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118 unit operating on oil will be used for pumping, blowing fires, or other ser- wice, when the gas plant is down. Al- lowing a distance of 4 ft. 3 in. between the forward bulkhead in engine room and the forward end of the shaft, which distance is 1 it. greater than that in the steam installation, we have an over-all distance between for- ward and after bulkheads in the en- gine room of 19 ft. 6 in. - The Four-Generator Plant. As previously stated, two arrange- ments of producer room are shown. The first, the four-generator plant, consists of four 6-ft. by 9-ft. genera- tors, each fitted with independent econ- omizers. The forward pair and the after pair are connected independently to two horizontal gas scrubbers, which are shown slung under the main deck beams. The gas passes from 'these scrubbers to independent motor-driven centrifugal gas-cleaning fans, whence it is delivered, either through common connection to a purge or blow-off pipe which also acts as a by-pass, or through two gas pressure regulator valves to the air and gas mixing valve at the engine manifold. The 6-ft. gen- erators require only one cleaning door each. 'As a result a single cleaning space suffices for the four, machines, allowing them to be grouped with ref- erence to athwartship space, so as to give ample room on each side of the vessel for coal bunkers. The _ total space occupied by the producer plant is 21 ft. 10 in. athwartship, and 15 ft. between forward and after bulkheads. The producer room weight including generators, economizers, piping and scrubbers, complete, of the four-gener- ator set, is 110,000 lb. This weight is estimated, [but has been carefully checked and completely covers all the mechanism. In addition to 'the above mechanism, there will be a heating boiler which is shown on the main deck. This boiler will serve to fur- nish low-pressure steam for heating the vessel and supplying hot water for washing down decks, etc. This boiler, with water, will weigh about 8,000 Ibs. The Two-Generator Plant. The two-generator producer plant, which will undoubtedly be the one in- stalled, will consist of two 8 ft. diam- eter by 9 ft. 6 in. generators, connected to independent air economizers and each fitted with an independent horizon- tal scrubber, located athwartship under the main. deck beams. The gas outlet at the scrubbers will be connected with a cross-over, so that either exhauster is estimated, but THe Marine REVIEW may operate either or both producer plants. The exhausters are installed in duplicate and are connected with com- mon purge or blow-off and common gas outlets leading either through one pressure-regulator valve, or through a by-pass direct to the air and gas mix- ing valves at the engine manifold. On account of the fact that the 8-ft. generators require two cleaning doors set at 120 deg. the double-generator unit plant will require the full athwart- ship space in the producer room. The approximate floor space occupied, there- fore, will be 30 ft. athwartship and 15 ft. between forward and after bulk- heads. The producer-room weight, in- cluding generators, economizers, piping and scrubbers complete for the two- generator set, is 82,000 lbs. This weight has been carefully checked and completely covers all of the mechanism. As in the case of the four-generator plant, a low-pressure boiler for heating service will be in- stalled. In the two-generator plant, however, this boiler will be located on the producer-operating floor, so that one set of firemen may suffice for both. Probable Fuel Consumption. The only guide we have for estimat- ing the probable fuel consumption for this service is found in the large num- ber of stationary producer gas power plants now in operation. Fortunately, in marine service, the load factor will be uniformly much higher than that found in any stationary service to which gas power is applied at the present time. The builders of this apparatus are prepared to guarantee one brake horsepower per hr. on one lb. of good bituminous coal, averaging 13,500 B. To Ue per Ib. The engineers who designed the steam plant, and who have spent years on the problem of the substitu- tion of gas for steam, have suggested that the coal bunker, which will be placed above the charging deck of the producer, should have a capacity of about 80 tons of coal. These bunkers will run from the charging deck to the deck-house roof and will have doors opening closely adjacent to the charging doors of the generators, so that little or no coal passing on the operating deck will be required. In making the comparison shown in the table, it is unnecessary to go into the cost of fuel, labor, hours of service, etc., as these elements vary with every class of service. In this particular proposition, it will suffice to state that the engineers who have been working: on this substitution problem have con- servatively figured that with the saving "May, 1909. in fuel and the increased cargo carried. the cost of the complete plant will pe saved in two years of operation, TABLET. COMPARISON OF POWER PLA GREAT LAKES FREIGHT-CARRIRR Oe Rength vover all se 306 ft. 50: ¢ oi 0 in, Beainee 2. eeu Ciel sere eae 45 ft. 0 in, Depth ..-.ccecessceccccecsececes 24 ft. 0 in, Displacetient: oi. 02.5. 6,600 tons net Gareo sini. a 4,200 net tons. 18 ft draught. Speed, 12 statute miles per hr. on 900 I. H. P. STEAM. Engine Room. Sater) See ear acseny Coe 18-30- y in. 1, : (eRe at Re P.M. 2 oe Auxiliaries steam-driven. Length between bulkheads, 22 ft. 0 in. Engine room weights, including auxiliaries and piping, 182,000 Ibs. Boiler Room. 2 single-ended Scotch boilers economizers, forced draft. boiler. overheads 11 ft. 0 in. Mean diameter, each, 11 ft. 10 in. Two 42-in. furnaces each. 244 ,234-in. tubes, each. Grate. surface, each, 36.75 sq. ft. Heating surface. each, 1,642 sq. ft. Boiler room weight, water in boilers, no fuel 170.000 Ibs. ; fitted with Length each Length boiler room 24 ft. 0 in. oe boiler room, includes bunkers, 30 ft. in. pee feet boiler room, including bunkers, Sauare feet. per: He <P. 0,9: Bunker canacity, 340,000 Ibs. Total weight, machinerv and fuel, 692.000 Ibs. Total length of machinery space including bunkers, 52 ft. 0° in: GAS. Engine Room. 4-cylinder, 4-cycle, double-acting, 24 in. diam., by 36 in. stroke. 1000 Bi. Po at 95 Rs PM. Auxiliaries motor-driven. Length between bulkheads, 19 ft. Engine room weights, 105,000 Ibs. gas engine, 6 iit Producer Room. Two down-draft gas producers and auxiliaries. Diameter shell, each generator, 8 ft. 0 in. Inside diameter, lining generator, 6 ft. 3 in. Height shell, each generator, 9 ft. 6 in. Grate surface, each generator, 30.67 sq. ft. Producer room weights, no water, no _ fuel, 82.000 Ibs. Length producer room, £t-< 0°: in. Square feet producer room, 450. Square feet per H. P., 0.45. Square feet producer room with four smaller generators, 330. Sauare feet per H. P.. four generators, 0.33. Runker canacity, 160.000 Ibs. Total weight, machinery and fuel, 347.000 Ibs. Total length of machinery svace, 34 ft. 6 in. Saving in weight, 355,000 Ihs. Saving in fore-and-aft length, 17 ft. 6 in. Saving in cubic space 17 ft. 6 in. by 32 ft. beam oby.20 it. hich: 11,200. cu. ft While the gas plant here described has neither been constructed nor or- dered at this writing, its forthcoming will not be long delayed, and this com- parison, while somewhat premature, is made to present the possibilities of ma- rine producer gas power to those in- terested in its future. A marine bituminous gas plant, sim- ilar in construction and operation to the one described, but of 300 H. P. capacity,- has been in commercial: opera- tion driving a six-cylinder, single-act- ing, reversing marine gas engine for over a year. The results obtained give ample security for the statements made in this paper, and point to the early adoption of this type of prime mover for our marine commercial service. includes bunkers, ~ 15