Changing Desiccant In Drying Chamber - ABB AK101 User Manual

...11 MAINTENANCE

11.3.3 Changing Desiccant in Drying Chamber

The need to change the desiccant in the drying chamber on the
Katharometer Analyzer panel depends on the condition of the
sample gas.
It is recommended that the Analyzer system is monitored
regularly during the initial phase of operation for indications that
the desiccant is exhausted. A suitable maintenance interval for
this task can then be established.
As the desiccant degrades, the white grains 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 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) Fill the drying chamber – see 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 procedure 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 Filament Block
44
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, remove the liquid using the
following procedure. This procedure should be undertaken as
required:
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.
Caution. 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 securing the mounting pillars to
the case – see Fig. 5.5.
e) Disconnect the interconnecting wiring at terminal block TB1.
Note. 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 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) Pass dry air or another suitable dry gas through the
katharometer at the normal sample flowrate for 24 hours.
Continued...