Machining weld fillets on a steel boiler

[Martin CottrellParticipant @martincottrell21329]

[Martin CottrellParticipant @martincottrell21329]

Hi all,

I am currently building a 4" scale traction engine for which I have purchased a professionally built steel boiler. The horn plates are to be bolted to the sides of the firebox into six of the stays on either side of the firebox. These stays have to be machined so that on either side they hold the horn plates approx 0.094" away from the firebox on each side, apparently to allow a small air gap to prevent the horn plates from becoming too hot during operation. The problem I have is that if I machine the stays to give the correct horn plate separation distance then the horn plates will be fouling the weld fillets on either side of the top of the outer firebox sides. My question is, can I machine the weld fillets down so they are flush with the outer edge of the boiler tube/firebox plate joint without compromising the structural integrity of the boiler or invalidating any future boiler test that will be required? Hopefully the photo will show the weld fillet in question which you can see is currently standing quite proud of the two plates that it is joining.

Regards Martin.

[AndyAParticipant @andya]

What model are you building? I would check all the measurements first. The gap is usually because the boiler is smaller than the distance between the horn plates. I wouldn't machine the welds without checking with your boiler inspector first.

[Chris GunnParticipant @chrisgunn36534]

Martin, why not leave the stays a little bit longer so the hornplates are slightly wider apart and clear the weld bead. Then you need to increase the length of all the shafts and spectacle plates by the difference, everything outside the frames will stay the same. From the picture it does not look as if you would need to add much.

Chris Gunn

[Martin CottrellParticipant @martincottrell21329]

Andy,

I'm building a 4" Little Samson.

Chris,

I had considered your option but unfortunately at least 2 of the stays are already lower than the protrusion of the weld fillet even before machining them all to the same distance from the firebox side plate. It would seem my only option if I can't skim the weld fillets is to skim the stays so they are all equal length then fit suitable sized washers between stays and horn plates to provide enough offset for the horn plates to clear the weld fillets.

Regards Martin.

[Boiler BriParticipant @boilerbri]

Took me ages to sand the stays flat. I made a parallel template the same size as the horns and kept trying it over until it was a good fit.

Took time but worked out well.

Brian.

[nigel jones 5Participant @nigeljones5]

the answer is yes. use a flapper wheel 80 grit to flatten them quickly. they add no strength to the weld (which happen to look ruddy awful) and so can be rermoved. I build steel boilers, was coded for many years, and I flatten all my boiler welds. And how many stays….massive overkill, but safer all the same.

[Paul LousickParticipant @paullousick59116]

Hi Martin,

Not sure what your code requirements are but ours in Australia requires that the stays protrude by 3mm. Best to ask your inspector before yo do anything.

Paul.

[michael darbyParticipant @michaeldarby61557]

The hump on the weld adds nothing to its strength at all, it is only there to prevent undercutting of the plate thickness. in actual fact it reduces its strength by creating !stress raising changes of thickness, ie a weak spot along the joint. If a load is applied the material will move, and the the increased thickness will move less,This will induce stress at the junction of the weld where the thickness changes.If this is a professionally built boiler, I would send it back. What are they professional at? decorating!

[Gordon WParticipant @gordonw]

Is that a hole at the T intersection ? That would be a big stress raiser. I agree that the raised weld does nothing for the strength, but this is model work and has to be passed by an inspector, so ask him before doing anything.

[Martin CottrellParticipant @martincottrell21329]

Fizzy,

Thanks for the encouraging reply, confirms my initial thoughts regarding no loss of weld strength.

Michael,

Likewise. Although an interesting comment regarding a thicker weld fillet possibly making the joint weaker, I'm not sure that the 120 psi working pressure of the boiler is going to cause any significant movement in the (heavily stayed) 10mm thick boiler plates. I'm also interested as to why you think the boiler should be returned to the manufacturer, do you consider it unsafe/unfit for purpose? The paperwork that accompanied the boiler confirms that the boiler has been inspected at various stages of construction and has successfully passed a 2 x working pressure hydraulic test.

Gordon/Paul

Unfortunately the build is going to take at least another 3 years before I'm at the point of needing a further pressure/steam test! This, together with the fact that I currently do not belong to any ME clubs who might have a resident boiler tester/inspector means I have nobody to consult directly who might have a future interest in testing my boiler. Hence my request for help from my forum friends!

Are there any current steel boiler testers/inspectors reading this post who may wish to comment?

Regards Martin.

[Paul LousickParticipant @paullousick59116]

Hi Martin,

You have said that "the boiler has already been inspected at various stages of construction". Why not ask the manufacturer if it is OK to grind back the welds. Get their answer in writing because if it is not acceptable to their inspector, their paperwork may become null and void.

Although your engine will not be finished for 3 years, I would suggest that you find a model club in your area and talk to their members who will have a wealth of information about boilers and engines. Seeing how others have built engines could help with the construction of yours.

Paul.

[Trev67Participant @trev67]

Hi Martin

You could contact the boilermaker and ask, if they say it is ok to cut the welds back then get them to put it in writing, if it is not ok, then the boiler is unfit for purpose because it doen't fit, so I would then send it back.

good luck with the build

Trevor

[Martin CottrellParticipant @martincottrell21329]

Hi Paul,

Good idea to contact the manufacturer, can't think why I didn't consider that one myself!! I'll also have a look through the boiler paperwork when I can locate the "safe place" I filed it in, there may well be some contact details for the guy who inspected & tested the boiler & he may be able to give me a definitive answer.

Regarding the club thing, unfortunately I've found my local club to be very "clicky" in the past and not really interested in welcoming new members unless they want to play trains or more importantly act as an unpaid navvy working on the club track infrastructure. In fairness this was a few years ago so things may be different now.

Thanks again for the advice.

Martin.

[Harry WilkesParticipant @harrywilkes58467]

Hi Martin

You asked why other think that the boiler should be returned I would suggest that if you gave the boiler marker a drawing of how the boiler should be constructed he would know that the stays have to be machined back to allow for horn plate to be spaced off the boiler then the fact that you cannot achieve the required gap due to bad welding then the boiler as not been made correctly ! Last thing you should do is take the matter into your own hands !!! You could have a word with Edward get his opinion on the boiler i would also add if the boiler has been made by either of the boiler manufactures Little Samson recommend I,m surprised they let it out of their factory

H

Edited By Harry Wilkes on 31/01/2016 21:46:22

[julian atkinsParticipant @julianatkins58923]

hi martin,

in fullsize loco boiler repairs the welds are always ground back to the plate. i dont see any reason not to apply the same procedure, and i cannot think of any sensible club boiler inspector disagreeing with this procedure. i totally agree with fizzy in this respect.

however not every club boiler inspector is sensible!

cheers,

julian

[Paul LousickParticipant @paullousick59116]

Hi Martin,

The model club which is closest to my home is also "very clicky" and only wants to play trains which is why I travel an extra 1/2 hour to a model club which is much more friendly and likes engines with a steering wheel and does not have to travel on rails. I am also a member of another club where I have to drive for 150km and where we play with full size engines. Only do it because I enjoy their company. Look around and find a club which suits you.

Paul.

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