Set up in D for life now

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Set up in D for life now

Postby Doug Coulter » Sat Aug 14, 2010 9:13 pm

Here's the sad but true tale on what it takes to get really serious about this fusor game.

We had to jump though a few regulatory hurdles, but we managed. I think we were probably raped fairly bad on the empty cylinder price (as it's about 5 or more times what I pay when I do this with welding gas on larger tanks, and the cylinder wasn't new, just newly hydro tested) but to be honest, the expensive regulator was a bargain according to some of my chemical engineer friends who buy this kind of thing for big outfits, and the gas really is research-grade pure -- I measure 99.999% on my own gear after anything bad I pollute it with (being careful not to, but contamination never goes out of things, only falls in, it seems). That is one less 9 than they claim -- decent. I can recommend that regulator (a two stage that goes to below atmosphere and has a leak tight shutoff valve on the output) as the best I've ever touched in a long life -- and I have a shop full of good ones, but nothing else even close to that good.

As usual, click the pic for a larger view.
Deuterium.gif
Invoice on D from Matheson


On second thought, what I go through to transfer this to smaller tanks is a heck of a lot of work to do right and not lose purity, so maybe even that wasn't a bad deal. If I valued my time at minimum wage for the tank cleaning, refurbing, vacuum baking, valve fitting and so on, it would come out about like this. Forgetting all the gear it takes to do that needing to be amortized.

Next time some old timer says you can get D for a hundred bucks (and there they are talking about 97% pure, not that good for fusors as we have tested here by deliberately contaminating the pure stuff to see the effects) -- remember that maybe they got a deal through their job, did it decades ago, or just are boasting of their scrounging prowess -- none of them would sell it to me at the prices they claim they got, or anything close, or at all.

This is a more than lifetime supply -- the fixed costs were enough to justify getting more gas, as the price at the margin wasn't that much more. Here I transfer it to little lecture bottle sized tanks for real use -- and for a run, I open the main tank valve for a second, then run all afternoon on what's in the tiny volume in the tank->regulator pipe. In fact, I can maybe do that about 3-4 afternoons worth without having to open the main tank valve again at all. I put about 400psi in the tiny tanks as they are modified small hospital O2 tanks with new hydrogen CGA valves, aluminum tanks, and I just don't want that much volume at risk in case of some accident (or I stupidly leave some valve open and lose it to some leak).

We had to provide a safety plan, an operating plan, a use justification, a security plan, and an emergency response plan. As luck would have it, I have a part time policeman working here, and a paramedic next door neighbor, so it was mostly a matter or writing up some stuff in advanced corporatese (had to give names and phone numbers), which as an ex-CEO was a simple exercise for me. And yes, C-Lab is my company, legitimate all the way, in operation for decades, pays taxes and all that stuff, which didn't hurt a bit. Neither does a name with "lab" in it hurt when trying to buy certain odd things.

For what it's worth.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Set up in D for life now

Postby Jerry » Mon Aug 16, 2010 2:09 am

Ouch, spendy stuff!

Those little hospital tanks are neat, maybe a foot tall with the valve. I have one, still charged. What I will do with it, who knows.

I also have a bottle of Excimer laser mix. Mainly Ar and a touch of F. My friend who works on LASIK machines says that bottle is about $1k.
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Re: Set up in D for life now

Postby Doug Coulter » Mon Aug 16, 2010 10:34 am

Yes, that was spendy indeed. You'd have liked what I did with the little hospital, tanks I think. I turned them enough to wipe off the labels and dings (but leave the stamped numbers), then powder coated them red. Bill had scored a bunch of CGA 350 valves for H, but they had tank ends that were too large and wrong thread for the O2 tanks. They had plenty of meat on them, though, so with some disassembly I was able to turn them down on the lathe and re-thread them to fit the tanks. I put them in with teflon tape and a teflon gasket, with a bit of fuel type pipe dope to keep them from screwing back out. I then put a few in my big vacuum tank with the valves open, and baked all day for a few days till I got back to near my usual base pressure. Then I backfilled the tank with argon, reached in and closed all the valves. That made them ready for my filling jig, which is a fairly simple affair.

GasXfer.jpg
Transfer plumbing


The gage, and my sense of safety limit this to 400psi output (only three times the ball valve rating, after all). To control the rate of flow, I tapped the inside of the supply side CGA 1/4-20 and screwed a threaded rod in there tight -- and you still have to be a bit careful on the supply tank valve or it's too fast. The ball valve lets me take the argon out of the receiving tank, pull it down to maybe e-5 millibar along with the inter tank plumbing, then shut off and do the xfer. After that, refills are easy, since you don't have to evacuate the receiving tank again.

