. Electrical news and engineering . supposing space to have been doubled whilearea through which piston has moved would be exactly line on diagram will vary as to position with differentmakes of engines, and can only be correctly ascertained by meas-uring engine on which test is being made. While steam confinedin clearance space does no actual woik during live steam period,just as soon as cut-off takes place it has ati effect on expansioncurve and raises terminal pressure as compared with steamexpanded from the admission line only. The engineer will note that any irregularity
. Electrical news and engineering . supposing space to have been doubled whilearea through which piston has moved would be exactly line on diagram will vary as to position with differentmakes of engines, and can only be correctly ascertained by meas-uring engine on which test is being made. While steam confinedin clearance space does no actual woik during live steam period,just as soon as cut-off takes place it has ati effect on expansioncurve and raises terminal pressure as compared with steamexpanded from the admission line only. The engineer will note that any irregularity or bad arrangementof valves can be readily detected by the position of the variouslines, while defects, such as leaky valves or piston, can only be. rt^ »,4 A, Atmospheric Line ; B, Vacuum Line ; C, Clearance Line ; D, Admission Line ;E, Steam Line ; F, Expansion Curve ; G, Exhaust Line; H, Compression Curve;I, Isothermal Curve (test.) detected by testing and comparing expansion curve, particularly if leak is a small one. A theoretical expansion curve to conform with above theorymay be constructed by several geometrical methods, but probablythe following will be the most easily understood by the averageengineer :— The diagram as drawn by the indicator will have the atmos- pheric line upon It as already described, and from this as a basisdraw in the line of no pressure or line of perfect vacuum. To dothis, draw beneath the atmospheric line a line as far beneath it aswill represent the vacuum line on the same scale as the springused in the indicator to draw the diagram. The clearance linemust then be drawn in accordance with rules already the length of the diagram into any number of equal partsby vertical lines at ri
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