It is my understanding that in 1:1 scale engines a fusible plug was in the top of the firebox. (In this case, the stay joints.) As the water level fell to dangerous levels, the water would not be able to absorb all the heat being generated in the firebox and the plug would melt. The resulting steam/water jet would douse the fire and relieve the buildup of pressure.
In the case of the mudring, my guess is with a small boiler the remaining water flashes into steam with the release of pressure, causing the mud ring joint to melt from the residual heat and allowing this pressure to be vented as well. Art Walker wrote: >>I think my problem with the notion is that soft solder (IIRC) melts at >>about 500 degrees F. Water, at atmospheric pressure(14.7 psia), boils >>at 200 degrees F. Explain to me how the boiler will be hot enough to >>melt the solder, and yet expel liquid water onto the fire? /me >>ponders... >> >Steam is a very effective fire douser, is it not ? >
