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114 process, and no tar is- found in con- densation in any portion of the plant after cooling. 'Coking or caking of the fuel beds is not detrimental, but on the other hand, assists in keeping the fire in the open porous condition, _ which is desirable and necessary where high rates of combustion obtain. This feature eliminates 'the poking neces- sary in the up-draft apparatus. The gas leaves the bottom of the producer through brick-lined connections, and a portion of the sensible heat is ex- tracted in passing through an econo- mizer. The gas is then cdoled and washed and passed through an exhaust- ing mechanism, whence it is delivered under pressure to the engine. This type of apparatus lends itself admirably to the thigh rate of fuel com- bustion, which for the sake of econ- omy in space and weight is desirable in marine service. There are in ac- tual commercial operation today, a number of plants of this type having an average fuel consumption of over 40 Ib. of good bituminous coal per sq. ft. of grate pér hour. These produc- ers are sold on a rating of from 18 lb. to 20 lb. of fuel per sq. ft. of grate per hour, which is almost 100° per cent - greater than the average rating of ae up-draft ee of producers, Measuring. the Tyo Systeme Undoubtedly a better method measuring the ability on success of of these two systems, is to make note of the number and capacity of plants of each type in actual operation on* en- gine service. A report of the com- mittee on gas engines of the National Electric Light Association, spring of 1908, showed that in gas engine power plants, of capacities of over 300 H. P. each, there were in operation 32 plants of both types 'having a total capacity Bt o12e0 ic OF these, 4 plants were of the up-draft type, having an. aggregate capacity of 4,050 H. P., and 28 plants were of the down-draft type, with an aggregate capacity of 53,175 H. P.. The latter contain the Loomis- Pettibone gas-generating apparatus, some of which has been in operation on engine service for 13 years. Three years have been devoted to the modification of 'these stationary plants for-marine service. The work involved a reduction in the size and weight of the generators; complete re- vision of 'the scrubbing, gas cleansing and exhausting mechanism; elimina- tion of all gas holders, storage recep- tacles, mixing chambers, etc. The plant as modified to date has a light, compact producer, which while retaining the same rate of combustion as the stationary apparatus, has mate- 40) Ib'to 70 1b. per, He Ps The MarINE REVIEW rially redu¢ed dimensions and weight of the shells, brick lining, fittings, -etc. The economizer boilers which were May, 1909 fitted with direct- connected - air pump - and used. on stationary work -have (been. abandoned, and replaced with light air- heating economizers. The gas-coolers 'no longer contain any coke or broken material, or wooden trays, and are built of very light, non-corrosive sheet metal, and arranged for either vertical or horizontal position, the latter ar- rangement being convenient for space which would be otherwise wasted in the vessel. The cooled and partially cleansed gas is drawn through the above portion of the plant by a centri- fugal gas-cleaning exhauster, driven by direct-connected motor. The gas pass- 'es directly from the exhauster under 'through an automatic pres- to the engine pressure, sure regulating valve, manifold. : That the plant is adaptable for ma- rine service with regard to space oc- cupied and wéight, may be seen from the following conservative estimate: Plants.of from 100 to 500 H.P. each. occupy from 0.4 to 0.5 sq. it. per H. P., and weigh from 70 Ib. to 90 lb. per HP. ineluding, all. auxiliaries, .prp- wig. ete; plants of from 300 H.-P. to 1000 H.-P: occupy 'from 0.3. sq. 1t...to O45-sq. tt. per He PB. and weigh. from including all auxiliaries, piping,' etc. Undoubtedly the rational eppertunity at the present time for marine gas power lies. it commercial service, in which regard the most rapid advance- ment in America has been made in the freight, ore. and. iuel carriers of the Great Lakes. Gas Installation for a Lake Freighter. We example a ship 'built from the designs of Messrs. Babcock & Penton within the last year. For the sake of clear- ness, the views show only the machin- ery, space; all of the. ladders, ways and grates have lbeen omitted from the plans, and the piping is shown only on the gas installation. The ma- chinery installation proper is all there, however, and while the parts elimin- ated are merely accessory, the contrast 'between the two plants would be all the more striking were they included. The boat:is a modern lake freighter and represents the best standard prac- tice in this service. She is 306 ft. long over all, 45 ft. beam and 24 ft. deep. Her present power equipment consists have therefore taken for our of a_ single-screw, triple-expansion, three-crank condensing engine, 18-30- 50 by 36 in. stroke. She _ indicates 1,000. GE PS ay OO 6°95 R: P.M' The engine is of the typical and jet-condensing type. box-column She is istair-- = has independent -- steam-driy- en reciprocating, bilge, sanitary and feed . pumps. The complete ens gine room weight, including Piping and all auxiliaries, is, in round figures, 182,000 lb. ' The boiler room equipment consists of two single-ended Scotch 'boilers 11. ft. 10 in. mean diameter each; 11 ft, length over heads, © operating on a working pressure of 180 Ib. per sq. in. Each boileris fitted withtwo 42-in. corrugated furnaces and has 244 2%-in, tubes. The grate surface is 3634 sq. ft. and the heating surface 1,642 3 f.- 10 each boiler. The 'boilers are atted with forced draft from a 66-in. steam-driven fan, The air for the draft is taken from the stoke hole and the fan is located in the engine room. The fan discharge passes through air theaters in the up- take and thence through ducts to the under side of the grates. The complete boiler room weight, including water in the 'boilers, but not fuel, is 170,000 Ib. These weights are actual figures. The coal bunker extends from 'the main deck to the 'tank top and is ar- ranged athwartship. It has a capacity of 170 tons. The bunker doors face the stokers on the stoke hole floor. The bunker is 6 ft. fore and aft. at the stoke hole. The distance from the forward to after bulkhead in the boiler toom is 24 ft. O°in.- Phev distanee from the forward to the after bulk- head in the engine room is 22 ft. 0 in., making a total overall length for the plant, including bunkers, of 52 'ft. 0 in. The coal consumption on this' vessel is from 18° 1b. to 2:lb per"T.-H, - Py hr. for all purposes. This coal is of ap- proximately 13/500°B. T. Ul. per lb. Two Different Arrangements Shown. The problem of substitution of gas for steam, aside from the design of the construction of the gas producers or cylinders of the gas engines, has been thoroughly worked out by the designers. The illustrations show 'two different arrangements of gas produc- ers with the same engine. The pro- posed gas four-cylinder, double-acting, reversing type, having cylinders 24 in. bore by 36 in. stroke, delivering 1,000 B. H. P. at 100 R. P. M. The reversing is accomplished by means of compressed air, which is used to shift the cams from the head to the stern position. 'Compressed aif is admitted to the cylinders by timed cams in proper cycle. The crank shaft of the engine is rigidly coupled to the tail shaft of the screw. The framed engine. engine is a illustrations show a column- Since making this lay-