. Official proceedings . esthrough the superheater and thus decrease the efficiency of high-speed engines. Until quite recently it was considered essentialto only superheat steam of comparatively low pressure, say 155or 160 pounds boiler pressure, in consequence of which the sizeof the cylinders was increased proportionately, but it is now be-coming common to use higher boiler pressure and make some re-duction in the diameter of the cylinders as compared with theolder superheater practice. Hence we have not credited thesuperheater with a saving in boiler maintenance because of low 228 Proceedi
. Official proceedings . esthrough the superheater and thus decrease the efficiency of high-speed engines. Until quite recently it was considered essentialto only superheat steam of comparatively low pressure, say 155or 160 pounds boiler pressure, in consequence of which the sizeof the cylinders was increased proportionately, but it is now be-coming common to use higher boiler pressure and make some re-duction in the diameter of the cylinders as compared with theolder superheater practice. Hence we have not credited thesuperheater with a saving in boiler maintenance because of low 228 Proceedings Railway Club of Pittsburgh. pressure. In all cases it is necessary to make the size cylindersto suit the mean effective pressure which may be expected fromthe particular superheater, bearing in mind its wire-drawing ten-dencies. Just as regards the compound locomotive we are inclined tothe opinion that unless careful investigation insures for super-heater engines a net economy, a simpler form of engine is Smoketube Superheater Emerson Type If because of restricting factors a locomotive is so limited asto be disproportioned. superheating may be resorted to as a meansof increasing efficiency and perhaps economy, but if such limi-tations do not exist and if a boiler is designed to absorb all ofthe heat which the firebox can generate, conservative practicewould favor for ultimate economy, a properly designed saturatedsteam locomotive, rather than a superheater engine, with its first Discussion—Choosing a Locomotive. 229 cost, cost of repairs, cost of cleaning, and cost of fuel lost inorder that the cleaning may be accomplished. The use of superheaters is too recent to permit of a definitesolution of the problem at this time, but when the comparisonsare made they should be between engines equally well designedand differing only in the parts affected by the trials should be made in actual service and last through aperiod of time long enough to enab
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