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38 THE BELLEVILLE GENERATOR AND ECONOMIZER. '"* (From Navy and Army.) About sixteen years ago it was gen- erally recognized by those responsible for naval engineering design that a 'limit had been reached in both the pressure and weight of steam which could be safely produced in warships TAE MarRINE REVIEW number of small tubes containing water and steam, while the flames and hot gases from the fire pass around the outside of these tubes before reaching the up-take and funnel. Each tube is thus subjected to an internal pressure of steam or water, and engin- eering science tells us that the thick- ness of the material of which each tube is made varies directly as the DPTAKE 79 FUNNEL, -- SMOKES BOX DOOR FOR ® Lio oa a nee ae ae ie Se VV sTEAM COLLECTOR BOX SMOKE GENERATOR @sicuz wove PLOW c eS Ree AT HOT WATER COLLECTC3 AY OTHER: ECONOMIZER: HERE -- GENERA TOR COLD WATER COLLECTOR AIR SUPRLY BELOW THE FIRE however, allowance has to be made for wear, and the lower rows of tubes next the fire in the Belleville genera- tor are about 3-8 in. thick. The re- maining tubes are thinner, generally about 1-5 in. The modern Belleville boiler consists essentially of two principal parts--the generator, in which steam is formed from water partly filling the tubes, a ANOTHEA®A ASH PAN Fig. I.--Front view as seen from the stokehold platforms, but with - the furnace, ashpit, and some of the smoke-box doors removed to show the interior. A down-take is shown at each end from a cylindrical (tank) boiler of a limited size and weight. It was, and 'is still, possible to produce from cylin- drical boilers the necessary power, but at the same time the weight of mater- ial would be about double that of the water-tube type, and either the ton- nage displacement must also be very langely increased, or some of the ar- mor and armament must be sacrificed. In a water-tube boiler there are a TOTLLWY fil: of the steam chest, baffles and feed pipes. Fig. -Ll.----side view in section, showing the flattened spiral con- struction of the tube elements, with the general arrangement of the The down-take pipe, conveying the water from the steam chest to the sediment chamber, is hidden by the casing. product of its diameter and the inter- nal-: pressure... This. a. cylindrical boiler of about 15 ft. diameter, such as fitted in the 'Hindustan,' working under 210 lb. per square inch internal pressure, must have a thickness of about 134:in., while a Belleville boiler tube of 4 in. diameter is strong enough to resist a working pressure of 300 lbs. per square inch when only 1-18 in,"in thickness. As a matter of fact, and the economizer through-which the water passes on its way from the feed-pump to the generator. The economizer is thus actually a feed water-heater, and its position above the generator ensures an economy by robbing the hot gases of part of the heat which would otherwise pass away up the funnel without being util- ized. The early Bellevilles were not fitted with economizers, and are thus