Wow! My how you guys carry on about this situation. (By the way, my congrats to Carlos L. for a fine bunch of pix. A great photo essay! Keep up the good work Carlos L.!)
OK, so you got a heavy scale build up, its happened before and it'll happen again.
Some of the questions I'd ask are:
1. Was this truely a case of not getting washed properly at the monthly inspection?
2. Was the water tested before each days work to determine how much treatment to add? Water quality does not stay the same especially after storms or changes in town water supply chemistry.
3. Was the proper water treatment being used and in the correct quantities. Use of good water treament pays off in less boiler repairs. But there is cost to it.
4. Was this engine used after bad rain storms or was the water supplied from a very dirty location (was there lotsa dirt was in the water)?
5. How clean was the (tank) or cistern?
6. From the look of the sheet, it appears to be thick (OK), so did it have a bluged, had a blue look or showed signs of leakage????? Or was this just caught at the boiler wash?
7. As previous comments mentioned, blow-off procedures may need to be modified. Blowing down in the morning before the fire (bank) is disturbed is the best time for using the mud ring blow-off cocks as the scale and most of the nasty stuff has settled and is not in suspension.
Before service (early morning) blow downs while in the 'house of course or not really appreciated safety wise unless you temporarily pipe them to the pit.
Suspended solids and bad chemistry is one reason that many boilers in bad water water districts went to using a constant surface blow-down. It doesn't use as much water as you would think and it helps to lower the conductivity as the concentrated acids and impurities are carried to the surface by the rising steam bubbles and are then blown off to the ground.
This doesn't mean the blowoff cock shouldn't be used while on the road, it just means that it is not as effective because the solids are in suspension and mostly at the surface.
Remember stories about "foaming" or priming? This was a very bad condition at the surface of the water within the boiler caused by a bad water condition.
Even the best of waters after 25 days or so will have high conductivity levels. And this promotes 'lifting' the water higher in the glass even when using the throttle in a normal manner. Priming is the end result, where foaming is caused by water impurities.
Not all water is the same even if it is drinkable and that doesn't mean it shouldn't be tested and treated as necessary.
Obviously, this condition was picked by the inspector(s) and the repairs are being done as has been the case in the past, burn out the sheet & bolts out and patch.
If this condition continues to show up in various amounts it might be necessary to wash the boiler more frequently than just once a month, especially if the locomotive in every day use and if water treatment is perhaps, a not affordable item.
It is a "good find" and well documented.
Tomorrow is another day of work, time to move on to the next problem.
Chris