Laying out for boiler makers and sheet metal workers; a practical treatise on the layout of boilers, stacks, tanks, pipes, elbows, and miscellaneous sheet metal work . steamwhen working, and the other in which the spring is exposedto the action of the steam when working. It is advisable tofurnish all safety valves with a lifting device by which thevalve may be raised from its seat from time to time, so as toprevent the moving parts from becoming corroded and stick-ing, thus preventing the free action of the valve in performingits duty, which is to relieve the pressure in the boiler when itexce
Laying out for boiler makers and sheet metal workers; a practical treatise on the layout of boilers, stacks, tanks, pipes, elbows, and miscellaneous sheet metal work . steamwhen working, and the other in which the spring is exposedto the action of the steam when working. It is advisable tofurnish all safety valves with a lifting device by which thevalve may be raised from its seat from time to time, so as toprevent the moving parts from becoming corroded and stick-ing, thus preventing the free action of the valve in performingits duty, which is to relieve the pressure in the boiler when itexceeds that at which the boiler is designed to work. The safety valve should have a large area, in order to pro-vide a large opening, for the escape of steam, with a smalllift of the valve, otherwise the pressure of the steam may con-siderably exceed the pressure under which the valve began torise before the valve lifts sufficiently to permit the free escapeof the steam. The valve should not allow the pressure of thesteam to rise above a fixed limit, and when this limit is reachedit should discharge the steam so rapidly that very little or no Pipe flci/?(je /oolis. Cavlk/rr^liner* She//: FIG. 5.—STEAM NOZZLE. increase in the pressure of the steam can take place, no matterhow rapidly the steam may be generated. The area for the safety valve of a boiler may be determinedfrom the grate area by the formula: A Y. Aa = V PWhere: a = Area of valve in square inches. P = Working pressure in pounds per square = Area grate surface in square our figures we have 27 X 4 108 •a = = — = square inches. Diam. =Y • V •7854 — 3-35, say, 3^/4 inches. From the evaporative power of the boiler the area of safetyvalve may be found approximately by the formulaE a = — 40 X V~PWhere: E = Evaporating capacity of boiler in pounds =: Working pressure. Substituting we have 4,860 a = = square inches. 40 X V ISOWhence diameter = , say,
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Keywords: ., bookcentury1900, bookdecade1900, bookidl, booksubjectsteamboilers
