> Put simply:

> The main cause of wear on flues is due to
> oxidation on the fireside due to excess air
> and pitting on the water side due to poor
> water chemistry management.

> Despite what we think, flues are a wear item
> on boilers.

> Cheers;

> PKurilecz

Is this because we still use the same steel for boiler tubes that we "always used" since the 1800's ?
Isn't there anything better ?

> Is this because we still use the same steel
> for boiler tubes that we "always
> used" since the 1800's ?
> Isn't there anything better ?

Don't forget, you change the metallurgy of the tubes, chances are you have to change the metallurgy of the rest of the boiler. I could be wrong but I don't think the "latest and greatest" water tube boilers use anything magic ? I have never read of anything past the "alloy" boilers designed to minimize water damage, and they caused more problems then they solved.


lamontdc@adelphia.net

Boiler tubes and their purpose have not changed much they still must resist cinder cutting and high heat and fatigue cycles, particularly on the firebox end. This is where the failures typically occur, not in the area exposed to water circulation. High tech steels are typically not suited for this application or method of installation required for a locomotive boiler. Proper installation is the best preventative measure one can take to extend tube life.

The area that has gone high tech, is the water treatment area, which I will leave to others more knowledgible than me. The mobility of the locomotive does somewhat limit the methods for treating water, as we do not enjoy the spaciousness of a powerplant or other fixed loction boiler.

RCT&HS web site
mtillger@enter.net

> I have never
> read of anything past the "alloy"
> boilers designed to minimize water damage,
> and they caused more problems then they
> solved.

How long ago are you talking about ?

Have we not made great strides in steel-making, during and since the "space race" that could benefit "new boiler" builders/users?

Not trying to be a smarta$$.

I don't know, I'm just asking.

> How long ago are you talking about ?

> Have we not made great strides in
> steel-making, during and since the
> "space race" that could benefit
> "new boiler" builders/users?

> Not trying to be a smarta$$.

> I don't know, I'm just asking.

I have a reference to the material from 1941 and thats the last I have heard of it ...did not turn out so well.

I should think that R&D would have been developed in something like power generating or nuclear energy that could have spun off into locomotive boilers. Nothing new in the former and nothing you could afford in the latter ...correct me if I am wrong.

Most of the work in steel plants has been to improve quality and lower variability while keeping costs under control. New product development is concentrated where it will pay as in automotive and oil. In the tubular market better drill and casing pipe has been developed, acid resistant sour gas well pipe etc. all developed to meet a demand. What usually happens is the "industry" partners with a steel producer to underwrite a new product complete with testing and new specifications and this has not happened with boiler products, they make them to the old reliable tried and true specifications.



lamontdc@adelphia.net

> Have we not made great strides in
> steel-making, during and since the
> "space race" that could benefit
> "new boiler" builders/users?

> Not trying to be a smarta$$.

> I don't know, I'm just asking.

I was just trying to address the most important aspects of boiler design and operation. In other words, it is more economic to address firing practices and water treatment than it is to use higher priced alloys and more expensive fabrication practices.

Could we ( meaning engineers such as myself ) come up with a material application that would address these issues? Yes, certainly! Would the solution be economic? I doubt it. If you were to use a 14-7PH Stainless Steel (or go for a 30 - 10 NiCr steel) , you could certainly reduce the wear from oxidation on the fireside and the material would certainly be less susceptible to oxygen pitting on the water side even in the absence of a halfway decent water treatment program. However would; would you be willing to accept a heat transfer rate of about 1/4 of a C-Mn alloy flue tube? I doubt it. Also would you be willing to accept a PWHT that required that the whole boiler be placed in an oven to accomplish the PWHT? Again, I doubt it.

In the engineering world we have to deal with compromises and part of that compromise is the economics of the problem at hand.

As far as boiler design goes, I would like to see the firebox made of a Cu-As alloy with Monel flues and a shell made of Ti-Al-4V with superheater flues made of 45-15 Incalloy with a design pressure of 250 psig and 250F of superheat. Just don't ask about the price! BTW, it would be a Belpaire design.

