OCR

Miscellaneous Features and Safeguards An Emergency Pull Cord extends the full length of the conveyors. Overspeed Control is maintained electrically. Should a conveyor exceed 115 percent of rated speed, a contact of the previously mentioned driven tacho- generator closes and an emergency stop takes place. This control is mechanically backed-up by a centrifugal switch which is set at approximately 120 percent of rated speed. This device is mounted on a different driven pulley. Belt Off-Line Protection is provided at both terminals of each conveyor by spring loaded limit switches. There is a delay timer in these circuits; which makes it necessary that the belt remain off line approximately TO seconds before the emergency stop is released. A Motor Overload automatically disconnects both motors of the conveyor and actuates the mechanical brakes and at the same time signals an emergency stop to the preceding conveyors. Shuttle Conveyor: This conveyor is 48 in. wide and travels at 490 fpm. The belting is five ply, nylon reinforced with a top and bottom breaker strip. The conveyor drive is a 30 hp motor-gear with a chain drive between the reducer and the drive pulley. The conveyor is track-mounted and has a three-hp motor-gear drive with a roller chain output for shuttle movement. The shuttle distance is 116-1/2 ft with a tramming speed of approximately 75 fpm. 5 Shuttle-travel is independent of the operation of the conveyors and is remotely controlled from a small control room or from either end of the shuttle conveyor. Truck L ading Bins: There are four circular steel bins under the shuttle conveyor. These are 30 ft in diameter, approximately 50 ft high and each has a capacity of 1500 LT. Having a surge capacity of 6000 LT makes it possible to isolate the operation of the conveyor from the trucking operation at the bottom end in the same manner as at the top end. Sand was Obstacle During Erection Engineering and erection were carried out jointly between the supplier of the mechanical equipment and the prime contractor-engineer. Details of the electrical supply and engineering were handled between the mechanical supplier and the electrical supplier--all with the approval of the prime con- tractor. The machinery, belting and terminal supporting structures, were furnished by the mechanical supplier with the contractor-engineer providing all buildings , intermediate structure and erection. There were joint field studies prior to the office engineering phase.