Most often used for pre-screening, the typical feed materials that require grizzly screens versus the typical vibrating screen are very coarse aggregates.
Grizzly Screens – General Kinematics
Able to handle both wet and dry materials, grizzly screens often handle materials such as minerals, ore, blasted or ripped rock, gypsum, foundry materials and large stone. Grizzly screens can offer multiple sizing decks on a single unit as well as side plates that provide additional height to ensure that large materials stay on the screen.
Grizzly screens can provide either linear or circular motion and each type offers its own advantages. Linear motion grizzly screens work best for scalping ahead of primary cone crushers in mining applications, while circular motion grizzly screens for heavy duty medium to fine pre or post-screening.
Primarily used for the heavy duty screening of undersized materials in bulk material handling applications, the most common industries that utilize grizzly screens include mining, construction, foundry, recycling and industrial.
Most often fed through either a pan or apron feeder, grizzly screens consist of an inclined or horizontal screen with parallel sets of grizzly bars that are held by spacers at varied openings depending on the size of the material being screened.
The grizzly bars are often constructed of manganese steel, but can also be made from ceramic materials. Typically, grizzly screens consist of a screening body is connected to a tray; materials enter the vibrating screen through a feed box located at the base of the tray. The vibrators are often either electromagnetic or electromechanical, and are placed at intervals underneath the screening body. While electromechanical vibrators are more common and simpler in design, electromagnetic vibrators offer a smoother conveying motion.
The suspending device supports the structural framework that the screens are mounted on and are typically either leaf springs or steel coil springs. These springs serve as shock absorbers as well as ensuring that the vibrations occur at a natural frequency. An electric motor is attached to the structural framework and causes the materials to be vibrated in a specific direction.
Grizzly screens are able to provide either linear motion or circular motion through the use of roller bearings, shafts or couplings.