7. Using the Wrong Deck Cover – Deck convers are the portion of machine that actually make the separation. Without friction between the deck cover and the material to be separated, no separation will result. Therefore, a cover must be selected that will perform well with a specific product. Using the wrong cover will cause poor quality separation, and very low capacity. Sometimes, an improper cover will cause sufficient damage to the deck that it must be rebuilt. Generally, the cover should have a rough surface texture and the openings should be as large as possible without allowing material to fall through. Oliver offers four standard decks cloth for small grasses 30-mesh wire for seeds the size of alfalfa and clovers 16-mesh wire for seeds the size of wheat and oats and 8-10 mesh wire for large seeds, such as beans. A variety of special decks to meet particular needs are available. Urethane coated overcovers are available.
8. Belt Slipping – Belt commonly slip on new machinery. New belts have a tendency to stretch slightly and should be checked frequently during the first couple of weeks of operation. To check a belt, turn off the machine and lock out the power supply. Then apply pressure to the back of the belt midway between the two pulleys. The belt should deflect approximately ½ inch.
9.Attempting to Separate Commodities Unsuitable For Separation – This is a very rare problem, because normally a gravity separator will make some improvement in any free flowing product. However, a gravity is a specialized machine designed to separate particles of varying density and similar sizes. If material does not fall into that classification, then it probably cannot be separated on a gravity.