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Old 06-05-2008, 11:32 PM   #1
rangerssteamtoys
 
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Default Medium sized monotube boiler

Since I have my gas steam engine. I need to make a boiler for it, I'm going with a monotube boiler made from 2 coils of 60' 1/2" copper tubing. The outer shell for this will be a small air compressor tank. I need some advice on what to do.





Here is what I need help on.

A feedwater pump, this boiler will be mobile so it cant be a water hose. I was thinking a hand pump converted to mechanical by attaching an eccentric.

A burner, I cant use propane but oil, wood, and any other suggestions are welcome.

I'm not a machinist, and I will need some parts made. Volunteers and any help would be appreciated.

I want to get about 120-150 psi with this setup. So can any one help me?Please mam/sir



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Old 06-06-2008, 12:00 AM   #2
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Default Re: Medium sized monotube boiler

Home made boilers scare the **** out of me...

I know that hundreds have been built to be perfectly safe and operate flawlessly.
Steam powered an entire era of manufacturing and mining in this country.
Many lives were lost to structural boiler failures in those days.

I've seen insurance photos of the aftermath of tiny 8 ounce toy boiler explosions.
Mangled fingers and disfigured faces caused by a pressure relief valve that had
corroded shut from the heat of moisture of the steam.
It was just a toy!

A boiler is a controlled bomb.
It's real easy to lose that control without knowing it has been lost.

Let's be CAREFUL out there!

OK I'll kick my soap box back under the sofa now...

Rick




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Old 06-06-2008, 12:07 AM   #3
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Default Re: Medium sized monotube boiler

Safey is a BIG thing. Thats why I chose a monotube boiler, instead of a traditional firetube boiler. If the copper pipe fails just a little steam flies everywhere. It beats the heck out of a giant 100-200lb boiler sending shrapnel.

My dad wont let me use a propane burner because it no safe enough. I think that too, the thought of a propane cylinder blowing up scares me.

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Old 06-08-2008, 07:12 PM   #4
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Default Re: Medium sized monotube boiler

PROGRESS!!!!!

I have got alot done with the shell, heres what I did so far today.

Finished grinding welds off boiler
Painted it black
Ground off the bottom cap
Pressure washed the inside of the boiler, lots of oil and metal gunk
Cut a hole for the chimney, Rough at first.
Smoothed out the hole
Mounted chimney w/ screws,
Painted the chimney
Took it outside for a cleaning test. More on cleaning test after pics

Its ALOT brighter in real life than in the pics, but self adjusting camera doesnt do it any good.







Rough cut hole with a grinder.




Smoothed out hole with air dremel




Simple metal drier pipe for chimney.


Put it on a rolling stand to take it outside, I'm lazy I dont want to carry it that far.


Me standing beside the boiler for size comparasion. I'm about 5' 5"


Took it outside and put it on a brick firebox


Looking down the chimney at the hole, I made the hole small so if I wanted I could make it bigger.


Thrown together brick firebox

I will get a fire going later. This is just the outer shell of the boiler, no copper tubing put in yet. I want to burn off all the oil and nasty crud that I didnt get with the pressure washer. Fire pics will be in a few hours,after it cools down a bit.

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Old 06-08-2008, 09:09 PM   #5
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Default Re: Medium sized monotube boiler

Ranger,
I just read this for the first time.

Steam is very different than air.

As Rick said...

THIS IS EXTREMELY DANGEROUS!!!!

120-150 PSI of steam is nothing to mess with! Steam at this pressure has TREMENDOUSLY MORE energy than air. Remember, this water will be over 350 degrees and will cause severe burns instantly! Not to mention the injury caused by shrapnel. In the event of some kind of material failure you will not only have hot, live steam spraying all over the place, but could also spray burning oil/wood/coal whatever for quite some distance.

If your plumbing develops even a pin hole the escaping steam has enough energy to cut through skin in an instant. If the steam is superheated you won't be able to see it so as to avoid it. The steam won't condense into a cloud until some distance from the hole. Believe it or not, steam is also quite abrasive. It will wear channels in your plumbing, weakening it to the point it will have a catastrophic failure.

