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IO MARINE REVIEW. ee er et Value of the Independent Condenser, “The Superiority of Independent Condensers for Marine Engines on the Lakes” is the heading of an article by J. F. Holloway, in a recent number of the American Machinist. The manifest fairness with which he treats the subject and the practical knowledge which Mr. Holloway has of lake marine engineering entitles it to partial reprint in the REVIEW, which has contained several papers on this subject. The article begins by saying that the value of any piece of machanism is the difference between the sum of all its good features, minus its bad ones. ‘‘It will be conceded by all, except possibly the inventors of special contrivances, that all machines possess both good and bad features.” It was not need- ed to preface what is to be said about independent condensers,as separate and distinct from other forms of machinery, but only to remind the reader that while it may be possible to prove many things as being theoretically failures, yet the fact often remains that they are practically and commercially a success. : “Tn the first place,an independent condenser of the Worthing- ton type is a separate and distinct machanism, having only one function to perform, and one which is inno wise greatly affected by the motion or rest of any other part of the machinery of the boat. The independent condenser can be set in motion before the main engine is started, and it can remain in action after the main engine is at rest, without involving any particular care from the attendant engineer. The risks of navigation have of late vears been largely increased, not only by the reason of the large number of steamships afloat, but as well by their increased size, which makes their passage through narrow rivers and con- tracted waterways a frequent and unavoidable danger. Then, again, the small harbors of the lakes are crowded with floating craft of all kinds, which, taken in connection with the narrow space between the piers and the sharp bends, makes the passage of heavily loaded boats a constant source of anxiety, not only to the master of the steamer, but as well as to those who happen to be near him. This fact exemplifies the necessity of a prompt _ response of the engines of a ship to the requirements of a some- - what at times dangerous situation. eet e “Having thus briefly outlined the necessities and require- ments ofa navigation which is entirely familiar to those living on the western lakes, but quite unknown elsewhere, it will be proper to indicate in what manner the difficulties of the situation are helped by the use of an independent condenser, instead of the attached air-pump and condenser. “In the first place, the attached air-pump and condenser be- ing driven by the main engine is dependent alone on the same for its movement ; the independent one, as has been shown, is not. In the compound, triple-expansion or simple-condensing engine, a large part of the total power of the engine is dependent upon the efficiency of the vacuum produced by the condensation of the steam used, and it is obvious that in starting such an engine its first movements must of necessity be slow and sluggish, until the engine has made a sufficient number of revoluions to establish a good vacuum, the number of revolutions and the length of time depending largely on the condition of the air- pump and its connections. To sum up the objections to the attached air-pump and condenser on a lake engine where it must be so often stopped and started, it may be added that the attach- ment of the air-pump to the main engine increases the number of parts of the main engine liable to get out of adjustment,and it prevents that ready access to the crank pins and main journals, which, at the high speed they are now run at, require not only constant care and attention, but also ready access for examination and repairs. The high speed now required of the main engine greatly increases the strains on the air-pump beams, links,buckets and valves, and the high velocity with which the injection water is lifted and forced through the air-pump, often causes rupture of the air-pump cover, its connection pipes and valves. ‘This engine speed has of late years so increased, that the usual large rubber valve of the air-pump bucket, foot and discharge valve can be used now only at a very considerable risk, and it involves, as well, the selection of the very best material. At every stoppage of the engine, the injection must be closed, and again opened when the engine is set in motion, and is it to be wondered at, that, when this labor goes on for hours, it is possible that the injection valve may at times be forgotten, and the result a flooded air-pump, and, as it sometimes happens, a broken one, should the engine be put instantly into rapid motion. “The operation of the independent condenser as connected with a lake marine engine, being to some extent a new departure, as applied to such marine engines, it may be well to explain wherein it possesses merits that should commend it to a wider use. In the first place, an independent condenser, when in use, will produce a constant and reliable vacuum on the engine at all times, irrespective of the action of the main engine. The degree of vacuum produced by the independent condenser 1s not limited by any consideration of the temperature of the feed water; there- fore, it can produce the highest attainable results, varying from 26 to 27 or more inches, instead of 22 to 24, as 1s commonly carried with. the old-style air-pump and condenser, and thus adding largely to the power of the main engine as well as to its instant availability. ‘The moderate and steady action of the independent condenser is a guarantee of its endurance and reliability, of great value to a steamer, especially in times of danger. 2 “The objection that will be raised, and possiby the only one, will be that the independent condenser, which is in so many ways desirable, does not use steam economically; or, in other words, less steam will be used when the air pump is attached to the main engine. It always takes a certain amount of power to produce a certain amount of work, but it does not always take a — certain and fixed amount of steam to do a certain and fixed amount of work, for in some cases the steam is used to its best advantage, while in others it isnot. The value of steam is in its temperature; high temperature means high pressure, and high pressure means large expansion. In driving an attached air pump the steam used is worked at its greatest economy, by reason of its being used expansively in the steam cylinder or cylinders of the main engine, and its pressure and temperature is reduced by the work it has done, but the final temperature it retains when exhausting is, in the main, thrown away in raising the temperature of a large volume of injection water, of which only a small part can be utilized in feeding the boiler. The -steam used in a direct-acting independent condenser can not be used expansively, consequently it requires a larger volume to do its work, bnt it retains at the end of its piston stroke a larger per cent. of the high temperature it originally had, and, if it were then exhausted into the atmosphere, there would, of ne- cessity, be a great loss of heat, which always means loss of coal in such cases. But by the use of a coil or tubular heater, through which such a portion of the injection water is forced as is required for feeding the boiler, the exhaust steam from the in- dependent condenser is utilized to its full extent by extracting from its remaining heat and transferring it to the boiler again, through the medium of the feed water, and therefore there is virtually no loss of steam or power beyond what is required to discharge the injection water overboard, and overcome the re- sistance of the working parts of the machine. By using this feed water heater, the steam from the auxiliary feed and «other pumps can also be returned to the boiler, thus saving what heat otherwise would usually be wasted in their exhaust steam. “To sum up in brief the advantages arising in the use of in- dependent condensers on lake marine engines, would be to say that by their use the highest obtainable vacuum can be had in — the cylinders of the main engine, and the highest degree of tem- perature be at the same time imparted to the feed water, thus increasing the power of the boiler, and contributing greatly to its durability. ‘The slow speed at which such a condenser, when properly selected, runs, insures freedom from undue wear, and liability to derangement. By its use the main engine is rendered more accessible and is relieved from a serious source of danger, to which it otherwise would be liable, by reason of its being con- nected under high speeds with the moving parts of the ordinary attached air pump and connections. By its use the condenser can be placed at any convenient location without reference to the main engine. And more than all else, by its adoption any con- densing engine can be as rapidly and promptly handled as in the old times were the smart high pressure lake engines, which for size, power, endurance and durability have never since been equaled.’’ For the benefit of readers of the REVIE lakes over half the year, a special rate of $ subscription is made. the United States or C be changed at any tim the winter. ’ W who are on the ! for six month’s The paper will be sent to any part of anada at this rate and the address may e. Order by mail before leaving boat for . = coe 3 i eS ae: x :