Author Topic: Monotube Boiler  (Read 33932 times)

Offline vtsteam

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Re: Monotube Boiler
« Reply #25 on: March 03, 2013, 09:54:46 PM »
Here's a photo of one found after some research.

http://www.wellman-group.com/boilers/products/stone-steam-generators

Also, just missed a scanned version of the Stone operator's manual -- the site where it was published closed down in the last 6 months! (www.locodocs.co.uk). Did a lookup of the site on the internet archive but they'd only archived the cover of the manual and not the contents  :(

I did however locate a used copy of the manual through Amazon, and it was reasonably priced enough to order it.

Wikipedia has a good article reiterating the details of steam (vapor) generators -- these were primarily used as railroad auxiliary saturated steam heat generators. Nevertheless very interesting for development of a low pressure monotube steam engine generator. I believe these were produced at least into the '60s. That makes it even more interesting.
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Monotube Boiler
« Reply #26 on: March 03, 2013, 10:21:33 PM »
Speaking of railroad monotube steam generators, there is a very intriguing passage in Experimental Flash Steam  describing the Besler steam railcar, put into service on the New York New Haven and Hartford Railway Co. (which would have brought them near to my own neck of the woods) about 1937.

1000 hp, @1500 PSI "The boiler is of continuous flow, non-water level type It has no drums or headers but is a continuous tube from the boiler inlet to the throttle. The water enters at the top and passes down through a series of flat coils where it is heated and then boils in the helical coils at the bottom surrounding the combustion space, afterwards passing to the superheater coils just above the firebox and emerges as superheated steam. The boiler is 4 feet in diameter and 6 feet 5 inches in height. The oil burner is of the pressure atomising type and of special design and construction.

"The train performs a daily total mileage of 317.26 miles and operates in almost continuous service from 6:00 A.M to 10:20 P.M"

Now that is tantalizing! I have never found more information about these railcars than the above. The scale, the regular usage, the type of transport are all unique, as far as I know for monotube steam. If anyone has or turns up more information about this chapter of steam transport, I would greatly appreciate hearing about it!
I love it when a Plan B comes together!
Steve
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Offline Raggle

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Re: Monotube Boiler
« Reply #27 on: March 04, 2013, 05:55:14 PM »
The search continues! I hope I can be more help.

Meanwhile, this is the book that spiked my original interest, borrowed from my local library

http://books.google.co.uk/books/about/Doble_steam_cars_buses_lorries_and_railc.html?id=eIVTAAAAMAAJ&redir_esc=y

and again after seeing the Stone's  -  that link is UK Google page but clicking "find in a library" I find a good number have it in stock. It doesn't seem to be available to buy. I suggest you try your local area from a similar (US) google page.

I hope your machine doesn't look like this:

http://www.dangerouslaboratories.org/genboiler.htm

Thinking forward your engine might possibly work part-time driving a wood chipper so you could have a hopper feed to the boiler  :lol:

Ray
still turning handles  -  usually the wrong way

Offline vtsteam

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Re: Monotube Boiler
« Reply #28 on: March 04, 2013, 09:24:18 PM »
Hey thanks again Raggle. I haven't begun to build the monotube yet. Just finishing up the conversion engine. It is together now, and needs to be run in and a leak sealed. I checked it on compressed air briefly this eveningand it does a sharp half turn but stops past BDC, but clearly it wants to go.I need to patch the leak (in a poppet valve chamber plug), and maybe change the timing. The cutoff is intended for steam, so quite short (55 degrees) for compressed air.

I may make up a second valve with a 180 degree cutoff just to get it running on air and broken in. Then I can start on the boiler.

The link to the boiler you gave didn't work for me, but I think I remember that one anyway. No It won't be like that one.

I have a wood chip burner built already, though not up to the capacity of my conversion engine. I intend to try the burner with some smaller model engines I have before tackling a larger monotube.

Last night I altered my search terms and found a video of the Besler monotube railway car mentioned above -- it's included in a promotional film also including the better known Besler steam airplane. Besler must have had quite a bit of financial backing to venture into such disparate monotube projects.

Here's the video -- pretty amazing detail -- I think you can see the monotube boiler in the plane when the cowl is open.
 
http://archive.org/embed/BeslerCo1932
I love it when a Plan B comes together!
Steve
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Offline 1hand

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Re: Monotube Boiler
« Reply #29 on: March 27, 2013, 12:19:51 AM »
Hey, I don't know much, but I like watching someone that does!

 make sure you post pics, when you start twisting metal!

