If the flues are allowed to become covered inside with soot and ashes, the formation of which becomes a non-conductor for heat, the product of combustion passes through the flues without leaving more than one-half as much heat as it would otherwise leave if the flues were clean.
BLOWER.
The Blower consists of a small pipe attached to the steam dome or top of the boiler with a globe or angle valve, and is situated near the stack. This pipe enters the stack just above the boiler, the end being bent up toward the top of stack and reduced to a very small opening. When steam is turned on through this pipe, it displaces the air in the stack, causes a partial vacuum in the smoke box, and the air rushes through the grates, fuel and flues to replace that which is blown out by the blower, and the draught can be increased as much as desired.
EXHAUST NOZZLE.
The Exhaust Nozzle, as generally constructed, is an elbow attached to the end of the exhaust pipe in the smoke box or smoke stack of the boiler, the end of which points upward, with the opening reduced so that the exhaust steam will be forced up the stack, and thereby produce the same effect as a blower.
The opening in the exhaust nozzle should never be made so small as to check the exhaust steam to any great degree, and cause back pressure in the cylinder, as the power of the engine would be diminished. The opening should be as large as possible, and still produce sufficient draught to keep the required steam pressure.
FUSIBLE PLUG.
Lunkenheimer
Fusible Plug.