Boiler Design and Material Selection

This forum is dedicated to the Live Steam Hobbyist Community.

Moderators: Harold_V, cbrew

User avatar
Fred_V
Posts: 4055
Joined: Sun Jan 12, 2003 3:26 pm

Postby Fred_V » Thu Oct 08, 2009 5:40 pm

here is what happens inside a model boiler after some years of use.
Attachments
HBoiler-09.jpg
Fred V
Pensacola, Fl.

User avatar
Fred_V
Posts: 4055
Joined: Sun Jan 12, 2003 3:26 pm

Postby Fred_V » Thu Oct 08, 2009 5:43 pm

cbrew wrote:Marty,
First off, thanks for starting this thread.
I have a question,
what are your thoughts on threaded stays that are seal welded?
I can how this can help with assembly of the fire box area.
Thanks
Chris

the Brits like to run the threaded studs into the firebox and put nuts on the studs. i don't know if they thread into the firebox sheet but i think they do and the nut is like a lock nut and eliminates welding on the inside.
Fred V
Pensacola, Fl.

CB&Q
Posts: 397
Joined: Sun Sep 06, 2009 8:11 pm
Location: Missouri Ozarks

Regarding A-36 Steel and 1018.....

Postby CB&Q » Thu Oct 08, 2009 7:51 pm

The A-36 supplied to me for use as drivers was a hot-rolled product. All of the 1018 I have seen was a cold-rolled material. This does not mean 1018 may not be designated when hot-rolled, simply that, I think, it indicates the carbon content. CB&Q

Edit: Undertow rumblings I sense herein suggest that the thread has only begun........

That can only mean I will eventually have to:

1) hide, ...... or,

2) reveal the numbers I came up with regarding original calculations for my boiler, and the results found through actual measurement of deflections of the flat plates at pressure.
One can derive far more personal pleasure and reward from observing Mother Nature's living things instead of Humanity's Madness.....

User avatar
Dick_Morris
Posts: 2050
Joined: Sat Jan 04, 2003 2:09 pm
Location: Anchorage, AK

Postby Dick_Morris » Thu Oct 08, 2009 9:08 pm

you operate at 100, but the safeties are set at what - 125?

My recollection of the regulations in Alaska is that they say a non-code hobby boiler not exceeding the dimensions for an ASME miniature boiler is limited to 100 psi. That would be the maximum at which the safeties could be set. I believe Texas based their law on ours, but don't know if they adopted the same language in the regulations. So it varies by the state law and regulations.

if you have a STAYBOLT TAP, it's easy, but try to find one these days.

If I needed one for model use I think I would try and modify a standard tap by grinding down the tip diameter and adding a pilot. The cutting edge geometry wouldn't be as good as the commercial product, but I think it would work. Once you got a good start on the threads you could probably follow with a commercial tap. If I'm not mistaking, some of our predecessors in the hobby would cut and harden their own taps from silver steel/drill rod by necessity.

User avatar
Marty_Knox
Posts: 1132
Joined: Thu Jan 09, 2003 6:50 pm
Location: Michigan, USA

Texas and Michigan Rules

Postby Marty_Knox » Thu Oct 08, 2009 9:39 pm

Dick, in Texas hobby boilers with an inside diameter of 12" or less and less than 2 square feet of grate area are exempt from inspection, as long as they are not used commercially.

Here in Michigan the state boiler division inspects hobby boilers of locomotives operated on track less than two foot gauge if they are hauling the public. You can operate at any pressure as long as you can demonstrate the boiler is safe at that pressure. The highest operating pressure I am aware of is 150 psi.

Harold_V
Posts: 16250
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Postby Harold_V » Thu Oct 08, 2009 10:59 pm

Marty,
Would you have any of the specifics for hobby boilers as they might apply in Washington State?

Harold

User avatar
Dick_Morris
Posts: 2050
Joined: Sat Jan 04, 2003 2:09 pm
Location: Anchorage, AK

Postby Dick_Morris » Fri Oct 09, 2009 12:14 am

Marty - I have been told that Alaska and Texas laws/regulations were pretty close, this is apparently incorrect.

