Re: NNG: Texas State Railroad

rehunn Wrote:
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> So it's made out of 2" thick. Match the shell and
> the firebox and use
> more flex bolts, it should work. 600 psi boilers
> certainly would have very
> similar issues.

That is the exact mindset that has caused the problems.

A locomotive boiler is subject to constant changes in firing rates as well as demands upon it's steam making abilities.

The firebox should be made of thinner material than the outer wrapper because it is in direct contact with the fire and expands and contracts at a higher rate than the wrapper. The firebox literally has no place to go. The too-ridged stays do not flex. The result is large divits are being created around the stay bolts. The area of concern is where the crown curves over into the side sheet. This is where the expansion and contraction forces run into each other. Around each staybolt is a divit 3/8" deep in a sheet 3/4" thick.

This is after the boiler has been in service a little over 400 days.

If this boiler sat in some building fired at a constant rate with a fairly constant load placed upon it, I doubt there would be a problem.

The new boiler for the Santa Fe Pacific is even worse - it has a firebox built out of 1" material. We won't even install it on the frame until it is redone.

Standard practice in the past was to make a boiler with 3/8-1/2" thick firebox with a wrapper of 5/8-3/4".