Believe it or not, I've had trouble selling those little tanks for $400, filled with 99.999% pure D, which is a lot better than the 97% CP grade those old timers say you can get for a hundred, or two hundred at most (but offering them $400 and getting turned down tells the whole story, doesn't it?). The idea with the little guys was to kinda amortize the big buy, and get the D I need fairly cheap, but refurbing those tanks is so labor-intensive that....well, it's a hobby. I run off one of the little guys, as it saves room around the rig and is safer in case of accident not to have 500l of D on tap.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Set up in D for life now

Postby William A Washburn » Fri Apr 15, 2011 10:20 pm

Do the labs represented here that use DU have hydrogen alarms installed to detect any DU leaks?
Just remember seeing some semi fabs with ceilings covered with hydrogen sensors to make sure they
didn't accumulate an explosive mixture in the lab. They were using ordinary hydrogen but it seems to
me that adding a neutron would leave the atom still electrically the same as hydrogen.
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Re: Set up in D for life now

Postby Doug Coulter » Fri Apr 15, 2011 10:58 pm

Actually, no we don't have hydrogen detectors (I think of DU as depleted uranium which is what most people mean by that). But believe me, we are careful indeed. No leaks! Nothing is left valve open ever. We use the D a fraction of a CC at a time, such that our SOP is to open the main tank valve for a second, and then make many runs (weeks worth) off just the gas in the little pipe between the tank and regulator. This is also why I built the system to transfer our bulk D into tiny tanks at low pressure -- both hazard in a leak situation, and heck, this stuff ain't cheap.
You just don't have that much gas in a 1 liter tank, so even if you lose it, not such a big deal.

Basically, if the main pressure gage on a regulator doesn't sit perfectly still for days after that momentary opening of the main valve, it gets fixed, stat. The amount of gas in that little pipe at a few atmospheres isn't enough to be a danger - only a few CC's. The semi boys use a heck of a lot more gas than we ever will, and at higher pressures besides. Somewhere else here I worked out how much we use per run, and I forget the number but it's on the order of .0x cc -- maybe .05?

Before I did this, and got religion about good plumbing, I had a hose pop off. And with no obvious ignition source, it was just on fire, instantly. Couldn't see the flame until the hose started burning at the end, but you could hear it, and by golly, that valve got turned right off.

Since this isn't a clean-room (more like the opposite extreme) things like H and He don't hang around -- they go out the roof vent real quick. I worry a lot more about the rems than the hydrogen.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Set up in D for life now

Postby Joe Jarski » Sat Apr 16, 2011 1:50 am

Those numbers sound about right Doug. I was just working some numbers on my sputtering system yesterday to get an idea of the level of contamination/purity that I was working with and considering the differences in the chamber sizes and some other factors, I ended up with numbers in the same ballpark as yours.

If my ~1L tank was released in my lab it might double the normal percentage of H in air - still far from being in proportion for an explosive mixture.
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Re: Set up in D for life now

Postby chrismb » Sat Apr 16, 2011 5:33 am

Your D2 looks like a bloody good price, compared with buying this stuff in the UK!!....

In regards sensors and flammability limits, the issue with H2 is not a calculation as to the percentage in a room, it is where it collects, which is, as you know, up at the ceiling. It can concentrate in flammable levels there, even if the overall %age is low.

I think it is only recently that flammability sensors have been mass produced on scales that make them cheap, but there is now a sensor mass-produced that means installing a flammability sensor is a very cheap thing to do. IIRC, these go off at about 5% LEL H2. I can't say I've tested them with D2 - but I'm not gonna go venting D2 just to test it out!! It works on oxidation at a semi-conductor junction, I think.

Recommended to install...:

http://cgi.ebay.com.au/Flammable-Gas-Le ... 0587562494

Looking inside one, it looks to me like it runs off of this sensor;

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0627745687

flammability_sensor_MQ2.pdf
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Re: Set up in D for life now

Postby Doug Coulter » Sat Apr 16, 2011 1:28 pm

Hmm, wonder if that's a hydrocarbon-only (some are) or will see just H. At any rate, and for entirely other reasons, not a bad thing to have around. The cheap, heated-wire sensors I've seen only do things like natgas and propane, but around here, those are the actual risks anyway. I'd guess ceiling collection would vary considerably depending on ventilation or just how tight the room is.
My particular situation isn't very tight -- and we have forced air pushing through the whole shop at all times -- from bottom basement to a turbine vent on the roof. Works pretty well at keeping the air fresh (I smoke), and also cooler in summer. We draw air in through the basement and suck it out of the roof peak 24/7 in summer. In winter, we draw air through a window, and push it into the basement and out the roof. Keeps the ground floor warm.

