Everett Lueck Wrote:
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> Here are a couple of shots from the files of the
> Southern Forest Heritage museum that may explain
> what others are talking about here.
> The black and white photo of Red River and Gulf
> #106 shows both the oblong Locomotive Superheater
> Co plate, just above the Baldwin builders plate,
> and the bolt cluster between the builders plate
> and the boiler jacket. The color photo is inside
> the smoke box of the 106. The super heater tubes
> are the smaller tubes wrapped inside the larger
> boiler tubes, with the superheater header at the
> top with the steam pitpes to the cylinder coming
> out of the header at the top. The large pipe in
> the middle is the exhaust or petticoat pipe.
Your black & white photo also shows an additional piece of
equipment that was frequently supplied with a Superheater
and that is a Superheater damper. The generating tubes and
larger Superheater tubes in a locomotive boiler have water
to cool them while the Superheater elements themselves depend
on a flow of steam from the boiler. When the throttle is
closed, particularly after a hard pull when a high degree of
Superheat is obtained, the Superheater elements can be somewhat
protected by the damper which drops down by gravity and pretty
much blocks the flow of flue gases across the Superheater. One
other device to accomplish this same thing was a drifting throttle
which supplied a small amount of saturated steam through an orifice
to keep the elements cooled. Some very modern boilers used
Superheated steam for the auxiliaries, thus asssuring a constant
steam flow through the Superheater. A drifting throttle could
also be worked carefully by the engineer by simply cracking it
open just enought to accompish the job.
The Superheater damper had that visible counterweight that could
be observed from the cab as to whether it was open or closed.
Steam pressure normally held it open.
It was mentioned that not all locomotives with piston valves were
Superheated and this is true...some current examples are the
narrow gauge 2-6-2 at the Georgetown Loop, former Quincy RR 2
at Niles Canyon Ry., the former Port of Grays Harbor 2-8-2 at
Mt. Rainier Scenic RR in WA.
There was also the 3T Heisler of Big Creek & Telocaset in Eastern
OR which had piston valves, but Saturated steam coming right from
the dome.
