Service and maintenance
9.1 Instrument verification
SITRANS SL
154
Operating Instructions, 12/2010, A5E01132948-04
Step 3: Purging with Nitrogen
Note
In the instruction it is assumed that totally oxygen free nitrogen is used. The concentration
value of the SITRANS SL during this procedure will not be lower than the oxygen content in
the nitrogen.
1.
Attach your source of purging gas (N
2
) to the needle valve on either the receiever or
transmitter side.
2.
Close the other needle valve.
3.
Purge the verification tube until the concentration value falls below 0.05 Vol% O
2
. The
gas flow should be in a range of 4-10 l/min and the pressure of the nitrogen between
2 and 5 bar absolute. The gas should escape trough the two capillaries on the receiver
and transmitter.
4.
Close the needle valve. Wait for 10 minutes. After this time the O
2
value should not have
increased to more than 0.15 Vol%. If the O
2
value exceeds this limit refer to section
(Problem handling: insufficient purging) at the end of this chapter for further proceedings.
5.
Remove the needle valve completely on either the receiver and transmitter side. This is
necessary to avoid any over pressure in the tube.
6.
Fill the verification tube according to one of the two alternatives below.
Step 4a: Filling the verification tube with ambient air
1.
Disconnect both the receiver and the transmitter from the verification tube. Verification
must be performed within 10 minutes from this step to prevent air from entering into the
volume behind the lenses.
2.
Swing the verification tube a few times in the air to remove the purging gas from the tube
and fill it with ambient air. Also swing the receiver and the transmitter a few times
carefully.
3.
Wait for about 60 seconds.
4.
Reconnect the receiver and transmitter to the verification tube. Be careful not to allow any
other gas than air to enter the tube, including breath.
Step 4b: Filling the verification tube with pressurized air
1.
Disconnect the nitrogen source.
2.
Attach your source of dry, oil free, pressurized air to the needle valve on either of the
receiver or transmitter side, and purge with a volume flow of approx. 4 liters/minute.
Verification must be performed within 10 minutes from this step to prevent air from
entering into the volume behind the lenses.
3.
Purge until the concentration value stabilizes (concentration changes less than 0.1 vol %
/ minute) and then turn off the gas.
4.
Set the manual temperature value in the LUI to the temperature displayed by the
thermometer.