[Steam-engine] lap seam calculations

[Ken Majeski]

Well.... You are asking for calculations on the Barrel while giving us 
firebox measurements. If I run you firebox thickneses and staybolt pitch I 
come up with about 111 psi with a safety factor of 4. This will depend if 
the .310 reading is just a localised pit I can see where you could get 125 
psi.

Now a lot of states have adopted the NBIC appendix C and they allow a joint 
efficiency of .74 for a double riveted lap and .58 for a single. Wisconsin 
never did penilise a small lap seam but we currently have a rule limeting 
lap seams over 36 inches in dia to 15 psi. Butt strap seams are allowed a 
joint efficiency of .82 for a double riveted butt and .88 for a triple.  If 
you have good material thickness on your barrel I see no reason to be afraid 
of 125 PSI.

Minnesota did have the 100 PSI lap seam limet but due the the efforts of the 
Minnesota Steam Engine assoc they got that changed and also can run lap 
seams over 36 inches now...

I would recomend that you and your friends form or join a group as they will 
listen to many people where just one or two will get no results. So far the 
groups in Wisconsin and Minnesota seem to have a good working relationship 
with the inspection dept.... But lets Face It... If you have a Bad Boiler 
you are in Trouble...

I am in the middle of this now as I am doing UT on my 24 Minnie and doing 
the calculations on it. What a Pain trying to lay out the grid and miss all 
the castings ect as much as I can. Of course all this has to be reviewed by 
the state inspector.....

Ken Majeski, Ellsworth Wis. Case Steam Engine, Minneapolis Steam Engine, 
Rumely Oilpulls H, F, & R. Website, Http://www.pressenter.com/~kmajeski/





>From: <steamman at ptdprolog.net>
>Reply-To: Steam-engine mailing list 
><steam-engine at lists.stationary-engine.com>
>To: <steam-engine at lists.stationary-engine.com>
>Subject: [Steam-engine] lap seam calculations
>Date: Mon, 12 Jul 2004 12:05:28 -0000
>
>Engine friends,
>
>I just came from a show in Maryland. Spent 2 hours with the Chief Inspector
>and his inspectors going over the interpretation of their antique boiler
>code. I was limited to 100 lbs. operating pressure because of my lap seam
>boiler. In PA I'm allowed 125 lbs.  They refer back to the 1971 code for 
>new
>construction of lap seam boilers. They will not even do any calculations 
>for
>a lap seam boiler, they flat out say 100 lbs.
>
>I'd like to know if anyone can calculate the difference from 125 lbs to 100
>lbs for a double riveted lap seam, What I'm really after is just how safe 
>is
>100 lbs vs 125 lbs.  My last ultra sound on my crown sheet last year was 
>.365
>around the fusible plug and found the lowest to be .310 in the rear left
>corner of the crown sheet. My stays are 4 15/16"x 5". It's a 1909 Frick 8 x
>10 and I very rarely work the engine. I ran a sawmill, thresher and a rock
>crusher once. I run a baker fan every so often for 15 minutes or so. Other
>than that I pull a sled just for show.
>
>Lets here everyone's thoughts and comments
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