Cheers;

PKurilecz

The water traetment question is not so much a case of available
space for treatment equipment, but the "Total loss" nature of the locomotive application. In a stationary plant, much of the steam after it is spent is returned to the boiler room as condensate.This is steam that has left the steam generator as steam and comes back as hot water and is returned to a hotwell or Deaerating tank where it is kept hot and has most of the oxygen removed from it by agitation and heat, as well as the addtition of chemical oxygen scavengers. The tank in elevated to provide the neccesary head on the feedwater pumps to enable the pumps to handle very hot water. In a loco you are introducing relatively cold water from the tender which is loaded with oxygen, and is introduced into the boiler where it tends to cause corrosion, especally between the normal operating levels where oxygen tends to get trapped between the water and steam. The additonal cause of problems is the introduction of minerals which became disolved solids in various amounts of cycles of concertration depending on water blowdown managment and this leads to scale and sludge in the boiler. The best way around this is use of demineralized water, either by using a water softener or a reverse osmosis treatment system.As far as the fireside, a oil fired boiler would be subjct to less scrubbing and erosion by solid particulate erosion, but in some circles would not be the most aesthetic means of firing a locomotive. There is no good answer to this problem, as steam boilers are a somewhat self consuming piece of equipment, and add the mechanical and engineering techicalities of take the same boiler and subject it to the vibrations and heat stress cycles when applied to a steam locomotive, the headaches only increase. As somone else mentioned in this thread, there is most likely a material list you could come up with that would minimize all the erosion and corrosoin factors, but who would want to pay for it.

captbuck@comcast.net

Guys, given the tubes must be removed for resurveying every 15 calendar years in any case, why not use what has been proven tried and true and is readily and economically available?

Boilers as well as tubes are just other consumable components of steam locomotives. Puffing Billy in Australia replaced boilers on their home built clones of Baldwin 2-6-2Ts every decade or so. Replacing riveted with welded boiler construction has allowed the more recent generation of boiler shells to survive with just firebox and tube replacement.

They run lots of very heavy and full trains of happy passengers and are not opposed to intensively utilizing their locomotives to generate passenger seat miles to more than recover the costs involved in heavy rebuildings.

Locomotives are tools to use in pulling trains. The only justification to use steam is emotional in the developed world today. Apart from addressing operating practices and water chemistry, the greatest strides are to be made in marketing the experience, and making it one that provides emotional gratification to an audience.

Scenery doesn't hurt either......

dave

irondave@bellsouth.net

One basic thing to remember: buy your materials - tubes, etc. from a good source. Make sure you have the certs.

If memory serves, C&TSRR had to do some refluing a few years ago and removed the tubes and flues from their locomotives that needed them - all at once. Then when they commmenced to install the new tubes, they were cracking while rolling. The whole heat lot was bad!!!! Now came the scramble to find tubes and get them in before the season started.

Where I work, our systems' materials are chosen very carefully, so I have thought about different "new" materials to be to prolong the life of the boiler and tubes. It would be interesting to have different materials in a boiler, but then you would have to educate the boiler inspector about these changes and the method by which you arrived at the operating pressure calculations.

Just my $.02

What about the issue of electrolysis between the different metals and the water chemistry?

> I was just trying to address the most
> important aspects of boiler design and
> operation. In other words, it is more
> economic to address firing practices and
> water treatment than it is to use higher
> priced alloys and more expensive fabrication
> practices.

> Could we ( meaning engineers such as myself
> ) come up with a material application that
> would address these issues? Yes, certainly!
> Would the solution be economic? I doubt it.
> If you were to use a 14-7PH Stainless Steel
> (or go for a 30 - 10 NiCr steel) , you could
> certainly reduce the wear from oxidation on
> the fireside and the material would
> certainly be less susceptible to oxygen
> pitting on the water side even in the
> absence of a halfway decent water treatment
> program. However would; would you be willing
> to accept a heat transfer rate of about 1/4
> of a C-Mn alloy flue tube? I doubt it. Also
> would you be willing to accept a PWHT that
> required that the whole boiler be placed in
> an oven to accomplish the PWHT? Again, I
> doubt it.

> In the engineering world we have to deal
> with compromises and part of that compromise
> is the economics of the problem at hand.

> As far as boiler design goes, I would like
> to see the firebox made of a Cu-As alloy
> with Monel flues and a shell made of
> Ti-Al-4V with superheater flues made of
> 45-15 Incalloy with a design pressure of 250
> psig and 250F of superheat. Just don't ask
> about the price! BTW, it would be a Belpaire
> design.

