I thought one of the major points of using a water column was that it reduced the effects of 'false level' such as slosh. For this construction to introduce a potential point of failure is, to me, a clear indication that something needs to be cleaned or blown out other than the glass.

.

In the commercial boiler industry, water columns are still very much standard for all types of high pressure steam boilers, fire tube and water tube alike. The turbulence of the water when boiling causes a very uneven water level, which can make the water dance in the glass if directly connected to the boiler. The water column is a "shock absorber", and gives the water a chance to find it's own level before then flowing to the glass or cocks.

The interesting part begins about 2:40 into the video:
https://www.youtube.com/watch?v=a0xZPl_bwHI

Part 2 of the video:
https://www.youtube.com/watch?v=tI3tWuSsX7c&t=27s

INTERSTATE COMMERCE COMMISSION

---------------

REPORT NO. 3396


Accident (boiler explosion) at Canadian, Tex., on April 1, 1951, caused by overheated crown sheet due to low water.(LINK)

"Measurements of the line of demarcation transferred to similar points on a locomotive of the same class indicated that the water had been 6 inches below the highest part of the crown sheet."

"The force of the explosion tore the boiler from the frame and hurled it through the roof of the enginehouse and forward. The boiler in its flight cleared power lines 32 feet above the ground and 95 feet forward and alighted in reversed position on its right side and back head, striking the ground 119 feet forward of the point of the explosion and making a depression 4 feet in depth and 12 feet in diameter."



Current Round House location:

Interesting points:

Overheated portion of crown and ends of staybolts heat-blued

Staybolt ends that were blued were cupped up to 5/16" -- I take this to mean the threaded portion deformed rather than pulling threads for some time

Elongation of holes rather than tearing out appears to be a contributing factor.

With one safety popping, the boiler pressure could not rise above 213psi BUT the boiler lost about 6" of level in 10 minutes. The indication of the forced-firing test may not be indicative of the level drop once the top of the crown is highly exposed and the engine is standing.