The tank I bought was used and it will indeed need to be hydrotested before the next filling (it's about 5 years old and the testing interval for aluminum is shorter). However, my understanding from talking with the welding supply place is that they have the equipment in-house to hydrotest them and it doesn't increase the cost of refilling much. I don't recall whether there is an option to swap if you own the tank. I bought it instead of rented because I didn't want to be tied to the one shop because I do not use much Argon and it will always be several years between re-fillings. I also bought an oxygen cylinder from them but that one is steel and almost brand new. The steel ones have 10 or 15 year test intervals (I can't recall which mine is). I haven't had to refill either one yet. Got the O2 in 2014 and the Ar in 2015. Sean On Fri, Nov 3, 2017 at 4:37 PM, John Gardner wrote: > 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 > have > > 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 > and > > 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 > about > > 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, > based > >> on a quick Google search, it seems like they usually use the same grad= e > >> 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 > do > >> an experiment to measure the density of Argon (I got a result which wa= s > >> only a few percent off of the textbook value). It was good practice > using > >> the flow-rate regulator, too. > >> > >> Even if you don't need pressure I would think that standard high > pressure > >> 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 micron= s > >> > > > 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 > > > -- > 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 .