Injectors

[NW Mailing List]

In a Worthington Feedwater Heater, like what was used on N&W wether it be
the newer type SA that is 3 separate pieces (A's, J's and Y6b) or the older
1 piece BL (most Y's, K's, some M2's and E's) they work the same.

A 1. turbine cold water pump puts tender water into the 2. heating chamber
were exhaust steam mixes with the water to raise its temperature.  Lastly 3.
a piston type hot water pump puts the hot water into the boiler.

If the engine is not being "worked" cold water would be pumped into the
boiler which would cause thermal stresses.  It this case an injector is used
since the water is heated from the steam that is used to inject the water.

John Rhodes

On Thu, May 12, 2011 at 10:41 AM, NW Mailing List
<nw-mailing-list at nwhs.org>wrote:


> Jimmy, thanks for the info. Can you explain how a feedwater pump works?  Is

> it a pump, like the airpumps? If so, is there a piston?

>

> Mike Rector

>

> ------------------------------

> *From:* NW Mailing List <nw-mailing-list at nwhs.org>

> *To:* NW Mailing List <nw-mailing-list at nwhs.org>

> *Sent:* Friday, March 11, 2011 12:07 PM

> *Subject:* Injectors

>

>  *"An injector puts cold water (ignoring the steam used to operate it)

> into the boiler, so an engineer could use his injector in such a way as to

> make life tough for the fireman by killing steam pressure with cold water

> while keeping the throttle way open."*

> **

> Gordon,

>     I guess we have all heard this same story and it has been ingrained in

> our brain as "that's the way it is". Here is another one you may have heard:

> "as the safety pop valves were going off, the engineer turned on the

> injector to put cold water in the boiler and knock the pops down." This all

> sounds plausable, eh?

>     The *end results *in each example are true. However, the way those

> results are achieved are different from what we have all been told.

> *    "Cold"*  water is a relative term. Water in the tender can be

> considered as being at the current ambient temperature or shall we say

> "Cold". Water in the working boiler is "Hot" and under steam pressure.

> Saturated steam *from the boiler *is routed from the turret to and through

> the injector in order to supply feedwater to the boiler. Inside the injector

> this steam directly comes in contact with the cold feedwater from the tender

> and actually is a type of "feedwater heater".

>     From this contact the steam thus heats the feedwater quite a bit.

> Naturally it can only heat the water a relative amount. However, this amount

> is quite a lot and thus the water entering the boiler at the check valve is

> not *"cold"* by any means. It is not as hot as the water in the boiler,

> but, it is not cold either. It can be said that feedwater from the injector

> absorbs, for all intents and purposes, 100% of the heat used to force the

> water into the boiler. By natuee, the injector can never supply "cold" water

> to the boiler. Now hold that thought.

>     Switching to the other side of the engine is what we all know as the

> "Feedwater Heater System". This includes a steam driven "Cold Water Pump",

> the "Feedwater heater" and a steam driven "Hot Water Pump".

>     *A very important note here is that the "Feedwater Heater" only

> supplys heated water when the locomotive is being worked and there is

> exhaust steam to mingle with the cold water.*

>     When the locomotive is *"working",* *(read under load),* the Cold

> Water Pump takes "cold" water from the tender and pumps it to the Feedwater

> Heater section. Here the "cold " water is heated, directly or indirectly

> (depending on the type of system), by exhaust steam used by the cylinders.

> Again this "cold" water can only be heated a relative amount by this exhaust

> steam. Once heated the "Hot Water Pump" is used to force the water into the

> boiler. This water is also not as hot as boiler temperature.

>     The amount of heat transmitted to the water by the "FWH" depends on how

> much exhaust steam moves through the heater which is determined by how hard

> the locomotive is being worked. Since the pumps of the "FWH" system are

> steam driven, it would be possible to actually force "cold" water  into the

> boiler.Thus the "FWH" is not used while the loco is sitting still.

>     But, *for the most part*, "cold" water never enters the boiler.

> Neither the injector or the feedwater reason can supply the boiler with

> water as hot as what is already there.

>     Back to the injector. As explained, when the injector is turned on, it

> uses live steam from the boiler to operate. The use of this live steam

> naturally reduces the pressure in the boiler in order to supply the boiler.

> It is this use of live steam "from the boiler" to supply itself with water

> is the root cause of the reduction of boiler pressure and not so much from

> the relative lack of heat of the water being fed to the boiler.

>     The savings in using the "FWH" is that it utilizes heat from the

> exhaust steam that has already been charged to the boiler. The effect on any

> boiler pressure reduction caused by the use of live steam to supply the FWH

> pumps is minimal.

>

> Jimmy Lisle

>

>

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