The Locomotive . n must be provided to take careof fluctuating demands for steam and to compensate for the los;5 ofresistance of the water as its temperature rises. One type of boiler (shown in Figure i) has the electrodes extend-ing downward inside of what resemble inverted metal cups — calledevaporation chambers. Steam is formed inside these chambers andrises to the top, where it is drawn off into a receiving, pipe. This re-ceiving pipe returns the steam to the boiler at another point. By 72 THE LOCOMOTIVE July, partly closing the butterfly valve shown in the sketch, pressure can bebuilt up
The Locomotive . n must be provided to take careof fluctuating demands for steam and to compensate for the los;5 ofresistance of the water as its temperature rises. One type of boiler (shown in Figure i) has the electrodes extend-ing downward inside of what resemble inverted metal cups — calledevaporation chambers. Steam is formed inside these chambers andrises to the top, where it is drawn off into a receiving, pipe. This re-ceiving pipe returns the steam to the boiler at another point. By 72 THE LOCOMOTIVE July, partly closing the butterfly valve shown in the sketch, pressure can bebuilt up within the evaporation chambers. This forces down the waterlevel in the chambers and leaves less of the surface of the electrodesimmersed, thus decreasing the flow of electric current and lowering therate of evaporation. By closing the butterfly valve completely thewater level may be forced low enough to uncover the electrodes — acondition that would stop evaporation. £/,£cr/po/?jF K^poje/:z//y&n/s£ -,. -jExrj5Ns;o/v rasEs 30/l£=J^^^£lL- Figiire 2 Other types of boilers have no evaporation chambers as dis-tinguished from the boiler proper but, in their stead, have a cylindricalmetal tube around each electrode. (See Fig. 2.) These tubes areopen at top and bottom and in as much as they are all connected to-gether mechanically by a bar which passes out through the boiler shell,they serve as the neutral. Their function is two-fold, for besidestending to prevent the formation of air bubbles on the electrodes byincreasing the circulation of the water immediately surrounding thelatter, they are so arranged that they can be raised or lowered to de-crease or increase the length of path between conductors and, as adirect result, control the electric input. 1928. THE LOCOMOTIVE 73 Still other boilers are controlled by varyinj^ the amount of feedwater so as to control directly the height to which the water extendsupward around the electrodes. Automatic control for almost all types
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Keywords: ., bookauthorhartfordsteamboilerin, bookcentury1800, bookdecade1860
