Was wondering is anyone could enlighten me on what factors of safety were legally enforced, and what factors of safety were used for new construction back in the steam days.
The reason that I ask is that I have gotten my mitts on the ASME locomotive boiler code from 1923 (will link it if people ask) and that includes a calculation for what max pressure your boiler is approved for. It says that new construction locomotives require a factor of safety of 4.5 and all boilers in service require 4.0.
I ran a few locomotives through this. Big Boy meets 300 psi with a factor of safety of 4.5. The Allegheny (which I'm most interested in) had a max boiler pressure of 265 (well, 266 and some change) with 4.5, but 300 on the dot with 4. I then ran the N&W A through it and only got 270 psi with a factor of safety of 4.5, and 305 with 4. Which returns me to the question above.
Did the ICC cap out factor of safety at 4, and not line up with the ASME. If so, was the ASME requirements not legally enforced?
Cause either I'm screwing up my calcs on the A specifically, 4.0 is the only legal requirement, or the N&W was being a little tricky.
How about showing your calculation for the A. Don't recall whether they had nickel steel boilers -- what tensile strength are you assuming for their steel, whatever it is?
As I recall, N&W used thinner boiler shells around combustion chambers, since they were stayed.
Alright. I will show all of my work.
Initially, I was interested in the Allegheny. With its absurd weight and low tractive effort it is a prime candidate for having boiler pressure increased. It has been said that the boiler was designed for 260 PSI and increasing would required thickening the steel and adding weight, but I wanted to confirm for myself.
In the following link is the 1923 ASME locomotive boiler code.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwje2Z_MuoaEAxXEEVkFHSPHD6g4ChAWegQIChAB&url=https%3A%2F%2Fasmedigitalcollection.asme.org%2Ffluidsengineering%2Farticle-pdf%2Fdoi%2F10.1115%2F1.4058068%2F7067075%2F1033_1.pdf&usg=AOvVaw1HfVvB-qVkxlnC_yiKLO5A&opi=89978449
point L-21 gives the relevant formula for the maximum working pressure on the shell of a boiler.
P=(T.S. * t * E)/(R*FS)
where
T.S. is tensile strength. L-11 gives this as 55,000 PSI.
t is thickness of steel
E is the efficency of the boiler seams
R is the internal radius of the boiler course
and F. S. is the factor of safety.
I initially calculated this with a factor of safety of 4. Allegheny has 3 courses (I will put all the variables in a chart at the end of this.) and the max pressure was 310 PSI for course 1 and 300 for 2 and 3. Holy cow. Looks like the Allegheny was designed as a 300 PSI engine from the get go.
However, looking at L-20 of that boiler code specifies that new boilers need a factor of safety of 4.5, and that the working pressure specified by that safety factor cannot be raised above that number later in service. With a safety factor of 4.5 the Allegheny has a max pressure rating of 266 PSI. In line with reality.
To confirm this, I checked against Big Boy and the second run of N&W A's (the ones that abandoned the nickel steel boiler plate), two locomotives that I knew had 300 PSI boilers. Big Boy indeed does have a 300 PSI boiler with a factor of safety of 4.5.
For the A I calculated a 264 PSI boiler with a factor of safety of 4.5, and 295 PSI with a factor of safety of 4. full disclosure, this may be slightly off as the arragement diagram that I had was for the first run and the boiler radiuses may be slightly different. I will get the correct radiuses tomorrow from the N&WHS.
So to confirm this, I went and got the relevant information from the Y6a, the first Y6 to abandon the nickel steel boiler plates. Again, with a factor of safety of 4 the PSI is 300, and with a factor of safety of 4.5 we are looking at a 265 PSI max engine.
Here are all the calculations in a convienent table.
and some notes.
1. my source for the Allegheny (The Allegheny, Limas Finest by Gene Huddlestonand Tom Dixon) gives just one seam efficency so some of these numbers may be slightly off.
