02 concentrators for non medical use can be obtained from jewerly supply companies without a prescription. Medical use ones max out at 4-5 Liter per minute… the stream can be discontinous as pointed out by royjohn… The medical ones cost a lot more… buy one that is non medical… saves a lot of money versus bottled oxygen… disposable 02 canisters are a rip off… takes 40 canisters to burn one of propane…high pressure (2200 psi) 02 bottles are expensive to buy but not too expensive to refill… one that is 80 or 120 cubic feet capacity will last a long time even if using for melting and casting. for soldering, a refill won’t be necessary for months… I have an 80 cubic foot oxygen bottle and an acetylene bottle that I’ve used for melting and pouring ingots… the temperature is very high and makes melting quick and easy… I also have a torches for cutting steel and welding… steel cutting uses up oxygen quickly…welding steel works better with an electric arc welder… I have a light duty MIG welder… used both to make heavy duty wind chimes that can take the ferocious winds that blow across western SD and WY… Both have two stage regulators… by adjusting the first and second stage pressures, propane can be used in lieu of acetylene and will work for any non ferrous metal applications…Bought the set ups ages ago and still have them… most of the work that i have done used only a cheap hardware store propane air torch…bernzomatic was adequate… they don’t concentrate the heat at all, so doing soldering is a challenge…especially with soft, medium and hard solders when building up staged pieces… still adequate but takes an acquired skill…
I know this is going off topic but to recap, if I did it over again, I’d go for an oxygen concentrator with a high enough output - 6 to 10 liters per minute… after the initial cost of a machine, oxygen is essentially for free… the way these things work is that there’s a synthetic zeolite that absorbs nitrogen from the air, leaving oxygen to flow thru… regeneration means flushing with air to wash out the absorbed nitrogen… it’s rather remarkable that it works at all since air is about 80% nitrogen. The approximate number of cycles that a concentrator runs before the absorbant becomes degraded and has to be replaced is 300…is 100 to 300 USD depending on the model.
unless output pressures and volumes are exactly matched, I doubt that it would work well…this question is for the manufacturer… 5L/min should be adequate for most applications including melting if using acetylene…takes less molecules of oxygen to burn a molecule of acetylene than to burn propane. Air propane torches generate 3,600 degrees F, which is why I’ve used cheap hardward store air propane torches with disposible canisters for most work… hot enough to melt, but slow…allowing for more oxidation…also not tunable for reducing and oxidzing flames… all are set for maximum temperature, which is oxidizing.
good deal! congrants… acetylene is more expensive and burns much hotter than propane… should know that molecule per molecule, acetylene uses much less oxygen to burn than propane…buring one molecule of acetylene takes 3 of 02, propane burns 10… since the oxygen is essentially free air oxygen, the cost lies in the acetylene.
02 concentrators work best at sea level… they stop working at 10K feet elevation… unless designed for high altitude, even at that, the 02 delivered drops to 86% or less… standard 02 concentrators work fine at 3000 feet or below… if you live out west, where elevations are 5000 to 7000 feet, optimal results won’t be obtainable… the other caveat is has already been mentioned by royjohn…medical devices often are designed to pulse the flow of oxygen on inhalation… they don’t provide a continuous stream… People should not buy a medical pulsed concentrator… costs a lot more and won’t do the job of producing a continuous stream.
Mine is a medical one and it works fine. The oxygen is a continuous stream. I put a bottle thing in it so maybe it accumulates the blood oxygen and releases it smoothly.
some of them are continuous flow medical devices. usual maximum output on continuous flow is 4-5l liters per minute for cheaper portable and stationary home machines…usual rate of maximum flow for patients is 4 liter per minute. There also are after market compressors that can store 02 in bottles for portable medical use. The machine or compressor has to be compatible.
