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...11 MAINTENANCE
11.3.2 Purge Gas Katharometer Calibration
Carry out a calibration check in accordance with Section 8.3.
This task should be carried out before using the katharometer for
monitoring a purging procedure.
11.3.3 Changing Desiccant in Drying Chamber
The need to change the desiccant in the drying chamber on the
katharometer analyser panel depends on the condition of the
sample gas.
It is recommended that the analyser system is monitored
regularly during the initial phase of operation for indications that
the desiccant is exhausted. Then a suitable maintenance interval
for this task can be established.
As the desiccant degrades, the white grains can be seen to have
a yellowish tinge and the granular form becomes more
consolidated. If liquid contamination occurs, the desiccant
becomes brown and consolidated.
Warning. Suitable safety precautions will apply to
the operation of the gas cooling and sample systems.
a) Isolate the sample gas system from the main system. Carry
out a limited hydrogen purging operation on the sample
system in accordance with the instructions of the
responsible authority.
b) Carry out the procedure given in Section 6.1.
c) After purging any residual air from the sample system in
accordance with the requirements of the responsible
authority, allow hydrogen to pass through the katharometer
again.
This task should be undertaken on the basis of instrument
response or at intervals of 1 year.
Stand-offs
Katharometer Filament Block
Fig. 11.1 Removing Liquid from the
Katharometer Block
40
PCB
Drain
Potentiometer
11.4 Repair Maintenance
11.4.1 Removing Liquid from Katharometer
Measurement Block – Fig. 11.1
If tests indicate that there is likely to be an accumulation of liquid
in the katharometer filament block, it may be removed using the
following procedure:
a) Electrically isolate the defective katharometer at its PSU.
b) Isolate the gas sample system to the particular katharometer
from the main gas cooling system. Purge the sample system
of hydrogen in accordance with the requirements of the
responsible authority.
Warning. The thermal insulation inside the case
must not be damaged or removed.
c) Remove the cover of the katharometer unit and dismantle
the internal sample system pipework.
d) Remove the fixing screws which secure the mounting pillars
to the case. See Fig. 5.2.
e) Disconnect the interconnecting wiring at terminal block TB1.
Caution. Do not insert any type of probe into the
gas system of the katharometer filament block assembly or
use compressed air to blow through the system.
f)
Remove the katharometer filament block assembly from the
case and tilt at 45° to the horizontal. This allows any liquid to
drain from the measurement block. See Fig. 11.1.
g) Pour a small quantity of rectified spirit (ethanol) through the
katharometer filament block. Allow as much liquid as
possible to drain out. Assist this by gentle shaking. Repeat
this procedure several times until all evidence of
contamination is removed.
h) Fit the katharometer filament block assembly into its case.
Replace the fixing screws and make the electrical
interconnections at terminals TB1 – 1 and TB1 – 4.
i)
Fit the internal sample gas tubing.
j)
Remake the sample gas tube interconnection couplings.
k) Replace the desiccant in the drying chamber in accordance
with the procedure given in Section 11.3.3.
l)
Carry out a leak test in accordance with the requirements of
the responsible authority.
m) Power up the katharometer unit by switching on the
appropriate PSU.
n) Arrange to pass dry air or another suitable dry gas through
the katharometer at the normal sample flowrate for 24 hours.
o) Isolate the katharometer unit at its PSU.
p) Make the remaining electrical connections at TB1 of the
katharometer unit – see Fig. 5.3.
q) Replace the cover of the katharometer unit.
r) Power up the katharometer unit from its PSU.
s) Carry out a calibration procedure in accordance with Section
8.3.
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