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Ofeldt boiler time

Posted by ron parola 
Ofeldt boiler time
December 24, 2015 03:41PM
Ok gents, winters here... it's RAINING!, in Calif!! So thoughts are turning to an indoor project; new boat boiler. I thinking to replace my 40 sq ft vft with an Ofeldt type for two main reasons; faster steamup and to lower my CG which with a canopy and rear cabin is REALLY high. My question is; are there any suppliers that sell small quantities of A-106, 6 or 8 in od, at reasonable prices? Yeah no problem buying a few hundred ft but just a few feet seems to be hard to come up with. Thanks Ronp
Re: Ofeldt boiler time
December 24, 2015 05:55PM
McMaster Carr has all pipe by the foot.

One note about using the Ofeldt with a wood or coal firebox, put some sort of heat deflector on the bottom of the center drum. The center drum is essentially a downcomer. Heat impinged on it may disrupt the internal circulation.

Re: Ofeldt boiler time
December 24, 2015 06:13PM
Ron, what price do you consider reasonable? And how long, wall thickness ? I'm sure someone else in the phorum knows a lot better than I do but I do a lot of looking. I'm trying to find much smaller tubing in 50' to 200 ' lengths. .375 OD and wall thickness of about .65 to .89 ".
Here is one site that sells custom lengths of A106. For me the 'Half Price' cost seems very high. But I don't have a good frame of reference to tell.
I'm trying to figure out a good lamont boiler of about 200 hp output and at least 85% efficiency . I'd prefer better .
Anyone interested in talking with me on this I'd appreciate it.
But you are in the right place for help. Good luck .
Re: Ofeldt boiler time
December 25, 2015 04:26PM
Well all I can find in McMaster is only up to 2in, darn it. And as far as flame impingement on center drum; I'm now using a Lune valley burner which does leave a "hole" in the center of the fire so a small shield would be pretty much all I need. Thanks rp
Re: Ofeldt boiler time
December 25, 2015 08:55PM
I think someone has replied with better information than I had. Previous post removed.

Re: Ofeldt boiler time
December 26, 2015 08:56AM

If I recall correctly, I had to phone McMaster and they obtained it for me. It seems the 6" schedule 80 A106 seamless was around $120 per foot. I only needed 14", so it was about 150. Then the drawn caps which I did not use were 75 each.

We purchased the shell and the A178? firetubes for another boiler, the 16" diameter X .375" wall A106 seamless was 150 per foot. That was purchased through Wolverine tube here in Michigan. They cut the flues and prepped the ends for rolling in to the sheets. Good bunch to deal with, I would try them for the 6" centerdrum.

Wolverine Boiler Tube Sales

12405 Churchill Rd,

Rives Junction, MI 49277

(517) 589-8271

Re: Ofeldt boiler time
December 26, 2015 09:24AM
Any commercial pipe shop should have cutoff around.
Make sure you get a Mill cert when you buy your pipe.
I scraped 8000 lb. of all sizes up to 16 inch last fall
Re: Ofeldt boiler time
December 31, 2015 07:00AM
The question is why steel tubing and not copper, what pressure are you going to run. I have a ofeldt in my steamboat made of copper works fine.Safety at 125 psi. I know this is a car forum but the steamboat forum is so spammed its unusable. Can the monitor correct this problem.

Re: Ofeldt boiler time
December 31, 2015 09:06AM
How about inviting the steamboat forum participants to post here? I think we do a pretty good job of keeping the spam out. There is even a separate steamboat forum, although no one has posted there in over a year and a half. Steamboat guys are naturally welcome in the "steam stuff" forum but they can use the steamboat category if they want to keep the conversations more on point.

SACA would certainly welcome their participation.


Re: Ofeldt boiler time
December 31, 2015 10:15AM
I participate in the forum at www.thesteamboatingforum.com based in the UK and it's very active and no spam.

The particular website you're referring to, I don't know the address (and I'm not going to go look for it), but I went to a steamboat related discussion site a few years ago and clicked on a picture and it totally crashed the old 32-bit PC I was on and I had to reload Windows to correct it. And I'm usually pretty good at getting rid of adware,malware etc. It was some really nasty stuff.

Copper boilers are fine, but since copper has a 406°F heat limit, be careful to not run it out of water. Steel is much more forgiving in that regard.

I've been involved in discussions regarding steel vs copper and thermal conductivity. Power plant engineers claim there is no advantage to a copper boiler and it's rated heat transfer coefficient over steel. They explained, once steel tubes are up to temperature, the heat transfer rate is the same. I'm a bit of Missourian* on these issues, but I'll take their word for it, as they are very knowledgeable.


