Well Deanna did a pretty good job of explaining our problems with our M20s on the other post. Basically we're on our 3rd unit in 3 months. Hopefully 3rd time will be the charm.
But I do have some more fundimental concerns with these units:
1. We've had the opportunity to work with a number of concentrators. They all have small pop out fuses to protect the units from heat, humidity, weird electrical current, etc. These units don't have this part. I'm wondering how much of the unit failures can be tracked to the lack of this pretty inexpensive part.
2. The numbers aren't matching up. This is ABR's discribtion:
http://www.dichroicimagery.com/produ...oducts_id=3297
The paperwork we got with the unit (3rd unit, the first two had NO paperwork) says: "Oxygen Concentration= 89+/- 4% @1-8
75+/- 4% @8-10
Operating pressure=16-20 Psig
75% seems really low to me on purity. If I would have known that I wouldn't have bought it. Sure, you can run a torch on that, but you have to turn the flame way down. What's the point in that?
3. These aren't really 10 lpm units. Again from the unit paperwork:
"NOTE: Running the unit at highter flow setting for extended periods may cause some flxuation in the flow." This is an understatement as the flame fluxuates from oxidation to reduction every 8 seconds. Makes it a little hard to work.
"If you need to run the flow at the highest setting, it is best lower the flow often to maintain higher levels of purity. For example, if you are using an M20 at a flow setting of 10, drop the flow back to 8 for a few minutes to allow the unit to build purity." The marble I made yesterday took 3 hours. I couldn't really back off the oxygen "often" durring that time.
I've been running ours at 7 1/2-8 with not much trouble, but I do need to keep the propane well down. I'm also scared to try 8-10 lpm as the last two units DIED at those settings. I also get what looks like fuming on my clear (yes, morretti clear) even at 8. It shows up then burns off as the glass reaches full melt. I'm not sure, but I suspect the lower ox. purity is causing this. Could be wrong on this one, but it is strange.
We're making it work. Jerry, Jack and Paul have all been very helpful. And I do see a serious need for a 10 lpm concentrator for under $1,000. But I'd have been much better off getting a second Devibillos (sp?). Our last one ran at 5 lpm at 10 psi for 6 years with no problems. Oh the pop out fuse popped out on occation (just let her cool down, pop it in and away ya go). But that machine was rock solid. Unfortunatly space and amps won't allow multiple consys at this time. Oh and we're using a barracuda torch. Deanna usually just uses the inner flame, I use both.
Peace,
Greg