Medium sized monotube boiler

Discussion in 'A Work In Progress' started by rangerssteamtoys, Jun 6, 2008.

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  1. Jun 6, 2008 #1

    rangerssteamtoys

    rangerssteamtoys

    rangerssteamtoys

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    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.

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    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
     
  2. Jun 6, 2008 #2

    rake60

    rake60

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    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


     
  3. Jun 6, 2008 #3

    rangerssteamtoys

    rangerssteamtoys

    rangerssteamtoys

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    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.
     
  4. Jun 8, 2008 #4

    rangerssteamtoys

    rangerssteamtoys

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    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.
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    Rough cut hole with a grinder.

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    Smoothed out hole with air dremel

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    Simple metal drier pipe for chimney.

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

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

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    Took it outside and put it on a brick firebox

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

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    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.
     
  5. Jun 8, 2008 #5

    ksouers

    ksouers

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    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.

    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.


     
  6. Jun 8, 2008 #6

    rangerssteamtoys

    rangerssteamtoys

    rangerssteamtoys

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    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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  7. Jun 8, 2008 #7

    Cedge

    Cedge

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    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

     
  8. Jun 8, 2008 #8

    rangerssteamtoys

    rangerssteamtoys

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    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.
     
  9. Jun 8, 2008 #9

    ksouers

    ksouers

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    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.


    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.
     
  10. Jun 8, 2008 #10

    rangerssteamtoys

    rangerssteamtoys

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    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?
     
  11. Jun 8, 2008 #11

    tel

    tel

    tel

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    You should be OK with the copper pipe at 120 - 150 psi, which is, after all, a pretty moderate pressure for a mono-tube. The trick is going to be limiting the pressure to that. You are going to need some sort of relief valve (safety valve) toward the delivery end of the system for WHEN (not if) the pressure tries to go above that. I would suggest some sort of manifold at the delivery end, incorporating at least two safety valves and two or three delivery valves.

    You are on the right track with the feed pump, but again, you should consider a second pump in the system in case of failure. All my (fire tube) boilers have both and engine driven and a hand pump. One consideration would be simply to keep your hand pump seperate from the engine driven one. Start on the hand pump and then switch over.
     
  12. Jun 9, 2008 #12

    rangerssteamtoys

    rangerssteamtoys

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    I will have an air compressor saftey valve set at about 160 psi. I want 150 psi max, so i will have the saftey set higher than that. Any ideas of the volume of steam from this boiler? I need alot of volume the engine I have is a air eater so I assume it will be a steam eater as well.
     
  13. Jun 9, 2008 #13

    mklotz

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    The formula is P=rho*h/144, where:

    P = pressure (psi)
    rho = density of water (62.38 lb/ft^3)
    h = head height (ft)
    144 = conversion from ft^2 to in^2

    A one foot head of water exerts a pressure of 0.433 psi. A 2.309 feet head of water exerts a pressure of one psi.
     
  14. Jun 9, 2008 #14

    rangerssteamtoys

    rangerssteamtoys

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    So 2.309X160=369.44 feet to over come 160 psi. WOW thats a pretty tall steam buggy. Can it fit in the garage?
     
  15. Jun 9, 2008 #15

    Bernd

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    Ranger,

    Quite a few have given you go answers to getting water into a boiler. On a model steam locomotive, and the prototype steam engines, there are three ways of accomplishing getting water into the boiler. 1. - hand pump, 2. - axle pump, 3. - steam injector. The first two are easy to understand and are used exclusively on models. The third is used on the real thing. The third is a bit harder to explain or understand. I suggest that if you are interested in steam power you study how steam locomotives and model steam locomotives are built and work.

    Here's a web site that you might find interesting, http://www.nelsonslocomotive.com/Shay/shay.htm. Scroll down to the "plumbing" section and check out his hand pump and axle pump. Also some where in there you'll probably find how to plumb up the hand pump and axle pump.

    Hope this is helpful to you. May I also suggest getting some books on this subject. Not everything can be found on the internet. ;)

    Regards,
    Bernd
     
  16. Jun 9, 2008 #16

    chuck foster

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    ranger..........i have a very limited knowledge about steam boilers and engines.
    one thing you mentioned is that your engine runs on about 50 psi. i think with the expansive force of steam you might be able to run the engine on a lower pressure.

    also do you have drains fitted to the engine cylinder?
    if you dont you might have problems with water in the cylinder. after you are done running the engine on steam and it cools down the steam will condense into water and the next time you apply steam or air the water in the cylinder might cause the engine to not turn over or blow the head off.
    i think what im referring to is hydraulicking ( guys......am i right??? ??? )

    with all that said i think you are doing a great job and i wish you all the luck in the world, you are proving to be one very smart young man and i look forward to more of your postings. 8)

    be safe and have fun ;D

    chuck
     
  17. Jun 9, 2008 #17

    rangerssteamtoys

    rangerssteamtoys

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    Yes thanks for reminding me about the water building up in the cylinder, I need to figure out how to drain water from the cylinder. Maybe a running it on air after every steam useage would get the water out? I'm using my converted gas engine, so I dont think there will be a way to connect a drain because the engine is vertical and single action. Only way to drain water out is to drilll a hole in the cylinder wall creating a uniflow exhaust.
     
  18. Jun 9, 2008 #18

    rangerssteamtoys

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    Thanks for the link, I believe that I can convert a hand pump to mechanical. All I need is an eccentric and a stephensons link, where to get one of those?
     
  19. Jun 9, 2008 #19

    ksouers

    ksouers

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    Ranger,
    Marv gave you the formula I was talking about earlier, to calc head.
    Chuck makes a very good point about the expansion of steam. That is what makes steam work. It is also the danger. One gallon of water at 350 degrees will expand into A LOT of steam. You probably won't need as much pressure as you think, there is A LOT of energy pent up in just a little bit of water.

    A couple things to consider:
    You probably won't need to pump water by hand. No water will be flowing while the boiler is warming up. Have some water in the tube during warm-up with all valves closed except the feed water return, when you start getting some pressure, maybe 20 PSI, crack the main stop valve (that's the valve between the boiler and your engine) and let the engine start running. When the engine starts running, open the stop valve fully, remember to crank it back towards closed about a quarter turn. Also remember it will be hot, wear gloves. You should have water circulating through the return line with the return valve fully open. As you start running out of steam and the engine starts slowing down, start closing down the return valve to increase pressure at the check valve/water inlet, but don't fully close it. Leave some running to keep from damaging the pump and linkage.

    You will probably find that your engine runs quite well on a lot less than 150 PSI.

    As for a drain on the engine: This is a converted Briggs & Stratton, right? Does it still have the spark plug hole? You could put a drain cock on that.

     
  20. Jun 9, 2008 #20

    rangerssteamtoys

    rangerssteamtoys

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    I really appreciate your help Kevin. Will the spark plug hole act as a drain? Since its a vertical engine I dont think water will drip out. I may want to go with a single uniflow exhaust hole, it will not be for exhust but simply drain water.

    Ok, now I just have about everything covered on the boiler, now for fire. I want to run on a gravity fed oil system, but any other suggestions will help. No Propane.
     

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