John and Scott,
Many thanks for your postings. It sounds like you both know a lot more
about steam engines than I do. I apologize for taking so long to respond
and even more for the monstrous length of what follows (anyone who just
wants "the bottom line," please scroll down to the last 2 paragraphs; those
of you who love plumbing, grab a lunch and read on).
After thinking about it, I still am not persuaded that the most important
benefit of feedwater heaters was fuel or water savings. I do get what you
are saying. I'm sure it's the majority view; in fact I think it's exactly
the conventional wisdom against which I was arguing in my last posting.
Don't misunderstand me; I agree with all your facts. The increased thermal
efficiency FWHs provide is undeniable; and as you rightly point out, that
translates into savings of fuel and to some extent water -- which then
allows trains to operate with fewer servicing stops, thus faster and more
efficiently. But I suspect that's not the whole story, or maybe even the
most interesting part of it.
If you were to ask me, for example, why I flipped on the light switch in a
room at 3:00 a.m., I wouldn't say it was because an incandescent bulb can
illuminate the dark space at low cost. Factually true though that may be,
it wouldn't tell you anything very useful about my motives. Somewhat the
same problem with citing themal efficiency or fuel savings as the reason
for using feedwater heaters. It begs the question of WHY the Burlington or
any railroad used them as they did (when, where, and on which
locomotives?).
John anticipates this objection when he cautions that the expected savings
had to be greater than the capital cost of installing, plus the ongoing
cost of maintaining the FWH system. And theoretically he is right, but that
raises the tricky question of how to measure savings. In reality, a lot of
considerations probably came into play when deciding when to use this or
any improved technology on new or existing engines. Some important costs
and benefits may have been perfectly real but less tangible and
quantifiable than, say, the price of coal consumed. If the addition of FWHs
helped reduce the need for double-heading, for instance, or of purchasing
new power, or if they just helped trains keep to faster, more competitive
schedules, they might be considered worthwhile even when they cost more to
install and maintain than they saved in fuel.
It's often the case that people (and companies) make economic decisions for
reasons other than the obvious, stated ones (economists worry about such
questions all the time, and some even have won Nobel Prizes for figuring
out the "reasons behind the reasons" for people's economic behavior). In
the case of steam technology, the choice of which extra appliances to add
to new or existing engines, like any management decision, undoubtedly took
into consideration information that was coming in from all over the
corporate structure -- from the accounting department at one end to the
shop foremen and engine crews at the other. Only by looking at the overall
pattern of how the railroad actually used -- or did not use -- feedwater
heaters can we get a fair sense of what they really thought were their most
important benefits.
The 1935 List of Assignments in Corbin and Kerka (Steam Locomotives of the
Burlington Route, p. 292) gives us the chance to do just that. As Scott
notes, Corbin and Kerka's 1935 list has a wealth of information on how
engines were equipped with various steam technologies, and geographically
where those engines were used. It thus provides a snapshot of the
Burlington's decision-making process at one point in time -- a very useful
snapshot, too, since it was a time when steam power was used in almost
every "niche" all over the system.
So which engines had feedwater heaters? Well, most obviously, newer, larger
engines -- just what you would expect. Big engines used the most fuel and
water, and they probably ran up the most miles too, so the savings would be
greatest, right? True, but bear in mind that feedwater heaters were not
included on new engines until the mid-1920s (the T-2 mallets are a special
case; they were built in 1910 with a split boiler, which provided a kind of
internal feedwater heating system). None of the mikados or Santa Fe types
built before 1925 had FWHs when delivered. None of the Pacifics did, nor
did the original B-1s. I think the B-1As (1925) may have been the first to
have them included by the manufacturer, and everything built afterwards --
the M-4s S-4s and O-5s -- had them as standard equipment. On all other
classes, however, they were retrofitted during the 1920s and 1930s.
Or not -- raising the question of which engines were upgraded with
feedwater heaters, and why?
Again, as you would predict, larger engines tended to be upgraded, smaller
engines not. The cut-off point for freight engines was about the 2-8-2.
