Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . FIGURE 50. points, lines and curves. Fig. 50 was taken from alarge vertical engine with the corliss valve motion. The engine being of slow speed and extremely longstroke (10 ft.) with a clearance of but 1 per cent., thecompression beginning at C and ending at B is some-what lighter than is ordinarily given to shorter stroke207 208 ENGINEERING engines. From B to D is the admission line, whichbeing practically perpendicular to the atmosphericline A, shows sufficient lead and ample port D t
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . FIGURE 50. points, lines and curves. Fig. 50 was taken from alarge vertical engine with the corliss valve motion. The engine being of slow speed and extremely longstroke (10 ft.) with a clearance of but 1 per cent., thecompression beginning at C and ending at B is some-what lighter than is ordinarily given to shorter stroke207 208 ENGINEERING engines. From B to D is the admission line, whichbeing practically perpendicular to the atmosphericline A, shows sufficient lead and ample port D to E is the steam line. Cut off occurs at E,and from E to F is the expansion curve. At F thepoint of release is quite sharply defined, as it shouldbe. From F to G is the exhaust line,, and from G to Cthe line of back pressure, sometimes called the line ofcounter pressure for the reason that the pressure indi-cated by it acts counter or in opposition to the forwardpressure of the steam on the piston. This engine, is a. FIGURE 51. simple condensing engine and the nearness of theback pressure line to the line of perfect vacuum Vshows that an excellent vacuum was maintained in thecondenser. Fig. 51 is from a Buckeye automatic cut off enginehaving a shaft governor and what is termed a ridingcut off, that is the cut off valve slides to and fro onthe back of the main valve. The engine is horizontalnon-condensing, the cylinder being 28 in. bore by 56in. stroke, and, at the time the diagram was taken, DIAGRAM ANALYSIS 209 developed horse power with a piston speed of728 ft. per minute. The steam consumption per I. per hour was 26 lbs., a rather high rate, but this wasowing to the fact that the engine was located too farfrom the boilers, and as there were a large number ofelbows in the steam pipe the pressure was greatly-reduced at the engine. Thus wire drawing of thesteam was caused, which is plainly indicated by thedownward inclination of the steam line, D E. In a well propor
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