I had some testing to do, I thought that this could be disproved with the aid of steam tables. However there exists a cylinder performance simulation from the British Prof. Hall. It is based on his analysis of the BR Rugby station tests.
Using a locomotive with 200 psi steam chest pressure @ 200 degree C. steam consumption is 25600 lbs/hr MEP is 64.5 psi and indicated efficiency is 9.66%
If steam is used of 180 psi @ 390 degree C. consumption drops to 17900 lbs/hr, identical MEP (which was the issue) and an efficiency of 11.9%.
Superheat is basically BTU's/Joules that can be converted to work, the evaporative heat that is in the steam cannot be released and is ejected. Low superheat also gives additional blast pressure due to the extra mass of steam needed to release the needed heat.
Right now I shy away from the subject of steam jacketing as this was not the discussion.
Kind regards
Jos Koopmans

Sorry Jos, a bit confused....one doesn't drop from 15600 to 17900, but increases to that level. Typographical error?

Yes, superheating provides efficiency and moves a load of BTUs per volume more than saturated. But, this is only when the temperatures are held high and being used. A locomotive that spends much time idling and running at low output with a larger proportion of time spent increasing the temperature of the superheaters and steam passing through them rather than running for a longer period of time at constantly higher output with heated up superheaters and high heat addition to the steam is not the common pattern for small tourist and museum operations.

For every particular set of circumstances, there's a point at which the cost of building and creating the superheat begins to make more sense than the relatively small cost of a bit more coal burned per day. If you are the Durango and Silverton, you gain a lot more from having superheaters than if you are the New Hope Valley RR or Strasburg. I don't know what the operators of 1385 envision.

For the purposes of this discussion I agree about the steam jacketing. I would however consider what other alterations beside superheating would create efficiencies at any operating pattern and can be applied at low cost and with minimal disruption of the rest of the locomotive - hence my interest in ring assemblies and packings and better drafting and front ends.

dave

No matter how badly you want to, or how hard you try, it makes no sense to spend the time, money and effort trying to transform a Model T into a Mustang.

There is a point where reasonable people will, if they have any sense, will say, "enough!"
What will we gain if we do this? Save a teaspoon of coal every year?

Perhaps a second phenomena described in Chapelon Genius of French Steam is related to this - that they discovered superheated steam has much less thermal conductivity.



Actually, it is very relevant to railway preservation, especially if a museum or tourist railroad is looking at a restoration/alteration, or new build boiler or locomotive. There is a lot to consider and I think the superheated argument has a lot of merit. However, there is some later, less publicized data to review for alternatives to superheat. The issue at hand is not just fuel rate, but how hard the boiler has to be pushed to perform - to which boiler efficiency and fuel carryover/smoke relate. Speaking as someone who has worked-on and driven Model T's I can say that one in good condition with a few mods (oil pump, overhead valve conversion, carb, mechanical advance) gives you something that is survivable in a contemporary environment, and I have met a few people who still drive them a lot. Since we are trying to haul passengers with coal-fired Model T's on a daily/weekly basis, it is very important to make them perform as best as possible for the operator and be less offensive to people not interested in them.

Yeah, typo, sorry!! It should be 25600 vs 17900.

As for the other arguments, what we really want in preservation is value for money as we want to pass heritage locomotives to the next generation in optimal condition.
The less coal is burned in a boiler the longer life it has, so the working cycle should determine superheat or not and improvements like better exhausts and the like.

Kind regards
Jos

Greetings:
Matt's point (and several others above) goes towards one of the main issues: how hard can the boiler be worked, over what period of time, how much will it cost to operate (fuel & maintenace) and how long will it last.
With all due respect to the ASME, in my opinion, a boiler built to just meet their code is not going to last in service other than on a park railroad with a circle of track and no grades. A limited life boiler.
When Dave Kloke was building "LEVATHAN", his initial intent was to just buy an ASME boiler. He quickly found out that since his boiler was out of the ordinary, it was going to be very expensive and still with the typical ASME widely spaced staybolts, thin sheets, ect.
But he wanted a "real" locomotive boiler (staybolts on 4" centers, etc.) that was going to last for a long time. He ended up designing (with assistance from an ME from Illinois Railway Museum, Bob Hunter) a durable boiler to meet both ASME and FRA requirements, getting his own ASME "S" certification and building the boiler himself.
Be well,
J.David

Crown Metal Products boilers were designed by an engineer who had retired from Porter. Locomotive boilers are not like other kinds.

Matt, it wasn't just the boiler - even the frame was being shaken loose in that service.

dave

My guess is that most modern boiler engineers, even those who understand how to make a fire tube boiler, would be surprised to learn how the output of a locomotive boiler changes in service, from start to stop and everything in between. It's a lot different than a boiler putting out steam at a steady rate mounted down in the basement.

Since we're on the subject of boilers and superheaters here, I thought I'd just toss out these two photos. These were taken Saturday on PRR No. 460, the famed Lindbergh Engine at the Railroad Museum of Pennsylvania. I've heard of leaking superheater units being pinched off, but I've never actually seen it before. From what can be seen, the offending unit was torched off and the leads into the header were flattened. This poor engine was rode hard and put up wet, with evidence of quite a bit of leakage around the header -- lots of lime deposits around the bolts. Many of the valves in the cab also display substantial deposits, including the try-cocks. The superheater flues and the boiler tubes have a lot of cinders and dirt in them, too.

Put it this way: How many locomotive designers "back in the day" could foresee their products lasting a century or more, or being used as most are used today?

I doubt "planned obsolescence" entered anyone's mind 110 years ago. Nor did the thought that locomotives would be used only infrequently (some might say sporadically) with long, long periods of non-use between those periods of use.

Or that they would in some cases sit around for decades between uses.

Information from an associate:

1) The C&NW altered the tube sheet arrangement by removing the small tubes on these 4-6-0s around 1910 - 1915 or so. They published an article about it in Railway Age or a similar railroad technical publication at that time period.


The reason for the change was the C&NW found that the bottom rows of small flues would be become plugged up by ash and the locomotive would still steam. Therefore, they decided to remove the bottom small flues from the boiler and replace them with several through-stay rods to maintain adequate staying of the front and rear tube sheets.


The pattern by which the small tubes were removed from the tube sheet duplicated the pattern by which the small tubes were found to be plugged by ash.


2) The problem with this modification was the bottom of the boiler barrel now became a reservoir of cold water since no heat could reach the cold water that filled the section. This created issues with boiler corrosion and cracking which the 1385 had several of events of, and the same problem occurred on other C&NW locomotive boilers that had this modification.

Tube plugging caused by a drafting problem involving the whole class?

Does anyone know the length and the diameter of the tubes? Plugging can also be caused
by a too small diameter for its length. L/D=100 appears to be optimal, but whether that was known at the time?

On another issue, is the weight of the welded boiler the same as that of the riveted original? We have had issues
with a supplier who saved weight on a welded boiler after which suspension became a huge problem.
Kind regards
Jos Koopmans

That could easily happen - using higher TS steel and 100% efficient welded seams could lead to thinner plate and lighter weight. I'm about certain in my own mind that optimally it makes sense to stick with steel with about 60K TS and use the same as original thicknesses unless it would affect the seams to do so - joining plate of different thickness issues. There will be a bit of loss in weight due to not doubling at riveted seams, but it will be much less overall.

dave