Most mikados had received feedwater heaters by the time of the 1935 list,
but a significant number (almost one third, in fact) had not, and what is
more interesting, many never would. Almost everything larger than a 2-8-2
was FWH-equipped by that time, though there were a few outstanding M1s or
M2s still using injectors only (interestingly, most of those are listed as
stored unserviceable, which tells me they were awaiting major shopping and
were about to have FWHs added; or they were about to be retired). No
smaller freight engines are listed as having FWHs. No consolidations,
prairies, ten wheelers or moguls. And no switchers.
For passenger engines, the cut-off point was the Pacific. Smaller passenger
engines -- e.g., Atlantics, ten wheelers, and prairies -- used only
injectors (I have seen at least one photo of a prairie with a Worthington,
and there may have been a few other exceptions, but this was the broad
pattern). The overwhelming majority of Pacifics (over 90%) were equipped
with FWHs by 1935. All heavy Pacifics, Mountains and Hudsons had them.
What does this pattern tell us? That more fuel is to be saved with larger
engines? Yes, but it's far from a perfect correlation. Does an O-3 drag
freight engine working tonnage at a tractive effort of 60,000 lbs really
use less fuel and water than a light passenger engine like an S-1A
(tractive effort 31,000 lbs.) pulling a 5-car train? I'd doubt it. Yet all
the S-1As were equipped with feedwater heaters, while a large number of O3s
(as well as some O2s and many O1s) weren't. Indeed, if we include the
"out-of-service" engines, the percentage of all 4-6-2s without feedwater
heaters (8%) was lower than the percentage of 2-8-2s (30%) or even 2-10-2s
(13%) equipped with only injectors.
Let's think about this from a different angle for a moment. As John and
Scott have explained, feedwater heaters save energy and thus fuel by using
waste heat (e.g., in the smokebox) to preheat water before it is admitted
to the boiler (some models recapture exhaust steam, thereby conserving
water as well as heat). Sounds great -- so then, why wouldn't a
conscientious engine crew use such a wonderful device all the time? Why use
the injectors at all? Well, consider the following scenario. You've just
crested a grade. You stop working steam, your fire is hot, and boiler
pressure is rising. What do you do? You're probably not going to throw open
the throttle again, especially if you're about to head downgrade. You could
just let the pop valve go, but THAT would waste steam, water, and fuel. You
could do some housecleaning and blow down the boiler. But why not inject a
little cold water and use that excess energy to heat it up, thereby
lowering the pressure a bit and conserving the water and energy you've
already invested? Here, using the injectors rather than the FWH would be
the better choice -- or so it was explained to me by one retired engineer.
All right then, so when do you benefit most from using preheated feedwater?
In exactly the opposite situations: i.e., where you need to work steam --
accelerating a heavy train, running a heavy train upgrade, or any other
time when a large volume of high-pressure steam must be replenished quickly
and/or constantly. And that, I would argue, is why FWHs appear to have been
so much more essential on the Burlington's light Pacifics than on its heavy
mikados. Because they really helped these relatively small-boilered engines
in accelerating heavyweight passenger trains and running them at sustained
high speeds, especially over the undulating topography of the western
lines.
As often is the case, it is the exceptions which prove the rule. Let us ask
which engines in a particular class did NOT receive feedwater heaters.
(Note: these figures are based on quick counts; my numbers may be off by a
few either way, but they're roughly correct.) In the case of the 112
Pacifics on the 1935 List of Assignments, the roster shows only 9 without
feedwater heaters: 4 unmodernized S-1s and 5 unmodernized S-2s; all are on
the Chicago Division. Why? Because these were not mainline or even
branchline passenger engines, but commuter engines, a service which did not
demand sustained steaming. (Commuter service is notoriously hard on
boilers. These engines were probably also considered near the end of their
useful service, and most were gone within 5 years.)
The case of the mikados is equally instructive. By 1935 most engines in
classes O-1A through O-4 had received feedwater heaters. But out of 336
total mikados on the roster, 101 still were using only injectors. To break
these numbers down, there were 46 out of 48 O-1s and 14 out of 148 O-1As
with injectors only. All 15 O-4s had acquired feedwater heaters by 1935.
