. American engineer and railroad journal . large flat valves or heavy un-balanced piston valves, to say nothing of the much greater wearand tear of the latter. Piston slide valves have the defect that, unlike flat slides, thepressure on the seat is not diminished during running when thesteam compression becomes too high. To avoid the injuriousshocks in the rods and motion due to this cause, hot steam loco-motives are provided with the contrivance shown in Fig. 3. This is a by-pass tube in. bore, connecting the two ends of thecylinder, having a cock in the center. When the steam throttleis
. American engineer and railroad journal . large flat valves or heavy un-balanced piston valves, to say nothing of the much greater wearand tear of the latter. Piston slide valves have the defect that, unlike flat slides, thepressure on the seat is not diminished during running when thesteam compression becomes too high. To avoid the injuriousshocks in the rods and motion due to this cause, hot steam loco-motives are provided with the contrivance shown in Fig. 3. This is a by-pass tube in. bore, connecting the two ends of thecylinder, having a cock in the center. When the steam throttleis closed this is opened, and the pressure on both sides is equal-ized. This cock is steam-heated, and to prevent it becomingfixed on its seat, it is only loosely fitted, the steam pressure fromeither side keeping it tight in its place during running. Thevalve stem is connected by a grooved and dovetailed slide, andthe grooves turned in the outer guide form a labyrinth packing,and so dispense with a stuffing-box. This is worked by hand with. FIG. 3. — BY-PASS TUBE CONNECTING THE TWO ENDS OF CYLINDERS. a key on the square end of the stem, and has taken the place ofa former self-acting arrangement, which was not found to work Septembi k. AMERICAN ENGINEER AND RAILROAD [OURNAL. :;:.! satisfactorily. The driver h;is to open the passage immediatelyon closing the throttle and must close it again before re-admit-ting steam to the engine, Lubrication.—A matter of primary importance in the use ofhot steam in locomotives is the provision of appropriate lubrica-tion for the parts working under steam -the piston and slidevalves—which, both in regard to material and arrangement, callfor special modification in details. The high temperature makes it necessary to use only puremineral oils of particularly high flash points, which must besupplied to the rubbing surfaces in determinate quantity accord-ing to the speed, i. e., the revolutions ot the driving wheels. Itmust be prevented
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
