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7835
Hydrazine Monitor
8. Cut all three drain tubes to a length of approx. 50 mm
(2 in.) below the bracket to leave angled ends.
9. Remove the mixing coil from the base of the sensor and
from the reagent dosing chamber outlet, unwinding it from
the coil former. Connect 7835 230 to the reagent dosing
chamber outlet and lead it behind the coil former. Wind on
closely and, without twisting, 4 complete turns and locate
the tube in the coil former slot. Connect to the sensor
base.
10. Remove the tube between the reagent dosing chamber
and the solenoid valve and replace with 7835 229 (second
of 2).
11. Remove the tube between the standard solution container
and the solenoid valve. Replace with 7835 228 but leave
container end unconnected.
12. Disconnect the reagent solution tube from the reagent
dosing chamber and hold over the tundish. Disconnect
the tube at the container end and allow to drain. Replace
with 0212 237, but leave container end unconnected.
13. Remove the 2 solution containers, drain and rinse.
14. Open the outlet valve of the standard solution container
and remove the stem completely. Remove the outlet union
with a 20 mm A/F spanner.
15. Use a smooth blunt needle to remove external and internal
O-rings from the union and external O-ring from the stem.
16. Replace with 0211 044, 0211 002 and 0211 068,
respectively (supplied in the retubing kit). Replace the
union and then the stem.
17. Fit the tube from the solenoid valve.
18. Fit the container onto the pillars. Tighten the screws.
19. Repeat the above for the reagent solution container; loop
the tube from the filter behind the standard solution tube
and over the electrical connection box.
20. Refurbish the sensor as required. Follow the procedure in
Section 9.4.5, page 25.
21. Follow the procedures in Section 5.1, page 13, from step
3 onwards.
IM/7835–EN Rev. P
9.3 Shut-down Procedures
9.3.1 Sensor Unit
If the monitor is to be shut down for longer than 1 week, perform
the following procedure:
1. Turn the sensor plugs, located on the side of the liquid
handling panel, a half turn anti-clockwise and disconnect
them by pulling them from the sockets.
Warning. The gel in the hydrazine sensor contains
silver oxide and sodium hydroxide. It is caustic and
stains skin and clothing.
2. Carefully pull the hydrazine sensor out of its mounting clips
on the sub-panel.
3. Holding the sensor over the drain tundish, pull off the
sample inlet tube and let the sensor drain. Leave the end
of the inlet tube dipping into the tundish.
4. Carefully dismantle the sensor and wash the components
thoroughly in high purity water to remove all traces of gel.
Dry and reassemble.
5. Replace the sensor in its mounting clips.
Warning. The reagent is extremely caustic and must
be handled with great care. Wear gloves and eye
protection.
6. Close the outlet valve on the reagent container, carefully
pull the tube off the reagent dosing chamber and remove
the reagent container. Either empty the contents into a
storage container or discard, rinse out the container and
replace in the sensor unit.
7. Clean the porous disc by attaching a piece of tubing to the
reagent dosing chamber outlet (see Fig. 4.6, page 11) and
place the other end in a beaker of high purity water. Close
the reagent dosing chamber sample inlet. Attach a large
syringe (for example 50 ml) to the reagent inlet and draw
the water through the disc. Repeat this several times.
8. Reassemble the panel, clean up any spillage and then
close the door.
9.3.2 Transmitter Unit
Isolate the electrical supply to the unit.
9 Maintenance
23
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