And all 52 O-2As had them, as well; the latter presumably were installed
when the O-2s were upgraded, since all 13 remaining unmodified O-2s on the
list still had only injectors (and seven of those engines were out of
service). Among the 60 O-3s, only 32 had FWHs, slightly more than half. We
can add, parenthetically, that some of these engines did receive FWHs at a
later date. But others did not, and as noted in my earlier posting, when
the Coffin-equipped O-3s lost their FWHs, they reverted to the use of
injectors only (and Gerald Edgar is correct; there were four such engines).
What accounts for this pattern? The case of the O-1s and O-1As seems
clearest. Those O-1As which had FWHs were probably regular road engines
used in freight service, while the unmodified O1s with injectors only were
being used as switchers or in transfer service. I'm sure this is not a
perfect correlation, but I'll bet it's close. Note, for instance, that
almost a quarter of those unmodified O-1s were assigned to the Beardstown
Division, where (thanks in part to John's superb monograph on the Q's coal
fields operations) we know that many were employed as mine switchers. And I
suspect that most of the other unmodified O-1s (in Denver, Chicago, and on
the St. Joseph Div.) were also engaged in switching or pinger service,
neither of which demands much sustained steaming. It's worth reiterating
here that no dedicated class of Burlington switch engines used feedwater
heaters -- not even the T-1s used in hump yard service during the
mid-1920s, nor the F-2s into which they were rebuilt (with their 61,000 lb
tractive effort), nor the USRA 0-8-0s.
The case the O-2s and O-3s is a bit more complex (these two classes were
virtually identical in many respects, the main difference being that the
O-3s were designed with greater thermal efficiencies, including firebox
arches, combustion chambers, improved superheaters, etc.). By the time of
the 1935 roster, many of the older O-2s had been or were being converted
into O-2As with the addition of similar energy-saving technologies,
including in all cases feedwater heaters. But as noted earlier, many O-3s
continued to operate their whole lives with only injectors. What was going
on here? Well, these were drag freight engines, designed to haul heavy
trains at slow speed. To do their job, they relied more on tractive effort
and momentum than sustained steaming, except where grades were encountered
(and they were not known to perform particularly well in such conditions).
If you check the List of Assignments, you will notice that 5 out of the 6
injector-only O-2s remaining in active service, as well as all of the O-3s
without feedwater heaters, were on the Lines East, where grades were fewer
and gentler. By contrast, almost all of the Lines West O-2s (i.e., O-2As)
and O-3s HAD been equipped with FWHs.
As for the O-4s (all FWH-equipped by 1935), they too were Lines West
engines, and as such regularly had to move tonnage up grades.
If exceptions can prove the rule, then exceptions to those exceptions
sometimes can be equally revealing. For instance, I just said all O-4s had
feedwater heaters. Well, yes and no. The parent company's O-4s all had
them, but the FW&D's E-4A2s, which were identical USRA heavy 2-8-2s, did
NOT. As I suggested in my last posting, I suspect this was because they
could operate well enough with just injectors over their essentially level
trackage. And only two of the otherwise unmodified O-1s DID have feedwater
heaters -- one assigned to Denver, one to Casper. But there is another
notable group of similar engines -- namely, the C&S's E-4A1s -- shown as
leased to the Beardstown Division in '35. ALL these were equipped with
Elesco FWHs. And remember that those engines, in their original service,
had been expected to contended with the grades along Colorado's Front
Ranges.
To sum it up, feedwater heaters DO save fuel and sometimes water. But like
most modern steam technologies, they do so marginally; they prove
economical in some cases and not others. And the decision of whether to use
them probably balances many factors. On the Burlington, FWHs seem to have
made the most critical difference in situations where they wanted to
improve an engine's capacity for sustained steaming -- in passenger engines
pulling increasingly heavy trains during the 1920s and '30s, in freight
engines where speed was required, and wherever the heaviest freight trains
had to contend with significant grades.
That's how the overall pattern looks to me, anyway. But as I conceded up
front, the two of you probably know a great deal more about this stuff than
I do. So please feel free to point out where the train of my reasoning has
hit the derail.
Jonathan
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