Service and maintenance
9.1 Instrument verification
SITRANS SL
Operating Instructions, 12/2010, A5E01132948-04
155
Step 5: Verification
1.
Watch or record the measured value for at least 20 seconds to ensure that it is stable (i.
e. concentration varies not more than ±0.05 vol % / minute).
2.
Take 5 successive concentration values and write them into the verification sheet.
3.
If the difference between the highest and the lowest concentration value is more than the
maximum repeatability value (see technical data (Page 181)), the measurements must be
repeated.
4.
Compare the average of the 5 values with the verification set point. If it lies within the
range between the set point and the total verification uncertainty, the instrument works
properly.
If the average value lies outside this range, please contact Siemens support.
5.
Put the removed needle valve back into place and close it.
Repeat all steps of one of the paragraphs "Filling the verification tube with ambient air" or
"Filling the verification tube with pressurized air" as described before.
6.
If the difference between measured value and verification point is more than 0.4 vol % O
2
the verification procedure should be repeated from the start.
Step 6: Purging with nitrogen
To make sure that the instrument was purged well all the time during the verification
procedure another purging procedure with nitrogen is necessary. To do so:
1.
Attach your nitrogen source to the remaining needle valve once more.
2.
Purge the verification tube for about 5 minutes until the concentration value falls well
below 0.2 vol % O
2
. The gas flow should be approx. 4 l/min.
If the O
2
concentration value does not fall below 0.2 vol % O
2
it is obvious that too much
oxygen has entered the volume behind the lenses during verification. The verification
procedure should be repeated from the start.
3.
Close the needle valve. Wait for 10 minutes. After this time the O
2
concentration value
should not have increased to more than 0.15 vol % O
2
.
4.
Note this value in the verification sheet.
Step 7: Restore
1.
Restore path length, pressure correction and temperature correction to original settings
according to the notes taken.
2.
After restoring correction settings, press button repeatedly to exit the menu. Select OK
when you are asked to save.
3.
Reinstall the receiver and transmitter at the industrial interfaces.