> Cheers;

> PKurilecz

> How long ago are you talking about ?

1930's and 1940's. Different kinds of alloys were tried, all of which turned out to be very troublesome, to the point that some roads ended up doing expensive re-boilering of some locomotives, using the old tried and true stuff.

Santa Fe comes to mind.

> Have we not made great strides in
> steel-making, during and since the
> "space race" that could benefit
> "new boiler" builders/users?

No, "we" haven't. That's your answer.

I had an metalurgist at my real job talk to me one time about Nickel steel boilers. He told me about "blue embrittlement" which had something to do with the heat treatment process (or lack thereof) when the nickel steel was rolled. This problem was discovered during the height of WWII and a lid of secrecy was put on it since the Allies had a lot of Nickel steels in service and they didn't want the Axis to learn of this potential weakness. So the general industry continued to manufacture the material and suffer the cracking.

After the war, the cause of blue embrittlement was determined and a solution found. Nickel steel rolled circa 1950 was of much better quality than nickel steel rolled circa 1940 and boilers built with it in the later years did not suffer the same fate.

If anyone out there knows more about this than what I remember, please feel free to correct or embellish this.

G. Mark

Tennessee Valley Railroad Museum
aw90@comcast.net

> After the war, the cause of blue
> embrittlement was determined and a solution
> found. Nickel steel rolled circa 1950 was of
> much better quality than nickel steel rolled
> circa 1940 and boilers built with it in the
> later years did not suffer the same fate.

> If anyone out there knows more about this
> than what I remember, please feel free to
> correct or embellish this.

According to back issues of RME and minutes of proceedings at the Master Boilermakers Society conventions, the subject of alloy steel boilers and the problems being caused by them were thoroughly analyzed and investigated. Mark's theory might be correct, but in addition to that, it was found that high alloy steels used in boilers, no matter what the quality of the steel, is VERY unforgiving.

In simple terms, all tools used, such as cutters, drill bits, taps, reamers, etc. must be as sharp as possible, and great care must be taken when working with the metal. Any nicks or imperfections in surfaces to be welded, in holes cut or drilled in the sheets, in threads or whatever inevitably led to cracks in service. The simple thing of a rivet gun slipping slightly off the head of rivet and leaving a mark on a sheet was enough to cause a crack. Welding and cutting techniques for this stuff were much differnet and more exacting than for the other steels in use at the time.

simply put, it was more expensive from the beginning, required more labor and skill to build and repair, and didn't last as long, all of which added up to higher operating costs and more downtime.

High alloy steels don't so well in boilers, especially in locomotive boilers which, by their very nature, see anything but constant pressure/demand service.

The original question was about flues. Flues are considered consumables. They have to come out to inspect the boiler shell, after which they can be re-ended and reused, several times if they are in good condition when removed and inspected. Using higher quality materials, even assuming something that would not end up with the same drawbacks as listed above could be found, would not even come close to being cost effective in today's service environment.

Most operators can't afford insurance or to pay their staff much more than minimum wage. What would be gained by spending 3 or 4 or more times as much for flues (not to mention new tools to properly install them) as they do now?

> I had an metalurgist at my real job talk to
> me one time about Nickel steel boilers. He
> told me about "blue embrittlement"

> G. Mark

Blue embrittlement is something you can see if you are sharpening a chisel on a grinder and the piece gets too hot. You can also see this on a railroad wheel that has over heated.

Good old reliable carbon steel up to about .50% Carbon contains nothing that will form very brittle phases upon cooling so a "blacksmith" can heat to form and cool and water quench.

In order to cold form steel the carbon must be low enough to minimise work hardening ...ductility ...as in rolling a flue, so the material does not crack. Flue sheets are given a very specific radius for the flange based on the cold working capabilities of the material while flues can be rolled over giving you a nice joint.

To gain stength alloying elements are added that change the phases formed when the product is cooled. Normal air cooling leaves the material in a very brittle state. To achieve "toughness" ...hi-strength, low brittleness.. the material must be reheated to a temperature based on the alloying elements and then control cooled to "temper" it. This is where they got into trouble with alloy boilers ...heat up to rivet and you ended up with the brittle state ...and nobody tempered the result. Alloy boilers would be fine if they were all welded, stuck in a large heat treat furnace and tempered, remembering of course that you could never do any "hi-temp" work on the boiler with going thru the heat treatment again.
Anybody ever noticed the little sign on some 18-wheeler tractor frames "heat treated frame, do not weld or burn. Needless to say this material was totally foreign to the fabricating and operating characteristics found on the railroads.

