. Electric railway journal . :^^s=3^^ lofopen) o(cios«!) IE 1 (Noon) A RECORD OF THE OPERATING RESULTS PRODUCED BY THE AUTOMATIC CONTROL WITH A 500-HP. WATER-TUBE BOILER May 15, 1920 Electric Railway Journal 1007 turn slightly, whereupon the valve gear and the pilotvalve piston are raised or lowered, since the hydraulicbalancing pressure must remain constant until theabove changes have taken place. As soon as the pistonof the pilot valve is raised or lowered water fromthe city mains is admitted to the top or bottom ofthe hydraulic cylinder, causing the piston to moveupward or downward, restori
. Electric railway journal . :^^s=3^^ lofopen) o(cios«!) IE 1 (Noon) A RECORD OF THE OPERATING RESULTS PRODUCED BY THE AUTOMATIC CONTROL WITH A 500-HP. WATER-TUBE BOILER May 15, 1920 Electric Railway Journal 1007 turn slightly, whereupon the valve gear and the pilotvalve piston are raised or lowered, since the hydraulicbalancing pressure must remain constant until theabove changes have taken place. As soon as the pistonof the pilot valve is raised or lowered water fromthe city mains is admitted to the top or bottom ofthe hydraulic cylinder, causing the piston to moveupward or downward, restoring the position of thewheel lever and automatically returning the piston ofthe pilot valve to a neutral or closed position. Theneutral position is attained as soon as the hydraulicpiston travels downward or upward as far as the mer-cury plunger traveled upward or downward, or in otherwords as soon as the hydraulic -pressure is balanced. Where engines or turbines are used for drivingstokers or fans a special chronometer valve is is designed to supply steam under graduated con-trol. In general, the valve is of the vertical piston typewith a rectangular opening through the piston and acorresponding rectangular port in the body of the length of stroke of the piston is determined by theauxiliary control, so that the flow of steam to the stokeror fan engine is varied to correspond with the require-ments. There is also provision for micrometer handadjustments which permit of turning the piston of thevalve to vary the width of the port to suit the require-ments of any particular machine. An accompanyingillustration on page 1006 shows the comparativerecord taken on a 500-hp. water-tubeboiler during consecutive hours of theoperation as controlled by the auto-matic system. The load chart is shownat the top and the damper positionjust below. The other simultaneousreadings plotted on the chart are theuptak
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