2.Don't have good details on the Big Boy. What I could gather was from this link https://www.railwayage.com/wp-content/uploads/2023/11/RailwayAge1941UPBigBoy.pdf . I also dont have a seam efficency, just a type (Sawtooth), which per ASME gives between .92 and .94 efficency.
3. I purchased the information on boiler thickness and seam efficency from the Norfolk and Western Historical Society, which is why those results are the most detailed. The following are the exact drawings:
B45779 Y6A boiler bill of materials
B38575 A (1210-1234) boiler bill of materials
B36044 Y6A boiler seams
B38682 A (1210-1224) boiler seams
J35974 Y6A logitudinal boiler section
And the A boiler section is on the wikipedia page. Again it may be slightly off.
4. B45779 specifies that the material is carbon steel per American Association of Railroads M-115. Per the below link this has a min tensile strength of 55,000 PSI, matching the ASME Spec.
In conclusion, it looks like the N&W was playing to a different set of rules than at least the C&O and UP. Very specifically for the C&O they could have either made the boiler thinner to support 260 PSI, reducing the weight and dodging that issue. Or they could have made a 300 PSI engine with 127,167 pounds tractive effort and a factor of adhesion of 4.00, which when adding a Franklin E booster as it was designed to accept without modification would have resulted in a starting tractive effort of 148,142 PSI, out pulling DMIR Yellowstones and Big Boy at the low end and then crushing them with even greater horsepower at the high end and being indisputably the most powerful locomotive ever by a substantial margin.
But, this leads back to the OG question with a bit of a twist. Was 4.5 or 4.0 leagally enforced. Because if it was 4.5 it looks like the N&W was breaking the law.
Looks like my convient table cut off all the spicy bits
So I will split it up.
As you see at
https://babel.hathitrust.org/cgi/pt?id=mdp.39015013032951&seq=481
the two front boiler courses on the 1936 A were "carbon steel" and the two rear were thinner nickel steel, and N&W said it was designed for 300 psi.
Third course was tapered -- guess you're supposed to use its largest radius in the calculation? Fourth course, around the combustion chamber, was only 3/4 inch thick, 52 inch inside radius. Presumably the staying made that legal. If later A's quit using nickel steel, do we know how thick their shells were?
What's the legal assumed strength for nickel steel -- 75000?
I think I used to know how to calculate seam efficiency -- it's just based on the rivet size and rivet spacing, nothing complicated. But don't recall where you read how to do it. Maybe The Steam Locomotive, but I sort of suspect not.
Looks like that is the railway age article from 1936. It only talks about 2 A's being built at the time. By the time they started their second run of A's in WWII they weren't allowed to use nickel steel and didn't want to even if they could. Apperantly maintenance was much more frustrating (weld repairs and all)
The bill of materials for the A's boiler that i used was all on this second run, and is all carbon steel.
To my knowledge for conical sections you just use the largest diameter.
ASME boiler pressure vessel code does tell you how to calculate seam efficiency, but in this case the N&W seam drawings just out and out say it. If pressed I can post those later tonight.
I don't see anything to argue with in your calculation. We can't explain why the 300-psi A's were kosher, if they were. For sure the 55000-psi limit hadn't gotten raised by then?
Did you check the J?
timz I don't see anything to argue with in your calculation. We can't explain why the 300-psi A's were kosher, if they were. For sure the 55000-psi limit hadn't gotten raised by then? Did you check the J?
The 55,000 PSI limit is imposed by the material. The material spec would not change, the material would. However the Y6a document that specifically calls out the material as A. A. R. M-115 is dated 1953, so right towards the end of steam.
As for the J I have not yet checked it. I do not think that I am going to see anything different from the Y and A. If you were to want to check the J the following drawings are what you would need.
B37941 for the boiler seams.
G37349 for the longitudinal cross section
and B37302 for the material and thicknesses. This is not necessary. It's carbon steel, and I think you can get the thicknesses from the seam info (I could for the other two anyway).
