Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/513927
31 AGGREGATES MANAGER May 2015 EQUIPMENT MANAGEMENT by Dave Anderson A vibrating grizzly feeder not only absorbs the shock of large dump loads, it also improves the efficiency of the primary crusher. I n the world of aggregate crushing, the word "feeder" can apply to many different devices. There are roller belt feeders, apron feeders, electromagnetic feeders, pan feeders, and others. This ar- ticle focuses on a feeder type that plays a critical role in the efficient operation of primary crush- ers — the vibrating grizzly feeder or VGF. The purpose of a VGF is twofold: to absorb the shock of large dump loads and to maximize the pri- mary crusher efficiency. It makes the primary crusher more efficient by supplying a constant, metered rate of feed to the crusher and by pulling fines from the feed material to keep it out of the crushing chamber. VGFs handle a variety of material types from large shotrock to sand and gravel; from high- clay aggregate to recycled concrete; from iron slag to gold-laced shale ore. The VGF also helps to clean and separate sticky or conglomerate type materials prior to entering the crushing chamber. The VGF takes a beating in most primary applications, allowing the rest of the circuit downstream to operate at an optimum level. For this reason, the VGF should be a point of focus for regular inspections and pre- ventive maintenance. Like all discussions on aggregate processing equipment, the starting point is to talk about safety. Al- ways follow the OEM guidelines and your company's lock-out/tag-out procedures prior to starting main- tenance or repair work on a VGF. Always use the correct lifting devices that have been inspected and calibrated for your requirements, and don't lift with your back. Since most VGFs operate on the basis of unbalanced weight rotation, make sure all stored energy has been relieved prior to working on the ma- chine. Work smart and stay healthy! Use the right settings for the application Vibrating grizzly feeders use medium speed rotating eccentric shafts to "throw" material down the feeder and into the crushing chamber. Even though most feeders operate at a lower rotations per min- ute (rpm) than typical material sizing devices (screens) — typically in the 500 to 800 rpm range — the bearings on the feeder shafts are still subject to the stresses of friction at a medium speed over long time periods. Friction leads to high heat generation, the enemy of bearings in any situation. This is one of the many forces acting to wear down your vibratory equipment. Maintenance personnel are charged not only with keeping equipment in good shape and running smoothly, but also attaining the most uptime from every piece of equipment and making it last as many years as possible. There are several Feed the Beast