As usual, in Metallurgy, another road was found. The British discovered a "self tempering" alloy steel and named it EN25. This product approaches 4340 in strength and eliminates heat treating. In a fit of madness we melted a heat (225tons) of this stuff, bottom poured ingots, and rolled it into 5" rounds for use in mandrel bars on a seamless mill, all with normal mill practices. The mandrel bars undergo a severe temperature cycle and this material not only survived but gave us much longer life. The kicker here is the product cost ... check nickel prices ... way too expensive for anything but very specialized uses.


lamontdc@adelphia.net

> What about the issue of electrolysis between
> the different metals and the water
> chemistry?

Hello All:

Sorry, I was being a bit facetious about the materials for my dream boiler.

On the serious side, let me take a few minutes to describe what goes on when an engineer selects materials for an application ... in this case a locomotive steam boiler.

Item 1:

What is the maximum temperature of the metal?

All metals exhibit a relationship between strength and material. Up to a certain temperature all metals will maintain their room temperature strength. Above that temperature, the strength will decrease dramatically.

At a boiler presure of 300 psi, the saturated water temperature is about 420F. At this temperature the application can be satisfactorily handled by most C-Mn steel alloys.

If the boiler has superheaters with a design superheat of 200F, then the steam temperature will be 620F. At this point, the designer can select an alloy with some Cr or Ni present to maintain strength, or use a lower strength value for a C - Mn steel.

Even considering the temperature differential between the fireside and water side, the temperature for the saturated portion is about 500F, still a C-Mn steel alloy is useful. For the superheaters, the temperature differential is probably 75 to 150F, so the maximum metal temperature would be about 750F. At this point some additional alloy elements are probably needed to maintain strength.

Conclusion:

Based on operating temperatures, use of alloy steels other than C-Mn are not warranted.

Item 2:

Strength to weight ratios.

The highest strength C-Mn alloys for boiler applications are about 55 ksi.

As the alloy content increases, the strength will increase. As a result the amount of material required will decrease.

Conclusion:

Take a simple calculation, such as barrel pressure strength, and look at the effect that increased tensile strength has. If the material is 25% stonger, then 25% less material is needed.

Item 3:

Fabrication costs.

Continuing on from Item 2, if a material with a higher strength is selected there are several additional items to be considered.

First, what is the cost differential between the Low strength and high strength material? Is the incremental cost of the higher strength material less than the difference in weight. After all, metals are priced on a weight basis. For the example if the lower strength material is $30/cwt, then the higher strength material has to cost less than $37.50/cwt. If not there is no cost advantage to using this higher strength material.

Unless, of course, there is some sort of weight restriction that needs to be met. Just ask any one with aerospace design experience.

Next, what will it cost to fabricate (i.e., bend, shape, form, and join) the higher strength material?

Generally, any material with a carbon equivalent higher than 0.3 will require specialized welding techniques. This includes, preheating, electrode materials, welding atmosphere, and post weld heat treatment.

Conclusion:

Is this incremental fabrication cost less than the cost differential of the materials? If not, there is no advantage to using the higher strength material.

Item 4:

Wear issues.

The wear rates need to be considered. This will include, corrosion, erosion, etc.

Again what are the wear rates of the higher strength material as compared to the lower strength material? If the wear rates of the higher strength material are not sufficiently less than that of the lower strength, then there is no economic incentive to use the.

Item 5:

Costs.

Just in case you haven't noticed, the selection of materials is highly driven by costs.

In the design process, this is described by the following statement:

"If the increase in cost of a machine does not sufficiently increase the utility of the machine, then the additional cost is not justified."

Again, my apologies for the earlier facetiousness.

I hope that this sheds a little light on the engineer's perspective of material selection.

The use of low Ni Steels in locomotive boilers was an attempt to increase the utility of the machine. However, like the application of new technologies, there were aspects of this material that were not fully understood when it was first utilized.

Cheers;

PKurilecz

UK Heritage Railways