Boiler design & construction ex Patriot thread.

Am I reading your plots right, red zones implying max Von Mises at 250Mpa? 36ksi...right on the yield point

Also, are those stays failing from the ID outwards, how did you model the attachement to the wrappers? Becuase I would assume the threads in the plates would be seeing the worst of the deformations, but I appreiate that your FEA package has not gone to that detail.

Modeling the whole shebang up and getting it into NASTRANS or ANSYS would be the answer, with 8 core processing so it finishes in a reasonable time.

I think there are other questions here too, like Monel stays behaving non-linarily with the steel/copper wrappers, thermal effects, compressive or straight mass loads of water sitting in the vessel/on the crown that need to go in to make the case comprehesive.

Hydrogen embitterment, IMHO, is indeed present in the lower foundation areas, if judging by a certain MN pacific boiler I saw cut up in the spring with enough chalk deposits to start making pottery with is anything to go by.

 

This seems the most appropriate thread in which to mention (from the 3801 Overhaul thread)

Inner firebox with foundation ring removeable, and several kinds of stays including some with ball-and-socket joints. Have these ideas been used in Britain? Should they be?

 

I can't think of a boiler where you can't remove the inner firebox after removing the stays, unless it were all steel and welded up solid? As for flexible stays, they are used on S160s and Tornado, but probably others too (maybe those with steel fireboxes?).

 

As Sheff says, flexible stays were used on steel boxes in the so-called "breaking zones". Bulleid avoided their use, apart from around the syphon necks, by using more and thinner stays, and wider water legs, to give greater flexibility. There are many images on work on flexible stay replacement on Santa Fe 4-8-4 2926 at http://www.nmslrhs.org/ (under the Photos tab), around 2015.

 

Thanks for the extra info - I was trying to visualise the boiler on the only Bulleid I've see 'undresed' - City of Wells - and couldn't recall seeing any.

 

Bulleid's paper to the ILocoE on the MN Class in 1946 is well worth a read (as is the Burrows and Wallace paper of 1958).

 

It's quite common for a firebox top to be wider than width of the shell at the foundation ring, which means even with all the stays removed it's only possible to remove the firebox by removing the backhead or throatplate.

 

Does that apply to all Bepaire boxes?

 

It doesn't have to but it would only apply to a small boilered loco. Whether it is a Belpaire or round topped firebox, once the boiler barrel diameter gets bigger than the firebox width, which in itself is governed by the width between the frames, the firebox will not come out (or go in)with the backhead in place. You could, I suppose, have a large diameter barrel and a narrow straight sided firebox but this would be a design nonsense as the reason for a larger diameter is to get more tubes in (heating surface) and the narrow firebox would negate this possibility.