 :worthless:

Offline vtsteam

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Re: Monotube Boiler
« Reply #30 on: March 27, 2013, 08:12:43 AM »
Thanks 1hand! Too much "knowledge" on my part and too little doing on this subject -- talk is cheap!

Still don't have my engine running so I can move on to the boiler. But as soon as that baby turns over on its own, I'll be onto the monotube trials here. And gradually work through plans A, B, C, etc. Wonder how many letters I'll go through this time?  :lol:
I love it when a Plan B comes together!
Steve
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Offline tom osselton

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Re: Monotube Boiler
« Reply #31 on: March 28, 2013, 05:40:08 PM »
Probably a to h that will give you the " AH " factor

Offline Tony

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Re: Monotube Boiler
« Reply #32 on: May 11, 2013, 02:18:00 PM »
I'm new to this so this is my first post!
I have been working on various designs of monotube boilers over the last few years and find the views on this forum most interesting. My original challenge was to design and build a 3HP double acting steam engine and boiler from scratch to fit in a dinghy. It needed to be light so much of the engine is ally with sealed ballraces throughout. The boiler had to be monotube for safety.
The engine is fine and chugs away quite happily at about 800 RPM. It has some unusual features. The flywheel is driven by a timing belt at 3:1 above crankshaft speed, this enables the use of a flywheel that is only 1/3 of the weight and also the engine can be mounted lower in the hull reducing shaft angle and lowering the C of G. The weight of the engine assembly including condenser and scavenge pump (but not the boiler) is only 34 lbs.
The boiler on the other hand is a different matter!  I needed about 80 PSI of moderately superheated steam (about 200 C). It was important that it was limited to <220 to avoid damage to the various O rings in the engine and valve gear. I started off with a monotube boiler and economiser coil in the flue controlled by a PIC and R/C servos and using gas burners from a domestic boiler. After much plying around with the control system it was moderately successful but I was not really satisfied with it so went for a Lamont design with separate superheater coil and burner. The pump was the problem here and I ended up with a much modified central heating pump. Again moderately successful but it was getting very heavy and I was worried about the separator tank which was, after all, a small pressure vessel.
So now I am looking at going back to a single coil again. There is much information on small units for hydroplanes producing amazing quantities of steam from 3/16 dia tube and a very noisy burner, but this is not suitable for a steam boat.
From what I understand, it seems necessary to have a feed flow of at least 1m/sec for removal of vaporisation bubbles forming on the inside of the tube. This leads to very small Dia tubing and a small surface area. I have noticed in the past that if you tap the coils lightly with a small hammer, the pressure rises quite dramatically for a few seconds (until the bubbles reform again?). I am now experimenting with an ultrasonic transducer fitted near the cold end of the coil in an attempt to shake these bubbles loose. Another idea would be to use a very oversized piston type feed pump which could shuffle the water back and forth in the tubing at about 1m/sec velocity.
What do you think?

Offline dsquire

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Re: Monotube Boiler
« Reply #33 on: May 11, 2013, 03:07:15 PM »
I'm new to this so this is my first post!
I have been working on various designs of monotube boilers over the last few years and find the views on this forum most interesting. My original challenge was to design and build a 3HP double acting steam engine and boiler from scratch to fit in a dinghy. It needed to be light so much of the engine is ally with sealed ballraces throughout. The boiler had to be monotube for safety.
.
.
.
.
use a very oversized piston type feed pump which could shuffle the water back and forth in the tubing at about 1m/sec velocity.
What do you think?

Tony

I think that you have made a great start on your engine and boiler. I am sure that there will be much interest by the members here. If you would be so kind as to go here http://madmodder.net/index.php/board,3.0.html and post an introduction telling a bit about yourself, where you are from, etc. It would help us all get to know you a bit better. I hope to see more posts on your projects in the future.

Cheers  :beer:
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and your better best

Offline vtsteam

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Re: Monotube Boiler
« Reply #34 on: May 11, 2013, 05:18:11 PM »
Hello Tony!

Great info! Thanks so much for your post.

It's a funny coincidence that I'm just about to start work on monotube boiler experiments since I'm just about completed with my 4 cycle to steam conversion.

