I know that the grid should be 1 foot intervals. How close do any of you shoot readings around the mud ring? Any other areas that you usually shoot closer intervals?

As far as running calculations, would any one be willing to share spreadsheets that they have used to do calculations? How about their formula sheets?

Two areas which need closer looks are areas of obvious visible deterioration either inside or outside of the boiler, and the areas which seem to deteriorate fastest in most boilers. In my experience, that includes the bottom of the FTS, the horizontal stretch along the courses where the water level fluctuates in service, the bottom of the barrel and the crown, bottoms of side, and door sheets. RTS below the braces can be troublesome, and if your crown or side sheets look like an upholstered cushion bulging out between the buttons, you have bigger issues. Also consider places against which the internal water circulation impinges against the metal and erodes it over time. Also obviously, if you start to find an area that seems to show a pattern of thinning, get close up and find out how thin and how far it goes. I almost never go smaller than 8"-9" at maximum on what I expect to be "good" plate.

Every boiler has its own set of calculations and formulae are readily available through technical libraries and regulatory agencies, some are in public domain. You need to figure out what you need and do a bit of networking and hunting.

If your purpose is to cosnider the likelhood of candidacy for operating restoration, compare what is there now with what was there as built. You don't need to do complete calcs to see if it is mostly there or mostly gone. If you do pursue it further, it might be well worth your trouble and expense to pay a qualified engineer to take a few hours and go through the number crunching with you. It is more than thicknesses, bracing and staying are much more complex than simple course and seam figgerin.

Good luck.

dave