*For our English friends, Missouri is the "show me" state.
Re: Ofeldt boiler time
December 31, 2015 01:28PM
The reason I was asking here rather than the boat site is I figured more car people are into Ofeldts than boaty types and there's not much activity on the boat half. And as to why steel vs copper; right now I'm looking for the main drum, copper in 6 or 8in sizes thick enough for a running pressure of 150 psi is even HARDER to get a hold of and as the central drum is a downcomer thermal conductivity is kind of a moot point. As to why steel tubes; copper has to be heavier wall than steel so the difference thermally is not much and it's easier to just weld in steel tubes than to weld in sockets and then silver solder tubes into those. In fact two years ago here (norcal) at the steamboat meet someone with a similar boiler to an Ofeldt did have a copper tube (an UPPER one, HOT!!) blow out of the drum, and with the firebox door open at the time got some nasty burns on his legs. Granted his wasn't a flooded tube type and possibly the water was low, but I'd like to avoid that. Now in the land of Chardonnay if I wanted to build it out of stainless, that would be no problem, the winery suppliers can supply anything you want, but plain old steel hard to come by around here, but getting the smaller sizes of A106 is not a problem. So after the New Year I'll be searching more seriously! cheers rp
Re: Ofeldt boiler time
December 31, 2015 01:38PM
Most of my steamboat friends run pressure less then 250 psi so copper works fine. its also easier to work when forming.

Re: Ofeldt boiler time
December 31, 2015 02:55PM
I offered some copper pipe for scrape prices.
No one took me up on it so I scraped the stuff. The eight inch had 0.200 wall thickness.
I don’t really like Ofeldt boilers as I think they have two much gas pass space, also most of the gas is passing through as Laminar flow.
But you sure did a very nice job on your boiler. I have built model copper boiler running at 150 PSI and my first boiler in my 25 foot boat was copper with steel manifolds. hydro’ed at 300 with no problems
Ran for the first thirty years.
Re: Ofeldt boiler time
January 03, 2016 10:01AM
"I don’t really like Ofeldt boilers as I think they have two much gas pass space, also most of the gas is passing through as Laminar flow."

They do look as though they would, but that isn't the case if built properly. It's important to put as many coils as possible around the circumference. On my Loco, 14" above the very intense burner is a simple galvanized sheet metal cover casing top and it shows no sign of excessive heating. It will boil two gallons of cold water in a little over a minute. From main burner ignition to propelling the vehicle is around three minutes. Not too many boilers will do that. That exhibits heat going to the water efficiently and not excessively out the stack.

With the flue gases passing horizontal tubing, there is breakup of the flow happening. Some turbulators for firetube boilers are just a wire coil, like an extended spring disrupting the gases. Laminar flow is logically created through a passage with smooth walls like that of a firetube - nothing to disrupt it. When the vehicle is moving the flame direction is changing as well further preventing laminar flow to establish.

When all things are considered, the Ofeldt is the best small power boiler ever designed. Cost, ease of construction, ease of control, steam generation, power to weight ratio, safety, high internal natural circulation without mechanical pumps etc. Some boilers beat it in one or more aspects, but none beat it in all the aforementioned aspects combined.

Re: Ofeldt boiler time
January 04, 2016 07:10AM
when building my ofeldt boiler I installed a aluminum plate, it looks like a flat donut over the main drum and extends to the end of the coils that sits on top of the coils to slow the hot gasses. this seems to work. I have a thermometer on the exhaust stack and the temp. just above 200 degs when steaming. The replacement boiler for loco and other steam cars of that type was a ofeldt. They must have known something back then.
Re: Ofeldt boiler time
January 04, 2016 01:40PM
I've heard of Ofeldt owners putting baffles in like that. Haven't shot the exhaust stack on mine yet, but it stays pretty cool. I may get by without dampening it. All those coils on yours, I'll bet it makes some serious steam.

Regarding the Ofeldt company startup, yep, they turned everything on it's ear back then and made their living swapping out stock car boilers/systems for their boiler/burner and control system. They did that for many years and then his son Frank went on to invent the "steam jenny" which is now known as Jenny products.

Re: Ofeldt boiler time
January 04, 2016 02:00PM
Typical smoke hood temperature for a normal Stanley burner - 280 Degrees C or 530F. Of course some of this can be recovered by a coiled copper economiser but much is lost out of the flue! I found in practice the best way to preheat the water was by a coil in the steam exhaust (after the feed pump) which worked very well and could send water at 190F to the boiler - forget the losses in the flue.

