Teledyne 2120XL - Trace Nitrogen Analyzer - Manual (Page 44)

Installation Model 2120XL
Teledyne Analytical Instruments 32
When installing a new analyzer or starting up an analyzer that has
been idle for a period of time, the sampling system should be purged for
several hours to cleanse it of contaminants and water vapor.
Although high-purity sample gas may be used to purge the
analyzer, argon with a minimum purity of 99.999% is recommended.
The exact purge method depends on the sample manifold design
and construction. In general, each sample inlet line must be thoroughly
purged. Sufficient purge time becomes critical when sample lines longer
than 10 feet (3 m) are used.
To purge the analyzer (see Figure 3-2):
Note: Do not purge long lines through the analytical cell. First,
purge them through the purge flow rotameter; then transfer
flow to the analyzer cell as suggested in step 6, below. This
eliminates the possibility of contaminating the analytical cell
and having to purge for an extended period to reach
equilibrium.
1. Close all valves on the sample manifold.
2. Open the valve on sample inlet line to be purged and any
shut-off valve that may be installed.
3. Connect purge gas to the sample inlet line.
4. Use a flowmeter on the purge gas and adjust flow rate to 1
cfh (0.475 slpm) at no more than 7 psig (76 kPa) and purge
for at least one hour.
5. Close the sample inlet valve, and then repeat steps 2 through
4 to purge any other sample inlet lines.
6. After the last sample line and the zero and span gas inlet
lines have been purged, close the purge flowmeter valve,
open the valve controlling flow through the analytical cell,
and purge the analyzer with the sample flow set at 1 cfh
(0.475 slpm). Purge the analyzer for a minimum of 6
hours.
7. If cylinder argon is used as a purge gas, reconnect the
sample gas to sample manifold inlet.
8. After purging, a calibration should be performed.