Steam & Excursion > Whistles

Gang, why do some/most steam whistles blow off big clouds of steam but some--UP 844, 4014--don't show any steam?

Saturated steam (white cloud)
Superheated steam (no cloud)

kurtarmbruster Wrote:
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> Gang, why do some/most steam whistles blow off big
> clouds of steam but some--UP 844, 4014--don't show
> any steam?

First, a lot depends on the weather, i.e. whether it is cool and dry (which produces big vapor clouds),or hot and dry (hardly any visible vapor).

Second, the whistle in many more modern steam locomotives, like 4449, 844, 3985, and 4014, are supplied with superheated steam, off the superheater header. That steam is a LOT hotter and dryer, which tends to produce much less visible vapor, especially on a hot day.

Ah, so, thank you very much!

You have to be specific about where the steam supply 
( off of the superheater-header casting:  pipes can be attached at the 
   Steam-in part of the header, or steam can be piped from
   the 'hot' side of the superheater)

An example is cross compound air compressors mounted on the pilot 
deck, under the smoke box of NKP S-2 Berks... the steam supply to the
compressors is from the area of the superheater header,
but it is heat-saturated steam (non-superheated).  The 
compressor supply pipe and it's valve to the compressors is from
the dry-pipe inlet to the superheater units...

Outlet-piping closer to the smokestack can be from the "hot side" of the
superheater header casting.   Even so, the superheated steam 
takes 'steady-beating', and a white-hot fire to produce superheat 
temperatures.   You don't get superheat-generating temps with a light,
train, in down-hill running, or while sitting around.

Starting in the morning, or after having sat for considerable time,
you generally won't get superheat-capable fire until the refractory 
bricks in the firebox become incandescent.   That takes about
20 minutes to half an hour of steady, hard beating and a consistent,
strong draft.... 

An ideal situation in steam days on PRR, was departing Altoona, west-bound 
towards Horseshoe Curve.  You have about a mile of flat track, leaving
the station, then a gentle uphill-pull toward the 'Curve.

Before entering the Curve region ( the 'grade' is flat, around the 'Curve --
- but train resistance and drag remains constant because of the number of cars 
and their 'flange-friction' presents a REAL, drag --- as if hauling cars upgrade)..
..... before entering the region is a hard-right curve over a brook: 'Scotch Run',
to the RRers.. that climb and 'Curve would be the unexpected  'stall point' for trains --- .
If you went past 'Scotch Run', and were still moving...the rest of trip to 
Gallitzin was a hard, but steady pull, not nearly as difficult as that first curve..
known as Scotch Run*

So, a fireman had a good draft to work with, a station stop to get his firebed
properly prepared, a steady pull before hitting the grade, getting near superheat,
and stong draft all the way to Scotch Run....then an easy, steady draft to the top..

He had a strong draft, and soon had glowing brick-arch, and superheat
temperatures were soon beginning to get to work.  It takes time to 
get everything running hot enough to produce superheat.

Just because it's called a "superheater", it ain't superheat 'til everything is 
roaring HOT!   That takes time and an intelligent operation of the throttle--
just yanking it open is the wrong way to manage your locomotive..
You have to be aware of the firebox temps and what your fireman's 
task is...

THAT'S  why engineers used to be groomed as locomotive firemen,
first.  Learning as a fireman you get familiar with the piping on locos,
then get familiar with the railroad 'territory', get to study the timetable's notes,
and the Rule book, then get to observe skilled engIneers as they operated
their engines, over tricky territory and tough situations..

Once in while, engineers let 'student' firemen run the train...for
easy portions... Soon, good firemen would be eligible for promotion...
but, it took a lot of diligent study and work.  The reviewing comments from an
influential engineer, could have great bearing on "higher-ups", as to which
firemen students deserved 'early' promotions...

​W.
 
( * Scotch Run has a more formal, map-name: a Scottish-name 
     on regional maps; but, my mind remembers the RRer's slang )