SV: Operatioin of Feedwater Heaters.

[nw-mailing-list at nwhs.org]

                    Another Suguestion.
 
                   Have  ben thougt a Third  reason for Top feed, Then
the Feedwater enters thru the checkvalves and heats up, the Oxygen in
the water goes out with the steam,
                   With  Side feed, feedwater mixes with the water
already in the bolier and  the oxygen reacts with the steel in the
boiler as corosion. 
                  
                   But some roads, NYC for example  mostly uses side
feed on their locomotives, maybe because they get rid of the Oxygen in
the Feedwaterheater?
                   Somebody  may know more.
 
                   //// Jan Soderlund 
 
 
 
 
Very informative; thanks. 

I remember reading somewhere that top checks, which were the standard in
the later days of steam loco design, were preferred because they heated
the water as it flowed in or something similar (avoiding having a cooler
spot in the boiler where the water came in?). I don't remember a mention
of side-swipes. but that would be a collateral advantage.

Pete Groom
On Oct 20, 2004, at 11:26 AM, nw-mailing-list at nwhs.org wrote:
Nathan,
 
Inasmuch as none of the steam experts among us has addressed your
question, I'll send this rather sophomoric explanation based partly on
my recollection from working several summers around N&W steam
locomotives and partly on various written sources.
 
Using the N&W "Y" class locomotives as an example, the Y3's (modernized)
through the Y6a's were equipped with Worthington Type BL-2 feedwater
heaters, whereas the Y6b's were equipped with Worthington Type SA
feedwater heaters.  In addition, all were equipped with an injector as
well.
 
A BL-2 is easily identified as being the large apparatus suspended below
the running board on the left side of an N&W locomotive so equipped.  A
BL-2 contains all of the devices to pump water from the tender, heat the
water, and pump it into the boiler.  It is only necessary to attach the
pipes, and it is ready to go.  Facing the side of the locomotive, on the
right of the BL-2 the top portion is the steam cylinder, the portion
below it is the cold water pump and the portion below it is the hot
water pump.  The steam piston and both water pump pistons share a common
piston rod so that both pump pistons make a stroke every time the steam
piston makes a stroke.  The left side of the BL-2 is the heater where a
portion (typically 15 - 20 percent) of the exhaust steam from the
locomotive cylinders is mixed with cold water from the tender to heat
the water.  When the steam valve in the cab is opened, steam flows to
the BL-2 steam cylinder pushing the steam piston alternately up and
down, causing the cold water pump to pump water from the tender into the
heater, and likewise causing the hot water pump to pump the heated water
into the boiler.  Because the cold water pump is a positive displacement
piston pump, it can draw water from the tender even when the water lever
in the latter is below the inlet to the pump.
 
In contrast, the SA feedwater heater is a three-component device.  A
steam-turbine-driven centrifugal pump mounted on the left side of the
locomotive under the cab delivers cold water from the tender to the
heater mounted mostly inside the top of the smokebox ahead of the stack.
Like the BL-2, the SA uses exhaust steam to heat the water in the
heater. The heated water is pumped into the boiler by a steam-driven
reciprocating piston pump mounted on the left side of the locomotive
outside the smoke box near its bottom.  Now, back to the cold water
pump.  The steam to drive the centrifugal cold water pump is regulated
by a steam valve operated by a float inside the heater such that the
centrifugal pump only operates as necessary to maintain the water level
in the heater.
 
You can see from this that either type of feedwater heater is controlled
by only one steam valve in the locomotive cab.
 
Injectors are a different animal from feedwater heaters.  They do the
impossible by taking steam from the boiler at, say, 300 psi and using it
to force water into the boiler against the same 300 psi.  This miracle
is wrought by nozzles in the injector body that accelerate the steam
though venturis that draw in water from the tender.  The water is
accelerated to a high velocity, after which an expanding section
converts the velocity energy of the water to a pressure that is
sufficient to force the water through the boiler delivery check valve
into the boiler.  The injectors on later-day N&W steam locomotives were
live steam, non-lifting injectors, meaning that they used live steam
from the boiler rather than exhaust steam from the cylinders (exhaust
steam injectors were called "poor man's feedwater heaters"), and that
they had to be located below the lowest level of water in the tender
because they could not raise water from a lower level.  This type of
injector was operated by one lever in the cab.  The injector can be seen
in many photos mounted underneath the cab, but the most distinguishing
feature is often the delivery pipe running from the injector to the
boiler check valves on top of the boiler.  Early locomotives had check
valves on the side of the boiler, but the N&W practice in later years
was to place the check valves on top where they were less likely to be
sheared off in a sideswipe accident.
 
I hope this helps more than confuses.
 
Gordon Hamilton
 
 
----- Original Message -----

From: nw-mailing-list at nwhs.org 
To: NW-Mailing-List at nwhs.org 
Sent: Friday, October 15, 2004 10:28 AM
Subject: Operation of Feedwater Heaters.

What is involved in the operation of a feedwater heater?  Does the
fireman have to operate the cold water pump and hot water pump
separately?  Or, do the two pumps turn on with the same control?  How
does this system differ from the operation of the injector system?
 
Nathan Driscoll

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