Re: Purpose of various steam locomotive parts

The mud ring is what the wrapper sheet, door sheets, side sheets, tube sheet and throat sheet rivet to at the bottom of the firebox area of the boiler. It may be designed to slope downward to the front to corespond to sloping grates or sloping firepan if oil burning or be flat ie.horizontal. Being the lowest point inside the water space of the boiler, it is where boiler mud/sludge/scale collects. This is why the blow down valve(s) are located just above the mud ring, but with the bottom of the pipe connection as close to the mudring as possible. With a sloping mudring the blowdown(s) are located at the lowest point(s) on one or both sides near the front of the firebox. On our #3 Heisler which has a horizontal mudring, the blowdown is under the cab, directly below the fire door facing the rear. The outlet pipe from the blow down valve has a muffler on it, so it doesn't blow back into the gear case and cellars or directly out the sides.