In all, it will set you back at least 20 bucks, 24 if you get all three.
Currently I'm aiming to hunt down the T1 boiler information. that would be a 300 PSI boiler from Baldwin and at that point I would know how the 3 big boiler manufacturers treated the safety factors (cause I already got Lima with the Allegheny and ALCO with the Big Boy).
And finally, the missing piece is what is actually enforced by law. If the ASME was more strict than the actual standard that would fine you as far as new build boilers go then the N&W is in the clear, and all those other guys are chumps for overbuilding their stuff. If the ASME was 100% alligned with the letter of the law then I guess the N&W were just a bunch of chad lawbreakers.
Turns out you can just buy the interstate chamber of commerce locomotive inspection laws.
I bought a copy of the 1937 edition,to my knowledge the revision that would cover these engines. Expect that in 2 weeks or so.
Also bought a 1941 version as apparently there were changes made in 1940 covered by that. Expect that next week
Is this enough for the T1?
https://babel.hathitrust.org/cgi/pt?id=mdp.39015013029791&seq=28
Looks like the T1 was a nickel steel boiler. I would like to keep everything carbon steel so that everything is as close to 1:1 as can be.
Those magazines do give enough information for me to run the DMIR Yellowstone through this with OK results. And perhaps they cover a 300 psi baldwin with enough detail to get a 1:1 comparison. But for figuring out safety factors that were adhered to the Yellowstone should give me that.
So I calculated the DM&IR Yellowstone, and in this case rearranged the formula to determine what the seam efficiency (the only variable that I did not have) would need to be in order to get 240 PSI as the working pressure for both 4.0 and 4.5 factors of safety.
The .76-.78 seam efficency required for a safety factor 4 boiler to make sense seems egregious for a quintuple riveted seam. Meanwhile the .86-.88 efficient seams are similar to what was availible for Allegheny. This seems to imply that baldwin too designed boilers aiming for a safety factor of 4.5., potentially leaving the N&W as the only major builder that designed to 4.0
Just wondering why this question is being asked. If it's just for historical info, I have nothing of value to add. But, if it has anything to do with the current requirements, the current requirements for operable steam locomotives (which are pretty extensive) are in FRA rules, not old ICC rules. See 49 CFR Part 230.
The difference between the Interstate Commerce Commission and the Association of Mechanical Engineers is that the ICC was a regulatory agency and the ASME was and is not. ASME standards could be higher or more strict, but they couldn't be enforced as such, even if more stringent than ICC requirements.
That doesn't mean a railroad couldn't use the higher ASME standard. Even today on some of the governmental regulation requirements, railroads may have more strigent requirements.
Jeff
Boiler insurance companies may have required a higher standard than the ICC, though I suspect most railraods were self insured.
I'm just asking for historical info. The current regs are pretty clear, I was just thinking that this would be the place to get info with regards to as built or what past regulations were enforced.
If this is the wrong place for it I apologize. I'm new.
jeffhergert That doesn't mean a railroad couldn't use the higher ASME standard. Even today on some of the governmental regulation requirements, railroads may have more strigent requirements.
Right now I suspect that the legally enforced safety factor was 4 for new builds, and that most railroads (or builders, wonder who has the say in that) built to the 4.5 that I know the ASME calls out just to be in the clear. Will know next week.
It would be interesting if it just say build to ASME though.
Conductor_Carl If this is the wrong place for it I apologize. I'm new.
I don't see any need for you to aologize as this discussion has brought up a lot of interesting information.
So at this point I want to get more data on the big three manufacturers. With only 1 datapoint for each, I want to see if the factor of safety is more dependent on the builder or on the customer
So I'm going to open this up. If you have any engine that you know the boiler thicknesses, seam efficencys, boiler diameters and boiler pressures I can calculate and see what the safety factors are. I mean, you can too, the formula is posted above.
The railway mechanical enginer magazine issues that tim posted is a decent source as it usually will provide everything but the seam data, and that is enough to reasonably predict safety factors.
