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Hello, Can I use aluminun for a boiler. I would appresaite any advice. Thanks. Tom
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steam boiler
- Thread starter tom arnold
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Some people do it successfully, so I don't see why not, provided it is the proper alloy and configuration. I wouldn't recommend any standard welded tubing. Machining out of solid would be preferable, but seamless tubing would be better than welded pipe. As a side note, I'd recommend very clean water. Store bought distilled water contains no contaminates that would lead to corrosion or at least scale buildup, a number one enemy of heat transfer. Or at least high quality bottled water, as most of it is filtered (some to RO standards) and is better than tap water which contains minerals and chlorine, and who knows what else.
I have a Barlow's Formula calculator that I can post which can help determine the best wall thickness for safety's sake. Let me know if you want a copy. It's my software, so I can give it away if I want. It's useful for determining hoop stress, etc. I used it when I was designing pressure vessels for RO systems using up to 1200 PSI. Never failed me.
I have a Barlow's Formula calculator that I can post which can help determine the best wall thickness for safety's sake. Let me know if you want a copy. It's my software, so I can give it away if I want. It's useful for determining hoop stress, etc. I used it when I was designing pressure vessels for RO systems using up to 1200 PSI. Never failed me.
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If you decide to undertake building a pressure vessel I would recomend a good read of the info in a recognized publication as a prelude. Steam does some funny stuff to metals and so does pressure. I would make absolutely sure that your material meets or exceeds the minimum safe thickness and tensile strength requirements. You do not want a boiler partially full of hot water and steam to burst and release all of it in your vicinity ever. Not to discourage in any way, just to introduce a little caution is my point. So be carefull and have fun. And dont forget the pics of your progress as you go too...
Bob
Bob
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- Nov 13, 2012
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- 165
I guess I have never seen an aluminum boiler, but there well may be some out there.
One concern would be that aluminum is a pretty active metal. Water at high temperatures can become quite corrosive, especially if it was distilled or RO water to start with. If you really want to use aluminum, some water treatment might be in order. I'm not sure which alloy would be good to use - it has to form well, have the hot strength and stand up to low pH water.
Most model sized boilers I have seen were made from copper, brass, or steel.
I have to also repeat Bob and Tony's disclaimer on safety. A ruptured boiler, even a small one, is a real scalding hazard to anyone nearby, not to mention the shrapnel danger. Find a design that has been proven. Unless you are an expert at ASME Section I, (fired pressure vessel code), this may not make a good experimental design exercise.
You did not indicate what type of boiler design you were looking at: simple tank, fire tube boiler, fire box boiler, etc. Some designs are a lot harder to make than others. You have to decide if the construction will be welded, brazed, riveted or whatever.
A few basic boiler design concepts:
1) No metal can withstand flame impingement and hold its strength. Flame and high temp combustion gases can only be allowed to touch metal that has water on the other side.
2) Metals loose strength as the temperature goes up. The temperature of boiling water is a function of its pressure. Higher pressures mean higher temperatures. For reference, 15 psig steam is 250 deg F. 55 psig steam is 300 deg F. You have to use the metal properties at the highest temp (and pressure) that you expect to operate. For model boilers running at 50 psig or less, this is usually not a problem, but needs to be considered.
3) The weak point on boilers often occurs where the head meets the cylinder portion of the vessel. Remember that the metal in the cylinder portion is being stressed in longitudinal direction as well as the hoop direction. Heads need to be dished or otherwise designed to withstand pressure. The forefathers used flat heads with internal bracing and stays, but I wouldn't recommend that. Use a dished head design.
I don't want to scare you off, but go into this in a safe way.
Terry S.
One concern would be that aluminum is a pretty active metal. Water at high temperatures can become quite corrosive, especially if it was distilled or RO water to start with. If you really want to use aluminum, some water treatment might be in order. I'm not sure which alloy would be good to use - it has to form well, have the hot strength and stand up to low pH water.
Most model sized boilers I have seen were made from copper, brass, or steel.
I have to also repeat Bob and Tony's disclaimer on safety. A ruptured boiler, even a small one, is a real scalding hazard to anyone nearby, not to mention the shrapnel danger. Find a design that has been proven. Unless you are an expert at ASME Section I, (fired pressure vessel code), this may not make a good experimental design exercise.
You did not indicate what type of boiler design you were looking at: simple tank, fire tube boiler, fire box boiler, etc. Some designs are a lot harder to make than others. You have to decide if the construction will be welded, brazed, riveted or whatever.
A few basic boiler design concepts:
1) No metal can withstand flame impingement and hold its strength. Flame and high temp combustion gases can only be allowed to touch metal that has water on the other side.
2) Metals loose strength as the temperature goes up. The temperature of boiling water is a function of its pressure. Higher pressures mean higher temperatures. For reference, 15 psig steam is 250 deg F. 55 psig steam is 300 deg F. You have to use the metal properties at the highest temp (and pressure) that you expect to operate. For model boilers running at 50 psig or less, this is usually not a problem, but needs to be considered.
3) The weak point on boilers often occurs where the head meets the cylinder portion of the vessel. Remember that the metal in the cylinder portion is being stressed in longitudinal direction as well as the hoop direction. Heads need to be dished or otherwise designed to withstand pressure. The forefathers used flat heads with internal bracing and stays, but I wouldn't recommend that. Use a dished head design.
I don't want to scare you off, but go into this in a safe way.
Terry S.
- Joined
- Jan 22, 2011
- Messages
- 8,031
You could find a med gas O2 bottle out of date and make your boiler out of it, if that's the style boiler you wanted. I have one, and it's pretty heavy walled.
Hello Tom,
Where to start . . .
My initial inclination, as it would be from 98% of the world's informed and safety-conscious model engineers and live steamers, would be to say this is without a doubt, for many reasons, one of the worst ideas we'd have heard of, but that response wouldn't inform or educate you or benefit other readers. I agree with most of the suggestions and cautions posted already but probably none of them are experienced model boiler builders or they would have said absolutely Not! (or words to that effect.) Another consideration is this, our personal resources vary considerably and very often our notion of the "right" way to do a thing (like build a boiler) is determined by whatever happens to be in the metals pile, the scrap bin, or is cheap to come by. None of us want to spend money unnecessarily but more so than any other area of model engineering, but "cheap" is the single most inappropriate reason for selecting a material for any boiler.
My suggestion, as someone has already posted, is to read all the information you can get your hands on about MODEL boilers and come to your own conclusion. Use "model" in your search, rather than "miniature" boilers, because there are "miniature" boilers which are also a category industrial boilers covered by the US ASME boiler code. These are not what we build, and in many States their ASME-based codes do not apply until you reach a certain size and capacity, so your search for information may be side-tracked by that terminology. What you will find, when you go back through 100+ years of model boiler making technology is that no aluminum boilers were reported built, and if they were built none survive to be written about. Copper yes, steel yes, stainless steel maybe (the argument still goes on), but aluminum no. The almost universally preferred material for small boilers, and I would define "small" as anything with a barrel or body of 4" or maybe 5" diameter or less, is silver-soldered copper. There is a message there for you.
Can you build and aluminum boiler? Of course you can, we can't control what you do in the privacy of your own garage, but the great fear of those of us who want the safety record of organized live steam to remain 100% world-wide is that an accident with your boiler will be seen on the nightly news or Youtube, and not in the good way.