Just Joined

[Spanky]

Thanks for the specs, in my design i use 16in schedule 40 for the exterior and 14in schedule 40 for the interior shell giving it a nice water leg. Is schedule 40 acceptable? or should i change it
to 80? and is MIG welding it together acceptable if we're only running 125 psi? sorry for all the questions before I even post my design...

[87gn@tahoe]

Josh,

Welcome to the forum from another relatively young guy (26) with a steam obsession.

Building a water leg into your firetube is a very good idea, as there is a significantly greater percentage of steam produced by radiant heat from the fire. Stays in the water leg area (between firebox shell and outer shell) may or may not be necessary, given the size and target pressure of your boiler.

Fredrosse has more info on the acceptability MIG welding pressure vessels. You could also search the forum, as I asked the same question about a month ago. Though my memory is not good enough to quote me on it, I believe it was stated dual shielded MIG (argon and flux-core wire .045") was acceptable with a TIG root pass.

wes

[artemis]

And for your library, I suggest:

Steamboats and Modern Steam Launches - this is a reprint of a magazine published from 1961 through 1963 - don't let this throw you; this is still considered the "bible" of hobby steamboating after 50 years. Available from Elliott Bay Steam Launch http://www.steamlaunch.com bound in hard copy on quality paper. You can built your own hobby steamboat from the matereial in it. And it is well worth the price. And I receive no recompense from the publisher.

Administrator take note - we need a Hobby Steamboating Books/Magazines page. So many titles have been listed that it's difficult to locate them - Sort of a "if you find a good book, send title, author, publisher, etc on to the administrator through a link on the list page and he will add it to the list".

Oh, yes - don't forget the huge Google Books data base. There are now thousands of books that have been scanned, everything from valve gear design to oil firing in small plants, etc.

[fredrosse]

For a 16 inch boiler shell at 100 PSI design pressure, the ASME Code would allow "Miniature" classification, which in turn allows a welded A53 pipe to be used for the shell. At higher pressures, or a larger diameter shell, A106 seamless pipe is recommended. Standard 16 inch pipe wall thickness is 3/8 inch (a little less than Schedule 40), and that has a maximum allowable working pressure of over 600 PSI, so that is plenty heavy enough. You could easily go to 1/4 inch wall and still be OK.

Using a 14 inch pipe for the furnace would only leave about a 5/8 inch gap between the outer shell and the furnace, and that is too small. For a 16 inch diameter shell, use a 12 inch pipe for the furnace, or smaller.

MIG welding on a pressure vessel is not recommended, unless you have a machine that can handle 0.045 inch weld wire. The smaller MIG machines just do not provide the kind of weld penetration needed, stick welding is generally more reliable. I like to use 3/8 wall pipe, and 3/8 thick tube sheets, this makes welding easier with high current stick welding.

[Spanky]

Fred I'm wondering how are the fluetubes oriented? As your comment about switching to a 12in furnace shell has me stumped on how to fit 61 3/4" tubes to the top of it... right now I have them perfectly vertical for ease in construction and because it just makes sense to have them that way. Should I decrease the distance between the waterside walls of the tubes? In my drawings it's 1/2" tube wall to tube wall.

Also I started a topic in the engines and boilers sections that I will post my CAD drawings to when I finish them.

Thanks to all so much for the welcomes and Ron I have buying the book on the top of my to do list, thank you for the link.

Josh

[Spanky]

Hey I was looking through the WI boiler legal lawyery stuff here: http://docs.legis.wisconsin.gov/code/ad ... 26_360/341

and i found this section:
http://docs.legis.wisconsin.gov/code/ad ... ew=section

I'm pretty sure this means I can build my own boiler. Whats your take on it?

[marinesteam]

It looks like it on first glance but be wary of this statement.

"Where it is not possible or practical to construct a boiler or pressure vessel in strict compliance"

I would also expect that obtaining a variance would be more difficult than just having the boiler designed and built by a stamp holding shop. I wouldn't think that an inspector is going to be too keen on reviewing every calculation and certification. This is what you pay a stamp holding shop to do, and what the inspectors expect to have been done by someone in the know. They may reject an application for the slightest miscalculation or ommission. Plan on getting all the meterial certifications when purchasing material and any other supporting documentation that may be needed and buying the code book to be sure that you have done everything. It's big $$$$

Also, you will need to prove that the person doing the welding of the pressure vessel has the skill to be doing so. This usually means having been certified in the particular style of welding on pressure vessels.

Talk to your inspector before starting down this road, you may find that it isn't all that difficult or conversly, that it just isn't worth the effort. You may also find that you can do some of the work yourself under the supervision of a stamp holding shop in order to save some money.

I don't whant to throw damp wood on your fire but you need to go into this knowing everthing that is needed to get the variance. It's going to be expensive to put a lot of money and work into a boiler just to find out that the inspector won't pass it. Talk to your local inspector.

Ken

[Spanky]

Just emailed the inspector for my district about the "special" certificate, hope to hear from him soon.

Josh