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Feedwater

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Feedwater
Posted by kenny dorham on Wednesday, September 22, 2021 4:01 PM
I had never Read/Heard this term before and have no idea how many variants there might be.

FWIW and in case it helps answer my question..........the below is a quote from page 122 of   "Portrait Of The Rails" by Don Ball Jr.

He is discussing a Leigh Valley Loco ...T-1 4-8-4
 
He says...................This Elesco feedwater-equipped brute was built by Baldwin in 1938.
 
Did a "feedwater pump" simply pump water from the tender, or was it recycling steam, or something like that.?

Thank You

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Posted by Overmod on Wednesday, September 22, 2021 4:23 PM

I cannot type any reply with sufficient detail on this crap phone before the crap forum system resets the page and blanks the answer.  PM me and I'll send you detail later.

Feedwater is the make-up water that has to be pumped from the tender to make up what has been 'boiled' to steam and used in the engine(s).

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Posted by kenny dorham on Wednesday, September 22, 2021 5:55 PM

No worries. I get the gist of what you are saying.

Thank You Smile

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Posted by SD70Dude on Wednesday, September 22, 2021 7:17 PM

Feedwater and make-up water are synonyms, as Overmod said. 

The Elesco corporation is probably best known for their feedwater heaters, which use exhaust steam to preheat the water before it enters the boiler.  

Greetings from Alberta

-an Articulate Malcontent

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Posted by Paul Milenkovic on Wednesday, September 22, 2021 9:12 PM

SD70Dude

Feedwater and make-up water are synonyms, as Overmod said. 

The Elesco corporation is probably best known for their feedwater heaters, which use exhaust steam to preheat the water before it enters the boiler.  

 

This is almost like the discussion about "hot water heaters."  People in the trade simply call them "water heaters."  You put cold water into them and hot water comes out because that is what happens when you heat water -- to call them "hot water heaters" is what grammarians call a "tautology."

Feedwater is the water you by some means inject or pump into a boiler, so yes, it is the "make-up water" to replace the water that makes steam or is discharge by "blow down" to remove boiler contaminants.

The oldest type of way of feeding water into a boiler, locomotive, marine or stationary, is with a piston pump operated by the motion.  This type of operation is inconvenient if the locomotive has to be standing under steam for a long time -- it is necessary to run the locomotive forward and backward to pump in more water to make up for steam losses.

The next appliance is the injector.  This gadget combines steam tapped from the boiler with cold water from the tender to "inject" the feedwater into the boiler against the boiler pressure, all without moving parts.  It has something to do with the Bernouli Principle that curves a curve ball baseball pitch and produces lift on an airplane wing.  It also condenses the boiler steam to produce the motive power to inject the water.  The injector is a standard apparatus on a steam locomotive, even if another means is used to inject the feed water. 

A proper feedwater heater takes some of the exhaust steam, and instead of exhausting it up the stack to make the draft to supply air to the fire, this portion of the spent steam heats up boiler water before it is put into the boiler.  In heating up the boiler water with steam that is otherwise discharged to the atmosphere, this saves on the coal consumption of the locomotive -- maybe by as much as 10%.

The feedwater heater became popular as a fuel-saving device starting in the 1920s.  The Elesco feedwater heater is that transverse drum in front of the smokebox, but later feedwater heaters were either hidden or partially hidden in the smokebox.

The thing about a feedwater heater is that once water is heated up, you can no longer use an injector to force it into the boiler because the steam supplied to the injector won't condense to make it go.  You cannot put the injector upstream of the feedwater heater because the injector heats up the feedwater using live steam from the boiler, and the feedwater heater cannot get the feedwater any hotter to get any fuel saving.  So a feedwater heater needs a mechanical pump.  The closed-type feedwater heater such as the Elesco needs only a single pump, but the open-type feedwater heater that became popular later needs two pumps -- one into the mixing chamber between exhaust steam and feedwater and one to pump the heated feedwater into the boiler.  Also, the open type needs a way of separating out the cylinder lube oil from the condensed exhaust steam that is mixed with the feedwater so that oil doesn't foam up the steam space in the boiler and "carry over" unevaporated water into the superheater and cylinders.

Another advantage of the feedwater heater is that in addition to saving on coal, it also saves on the amount of water you need to supply from the tender.  This saving comes from the portion of the exhaust steam condensed in the feedwater heater and resupplied to the boiler.  A locomotive with a feedwater heater becomes "partially condensing."  The problem with condensing on a locomotive without a free source of cooling water as on a ship is rejecting heat to condense the water.  That portion of the exhaust steam that heats the feedwater uses the feedwater to reject heat to allow it to condense, but because of the energy balance, this only allows condensing maybe a 10% portion of the exhaust steam that way.

