It's Boiler Code Week time again!
The BPV1 Locomotive Boilers SG will be having a Zoom meeting this upcoming Monday, July 26th, from 9:00am to 12:00n EDT.
The Zoom meeting number is 997 1862 3151 and the passcode is 285708.
Overmod It's Boiler Code Week time again! The BPV1 Locomotive Boilers SG will be having a Zoom meeting this upcoming Monday, July 26th, from 9:00am to 12:00n EDT. The Zoom meeting number is 997 1862 3151 and the passcode is 285708.
Have you attended one of these? What should one expect?
I imagine there will be a great deal of specialized technical detail, but I also figure meetings like this are important to any person or group building, restoring or operating steam locomotives and traction engines?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
I don't know what the pandemic-compliant version will be like. In the past, Mr. d'Urso sent me the meeting agenda as well, but I didn't see one this time; the 'official' ASME page with CrowdControl registration and sign-in is here:
https://event.asme.org/Boiler-Pressure-Vessel-Code-Week/Schedule-of-Meetings
but I did not get far enough into it to find agenda pages before my Internet bandwidth crashed.
Expect that your technical questions will be understood, and answered wisely and well; if you have insights expect to have them fairly considered. This has been a good SG since its (re)establishment.
I expect some discussion of the specific boiler fabrication to go on 1361, btw.
[Bob Smith -- I can't get to PM on a phone; can you forward all this information to Robby Peartree on RyPN or post it there?]
I posted it on the RYPN interchange, per your request.
Greetings from Alberta
-an Articulate Malcontent
Summary of meeting:
The Agenda was covered in the first two hours, so this didn't overtax the "sit muscles."
The meeting had some aspect of "how sausage is made" (it was supposedly 19th century German statesman Bismark who likened the drafting of legislation -- in this instance boiler codes for steam locomotives -- to sausage making in that you really don't want to watch it being done and know all of the ingredients).
One of the participants who spoke from experience scolded the group for drafting minutes that included the level of detail of quoting what people said in the meeting. He explained for liability and other technical reasons, you don't want to go into this level of detail -- the minutes should just list bullet points of what topics were discussed and the outcomes of votes on them. Good to know if your train club/historical society/passenger advocacy group makes you take the minutes.
If I was paying enough attention, there were 3 topics discussed -- whether the Boiler Code should say anything about the thinning of boiler tubes resulting from "rolling" to fit them into the tube plates, the material used for staybolts and finally, whether the Code should allow for welding of overlapping boiler plates.
In the spirit of the recommended minute-taking (although these are my impressions, not official minutes), "rolling" a boiler tube to obtain a press-fit into the tube plate necessarily thins the tube, where the tube thickness had been specified for a given operating boiler pressure. The decision was not to include this in the Code because that would dictate a process to be used, not only limiting what boiler manufacturers could do, but writing this into the Code would require the Committee doing the analysis on any stress concentrations resulting from the change in tube inside diameters that should be left to manufacturers, checked either by analysis or by pressure testing.
There is some preferred steel used for staybolts since a long time, it is a good material because its yield strength, the important value, is high relative to its final tensile strength, but there was some concern about boiler manufacturers being able to get this particular alloy or substituting a steel with a higher tensile strength but lower yield strength.
Finally, riveted boiler by necessity overlap the boiler plates, otherwise, there is no place for the rivets to go to hold them together. Accepted welding practice, and this acceptance came from the Federal Railway Administration back-in-the-day based on what welders were able to do at the time, is to butt-weld the sheets at a non-overlapping seam. The question was posed as to allow welding overlapping plates by having two weld seams, one on each end of the overlap. No action was taken on this because it was felt there was no compelling reason offered to do this.
Oh, and the next meeting is in-person in New Orleans on Monday Nov 1 (this Zoom meeting was ever so convenient for a "lurker" like me who wanted to experience one of these meetings).
The 'preferred' idea for boiler tubes is to do full-penetration welding at one end, usually the firebox end, and prosser the tubes at the other end (I prefer the idea of roller expansion with greatest 'stretch' of the tube metal at the middle of the tubesheet thickness) followed by seal welding. This was supposed to best handle differential expansion issues between tubes and flues with minimal distortion stress in the tubesheets. If there were to be an issue with tube wall thickness, the easiest 'code-compliant' procedure might be to require safe-ending the tube with slightly thicker stock, or use a thicker ferrule.
I trust you see the dangers inherent in a higher-strength metal that has lower yield strength being used for staybolt work according to code calculation. Some of the reason to keep using high-grade iron for staybolts (which are far better threaded than fillet-welded by your usual boiler 'techs'... perhaps by anybody) was the more predictable behavior under cyclic stress.
It is difficult to conceive why anyone would want a lap seam in a welded boiler unless trying to pretend the structure was 'historical' (perhaps then adding dummy rivets?) If implemented as a pair of full-pen welds there is eccentric stress across the doubled joint; the likelihood of 'stuff' being in the trapped void or getting into it subsequently is not pleasant. I think it has been amply demonstrated in Britain and Australia that a welded version of a historic riveted boiler, even when taken as dimensionally identical as possible, cannot and should not ape the riveted boiler plate sizes or joining methodology; enhanced dangerous cracking can result far below the nominal factor of safety even when the wrong 'historic' thicknesses of plate are correctly fusion-welded.
Overmod It is difficult to conceive why anyone would want a lap seam in a welded boiler unless trying to pretend the structure was 'historical' (perhaps then adding dummy rivets?) If implemented as a pair of full-pen welds there is eccentric stress across the doubled joint; the likelihood of 'stuff' being in the trapped void or getting into it subsequently is not pleasant. I think it has been amply demonstrated in Britain and Australia that a welded version of a historic riveted boiler, even when taken as dimensionally identical as possible, cannot and should not ape the riveted boiler plate sizes or joining methodology; enhanced dangerous cracking can result far below the nominal factor of safety even when the wrong 'historic' thicknesses of plate are correctly fusion-welded.
I thought the same thought about corrosion getting started in the overlap portion of the boiler plates.
Maybe the fabrication is simpler because for a butt seam, you have to get the width of the boiler plate exactly the right amount?
I think enough of the people on the meeting were thinking a welded lapped seam was not a good idea and spoke up that the Boiler Code should not include such a thing until someone could offer a strong reason to do it that way.
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