[b] PLEASE, FOR YOUR SAFETY, RECONSIDER THIS VENTURE!! STEAM AT ANY PRESSURE IS NOT A TOY![b/]

Something to consider: Those boilers of old, in steamship and mine accidents, were "only" running 75-100 pounds of pressure! Catastrophic failure was often below 200 PSI. It wasn't until the very late 1800's that they got over 200 PSI and that was considered high pressure.

On the ship I sailed boiler pressure was 450 PSI. The only equipment that used that working pressure was the main and auxiliary turbines. All other steam engines used less than 75 PSI, and the eductors used 20-25 PSI.

The pressures you are considering are much too high for a hobbyist to be working with.

Ranger, please understand I'm not trying to be an old fuss-bucket and keep you from having fun. But I feel I have to warn you that this is entirely too dangerous and why.

By all means, build a smaller boiler with much lower pressure. 15 PSI is a good pressure to get some experience with. Build a small engine, run it on air, make it do some work. Then run it on steam doing the same, or more, work. Learn the difference between saturated and superheated steam.

Ok, now I'm off the soapbox.

Good luck, and keep us up to date on what you are doing.


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Old 06-08-2008, 09:31 PM   #6
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Default Re: Medium sized monotube boiler

I KNOW THIS IS DANGEROUS

Steam hobby alone is dangerous, I have felt the results before. A monotube boiler is the safest boiler I could find. If the tubing fails, steam and water stays inside the outer shell and doesnt effect me. If it fails in the plumbing going to the engine, the pipes will be insulted and NO WHERE NEAR ME. I will hear the leak and turn on a valve that puts water directly on the fire, putting the fire out. I have about 80% of this figured out. enigne, copper tubing, fire, pulmbing. The only one I havent figured out yet is a water pump, thats why i have a question and the Q and A section.

If you think about a fire tube boiler, well it could send shrapnel no matter what i try to hold it with.
Look here http://www.mikebrownsolutions.com/stmpwr.htm

ANY WAYS
I lit a fire underneath the boiler to clean out the insides of the shell. This still doesnt have coper tubing in it yet, just cleaning the boiler, to get any rust or things like that off.






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Old 06-08-2008, 09:34 PM   #7
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Default Re: Medium sized monotube boiler

Kevin
I think we got to him enough to put him off a pressure vessel type boiler. He's going with a tube type flash boiler which is at least a little less danger of explosions. From the outer shell he's posted above, it appears he's thinking something along the lines of the old Doble automobile boiler.

If I thought he was working on this,unsupervised, I'd be for tracking his dad down for a brief but serious discussion. I strongly suspect Dad has been watching over the project. If he hasn't been, then Ranger needs to drag him into it at least enough to insure he isn't going to get hurt or blow up the garages.

I've watched Ranger for a quite while now. He's not afraid to ask questions and it seems he listens when it's important. His "childhood" is something to envy. He's had the freedom to explore his ideas, the leeway to make a few mistakes and parental support for his efforts that I'd have killed for at his age. He's probably as close to living a Huck Finn experience as any kid I've encountered in years.

If he ever gets his hands on proper tools he'll be really entertaining to watch....LOL He's just about learned all the hard ways to get things done and he's still just 14.

Hang in there Ranger, but proceed with due caution and ask for advice when there is even the slightest doubt about safety or proper methods.

Steve

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Old 06-08-2008, 09:43 PM   #8
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Default Re: Medium sized monotube boiler

Quote:
Originally Posted by Cedge
it appears he's thinking something along the lines of the old Doble automobile boiler.

If I thought he was working on this,unsupervised, I'd be for tracking his dad down for a brief but serious discussion. I strongly suspect Dad has been watching over the project. If he hasn't been, then Ranger needs to drag him into it at least enough to insure he isn't going to get hurt or blow up the garages.