Okay, so now for the opinion piece.....

I think that the 1 meter/sec quoted  is just a theory, not necessarily written in stone. Few people if any have ever watched bubbles form inside a monotube. There are many explanations, theories, and statements of "common knowledge" made on the internet and repeated, but very little proof of these conjectures. Basically, anecdotal experience when somebody changes something and sees either an improvement or performance decrease.

Here are just a few reasons why I have doubts that we are anywhere near a state of certainty on monotube function. It seems obvious that steam bubbles can form at different internal skin temperatures, different pressures, different material heat transfer rates, different relative surface to volume ratios of the conduit, etc. There are just lots of diverse factors besides flow rate. One example? If pressure is high enough, and maintained superheated water obviously can be conveyed all the way to an injector and engine --  as in true "flash steam". Where along the length of the monotube do the bubbles form there? Nowhere. What speed is critical to attachment? No speed, as long as the pressure is maintained.

And re "bubbles" -- what do we mean by bubbles? Is the insulating value people have observed a result of actual "bubbles", or a sheets of steam, and if bubbles, how large are they -- do they fill the conduit, are they a small percentage of the conduit?

There are just millions of questions as I see it, in a subject of much greater complexity than some arbitrary rate is going to answer.

Not saying ignore the theory completely -- might be a good rule of thumb for low pressure of a specific size boiler and material tube. But I think there's room for a lot more knowledge and development.

Which is a very good thing!
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Monotube Boiler
« Reply #35 on: May 11, 2013, 05:38:19 PM »
Tony to respond to your other questions, I guess virbrating the tubes could help detach small bubbles if they are truly what is happening. But it sounds like you want to move in the direction of simplicity and low weight. The more electronic gear you use and the greater the system complexity, cost, and failure modes.

Why not try to locate your bubble formation problem area in the monotube and increase pressure there by constriction, rather than having a uniform diameter tube? Then reduce pressure to your engine's tolerance level by increasing tube diameter when you approach the inlet?
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Monotube Boiler
« Reply #36 on: July 11, 2014, 12:23:21 PM »
I'm finally getting back to this project -- 18 months later and I have my 3/16" stainless tube to make a monotube. But I wanted to read up on a couple more things before bending it. I don't think stainless will take a lot of re-bending, so I want to pick the right shape first. I'm still up in the air about coils vs figure 8  in a horizontal monotube, or just random bending.

I found a really interesting article in issue # 3355 of Model Engineer, mentioning a successful monotube at the very end, with a photo, but I don't have the follow-up issue #3356 -- my stack jumps to 3357!  I must have lost it :doh:

Can anybody send me or link to a pdf (or just page photos) of  the continuation article "Model HUNT Class Destroyer" by T.B. Rose  in Vol 134, Number 3356  (Nov. 1968) ?

Or I'd be happy to buy the issue if someone has it, and no longer needs it.

Thanks!
I love it when a Plan B comes together!
Steve
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Offline tom osselton

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Re: Monotube Boiler
« Reply #37 on: July 11, 2014, 04:03:09 PM »
You will probably find this interesting it's one of Jay Leno's  steam cars telling a fair bit about the steam generator.


Offline vtsteam

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Re: Monotube Boiler
« Reply #38 on: July 11, 2014, 04:15:43 PM »
Hi Tom, I'll check that out tonight.

I got tired of waiting to do something on this today and just dug in. I wound a plain coil of the stainless tube on 3" dia. form. I was a little worried about kinking, but it bent fine.

I love it when a Plan B comes together!
Steve
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Offline tom osselton

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Re: Monotube Boiler
« Reply #39 on: July 11, 2014, 04:34:33 PM »
Look good

Offline S. Heslop

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Re: Monotube Boiler
« Reply #40 on: July 11, 2014, 10:45:26 PM »
Great to see you're back at this! I was just reading the thread about a week ago since I was curious about monotube boilers, and thought you might've given it up. It does seem difficult to find any concrete information on them, or even boilers in general.

Offline vtsteam

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Re: Monotube Boiler
« Reply #41 on: July 12, 2014, 11:55:28 AM »
Thanks Simon. What I've got is probably too short (about 20 feet) for what I want to power, and the coil size seems big in diameter to me, but we'll pursue what we have here anyway and see where it takes us.

