Adding Nitrogen Exchange Gas

Before the actual transfer of LN2 to the MB, nitrogen exchange gas must be added to the IVC. The exchange gas provides thermal flow - it allows the interior of the IVC/Mixing Chamber (MC) to cool by proxy. If there is no exchange gas, it would take much longer than 12-15 hours to cool the IVC.

1. Isolate the leak checker from the IVC.
2. Close all valves on the pumping manifold and all valves leading to the IVC.
3. Make sure a clear hose is connected from nitrogen gas supply to the pumping manifold, but keep it isolated from the pump and IVC.
4. Open the nitrogen gas supply from the tank in the pump room. Make sure that the N2 valve on the gas line being used as the nitrogen gas supply source is closed.
5. Isolate scroll pump (it should be already).
6. Turn on scroll pump.
7. You are going to pump on the clear hose to evacuate any gas or air because this hose will be used to deliver nitrogen exchange gas to the IVC and we want this to be clean. You will use the scroll pump to do this. Open the scroll pump.
8. Open green regulator valve. Note that the little pressure gauge above the green regulator valve should read -30 in-Hg (though the pressure is actually lower than this!).
9. Close green regulator valve tightly.
10. Open the nitrogen valve (green) on the gas supply line to let nitrogen gas into the clear hose (still isolated). The little pressure gauge should read 2-3 PSI.
11. Isolate scroll pump and turn it off.
12. STOP! DON'T DO ANYTHING ELSE. Here's a thinking moment… how are you going to let nitrogen gas into the IVC? There are two options for doing so. One is more risky than the other. Read the options below:

This is a 1-shot method.

1. Open the black valve adjacent to the green regulator valve that leads to IVC line.
2. Open the IVC valve on top of the platform.
3. VERY SLOWLY open the regulator valve and keep an eye on the pressure reading. Only allow 1-10 mbar into the IVC, then close the regulator valve tightly. You should aim for 4.6 mbar.

With IVC sealed off. The volume in the IVC line is about 8x smaller than the IVC, so youll need to compensate with 8x greater the amount of nitrogen gas pressure in that line. This method is less risky because if you let in too much nitrogen gas you can pump it out more easily. Do NOT forget to open valve to IVC after gas is in the line.

1. Open the black valve adjacent to the green regulator valve that leads to IVC line.
2. VERY SLOWLY open the regulator valve and keep an eye on the pressure reading. Only allow 8-80 mbar into the IVC, then close the regulator valve tightly.
3. Open IVC valve on top of platform to let nitrogen gas into IVC.
4. Close the nitrogen gas supply on the gas line and tank.