Purge Valve Fitting

Overview

Any time an APNVG housing is opened — an image tube swap, optics work, or any repair that breaks the seal — ordinary room air gets closed up inside it, and room air carries moisture. The first cold night out, that moisture condenses on the inside surfaces of the optics, and you cannot wipe it off because it is on the wrong side of the glass. This fitting threads into the purge port on the housing and gives you both steps: draw the cavity down under vacuum to pull the wet air out, then backfill it with dry nitrogen. Once that is done, the optical path stays clear. This is a user-level fitting rather than production tooling — it comes off after the purge and lives on the bench.

Key Features

1) Threads into the purge port on the APNVG housing so you can evacuate and refill the optical cavity yourself;

2) Evacuates the cavity under vacuum and then backfills it with dry nitrogen;

3) Comes off after the purge; the port is closed again for normal use;

4) Addresses the unpurged symptom — internal fogging that appears the first cold night and cannot be wiped away;

What's in the Box

One purge valve fitting

How to Operate

1) Thread the fitting into the purge port on the housing and bring it down until it seats;

2) Draw the cavity down under vacuum to pull the moisture-laden air out;

3) Backfill the cavity with dry nitrogen;

4) Unthread the fitting and close the purge port again with its own screw and seal;

Compatibility

ARGUS PNVG-18 (APNVG) four-tube panoramic night vision goggle.

Why the ARGUS Part

The threads and the seat are cut for the purge port ARGUS puts on the APNVG housing, so it seats straight and holds vacuum while you draw the cavity down.

The tell that a housing went back together without being purged is fog on the first cold night. This fitting is the closing step of any job that broke the housing seal, so have it on the bench before you open the goggle rather than after you have closed it.

Shipping note: this item currently cannot be shipped to Japan or Taiwan.