. Science of railways . cars. In freezing w^eather, if cars are to be laid up, orstand thirty minutes after engine is uncoupled, thehose throughout the train must be uncoupled, and alldrip valves or blow-off valves opened. THE MASON LOCOMOTIVE REDUCING VALVE. This valve is designed to automatically reduce andmaintain an even steam pressure for heating carsfrom the locomotive. It is placed in the steam supplypipe leading from the boiler to the heating systemand regulates the amount of steam passing to the sys-tem, allowing only sufficient steam to maintain thedesired pressure. The principle upo
. Science of railways . cars. In freezing w^eather, if cars are to be laid up, orstand thirty minutes after engine is uncoupled, thehose throughout the train must be uncoupled, and alldrip valves or blow-off valves opened. THE MASON LOCOMOTIVE REDUCING VALVE. This valve is designed to automatically reduce andmaintain an even steam pressure for heating carsfrom the locomotive. It is placed in the steam supplypipe leading from the boiler to the heating systemand regulates the amount of steam passing to the sys-tem, allowing only sufficient steam to maintain thedesired pressure. The principle upon which the Mason reducing ^ alveworks is that of an auxiliary valve, 11, controlled bythe low pressure in the heating system through themedium of a metal diaphragm (23), and admits steam 82 LOCOMOTIVE APPLIANCES. from the initial side of the valve, through a port (JVN)to operate a piston (17), which in turn opens themain valve (16) and admits steam to the referring to the sectional view here shown, it. Mason Locomotive Pressure Reducing Valve, will be seen that the steam enters the valve at theside-marked inlet, a small portion of it passing upthrough the auxiliary valve (11). This valve (11) is forced open by the compression ofthe large spiral spring (8),acting on the button (10) LOCOMOTIVE APPLIANCES. 83 through the diaphragm (23), so that, in opening thevalve (11), the diaphragm is also forced down. Assoon as the valve (11) is opened, steam passes throughand into ports (A^ N) to the under side of piston (17).By raising piston (17), the main valve (16) is openedagainst the inlet pressure, since the area of valve (16)is only half, that of piston (17). Steam is thusadmitted to the system. When the pressure in theheating system has reached the required point, whichis determined by the spring (8), the diaphragm (23) isforced upward by the low pressure which passes upthrough port (A) to chamber 0 0, under the dia-phragm, thus allowing auxihary valve (11) to close
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