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Posted: 6/22/2014 3:44:08 PM EDT
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So ive heard some about purging, I see lots of guys taking units apart for pics of the tube and stuff.
exactly what part of a pvs14 holds the purge? will taking the unit apart or taking the tube out to look at it break the purge or is the actual tube itself whats purged? ive seen the purge screw for sale and dont see it anywhere on the outside of my housing so im assuming the tube itself is what holds the purge. on another topic I have a buddy who is ex mil and was at Fort Huachuca in AZ, he said alot of what he did was purging and replacing parts in nods that had been over in the sandbox. From what ive seen on here for a unit to be a contract unit it has to be assembled in house at ITT or L3, would they not have to send those units back to the factory to have this done or did the .mil have armorers that were allowed to work on them as well? |
There are people on here that can explain it better than I, but I will give it a go. First the reason to purge is to reduce fogging. You do this by replacing the air (which has water vapor in it) with an inert gas. The gas of choice is nitrogen. When most if not all units are purged the air is removed from the unit by vacuuming it out and replaced it with nitrogen. most units have one purge point which allows you to remove and replace the air between the photo cathode and objective lens, around the tube and power supply and between the screen and eyepiece. hope this helps
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Hugh nailed it. I will add a few things. You are not purging the tube itself. The tube is vacuum sealed and encased in a elastomer potting compound. You are just purging the air inside the scope out. The purge screw on a 14 is right above the on/off switch. The vac part of a purge also tests for seal integrity. The purge screw on a PVS-7 is between the eyepieces at the bottom. Purging is a milspec requirement but the night vision device does not NEED nitrogen to work.
If you are not having internal fogging issues I would not worry about it. I am sure the military has night vision field techs who do minor repairs. Anything major would most likely be sent back to the manufacturer for warranty work. |
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