Using a Controlled Atmosphere Glove Box with an exterior liquid nitrogen tank

By Bob Applequist, Senior Application Specialist

On July 10, 2014 in Articles

Sometimes a simple question can make something seemingly complicated suddenly very simple and easy.  When setting-up a Controlled Atmosphere Glove Box to achieve and maintain very low oxygen and moisture levels in the inert atmosphere, the question is: “What is your source of nitrogen?”

• A compressed nitrogen tank, (aka K -size cylinder of compressed nitrogen)
• A building supplied nitrogen originating from a big exterior liquid nitrogen tank

The Answer: “We have a large exterior tank filled with Liquid N2.”

This answer addresses the issue of how much nitrogen you can use to simply flush a glove box to a "clean condition."

With a house supplied nitrogen gas system, you have pure physics on your side.

If all parties agree, you can simply connect a nitrogen gas line to a glove box manual valve, and exhaust the vent line through the glove box manual valve routed to a fume hood.

Then adjust the two valves to achieve a low-volume constant bleed of nitrogen gas passing through the glove box main chamber (maybe up to a liter a minute for first time clean-up, or lower for maintaining a specific ppm level of oxygen and moisture).

The constant flushing of pure nitrogen will dilute the glove box interior atmosphere to a very clean concentration.

This is advantageous on two levels.

1. There is no requirement for costly electronic pressure control accessories.
2. The operator will not spend time manipulating the electronic controls at the glove box to reduce the oxygen and moisture levels.

Set-up the constant bleed of nitrogen gas and you’re done. Just walk away from the glove box.

The disadvantages of this operation method are that the nitrogen gas is used constantly, and the constant flush purification/operation method is slow. But you get to spend your time on something more important than working the glove box main chamber pressure system.

Since you will still need to get materials in and out of the glove box main chamber, there is still a requirement for connecting a nitrogen gas line and a rotary vacuum pump to the transfer chamber’s manual pressure control valves.

The transfer chamber on Labconco Glove Boxes can withstand an absolute vacuum level; therefore, cleaning up the transfer chamber goes quickly. The transfer chamber can be quickly evacuated down to -25 to -29 inches of mercury gauge pressure, and then refilled with nitrogen gas. With a clean transfer chamber, your materials can be moved into the main chamber without contaminating the main chamber atmosphere. The extreme vacuum level cleans up the transfer chamber and the materials quickly.

The total equipment list boils down to these three things:

1. Controlled Atmosphere Glove Box
2. Rotary Vacuum Pump
3. Tubing Kits

That’s as simple as it gets!