If you buy a tank you need to be aware of the manufacturing date. Theoretically you can get them re-certified, for about 3X the cost of replacing the cylinder... Last time I looked, anyway - It's been awhile. On 11/3/17, Denny Esterline wrote: > As luck would have it, I just bought a welder for my shop and I still hav= e > the receiving paperwork on my desk.... > In Tucson AZ, USA. I bought two 125 cubic foot rated steel tanks for > $196.10 US each. > One filled with 75% Argon, 25% CO2 - the gas cost an additional $19.23 an= d > the other filled with "pure" argon which cost an additional $17.89 > As this is sold as welding shield gas, I'm going to assume "pure" is abou= t > 99.999%. > > > Man, I really need to clean off my desk. > > -Denny > > > On Fri, Nov 3, 2017 at 12:15 PM, Sean Breheny wrote: > >> Hmm, I wasn't aware that balloons used lower grade helium (in fact, base= d >> on a quick Google search, it seems like they usually use the same grade >> as >> is used for welding shielding gas, which is grade 5 (99.999%)) >> >> I don't think there is an inexpensive source of Krypton or Xenon. The >> source for those gasses is the same as argon (fractional distillation of >> ordinary air) and the abundance of Kr and Xe in air is extremely small, >> whereas Ar is almost 1%. >> >> I bought an aluminum 2200psi, I think 40 cubic foot (at STP) cylinder of >> ultra-pure Argon for about $130 at my local welding supply two years ago= .. >> I >> still have half of it. Most of that cost was the cylinder and valve. I >> think a refill would be about $40. I had to purchase a regulator >> separately. It is eventually going to be used to seal alkali metals >> (sodium, potassium) in ampoules under inert gas. So far the only thing I >> have done with it, which ended up using about half of the tank, was to d= o >> an experiment to measure the density of Argon (I got a result which was >> only a few percent off of the textbook value). It was good practice usin= g >> the flow-rate regulator, too. >> >> Even if you don't need pressure I would think that standard high pressur= e >> tanks would be the most cost effective for you because of the quantity >> they >> can hold in a compact space. I chose to buy the tank but you can also >> rent >> them for much less. >> >> Sean >> >> >> On Fri, Nov 3, 2017 at 12:13 PM, Van Horn, David < >> david.vanhorn@backcountryaccess.com> wrote: >> >> > I have local sources for helium balloons that use actual helium, not >> > "balloon gas" so I pay about $1 for 2 or so liters of gas in a >> > convenient >> > disposable container. >> > I don't need pressure, I'm always pulling the gas anyway. >> > My Neon and Argon come in glass flasks for $70/2l >> > Still working on a cost effective source for Xenon. >> > >> > -----Original Message----- >> > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On >> > Behalf >> > Of Sean Breheny >> > Sent: Friday, November 3, 2017 10:02 AM >> > To: Microcontroller discussion list - Public. >> > Subject: Re: [EE] Vacuum plumbing >> > >> > Is there any reason you don't use argon as your rinse gas? It's much >> > cheaper. >> > >> > On Fri, Nov 3, 2017 at 11:15 AM, Van Horn, David < david.vanhorn@ >> > backcountryaccess.com> wrote: >> > >> > > Fortunately my only use for helium is as a rinse gas. Vac the >> > > system, >> > > fill with He, then vac it again, and call it clean. :) >> > > >> > > -----Original Message----- >> > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On >> > > Behalf Of alan.b.pearce@stfc.ac.uk >> > > Sent: Friday, November 3, 2017 3:30 AM >> > > To: piclist@mit.edu >> > > Subject: RE: [EE] Vacuum plumbing >> > > >> > > > I still wish I could find a book/document/etc that describes the >> > > > building of a vacuum system for the range of 1 torr to 10 microns >> > > > or >> > so. >> > > > Seems to be a black art. >> > > >> > > Judging by the difficulties a program I am working on is having >> > > sealing helium over a temperature range, it is very much a black art= .. >> > > >> > > Thankfully I'm only involved in the electricals ... >> > > >> > > >> > > >> > > -- >> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> > > View/change your membership options at http://mailman.mit.edu/ >> > > mailman/listinfo/piclist >> > > >> > > -- >> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> > > View/change your membership options at >> > > http://mailman.mit.edu/mailman/listinfo/piclist >> > > >> > -- >> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> > View/change your membership options at http://mailman.mit.edu/ >> > mailman/listinfo/piclist >> > >> > -- >> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> > View/change your membership options at >> > http://mailman.mit.edu/mailman/listinfo/piclist >> > >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .