(erielack) Stainless steel flues, and what ifs

[Hhaines_@_aol.com]

Dear Josh,

Stainless steel flues?  My first reaction would be "not cost effective." Must 
be the engineer in me.  What inspired you to suggest that material? Better 
corrosion resistance (as obtained with the use of stainless steel) could be 
achieved by several boiler water treatments that would have been less 
expensive even in the 1920s.  

You identified that the initial cost might be high--but the cost would have 
been really high before 1938-1939 when the processing of stainless steel 
changed and the cost dropped significantly.

Even in the 1960s such flues would be expensive, and were not cost effective 
for most boilers below 650 psi.  Indeed, stainless steel was some of the 
material used in the ACE steam locomotives designs of 1980s when they tried 
to bring back powdered coal as a fuel in a fluidized bed combustion chamber. 
The coal and water would have been prepackaged and stored at locations so 
that these engines would possibly be refueled at many locations.  (I noticed 
none of the 'what ifs" went as far as using a coal-fired loco in their quest 
to continue EL into the 1980s.  The ACE (American Coal Enterprises) 
locomotive(s) superstructure looked like F-45s, with a different radiator 
section and a combined container car for fuel and water. I recall an article 
on these back in the 1980s (maybe Model Railroader?). I colored one for EL 
and another for NYSW back in the 1987 when I was working on another (diesel 
fueled) mobile steam engine design using triple expansion and high pressure 
steam.  Most but not all of the water was to be recycled on the ACE units, 
but that is off this topic.

My initial reaction for stainless steel flues in the 1920s would have been 
"not cost effective."  Also, any maintenance would be more costly because the 
stainless would have been harder to work, even if replacement periods were 
extended.   

I am guessing that if the AMC could not find combustion chambers and siphons 
cost effective, stainless steel would have been way down the list.

I do not think the economics would have changed much for locomotives in the 
1930s, and internal combustion engines were making inroads by the 1940s. The 
internal combustion engine was a double punch to steam because it developed 
its maximum horsepower at a lower speed (20 rather than 40 mph, and what drag 
freights went at faster speeds), and it significantly reduced labor and parts 
required for maintenance (compared to steam).

I would need to do more checking on metallurgy, but for a mobile application 
(like a locomotive), I think the stainless steel flues would need more fuel 
to develop the same steaming capacity.  The lower heat transfer coefficient 
(for some stainless) would combine to cut down on heat transfer, and would 
require more fuel/grate area for the same power. Also, other parts of the 
boiler would need to be made of stainless to take up the thermal expansion 
differences.  Another problem would be that the flues and other parts would 
weigh less--how much less would be determined by the design.  However, such 
material would be taking weight off the drivers, and possibly reducing 
traction effort.  

In short, stainless steel flues may seem more practical now for a steam 
locomotive, but probably not during the first half of the last century.  
Recent steam locomotive designs  employed modular parts, containerized fuel 
and water, and newer combustion and steam engine technology for locomotives, 
as adapted from stationary power plants.
  
H Haines

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