To clarify what I said about pulsed concentrators…I have a 5 l/min roll around concentrator like many of you. Yes, they also come in 10 l/min models. They are continuous flow 02, more or less. The pulsed ones I referred to in a prior post are the small portables run on a battery and I don’t think they would work well for our purposes. The 5 l/min ones we’re talking about are not portable, they plug into a 110V household outlet. I don’t see why two 5 l/min concentrators wouldn’t work if ganged together, if they outputted the same pressure…like two identical models…you’d have to consult the manufacturer’s data sheets. Simpler to buy one 10 l/min model, which would be more expensive than one 5 l/min, but a lot cheaper than two of the latter. -royjohn
agree… manufacturer’s specs. Stationary 02 concentrators for medical and non medical uses put out 10 liters…one should not buy medical grade as they are always more expensive.
royjohn…You are asking a question that I have asked myself. Will two, 5 lpm concentrators connected in parallel provide more, or at least the same amount of O2, as one 10 lpm concentrator? I don’t know the answer. I am sure that it is tied up in flow rates, pressures and tubing sizes. I had a 10 lpm machine years ago and I didn’t find a big difference between a 5 and a 10 lpm machine. There are times when I would like a bit more O2, especially when I am doing a melt. My solution is to either use my electromelt furnace or bring in a regulated O2 cylinder that I keep in the shed and connect it in place of the concentrator just for a melt. Don’t worry, I have all the necessary backflash and check valves in place. We seem to be beating this 5 vs 10 lpm distinction to death. I have been more than happy with my 5 lpm concentrators with the exception of when I am doing melts. The 5 lpm machine will support a 2 ounce melt, but it takes time. Being impatient sometimes, and having the ability to do so, I accelerate the process with and electromelt or O2 cylinder. In my experience, a 5 lpm concentrator will do most, if not all, that I ask it to do. We seem to be inclined lately to go off into very theoretical discussions on many subjects and, as a Physics teacher, I can appreciate them, however, as an artist, I am just looking for what will work for me so that I can get on with making my art. My 1lb. propane camp stove cylinder/5 lpm concentrator setup does it for me and I really don’t need to know why…Rob
Hi Rob,
Thanks for that reminder to not make the perfect the enemy of the good. While we are on this subject, another related question. I also have an electromelt furnace…not the older Kerr type that lets you just pickup the furnace like a coffee pot and pour, but the newer Chinese type where you lift the graphite crucible with tongs out of the furnace. I wonder whether it is necessary to play a torch over the metal as you pour, or whether the reducing atmosphere created by the graphite crucible is good enough to prevent oxidizing, fire scale, porosity, etc. Thanks for any insight you or others can give. -royjohn
A couple of years ago, I stumbled upon a website for glassblowers and some were using exactly that – connecting oxy cons in parallel. If you’re interested, try “Googling” something like “oxy concentrators for glassblowing”. Not sure how I found it way back when, but I would love to hear what you find.
royjohn…I play the flame over the pour regardless of what type of crucible or mold I am using. Just habit, I don’t know if it makes a difference or not…Rob
My oxy concentrator has a bottle that connects to the output valve to normalize pressure. I could easily imagine two inputs finning into it with one output. Should be easy.
how often do you need to melt and pour ingots, or are you doing it regularly with casting?
one ingot and a one rod goes a long way when rolled into sheet and wire…
I used oxyacetylene for melting because I had the equipment for welding and cutting steel… otherwise propane air sufficed for fabrication…
I also don’t see why not two 5L/min 02 concentrators in parallel so long as the output pressures and volumes are calibrated to match…unless they go against manufacturer’s recommendations…high flow out of one concentrator will require more frequent regeneration for it than the other… don’t know whether back pressure against the other will cause it to malfunction…one solution to melting could be to use a hardware store cheap propane/air disposible canister torch to bring the metal to incipient melting, then switch to gas/oxygen to bring it to a complete melt…if your campstove propane with supplemental oxygen does the job, then there’s no problem.
A common propane/air flame burns at about 2,250 K (1,980 °C; 3,590 °F), a propane/oxygen flame burns at about 2,526 K (2,253 °C; 4,087 °F) , an oxyhydrogen flame burns at 3,073 K (2,800 °C; 5,072 °F) and an acetylene/oxygen flame burns at about 3,773 K (3,500 °C; 6,332 °F)
Temperature of combustion is not where the problem lies, it’s with heat output… Heat output depends on flow rates of fuel and oxygen… A weed burner using air/propane would do but is overkill…