I didn't want to risk kinking by winding tighter, though maybe I might have been able to. What I will probably do to compensate is run a cylindrical baffle down the center of the coil to force the combustion products over the coils instead of taking a path of least resistance through the center.

I might space the coils out a little farther so I get more penetration between coils instead of the gas just running over them. There is something to be said for irregular coils rather than a nice neat cylinder like it is now, but it can look pretty crude that way. We'll see -- might end up as spaghetti just to find out what happens after testing it "neat" and cylindrical. But it's easier to go in that direction rather than the opposite: start with a rats nest and end with a neat coil.
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Monotube Boiler
« Reply #42 on: July 12, 2014, 12:11:06 PM »
Could you lay it out like they do for ground source heat pumps. Essentially your neat coil pushed over sideways so you have overlapping loops looking like the swirls left by a vertical milling tool. Apparently it maximises the surface contact which is a similar need to your boiler.
Andrew Mawson
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Offline S. Heslop

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Re: Monotube Boiler
« Reply #43 on: July 12, 2014, 03:24:34 PM »
Thanks Simon. What I've got is probably too short (about 20 feet) for what I want to power, and the coil size seems big in diameter to me, but we'll pursue what we have here anyway and see where it takes us.

I didn't want to risk kinking by winding tighter, though maybe I might have been able to. What I will probably do to compensate is run a cylindrical baffle down the center of the coil to force the combustion products over the coils instead of taking a path of least resistance through the center.

I might space the coils out a little farther so I get more penetration between coils instead of the gas just running over them. There is something to be said for irregular coils rather than a nice neat cylinder like it is now, but it can look pretty crude that way. We'll see -- might end up as spaghetti just to find out what happens after testing it "neat" and cylindrical. But it's easier to go in that direction rather than the opposite: start with a rats nest and end with a neat coil.

Could you wind them tighter by packing them with sand and plugging the ends, or maybe even something like a wax you could melt out later?

Offline tom osselton

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Re: Monotube Boiler
« Reply #44 on: July 12, 2014, 03:48:54 PM »
I remember dad telling us about bending pipe filled with rosin so they would not kink.

Offline awemawson

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Re: Monotube Boiler
« Reply #45 on: July 12, 2014, 04:02:57 PM »
"Cerrobend" is the bees knees for pipe bending. An alloy of (I think) bismuth that melts at about 70 centigrade. Melt in a water bath, pour in, bend, melt out in a water bath.

http://www.csalloys.com/products-cerrobend-alloy.html
Andrew Mawson
East Sussex

Offline tom osselton

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Re: Monotube Boiler
« Reply #46 on: July 12, 2014, 04:06:39 PM »
I was thinking of that too but haven't played with any yet.

Offline tom osselton

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Re: Monotube Boiler
« Reply #47 on: July 22, 2014, 08:12:18 PM »
I thought you might find this interesting (at the bottom of the page)

http://photos1.blogger.com/img/252/5340/640/DSCN0185.jpg

http://steamprojects.blogspot.ca/

Offline vtsteam

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Re: Monotube Boiler
« Reply #48 on: July 22, 2014, 09:45:37 PM »
Thanks Tom. Not a monotube boiler but a vertical water tube boiler with external coils. Funny thing is the PM model boiler I'm making now in the other thread is a very simple horizontal version of the same thing.

For occasional use like my model version, copper water tubes are usable. And in this specific case they are easily replaced since they are attached by screw fittings. But I do wonder how long lived they will be in a full sized marine boiler, due to oxidation. I think It will be important to control and reduce excess combustion air for the tubes to last well.
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Monotube Boiler
« Reply #49 on: August 05, 2014, 08:35:41 PM »
So, returning here from the PM boiler experiment in another thread and having done it's first steam this afternoon , an interesting thing I saw today was that the copper coil under the main boiler barrel was glowing cherry red.

How is that possible I'm wondering, if the barrel is full of water and the steam pressure is less than 20 PSI?

Does that mean that there is no water in the coil (where it was red hot), just steam?

I wish I had noticed how much of the coil was red, but I didn't.

Is it completely empty of water, or is water crculating and being converted along its length into steam before reaching the red section? And would this mean it is acting like a separate monotube connected to the main boiler barrel?

Is water traveling through the coil or just vapor locked out of it?

Questions, questions....
I love it when a Plan B comes together!
Steve
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