The feedwater wasn't universally applied to steam locomotives.  Besides the feedwater heater chamber itself, it is a complicated contraption involving pumps and a lot of extra plumbing.  It is another "gadget" that requires potentially expensive maintenance.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?

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Posted by kenny dorham on Wednesday, September 22, 2021 11:42 PM

Thanks for all the info.

I have just a casual interest in trains, but i was still a bit surprised i had never seen the term before.

I look at a circa 1930 steam locomotive, and i see all the pipes and valves and pistons and rods..............the thing is COVERED with it.

It sort of reminds me of a jet engine. One reason jets replaced the IC Piston motor was because it was "So Simple". Yet, when you look at a jet motor, there is all kinds of stuff. Plumbing every where. Hundreds of odd bits and pieces that are not seen on other things in life.

It does not have all the bearings and moving parts of a piston motor, but it does not LOOK "simple" :)

Anyway. Thanks Again for the replies.

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Posted by MidlandMike on Thursday, September 23, 2021 8:09 PM

Those feedwater heaters with pumps sounds complicated, so did those engines also have injectors just in case?

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Posted by MidlandMike on Thursday, September 23, 2021 8:15 PM

Paul Milenkovic
...The next appliance is the injector.  This gadget combines steam tapped from the boiler with cold water from the tender to "inject" the feedwater into the boiler against the boiler pressure, all without moving parts. 

I got to think that at least it had check valves.

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Posted by Paul Milenkovic on Thursday, September 23, 2021 8:39 PM

MidlandMike

 

 
Paul Milenkovic
...The next appliance is the injector.  This gadget combines steam tapped from the boiler with cold water from the tender to "inject" the feedwater into the boiler against the boiler pressure, all without moving parts. 

 

I got to think that at least it had check valves.

 

 

OK, OK, alright already, there is a check valve -- what the British call a "clack" valve.  But there are no moving parts in an injector in the way either a piston or a turbine feedwater pump has moving parts.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?

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Posted by Overmod on Thursday, September 23, 2021 9:09 PM

MidlandMike
Those feedwater heaters with pumps sounds complicated, so did those engines also have injectors just in case?

Yes, by law there had to be two independent ways to supply feedwater, and an injector was almost always the 'backup'.

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Posted by BigJim on Friday, September 24, 2021 9:09 PM

Overmod

Yes, by law there had to be two independent ways to supply feedwater, and an injector was almost always the 'backup'.

That depends on if the engine is moving or standing still!

.

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Posted by Overmod on Sunday, September 26, 2021 12:10 AM

BigJim
Overmod

Yes, by law there had to be two independent ways to supply feedwater, and an injector was almost always the 'backup'.

That depends on if the engine is moving or standing still!

The Government disputes that with you:

https://www.law.cornell.edu/cfr/text/49/230.57

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Posted by BigJim on Sunday, September 26, 2021 6:59 PM

Overmod

 

 
BigJim
Overmod

Yes, by law there had to be two independent ways to supply feedwater, and an injector was almost always the 'backup'.

That depends on if the engine is moving or standing still!

 

The Government disputes that with you:

 

https://www.law.cornell.edu/cfr/text/49/230.57

 

Nothing there disputes what I said. In fact, it supports what I said.. Keep in mind that the feed water heater cannot provide heated water unless the loco is moving! That makes the injector the main way to feed the boiler!

.

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Posted by BEAUSABRE on Sunday, September 26, 2021 9:35 PM

Steam Locomotive Feedwater Heaters

Drawings for Elesco Feedwater Heater - The Home Machinist! (chaski.org)

elesco feedwater heater for locomotives - Bing images

My understanding is that you can have feedwater heated with exhaust steam in a device called a "Feedwater Heater" and you can have a seperately fired device or one using flue gas drawn from the main boiler to heat the feedwater and that is called an "Economizer". The later are commonly used in power plants and maritime applications.

Feedwater heater - Wikipedia

By the way, Elesco was known for a lot more than FWH's. The name comes from "Locomotive Superheater Company" abreviated "L S Co" and pronounced as "El Es Co". They were the North American licensees of the Schmidt patents applied to almost any steam locomotive after about 1910 or so. 

 

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Posted by Overmod on Monday, September 27, 2021 2:04 PM

BigJim
Keep in mind that the feed water heater cannot provide heated water unless the loco is moving! That makes the injector the main way to feed the boiler!

