Hello Mike, I too have heard the term used in connection with various applications. I don't know that you can directly compare the "moment of a boiler" to the "moment welds" as I believe they are somewhat different by definition. I have always believed that this term was for describing a special type of connection joint in the framing of a structure relative to it's ability to withstand seismic energy in an earthquake. After I read your post I went to "Ask Jeeves" and asked about moment connections. Unfortunately it didn't really give a definition either of the specifics of that term, although it did lead me to some information that spoke of differences in types of connections for connecting structural members. Some of these were described as shear type connections and others were described as moment connections. Thus I would imagine that it might require the response of a structural engineer or a civil engineer. I would take a wild guess and say that a "moment of a boiler" might be the point at which the boiler could no longer withstand the pressure that is contained within it and it explodes, just a guess here though. Great question Mike, I am looking forward to a reply from anyone with a concise answer. Regards, Allan

Without digging out some old textbooks, a "moment" is a force that is rotated around a fixed point.  If you were to weld a 1 ft. long beam to a column and put 1 lb. of force on the unwelded end of the beam, the "moment" at the weld would be 1 lb./ft.  This is basically torque.  Here is a link to illustrations of different types of steel connections:

http://wwweng.uwyo.edu/connections/index.html

If you have PowerPoint, this is also good info:

http://www.aisc.org/Content/ContentGroups/Documents/University_Relations3/ConnectionsBracing1.ppt