My main tank is down to 500 psi or so -- so maybe that wasn't a life supply, but then we've sold some, and leaked some before I got as serious about this as I should have been all along. At any rate, now the paper work is all handled, and a refill shouldn't be so bad. It might require a drive up to the nearest place ( about a 10 hour drive) that has it, but they should refill the tank no problems -- when I need that. The Hazmat shipping junk they force you through was a big part of that cost, and it might actually be cheaper for the drive and hotel room...They seem to insist on putting that little tank on its own pallet and shipping it in an otherwise empty tractor trailer -- dumb and wasteful.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Set up in D for life now

Postby chrismb » Sat Apr 16, 2011 3:53 pm

It says hydrogen on the data sheet, and there's a plot line on the graph for H2, so it surely claims it does.
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Re: Set up in D for life now

Postby Doug Coulter » Sat Apr 16, 2011 6:05 pm

I'd suppose if you have a fairly tight lab, or you're the worrying type, you should have these. My own (one) experience was that it lit instantly at the leak (static electricity? The HV supply wasn't even turned on at the time.) -- never had time to collect at all -- and even if it had, maybe 10cc or so got out before I shut the valve. No big deal, that stuff is darned flammable, like nothing else I've ever worked with -- it might be tricky to get it to collect before it lights, actually. In actuality, losing a liter isn't likely, and a whole liter with a perfect mixture would indeed frighten you into needing new under-shorts, but probably not even pop out a window -- 1/22.4 mole, after all, not a ton of joules (nothing like acetylene of which a liter with O2 would be quite nasty). At the price of the stuff, you'd not lose many liters before going broke!

We should probably talk some more on the gas handling threads, or direct any readers to some words over at fusor.net that Richard wrote. The word is -- all metal plumbing, period. I've tried various non-metallic tubings -- and they either leak H out, or air in as shown on my mass spectrometer. Neither is acceptable for operation, forgetting about hazards for a moment. I have tried silicone, latex, teflon, and hardware store poly-something -- none get it done without problems. Copper is the way, probably stainless steel is good too, but copper seals and solders easier and doesn't have embrittlement issues. The plastic tubing let air diffuse into the pure H inside it, even when that H was at a few psi above atmosphere. It's a nasty problem.

As I said, in actuality, the acid test is to momentarily open the tank main valve, and record the gage pressures -- main and regulated, with all other valves closed. It had better be the same the next day (or a few) or you've got an issue that is the most important one you need to fix -- NOW. If for no other reason than it's going to mess up your results and cost you money, both. The tiniest of leaks will cost you money if it's "out" as that stuff ain't cheap -- even if it's far slower than an electrolyzer running on a flashlight cell (and the above test will see incredibly smaller leaks than that). And, given that we're in the .0x cc per run gas level - and want those 5 nines of purity, then we don't want an in-leak (or osmotic diffusion) even in the range of .0x e-5, a doggone small number. So, perfect is the word. Luckily, standard copper plumbing, either flare, swage, or sweated with solder, satisfies this fairly easily. Valves, you have to worry about more, as they may have stem-seal leaks. Ones rated for hydrogen should be used, or seal-less valves (bellows or magnetic). For what it's worth, the tiny needle valve I used before I got the solenoid valve mentioned elsewhere going didn't have any issues, and was merely viton O ring sealed at the stem. That was so tiny it couldn't have leaked much -- I think the stem shaft was about 3/32" including the O ring. I've been using 1/8" OD Cu tubing for plumbing, soldering it into larger fittings at the tank end and valve ends, and that's working quite well (and easy to take apart when needed). It also turns out that the standard capillary tubing sold at McMaster (and probably elsewhere) is 1/16" OD, and fits inside that with a slight reaming job from a drill bit -- so that gives you a set of relatively cheap plumbing supplies for this job.

I get a good number of runs (I never counted, but it's a lot) with just one momentary opening of that main tank valve, and no one should accept less -- that's a few CC of gas stored in the little pipe between tank and regulator, and you should be getting the benefit of nearly all of it -- maybe 100 runs, but surely 20 or more. If it all leaks out in a week, it's not really a hazard, but it's money tossed out the roof vent. Being a bit of a Scot, I find that idea unpleasant all by itself.

Note, I do have my vacuum system exhaust piped to the out of doors, not because of worries about this, but who knows what I might get up to in the lab in the future, and why have reasons to worry? This is going to make it handy to plumb in that beta counter in the exhaust gas stream to see if we can see any T created during a run besides. It's going to be a bit of a job to get that in there, mainly due to where it needs to go, but I'm guessing it will be worth it. Might get it done tomorrow, since I managed to bodge that new trailer hitch onto my truck today...a day ahead of schedule for once.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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