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Unloader Outreach Increased by Installing Thrower By Deo Dewsen’ HE unloading of T= the storage of small aggregates such as sand and gravel present real problems for harbor’ dredges, that are often difficult of solution. The ordin- ary type of belt con- veyor deposits its load in a pile directly be- neath the end of the boom and consequently the storage pile is lim- ited in area by the length of the boom or the closeness with which the vessel can approach the shore. A unique and satisfactory means of increasing this storage capacity has been adopted by the Northwestern Sand and Gravel Co. in the unloading equipment aboard its freighter Frrep W. Green. This vessel has a capacity of approximately 3000 tons and is fitted with two derricks each with 2%-yard buckets. These buckets give her a loading speed of between 200 to 400 tons per hour depending on the depth of sand or gravel de- posits. These two derricks with their buckets are also used in the unload- ing process. At times as high as 1000 tons per hour has been unloaded. Unloading is the reverse of load- ing, with the added advantage of ine crease in speed by the shorter haul of the buckets and the use of a 100-foot boom conveyor fitted with a 36-inch wide belt. The buckets first unload upon a horizontal conveyor, which runs along the deck and discharges The author, Deo Dewsen, is a mem- ber of the technical staff of the West- inghouse Electric & Mfg. Co. MAXIMUM WITHOUT THROWER ABOUT 110 FEET SELF- UNLOADING FREIGHTER The Fred W. Green Unloading on Beach at Traverse Bay, Lake Michigan upon the boom conveyor which is lo- cated well forward of the bridge. The boom can be swung and used over a very wide angle, extending from the port side to dead ahead. This loca- tion of the boom allows the vessel to unload in practically any locality re- gardless of depth of water. If the coast is shallow, the vessel can head into the shore and unload, and still have the propeller always in deeper water with no danger of fouling. While the boom conveyor is 100 feet in length and will deposit the cargo quite a distance from the shore, the equivalent of added length of boom is obtained by means of a Stephens- Adamson heavy duty box car loader installed on the end of the boom con- veyor. This loader consists essentially of a thirty-inch wide belt, nearly eight feet long mounted in a special frame work. The frame is pivoted to the end of the boom conveyor and can be lowered for use or raised out of posi- tion by means of a hand winch lo- cated on deck. WITH THROWER 20 FEET ADDITIONAL i STORAGE PILE | CENTRIFUGAL THROWER There is one point in delivery where the water is shallow for near- ly one-half mile off shore. To reach this point the vessel takes a start of about one mile with engines wide open and it is practically impossible to stop in exactly the right place. When this happens in order to reach the stock piles, instead of having to unload material in the wrong place or to go to the trouble of lightening, the stacking conveyor is lowered into position and operations are begun after only a few minutes. The belt of the unloader is driven at a speed of 1800 feet per minute by a West- inghouse induction mo- tor. This motor is of the latest type devel- oped for this class of service and is water- proof. It has a normal rating of 10 horsepower at 1750 revolutions per minute when supplied 'with three phase 60 cycle, 220-volt power. The motor which is totally en- closed is of the standard squirrel cage type with end bells or brackets made of solid material. These end bells are fitted with webs to aid in the dissipation of heat and also to direct the flow of air from the two fan blowers mounted on either end of the motor rotor. These blowers are of cast aluminum con- struction and are keyed and clamped to the shaft, but so arranged that their removal is easily accomplished. These blowers force air over the stator iron for cooling the motor. To protect the revolving fan blades, and to give added insurance that no for- eign material will fall on vital parts, perforated end covers are placed over the ends of the motor. These end bells also enhance the stream lines of the motor, giving it a pleasing ap- pearance. Thus the unloader is equipped with driving apparatus, in which every effort has been made to reduce possible failure to a minimum. The motor drives the unloader through the medium of a two-strand THROWER IN LOADING POSITION oh iss 130 gees qaRhes See ET ee DIES EDLLS Eig D SVEMe we Waley = WH TW NEWS SSS WS WUE HENS NSW SWS EM SANS WE Nee WW == BED =_ S-A MFG. CO. 7426-R == \\ Diagram of Unloader on 8. g. Fred W. Green. Upper Right—Detail of Thower on End of Boom MARINE REVIEW—June, 1931 37