Hang in there Ranger, but proceed with due caution and ask for advice when there is even the slightest doubt about safety or proper methods.

Steve

I am thinking of a doble steam boiler, look here http://www.jaylenosgarage.com/video/video_player.shtml?vid=213453
And yes my dad watch over me closely, infact without him, I would not have copper tubing or the outer shell. I have been asking for advice, but only one person has answered my question under the Q and A section.

I cant figure out a water pump to use, or why steam doesnt siphon water through the tubes. If steam is leaving a tube shouldn't it be drawing water in? I know that water wont siphon into the tubes but my dad doesnt, he needs PROOF that it wont.
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Old 06-08-2008, 10:20 PM   #9
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Default Re: Medium sized monotube boiler

Steve,
Thank you for the reassurance. I don't want to discourage his exploration, but I don't want to see him get into any trouble either. And thank you for supervising and encouraging his work.


Quote:
Originally Posted by rangerssteamtoys
I am thinking of a doble steam boiler, look here http://www.jaylenosgarage.com/video/video_player.shtml?vid=213453
And yes my dad watch over me closely, infact without him, I would not have copper tubing or the outer shell. I have been asking for advice, but only one person has answered my question under the Q and A section.

I cant figure out a water pump to use, or why steam doesnt siphon water through the tubes. If steam is leaving a tube shouldn't it be drawing water in? I know that water wont siphon into the tubes but my dad doesnt, he needs PROOF that it wont.
Ranger,
Simple physics, high pressure always flows to low pressure. Water won't syphon back in because the steam is always expanding until it runs out of water to turn into steam. That's also why it is so dangerous. The pressure of the steam will always push the water back until and unless the pressure of the water is greater than the pressure of the steam. That is why you need a check valve on the inlet side.

Now, consider if you had a container of water higher than the boiler. The water has weight, it pushes down. If you ran a tube from the container to the boiler inlet, that tube will have a certain amount of pressure at the inlet. It's called head pressure. Head is the distance the water has to fall. The more water above it and the farther is has to fall the more pressure it has. Head pressure is the weight of the water in a water column, the tube, often referred to as so many feet of head. The volume of water in the container is not important, it's the height that is important. There is a formula for calculating the head in a water column that escapes me at the moment, you could probably google it. This will tell you how high to put the container to reach the pressure that you need to overcome the steam pressure and feed water to your boiler. If you find that the height required is too much, say 30 feet or something, look for a pump that has 30 feet of head (yes, they are rated that way). I would suggest using a centrifugal pump. You would want to regulate when and how much water is fed to the boiler, a positive displacement pump will be damaged or cause damage if the flow is stopped. A centrifugal pump will just spin in the water, it won't like it much, but it will survive.

One consideration is making a piston steam engine and powering a piston pump for your feed water. That's what we used on the ship as a backup. The main feed pump was a steam turbine powering a centrifugal pump. If you use a positive displacement pump such as a piston or diaphram pump, put a return line on the pressure side. It would also be a good idea to have a return line on a centrifugal pump. Put a valve on the return line to regulate the pressure.

Hope this answers your question. If not, keep asking. We'll get there eventually.

Good luck.
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Old 06-08-2008, 10:43 PM   #10
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Default Re: Medium sized monotube boiler

Thank you Kevin, Finally an answer that can help. A gravity fed system to fill the boiler, that could work. This is the kind of help I need.

This is my idea, a mechanical feed pump that is also hand operated. A simple stephensons link to switch from mechanical or hand pump. My idea is a small pump like this one http://www.tinypower.com/store2.php?crn=57&rn=276&action=show_detail
I get an eccentric to make it work off the engine and in between the eccentric is the stephensons link. For the first few minutes I have to hand pump after I get about 50 psi I can start the engine. 50 psi is the optimal starting pressure for the engine I have. I switch to mechanical and let the engine fill the boiler, a valve will control the water input.

Now another question, about the copper tubing itself. How much pressure will 100' of 5/8" OD 1/2" ID copper water tubing hold?
What is copper water tubing? Is it any good?



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