Can someone post a how to for purging NVGs the expedient way. Where do you get the Nitrogen and how do you expell the Oxygen and fill with the Nitrogen? I have heard of using plastic bags, shop vacs and plastic tubing. Please make a how too!

I can answer the first part.  You get nitrogen from a welding supply place.  For small bottles, you normally buy the bottle (tank) and pay for the fill.  Usually you get a used tank for your first purchase and just exchange with a used full one when needed.  You need a regulator to get from the high pressure of the bottle to somethign reasonable.  The cleapest way to do this is buy a regulator for MIG welding with a flow meter.  Make sure it is for Argon and argon mixes and not CO2 (which uses a different fitting at the tank.)  You can buy a cheap end on off ebay, or get a USA made Smith for about $60.  The low pressure connection is some sort of a weird fitting, I bought mine at the Local Airgas dealer for $15 and you can put any kind of hose on it you want.

20 or 40 cu ft is about the smallest tank, and is usually in stock because of HVAC and plumbing guys who haul them up on rooftops and such.  This is the exact same cylinder use in the portabel oxyactelyene outfits at home depot.  Harbor freight has the tank (with an oxygen valve) for $99, and has 15% cupons all overe the net.  Ask you local weldign supply if you can trade a 20 cu ft oxygen for a nitrogen cylinder if there price is over $85.  Mine lets me do it all the time.  BTW, the HF cylinder is USA made.

BTW, 20 cu ft, means 20 cubic foot at atmospheric pressure.  the cylinder is about 6" in dia and weights 15 lbs.

I won't comment on purging, but there are two strageties for purging in general : Flood with 3-10x the volume needed to wash the moisture laden air out (dilution is the solution to polution), or pull a vacuum and then refill with nitrogen.

If you are dealing with you local welding supply for more then a one time purchase, apply for an account, they treat you better, and you can rent a tank when needed.  I have acocunts with 3-4 places, and used to be more then that before there were so many buyouts.  There is almost a perceptable mistrust of those without accounts, as if you are filling stolen cylinders.

You may be able to get small N2 tanks at local HVAC supply places as well.  I stick with the welding places for safety.

I've purged off my welding argon bottle before.

Is it worth trying to do yourself vs. just taking it to a local professional? I have a local binocular shop that can do it, but if I have to open the NVGs up for them to do it  I am not sure they will know how to put them back together themselves. DannerTrax

The tiny screw above the on/off switch on a 14 is the purge port. Depending on the type of purging kit they have an adapter may be needed. The professional NV purge kit pressure checks the system as well as purges it. If you have dust on the tube or lenses that almost always requires taking the whole scope apart. A simple purge to just remove moisture is quick and easy. Flooding the scope through the port with Argon or Nitrogen will work well.

Canned air is not really air. It is a inert gas suitable to purge moisture. Helium will poison your tube so don't use that. It also will never stay in your scope very long. Argon is the best as it has a bigger molecule than nitrogen and tends to last longer. Nitrogen is cheap and works well. Argon is more expensive but is used in many high end optics. Lots of your wine preservation canisters contain argon, nitrogen or a mix of the gases. I mostly just used the canned air duster for my own gear.

Like I said it is not air and is cheap. It also works good for cleaning dust off the lenses and tubes. I take stuff apart so often that many times I don't bother to purge it unless it is for someone else. If I have a moisture issue I purge it, if not I don't bother.

I have never perged a PVS-14 but have dropped out the tubes in PVS-7B goggles regularly. When re assembeling the unit I just crack open a dive tank and assemble in the air flow excapeing the tank as its dry air or at least a mix of air and dry air. Have never had a fog issue in the 10 or so years I have been doing it.

The keyboard spray (compressed air) may work too. The old ones were inert gas (I think helium)....don't know what the new ones are now.

Tag for later, since I have both Ar and C25 cylinders out in the shop.

Have a look on the tin. It's most likely R134A or modern Refridgerator Gas... As used in air duster all over the world.

 

R152A is in Ultra Duster!

I am curious.  How much are they asking for doing it?

I use Dino's canned air trick it's worked for me for many years plus its easy!

I finally called the other day, they said only $10 or $15. So I'm taking it there.DannerTrax

So the HFC-152A in duster will not harm the nods?  From what I understand it is basically modified acetylene.  If it is safe for the inside of nods then I guess I am good to go for rebuilding my PVS-7s.  

Hitchhiker out

Has anyone tired going to a tire store that does nitrogen and filling up a small air tank and using that?

I like the Can Duster. Works, with no Drama.