Re: Ofeldt boiler time
January 05, 2016 08:21AM
the ofeldt in my boat steams to about 25psi from cold in about 5 mins. Then the pressure goes up quick from that point, it's safety at 125 psi, but I run it between 50 and 80 psi no sense wasting fuel when not needed at that pressure I can do 4 to 5 knots.
In my likamobile using a winslow boiler with a 12 volt oil burner and safety at 250 psi it get up to pressure of 100 psi in less then 5 mins. then 250 psi comes fast from that point. I need 100 psi to move the car when the wheel are off the ground I can run the engine at 30 psi.
Re: Ofeldt boiler time
January 05, 2016 09:28AM
This is one of my marine boilers designs. It was built with copper tubes and steel manifolds by a friend of mine, Will Widler.
Total radiant heating around the combustion chamber and 100% turbulent heat over the combustion chamber.
Tube spacing is held as close as possible to one tube diameter for wood firing.
The boiler hydro’s at 450 PSI for a 300 psi working pressure but he can maintain his max speed at less than 150 psi.
His 29 foot boat does 14 Knots


Re: Ofeldt boiler time
January 05, 2016 01:18PM

That's a nice boiler.

Re: Ofeldt boiler time
January 05, 2016 03:54PM
Super job. I like the idea of the crossover of the up tubes and the fore and aft layer connected to the back wall tubes. It's hard to think of how to get more pipes in there. A lot of work went into building it.


Edited 1 time(s). Last edit at 01/05/2016 03:58PM by Mike Clark.
Re: Ofeldt boiler time
January 05, 2016 05:45PM
The copper version is a takeoff from my ASME code boiler.
Several other versions in different sizes have been built. There are no return bends, two rows of tubes are all around the combustion chamber and cross each other. And go directly into the top drum, making eight rows over the combustion chamber.
The national board based on the calculations would only except the 385 Lb. per hours but in test with vaporizing oil burner it did close to 600 Lb.
The copper one and the ASME code one,s have superheaters in them.
My boiler is now set up for wood firing. And another on the west coast has a Becket Oil burner.

Re: Ofeldt boiler time
January 14, 2016 09:05PM
The sheet metal shell for an ofeldt has to extend down far enough to allow room for firebox in a wood fired version. But it would get exceedingly hot around the fire. Is some kind of refractory insulation used to keep the shell cooler and send heat up instead of out? (I need to get mine finished) I'm thinking maybe double wall with insulation.
Re: Ofeldt boiler time
January 15, 2016 09:25AM
One inch of Fiberfrax insulation and 310 combustion grade S.S will make a great fire box
Re: Ofeldt boiler time
February 08, 2016 12:56PM
OK, got my pipes and got my coils wound, BUT... I was thinkin' ( yeah I know, bad idea). Since there is a lot of free space within the coil clusters has anyone put vertical tubes within them? With 18 coils there is room for 6.3 sq ft of tubing in just one of the open areas of the coils, ASSUMING you could even assemble such a thing. Any thoughts on that, or would having coils ten feet long and vertical tubes two feet long short circuit flow? Cheers ronp
Re: Ofeldt boiler time
February 09, 2016 08:36PM
I don't think it would hurt circulation, but my coils are so meshed there's no room for any verticals inside them. I was dreaming up a watertube curtain that surrounds the firebox, (wood fired) but about decided it would complicate things too much for the current project. Better off just making an insulated shell and let the heat rise.
Re: Ofeldt boiler time
March 24, 2016 08:52PM
By the way, what kind of welder works best for steel boiler welding? All I've done is stick welding with lincoln AC and AC/DC welders. 33 years worth. Enough to know what it takes to make good joints. With a boiler that means preheat and then stress relief heat treatment for the whole unit before use. But I'm thinking perhaps a TIG welder might be better, no flux crap to get in the way. Sometimes I need to do precise welding jobs where I think a TIG welder would do it much better, thinking of getting one.
Re: Ofeldt boiler time
March 25, 2016 06:23AM
TIG is good and purging id with same welding gas makes for really good welds, a must with stainless. Inside looks as good as outside.
Re: Ofeldt boiler time
March 25, 2016 09:16AM
If you want to stick to ASME code work stick to the stick welding.
Open route, deep red first pass then 7018 for the rest of the weld.
Heat every weld area up to 500F before welding.
After the complete boiler is built hydro it to 3.5 times it’s design pressure, then send it out and have the complete unit stress released. Then hydro it again.
Re: Ofeldt boiler time
March 26, 2016 10:35PM
Don't need ASME legally for where it'll be worked, but I won't compromise safety. Although I'll see if I can rig up my own stress relief treatment. Supposed to heat in furnace to 11-1200 F hold for one hour and then cool slowly. I think I will get a TIG welder, been wanting one for a long time anyway since I keep running into need for it.
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