. A manual of marine engineering: comprising the design, construction, and working of marine machinery. n the design of the air-pump for a surface-condenser, as thesuccess of many an engine has been marred by a bad vacuum; and doubt-less an inch or two of vacuum tells wonderfully on an engine, especiallyon a compound engine, where the vacuum can almost be told by the speed AIR-PUMP. 241 of the engine. Since, however, the surface-condenser was only requiredto work as a jet-condenser, when so fitted, in cases of emergency, whichseldom happen, and when such a case does occur it is not of importan
. A manual of marine engineering: comprising the design, construction, and working of marine machinery. n the design of the air-pump for a surface-condenser, as thesuccess of many an engine has been marred by a bad vacuum; and doubt-less an inch or two of vacuum tells wonderfully on an engine, especiallyon a compound engine, where the vacuum can almost be told by the speed AIR-PUMP. 241 of the engine. Since, however, the surface-condenser was only requiredto work as a jet-condenser, when so fitted, in cases of emergency, whichseldom happen, and when such a case does occur it is not of importancethat the engines shall work at the highest efficiency or maximum speed,it seems better so to design the air-pump as to best suit surface con-densation, rather than to make it of the larger size, and sacrifice a largeamount of work in driving it during the long period, when jet condensa-tion is not necessary. In short, the pump should be of such a size asto give its maximum efficiency during the longest time, and if for asurface-condensing engine, it should be designed for that particular -■■^■■-■-■-■■^^ Fig. 73.—Air-pump of Ordinary Type. Such reasoning did not rigidly apply to the machinery of warships,as a mishap in action might necessitate the use of the jet injection, andat such a time there must be no diminution of speed and efficiency; forthis reason it was customary for the Admiralty to stipulate that the air-pump should be of sufficient size to produce a good vacuum when jetcondensation was resorted to. But the Admiralty no longer provide forworking with jet injection. 242 MANUAL OF MARINE ENGINEEIRNG. In the mercantile marine, especially in mail and passenger steamers,it was customary to effect a compromise by making the pump larger thanabsolutely necessary for surface condensation, but less than is usual forthat purpose. The Single-acting Vertical Air-pump (fig. 73), having valves in thebucket as well as foot and delivery valves, is by fa
Size: 1715px × 1457px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidmarineen00seatmanualofric
