m-15/ex-15 vs. dual concentrators?

[ruca]

i posted my question in the base tips & techniques area, too, but this is a more appropriate area for it. i got some answers to my original question which steered me in the right direction & helped me learn a lot more about oxycons in turn. thanks to the guys that helped me out for that. ;) but now after all that reading i'm kinda torn between two options, & some input would be very helpful as i've never used or even seen an oxycon being used (in a lampworking setting) in person. i want to make sure i'm processing all this info correctly.

so, i'm thinking about getting an oxycon for my national 3b with ht-1 tip (12 hole hush) for a multitude of reasons, mostly because a) it would help me save for the set up i want when we move into a house & b) it would be a lot easier for the time being than dealing with tanked oxy.

okay, so a m-15 runs (up to/at/whatever) 15psi & 8lpm & the tip i have wants 6psi & 8.5lpm. if i ran dual 5lpm machines & ran both of them to equal 8.5lpm (say one at 4 & one at 4.5, i don't really know if you can set it *that* accurately) would this actually be better -- wouldn't that .5lpm make a difference in flame quality? also, i remember reading that running dual machines at a lower lpm results in better purity, although i'm not sure if running it under by just 1 or .5 lpm will actually make any difference. i know no matter what its not going to have to purity of tanked oxy.

i'm also curious about what a ht-2 runs at & if either of these options would run it properly, since i'm more likely to go up a tip size before i upgrade my torch.

the cost of an m-15 vs. two m-5's isn't enough to sway my mind one way or another, i just want to attempt to make a smart decision.

thank you in advance. :D

[ArtcoInc]

When you set the flow rate on any oxycon, you open the oxygen valve on your torch all the way (with the torch not lit), and adjust the flow rate at the concentrator to whatever you want. When you have the torch lit and running, the actual flow rate will depend on how wide open you have the torch valves. When you have the torch throttled back, your flow rate will be less that what you set at the oxycons.

When you run 2 oxycons together, set them both to the same flow rate. The flow meters on these machines aren't really fine enough to worry about a half lpm here or there.

One 'rule of thumb' is, in order to keep the oxygen purity up, that you don't really want to run a concentrator more than 80% of it's rated output. This means that you should run a 5 lpm machine no higher than 4 lpm, and a 8 lpm machine no higher than 5.6 lpm.

The HT-1 tip wants 18 cfh (8.5 lpm), the HT-2 tip wants 22 cfh (10.4 lpm), and the HT-3 tip wants 25 cfh (11.8 lpm).

In your application, I would recommend using 2 of the M-15/EX-15 machines. Yes, I know it will cost more. But, this would be the only way to get the flow you need at a purity level you want, and give you a little room to grow.

Malcolm

[ruca]

hmm.. i guess i'm going to have to go back & do some math & see what will cost less until i set up how i want to set up.

thanks for the well thought out & helpful response. :D anymore input would still be helpful. i'm open to all sorts of suggestions.

[Trey Cornette]

Go with the M-15. That way when you grow out of the National torch you will have a concentrator you can work with. That higher pressure could come in handy if say you want to grow to a larger better quality torch.

[ruca]

i like your thinking, trey, especially when i do upgrade my torch i'm getting a phantom & a m-15 would power the lynx centerfire nicely (so i've read)

i wish i could swing two m-15s, but i'd probably go for a tornado before i went that route. i'm just worried the single m-15 won't have enough oomph, but the tornado seems like it'd be overkill. i guess i could also consider a holding tank for the m-15 to give me that extra push when i need it..

i'm not sure if at this point i'm confusing myself or getting oxygen-greedy.

[Mr. Smiley]

That's my suggestion too... Trey and I are both fans of the M-15... You can always ad another later and you'll have that extra PSI larger torches and boro like. ;)

[ruca]

all i work is boro, that's why i'm so worried about it. :(
but the m-15 has enough psi for the particular tip i use (since its recommended at 6 psi) & premix is gonna melt boro, anyway, so i guess i shouldn't sweat it. i think the lpm side of it is what i'm confused about.

ETA: i know what lpm is, i just don't understand how it effects flame chemistry, exactly. i guess.

[SharonP]

I have two EX-15's linked together (got em from Malcolm!) and they run both the centerfire and outerfire of my Bethlehem Starfire just fine.

*s*

[ArtcoInc]

ETA: i know what lpm is, i just don't understand how it effects flame chemistry, exactly. i guess.

lpm is the *volume* of oxygen flow. Your flame needs so many parts of gas to so many parts of oxygen. If you max out the available parts of oxygen, you max out the flame size *at the correct mixture*. You can always add more gas, but you will have a reducing flame.

When you read that Brand-X concentrator will run Brand-Y torch at Z%, it means that the concentrator can supply Z% of the oxygen needed for the *maximum* flame size. The National tips are all rated for their maximum flow. But, how often do we all run our torches at the maximum possible flame size? You can always run the torch at less than maximum. A single M-15/EX-15 will give you about 80-85% of the maximum possible flame out of a HT-1 tip. You can push it higher, but your oxygen purity will suffer.

And, you can always add a second M-15/EX-15 later.

Malcolm

[ruca]

thanks malcolm, this makes it a lot easier for me to understand exactly what i need & why. ;)

[Trey Cornette]

I run both a Barracuda and a Phantom Off of 2 M-20's. One at a time not both at the same time. I use an 11 gallon holding tank to smooth things out. Working on a new project to compress my O2 from the M-20's up to 100 psi into a 80 gallon holding tank. Then I will really be able to rage!!!

Another thing to consider is that the numbers put out by the torch makers may be accurate numbers for maximum flame but they don't mean as much at the bench. There are times when certain flame chemistry's are required to achieve a certain effect that may be off the charts of the torch builders specs. The numbers are just not applicable to real world applications. Yes they are good to know but don't live by them.