Helium Recovery Line

As of May 18, 2018, the Yavuz lab is hooked up to the University's helium recovery system. The recovery system connects to equipment that outgasses helium and pipes it back to the liquid helium and nitrogen facility in Engineering Hall.

There are two inputs to the system in the lab. Each input consists of a check valve, a valve to the main line, and a purge valve. The check valve has no external handle and the main line valve is the larger of the two valves with handles (also, just from looking at the piping it should be clear which one is the main valve and which is the purge valve).

The check valve is to make sure that no helium that is already in the system leaks into the lab due to the fact that the system is slightly above atmospheric pressure. You do not need to worry about the check valve, since it regulates itself.

The valve to the main line is pretty self-explanatory. When it is open, helium can be sent into the recovery system. If nothing is hooked up to the input, then this valve should be closed.

The purge valve allows you to clear the input of any other gas before sending helium into the system. Start with the main line valve closed and the purge valve open. Hook the helium up and the input will be cleared fairly quickly. Open the main line, then close the purge valve to avoid any pressure buildup.

One of the inputs hooks up to the cryostat. Once the transfer line is cool and the cryostat is outgassing, it should only take five or ten seconds to clear the input of extraneous gasses. Once this is done, open the main line valve, then close the purge valve. This input has a safety valve that will pop out and cause the helium to outgas into the lab if the pressure in the pipes gets too high. I can't remember exactly what the pressure threshold is, but I think it is something like 5 or 6 psi.

The other input is for outgassing from the dewar itself. A latex tube goes from the recovery system input to the relief valve on the dewar (the conical one). This is to recapture the helium released when depressurizing the dewar and helium released when the dewar is just sitting there overnight (about a liter a day). Hook this input up as soon as you get the dewar. Since the outflow from the relief valve is very slow, let the system purge for a few minutes, then open the main line valve (which is probably already open. This input's check valve has a higher threshold pressure) then close the purge valve.

When putting the transfer line into the dewar BE CAREFUL! Put the line in slowly to prevent the dewar pressure from climbing to high and to not overload the input valve. Also note that the latex tube will freeze solid when you do this. Try not to move it around until it thaws.