Video Transcript
When shutting down a vacuum line, in
which order should the following actions be performed? (1) Turn off the vacuum pump. (2) Remove the Dewar of liquid
nitrogen. (3) Vent the vacuum line.
The first step in shutting down a vacuum
line is always to turn off the vacuum pump. If you were to vent the vacuum line with
the pump still on, you’re simply going to draw air through the pump. Where still if you have the Dewar of
liquid nitrogen still in place, you’re going to draw air through your cold trap. Drawing air through a cold trap is a
great way to condense liquid oxygen, which is a real hazard, so we want to avoid that.
For that reason, the next step is going
to be to remove the liquid nitrogen. This must be done before you vent the
vacuum line to the atmosphere. This means that venting the vacuum line
is our last step. So our answer is (1), (2), and then
(3).
