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Reduce Lake Vessels’ Fuel Bill-TV A Study of the Influence of Boilers, Main Machinery and Auxiliaries on Earnings of Great Lakes Cargo Vessels NY owner who presents’ the builder with a clear specifica- tion prepared with knowledge of the subject as to engineering and the conditions affecting operation may look for results provided he does his own part afterward. A few examples from actual prac- tice as showing the possibilities of application of the above principle are given below. First, however, the con- densed trial report of ships Sl and S2, Table I, which appeared in the first part of this article is presented because the ships not only exhibit results considerably better than the average and better than any of re- cent years, but the trials were so painstakingly conducted as to be note- worthy. Trials Carefully Conducted These trials were conducted in 1894; over 32 years since. Both ships were almost new; both were fitted with triple engines and with Scotch boilers with positive heated draft. All aux- iliaries were attached to the main en- gine except the fan. The trials were conducted by the head ef the engi- neering department of a midwestern university and a corps of student as- sistants on Lake Superior during the summer vacation. Both ships had con- sorts, giving ample time for observa- tions and repetitions. The exhaust steam from fan and steering engine © was condensed in a tubular heater, converted to use as a surface con- denser, and weighed. The _ cooling water for condensation was supplied by the cold water pump on the main engine making an additional pump unnecessary. The boiler feed water was weighed through two tanks of about 100 gallons capacity each, the upper mounted on scales and filled from the air pump discharge and emptied by gravity into the lower which supplied the feed pumps. All trials were with saturated steam, no superheaters being fitted. Coal was weighed as used, over a_ platform scale in the fireroom. Samples were collected by riddling and about 10 pounds dried out over night in the oven of the galley range, to determine moisture. Three samples were sub- jected later to chemical analysis and This is Part IV and completes Mr. Penton’s article, which began in the February issue. By Henry Penton three to calorimeter tests and the B.t.u. values are the means of these determinations. Three trials were run of 12 hours each and at the same duty, that is to say, without change of conditions and in order to check observations. Indicator diagrams were taken every half hour at first and later every hour. The writer was present in both cases as the repre- sentative of the engine builder but took no part in trials or collection of data and offered no suggestions beyond that of subdividing the firing 100% Ship AA Boilers Aux, Ship BB Boilers Aux. Ship CC Overall Ship DO Overall Ship EE Dratt Ship FF Auxitlaries Ship GG Drast Ship HH Grates &Ventilation .49 Mile pet hr Ships JJ KK, LL.MM - Boilers Aux. | hipNN- tare Fiea.2 IMPROVED EFFICIENCIES IN LAKE VES- SELS AFTER CERTAIN MODIFICATIONS IN POWER PLANT. THE BLACK AND SHADED PORTIONS INDICATE IMPROVE- MENT IN FUEL PERFORMANCE AFTER ALTERATIONS period so that instead of following the practice usual among firemen of firing all doors at the same time the period was equally divided and one door fired at each interval, al- ternating boilers. A condensed report of these trials appears in Part I of this article, in Table IV, on page 64 in the Feb- ruary issue of MARINE REVIEW. During these trials the only auxili- aries in use were the fan and steerer and during the last trial the steam steerer was thrown out and the ship MARINE REVIEW—May, 1927 steered by hand to determine the steam used by each. Following the trials reported above the attached feed pumps of Sl were cut out and the boilers fed by the general serv- ice pump of the duplex, outside-packed plunger type, and the water weighed as with the attached pumps. This trial covered six hours. The pump valves and pistons were examined and tested for water and steam tightness. The former were found tight; there was about the usual leakage at the lat- ter. The steam consumption amounted to 422 pounds per hour, or about 325 pounds per horsepower based on the calculated work done. This com- pares with 12.05 pounds when done by the main engine. Of course there was no exhaust heat recovery dur- ing these trials because the exhaust steam was all going to the surface condenser. Efficiency Not Improved _ These trials show very clearly that both as to steam and fuel the later ships do not exhibit any improvement over earlier examples, rather the con- trary. The good boiler work is due in part to the quality of the fuel but chiefly to the high efficiency of the draft system and which in turn is due in considerable measure to the firing system referred to. It is de- sired to call attention to this because the universal practice in firing de- feats in large measure the very end and aim of the draft system. The result is that at the time when the largest volume of air is needed and at the highest temperature the latter is at its lowest, whereas if rotation is insisted upon the temperature of the draft air will be more nearly uniform, combustion improved and smoke re- duced and the temperature of the stack lowered. The low stack tem- peratures observed are partly due to this but still more to the liberal pro- portions of air heating surface and air passages and the care with which they were arranged to produce low velocities and allow time for heat ab- sorption. Lack of attention to these features is responsible for much of the relatively inferior performance of many ships. Concentration on this one. feature along of getting high draft temperatures, low stack tem- peratures and methodical firing will 33