Now if anyone has specific information on the following I would be very interested.
1. Great Northern R-2s. Apperantly these were homebuilt so can see if they strayed away from 4.5.
2. Santa Fe Northern. As I was looking at this I saw another thread that said Baldwin refused to sign the documents saying the boiler was rated to 300 psi and the Santa Fe engineers had to sign for it.
Apart from that I will add locomotives to this and take any recommendations until the ICC regs get here.
So I got the 'Interstate Commerce Commission Bureau of Locomotive Inspection Laws Rules and Instructions For Inspection and Testing of Steam Locomotives and Tenders and their Appurtenances' and learned the following.
1. the lowest factor of safety for a locomitove in service or under construction is 4.
2. Unlike the ASME standard, if the properties of boiler steel is not known the tensile strength is set to 50,000 PSI as opposed to 55,000. More importantly, if you have test data accompanying your material you can use that tensile strength, as opposed to the ASME standard that forces you to use the lowest allowable tensile strength for your matierial. This very likely improves the factor of safeties for all the engines that I had calculated for (Allegheny, A and Y, Big Boy).
3. No boiler inspection requires measurement of the boiler courses. If the boiler visually looks alright and passes a hydrostatic test at 25% above the usage pressure, you are good. This is easier to pass than if all the dimensions were taken and the boilers factor of safety recalculated each time the boiler was inspected.
So from this, I have the following conclusions.
1. The N&W were not a bunch of chad lawbreakers.
2. I would think that most railroads, given the choice, would build to the much less stringent ICC rules than ASME. The ICC rules have a lower factor of safety, allow higher tensile strengths in the calculation, and are also much more lenient in boiler modification (for example, ASME does not allow you to ever lift working pressure past what you first tested it at and ICC does). But it seems like most roads and builders went with the ASME rules. apart from the N&W, Santa Fe, and Pennsy basically noone I calculated for built to 4.0 standard. Perhaps most railroads felt more comfortable with the ASME rules as they basically gauranteed that the ICC couldn't complain about the boiler.
3. The Allegheny (which was what sent me on this little endeavor to begin with) was absolutely able to be raised to 300 PSI without breaking any rules. I think that I shall make a different post about this later.
Erik_Mag Boiler insurance companies may have required a higher standard than the ICC, though I suspect most railraods were self insured.
I'm beginning to think that this makes the most sense. Any idea how I would go about confirming this? I haven't a clue.
Study copy of ASME Boilers I with section PL (locomotive boilers) commencing around p.161.
https://studylib.net/doc/26070157/asme-bpvc-2021-section-1-pressure-vessel-code-workbook
The relevant current language you want is 49 CFR 230.24(b) which establishes 'not less than a factor of 4'.
Also see the NBIC (National Boiler Inspection Code)revised every odd year (so no revision this year) and maintained by the National Board of Boiler Inspectors
(www.nationalboard.org)
Note the NBIC Committee - Working Group, Locomotive Boilers. You may see some familiar names who would be good resources for some of the questions you have.
Next NBIC meeting is in Louisville July 15th-18th - reservation required, but free.
I have now moved away from the original question (did the ICC and ASME rules for boilers differ during the age of steam construction? Yes) and to a more nebulous question. If the ICC rules were less stringent and would give you a locomotive of superior performance to a ASME engine for the same weight, why did the majority of roads build to ASME specs?
A 300 PSI engine built to ICC rules would definitionally be less expensive on the front end than one built to ASME as you have a .5 factor of safety lower (so less material) and can use higher tensile strength in the calculations if you have material test data. And if you built to the same boiler thickness (assume the same boiler on both engines, just one is going by ICC rules) the ICC engine will have much higher allowable pressure and will be a greater benefit to the railroad in terms of hauling.
So why did the majority of roads pick the more expensive, less efficient standard to build to?
I'm currently trying to chase down the boiler insurance hypothesis without much luck. May be better to start a new thread as I now have a new question.
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