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 Iām 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 Iām 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. Donāt recall whether they had nickel steel boilers ā 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.
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.
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 rais
the two front boiler courses on the 1936 A were ācarbon steelā and the two rear were thinner nickel steel, and N&W said it was designed for 300 psi.
Third course was tapered ā guess youāre 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 Aās quit using nickel steel, do we know how thick their shells were?
Whatās the legal assumed strength for nickel steel ā 75000?
I think I used to know how to calculate seam efficiency ā itās just based on the rivet size and rivet spacing, nothing complicated. But donāt 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 Aās being built at the time. By the time they started their second run of Aās in WWII they werenāt allowed to use nickel steel and didnāt want to even if they could. Apperantly maintenance was much more frustrating (weld repairs and all)
The bill of materials for the Aās 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 donāt see anything to argue with in your calculation. We canāt explain why the 300-psi Aās were kosher, if they were. For sure the 55000-psi limit hadnāt gotten raised by then?
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. Itās 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 Iām 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.
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.
Just wondering why this question is being asked. If itās 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 couldnāt be enforced as such, even if more stringent than ICC requirements.
That doesnāt mean a railroad couldnāt use the higher ASME standard. Even today on some of the governmental regulation requirements, railroads may have more strigent requirements.
Iām 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. Iām new.
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.
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 Iām 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.
Great Northern R-2s. Apperantly these were homebuilt so can see if they strayed away from 4.5.
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 āInterstate Commerce Commission Bureau of Locomotive Inspection Laws Rules and Instructions For Inspection and Testing of Steam Locomotives and Tenders and their Appurtenancesā and learned the following.
the lowest factor of safety for a locomitove in service or under construction is 4.
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).
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.
The N&W were not a bunch of chad lawbreakers.
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 couldnāt complain about the boiler.
The Allegheny (which was what sent me on this little endeavor t