Inert your rebreather oxygen sensors

Diver Dave's Inerting your Sensors

Oxygen sensors for rebreathers are expensive, and have a finite life. Here in the Diveshop of Horrors, I keep about a dozen sensors healthy at all times, and that represents over a thousand dollars worth of the darned things. Since a sensor is really a fuel-cell, or battery, they can have their lives increased by reducing the amount of 02 that they see, thus reducing the amount of anode and cathodic material that is used over time. The best way to prolong their lives is to store them in inert gas. Now, you can simply place them into a plastic bag, assuming that they will "eat up" the 02 in the bag after a short while, and thus going nicely back to sleep. But there's a better way, especially for larger items that incorporate 02 sensors, and especially if you use them frequently. That's to simply make up a storage box that's easy to fill with inert gas. Here's my system:

Basically, the way I chose to do this was to simply add a fitting to a Pelican Box to allow me to blow inert gas into the box. Pelican boxes are O-Ring sealed, so they hold gas. Here I've taken a standard BC inflator fitting, and threaded the end where the hose connects. Then I made a matching nylon cap so that after I blow the box full of whatever inert gas I have handy, I can cap it off and keep the box gas-tight.

Drilling the Pelican Box and tapping the hole took about 2 minutes. I screwed in the new BC inflator fitting, and here it's shown with the cap installed.

A VERY important part of this is to make sure that you open the purge valve on the box BEFORE adding inert gas. Otherwise you'll have the loudest Pelican Box in the world, but just for a moment.

And here's my box, shown with a bunch of stuff ready for storage. There's a 3-sensor display complete with sensors, an Oxygauge, three or four other cells, and my Draeger P-Connector interface for the VR-3. There's plenty of room left over as well. Now all I need to do is to blow it for a few seconds with a regulator hooked up to a BC inflator hose and an inert gas source. I use Helium, since I have it here in the shop. Argon is far cheaper, as it's an industrial welding gas. You might be able to strike up a friendship with a local welder to let you hook up to his nearly empty cylinders that he's returning to the gas supplier every now and then, or you might want to keep Argon around anyhow for suit inflation. I don't do either, and just use Helium since I keep it here for trimix blending.

Now, you say that you don't need all that space? No sweat: Modify a smaller box. This is an Underwater Kinetics storage box.

First thing is to modify the box with a bleeder screw, since unlike the larger Pelican Boxes, these aren't provided with one from the factory. Having a lathe handy, I just cut an O-Ring groove into a 1/4-20 brass machine screw to make the bleeder.

Then I stuck an O-Ring on the screw.

The I drilled, tapped, and then chamfered a hole into the UK Box. This could also be done to a small Pelican Box, Otter Box, or any of the similar dry boxes.

Here's the box with the screw. Next I added another BC inflator stub, with another cap just like on the larger box above. Result? A small box that's just right to store three cells and maybe some other goodies.

That's all folks! Take me Back to the Projects!

		Basically, the way I chose to do this was to simply add a fitting to a Pelican Box to allow me to blow inert gas into the box. Pelican boxes are O-Ring sealed, so they hold gas. Here I've taken a standard BC inflator fitting, and threaded the end where the hose connects. Then I made a matching nylon cap so that after I blow the box full of whatever inert gas I have handy, I can cap it off and keep the box gas-tight.
		Drilling the Pelican Box and tapping the hole took about 2 minutes. I screwed in the new BC inflator fitting, and here it's shown with the cap installed.
		A VERY important part of this is to make sure that you open the purge valve on the box BEFORE adding inert gas. Otherwise you'll have the loudest Pelican Box in the world, but just for a moment.
		And here's my box, shown with a bunch of stuff ready for storage. There's a 3-sensor display complete with sensors, an Oxygauge, three or four other cells, and my Draeger P-Connector interface for the VR-3. There's plenty of room left over as well. Now all I need to do is to blow it for a few seconds with a regulator hooked up to a BC inflator hose and an inert gas source. I use Helium, since I have it here in the shop. Argon is far cheaper, as it's an industrial welding gas. You might be able to strike up a friendship with a local welder to let you hook up to his nearly empty cylinders that he's returning to the gas supplier every now and then, or you might want to keep Argon around anyhow for suit inflation. I don't do either, and just use Helium since I keep it here for trimix blending.
		Now, you say that you don't need all that space? No sweat: Modify a smaller box. This is an Underwater Kinetics storage box.
		First thing is to modify the box with a bleeder screw, since unlike the larger Pelican Boxes, these aren't provided with one from the factory. Having a lathe handy, I just cut an O-Ring groove into a 1/4-20 brass machine screw to make the bleeder.
		Then I stuck an O-Ring on the screw.
		The I drilled, tapped, and then chamfered a hole into the UK Box. This could also be done to a small Pelican Box, Otter Box, or any of the similar dry boxes.
		Here's the box with the screw. Next I added another BC inflator stub, with another cap just like on the larger box above. Result? A small box that's just right to store three cells and maybe some other goodies.