If anyone is interested, I looked up the relevant section of Alaska's regulations to refresh my memory. Exempt are:

(7) manually fired miniature boilers for model locomotive, boat, tractor, or stationary engines constructed or maintained as a hobby for exhibition use, having a volume less than five cubic feet and grate area less than two square feet and equipped with an American Society of Mechanical Engineers coded safety valve of adequate capacity and size, a water level indicator, and pressure gauge;

And the definitions say _

(B) miniature boiler - a power boiler or high-temperature water boiler that does not exceed the following limits:
(i) 16 inches inside diameter of shell;
(ii) 20 square feet heating surface; this sub-subparagraph is not applicable to electric boilers;
(iii) five cubic feet gross volume exclusive of casing and insulation;
and
(iv) 100 psi maximum allowable working pressure;

User avatar
Marty_Knox
Posts: 1132
Joined: Thu Jan 09, 2003 6:50 pm
Location: Michigan, USA

Washington State Rules

Postby Marty_Knox » Fri Oct 09, 2009 7:05 am

Harold, Washington State will inspect non-code hobby boilers that do not exceed 16 inch inside diameter, five cubic feet of volume, twenty square feet of heating surface, and 150 psi. These apply only if it is not being used commercially or in industry.

User avatar
Bill Shields
Posts: 4701
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Run and Hide

Postby Bill Shields » Fri Oct 09, 2009 9:49 am

CB&Q

If you built a conventional water-leg loco boiler without any stays whatsoever, and think that because it doesn't seem to deflect too much under pressure, the running and hiding should be on the part of anyone with any engineering sense any time you decide to steam that boiler.

This is a personal / technical opinion offered based on 30+ years of boiler design, repair and troubleshooting experience and working with ASME and EU boiler codes. It is not necessarily shared by others on this site, but may be.

Then there is the question of you using 4130 as a base material, which is also not a terribly good choice, considering the thermal cycling that a boiler goes through. In fact, short of stainless steel, I cannot think of a material lower on the list of choices than 4130, but again, that is based on years of following ASME recommendations and understanding why they make such recommendations, not from actual experience of using 4130 (which violates every boiler code I have ever see, USA or EU).

User avatar
Bill Shields
Posts: 4701
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

Threaded Stays and Nuts

Postby Bill Shields » Fri Oct 09, 2009 9:52 am

One of the first copper boilers I built was with threaded stays and nuts inside the boiler.

Getting threads in the firebox was really tough - needed a long STAYBOLT tap, and eventually I gave up on that idea and used the nuts to fix the stays and silver soldered the lot together.

It wasn't a bad looking job, but there were places where the firebox wasn't flat where stays came through, making the nut contact surface a bit odd to work with.

The boiler passed tests and steamed very well, and last I heard was still running - but I wouldn't do it again.

My most recent boiler has drilled through stays that are just silver-soldered at either end - much easier to do and quite a bit stronger for the same OD of stay (no root diameter to worry about).

User avatar
cbrew
Posts: 2608
Joined: Sat Jan 04, 2003 12:17 pm
Location: Vancouver Wa

Re: Threaded Stays and Nuts

Postby cbrew » Fri Oct 09, 2009 10:27 am

Bill Shields wrote:My most recent boiler has drilled through stays that are just silver-soldered at either end - much easier to do and quite a bit stronger for the same OD of stay (no root diameter to worry about).


Steel or copper boiler and stays??

Im just worred about being able to weld the stays inside the firebox.
If it is not live steam. its not worth it.

Visit my website here.

User avatar
Bill Shields
Posts: 4701
Joined: Fri Dec 21, 2007 4:57 am
Location: Somewhere in the World
Contact:

boiler

Postby Bill Shields » Fri Oct 09, 2009 10:34 am

sorry...all copper

it's a 3/4" Atlantic 4" OD


Return to “Live Steam”

Who is online

Users browsing this forum: AnthonyDuarte, Bing [Bot] and 14 guests