Properly-designed feedwater heaters, including most of the ESIs, did not require exhaust steam to operate.  Note that Part 230 says nothing about when the two systems operate, only that they have to be functional.  This came up in the National Board ESC discussions a few years ago, whether the FWH could in a pinch substitute for a bad Nathan 4000 or whatever; the conclusion was that it could, be it ever so wasteful: in a pinch just running the cold-water and high-pressure pumps together will get water into the boiler...

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Posted by Overmod on Monday, September 27, 2021 2:13 PM

The issue of economizers is an interesting one, as it represents a lavish source of remarkably high-grade heat to go into convenient points in the Rankine cycle.

The locomotive 'feedwater heater' is generally understood to be a steam-to-water exchanger.  The Elescos and the early Worthingtons appear to have assumed the same exhaust-steam pressure (back pressure) as in the early automatic-control tests in the early '20s.  Many of the evolved ESIs (exhaust-steam injectors) were said to function effectively on 1.5psi (that's psig, not psia if course!) which is well below even advanced modern front-end spec and arguably in the range of practical drifting steam.  The Snyder air preheaters ran effectively on the exhaust from a closed FWH; I do not now recall whether the jet pump of Cunningham circulation would, but presumably the combination of those devices would efficiently use whatever useful heat could be recovered from a modern engine.

We now turn to the gas exhaust, which may still be over 750 degrees F at the point it ceases to have meaningful heat transfer or overcritical boiler water (it can edge lower in a Chapelon/Porta sectional where the front 3' or so acts more as a last-stage FWH than a meaningful power-steam generator).  One of the 'practical' schemes to recover this were the Crosti and Franco-Crosti systems, famous and infamous in Italy and Britain, where the limit on recovery was down around the dew point of sulfur compounds derived from coal, where accelerated corrosion in penny-pinching portable construction became too extreme.

Note that this is well shy of the magic number for package boilers: the point where the water of combustion (and of steam injection for nitric oxide abatement) gives up its latent heat of condensation.  The principal 'catch' here is to provide enough heat transfer to very cold feedwater to get the heat of condensation out -- alert readers will be thinking about the fact that one gallon of condensate brings over 6 gallons of feedwater sll the way from ambient to boiling...

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Posted by BEAUSABRE on Monday, September 27, 2021 11:54 PM

Overmod
 One of the 'practical' schemes to recover this were the Crosti and Franco-Crosti systems, famous and infamous in Italy and Britain,

For those unfamiliar with the Franco-Crosti, see the ever wonderful Douglas Self

The Franco-Crosti Boiler System. (douglas-self.com)

 

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Posted by selector on Wednesday, September 29, 2021 4:03 PM

Overmod

... -- alert readers will be thinking about the fact that one gallon of condensate brings over 6 gallons of feedwater sll the way from ambient to boiling...

 

I was one, I was one! Whistling

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Posted by Paul Milenkovic on Thursday, September 30, 2021 7:58 AM

selector

 

 
Overmod

... -- alert readers will be thinking about the fact that one gallon of condensate brings over 6 gallons of feedwater sll the way from ambient to boiling...

 

 

 

I was one, I was one! Whistling

 

 

Yes, but!

 

Most locomotive feedwater heaters bring the feed water near the atmospheric boiling point of water.  Apart from Porta's theoretical schemes, I know of no feedwater heater, even the closed heat exchanger type, that could bring the feedwater up to the boiling point at the rated boiler pressure.  A feedwater heater would need to do that to realize the full thermodynamic benefit.

Wardale talked about a scheme where the "blowdown" pressure of the cylinder at exhaust valve opening would work against a check valve, providing higher pressure steam to raise the feedwater outlet temperature.  Given all the troubles he had with Herdner starting valves, I question the practicality of such a scheme.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?

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Posted by daveklepper on Monday, October 25, 2021 5:37 AM

Like 4-wheel trailing trucks and boosters, the PRR generally did not use feedwater heaters. There were exceptions, but genrally, they considered the fuel and water savings not worth the additional maintenance.

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Posted by Flintlock76 on Monday, October 25, 2021 8:47 AM

daveklepper

Like 4-wheel trailing trucks and boosters, the PRR generally did not use feedwater heaters. There were exceptions, but genrally, the considered the fuel and water savings not worth the additional maintenance.

 

I've seen photos of steam locomotives toward the end of the steam era with the feedwater heaters removed.  By then it was "Just keep them alive until the diesel replacement shows up" so the extra mantainence required of a feedwater heater wasn't considered worth it.

If the locomotive had a Worthington feedwater heater it's pretty obvious the thing's been removed, there's a big gap on the side of the locomotive where it was located.

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