resulting in higher capacity for the same size of screen. In addition, smaller rolls make rounder and more compressed green pellets. To have desired linear velocity, smaller rolls should have higher angular velocity, which results in higher performance and better material flow on the screen.
- Removable shaft with easy and quick disassembling.
- Overlapping seal plates (inner and outer) preventing dust contamination of the bearings and drive case.
Chain Tensioner System
- Two different types of chain tensioner is suggested.
- Depending on available space around the roller screen/feeder, proper type will be designated.
Sealing and Lubricating System Options
Air sealing: It works by positive air pressure inside the sprocket box. The box doors are equipped to sealing rubbers and an air filter is used in order to prevent dust penetration in balance or negative box pressure.
Automatic grease lubrication system: It is suggested for roller screens/feeders with individual drive for each roll. Both lubrication and grease sealing can be supported automatically with this system.
Flexible Chain Guide System
FMS suggests tyre-flex couplings and cardans with universal joints for higher life time of gear-motor bearings in multi-drive roller screens/feeders.
Direct connection between gear motor and rollers, especially for long rollers, damages bearing and sealing system of bearings or gear-motor.
Skirts are fitted at the end of rolls, above the shafts. Skirt material are UHMW which prevent premature wear and tear caused by the accumulation of abrasive pellet
FMS has successfully experienced complicated large roller screen installation.
FMS Roller Screen features
FMS specifically focuses on manufacturing of rollers as the main part of roller screens. Depending of roller screen application, classifying green pellet or scalping iron or concentrate, particular rollers is designed by FMS. Different rollers and coatings have been tested successfully and real application in plants.
Most common base material and coatings are categorized as follow:
- Stainless steel 304
- Stainless steel CA6NM
- Chrome plated coating
- SF series coating
- AF series coating (High wear and corrosion resistant thermal spray coating)
Stainless steel uncoated rollers have acceptable performance in pellet screening while long time working deforms outer diameter along roller that affects screening efficiency.
Chrome plated rollers have higher life time comparing uncoated rollers and usually suggested for impact rollers.
FMS new coated roller known as AF Series (AF190 to AF 210) has significantly high wear and corrosion resistance, constant outer diameter and constant surface roughness and re-gapping needless during the working time. Although, exact life time may differ upon feed capacity and properties of pellet composition, estimated life time for AF rollers is expected to be more than 3 years.
In case of scalping application, specific SF coating is suggested. The innovative SF coating prevents sticking high humidity material to the roller; moreover, it dramatically increases roller life time. Coating can be applied on carbon steel base material which results in reducing manufacturing cost.
All roller coating creates the chance of recycling roller base material and re-coat it.