Gas lines for spectroscopy
Emptying the IR Cell
The following steps guide through the process to evacuate the gas from an IR cell.
1 ) Evacuating the IR cell
Return the IR cell to the line, reopening taps 4 & 5 to connect the cell to the manifold. Then tap 3 can be opened to evacuate the cell.
2 ) Air dilution
To encourage effective removal of all traces of the gas, it is often desirable to return the manifold to passive vacuum and bleed air into the manifold to dilute the gas and aid its removal.
Close tap 3 to place the line under passive vacuum, and open tap 6 carefully to bleed air into the line.
3 )Reevacuating
With the manifold and cell filled again with air, close the air bleed (6) and reopen the manifold tap (3) to return the line to active vacuum. It may be desirable to repeat steps 2 & 3 several times to ensure total removal.
Once the cell has pumped down for a while, close the manifold tap (3) and the IR cell (4 & 5) and record a spectrum to check the cell is empty. If traces can still be seen, repeat the evacuation procedure again.
Shutting down a line
The following steps guide through the process to evacuate the gas from an IR cell.
1 ) Isolate the line
Close the manifold tap (3) and carefully bleed air into the line from the manifold air bleed (6) to return the line to atmospheric pressure.
2 ) Air dilution
If fitted, remove the liquid nitrogen from around the trap, then open tap 1 and switch off the pump. Empty the trap of any contents if present.
3 ) Ballasting the pump
If the trap was already clean, or after its removal where required, turn the pump back on and allow it to ballast as required. Once the pump has ballasted sufficiently, turn the pump back off.
