Yokogawa GC8000 Process Gas Chromatograph - Manual (Page 394)

<6. Maintenance>
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IM 11B08A01-01E
• When the stream switching valve is a pneumatic valve, change the analyzer status to
Manual and turn on the stream switching valve on the sample line to let the purge gas fl ow
in.
• When the stream switching valve is a stop valve, close all the stop valves and open the stop
valve on the sample line to let the purge gas fl ow in.
(4) Close all the stream switching valves.
IMPORTANT
• During the purge, purge gas may fl ow into the sample return line, causing pressure
fl uctuation.
Prepare the sample return line and collection tank, if necessary.
• Prepare the sample return line so that the sample does not return.
(5) Stop the supply of power.
CAUTION
The isothermal oven is extremely hot after turning off the power immediately. Keep the purging
air supplied for more than an hour after turning off the power. Keep hands away from the oven
components.
(6) Turn off the supply of the purging air and the carrier gas. For a detection system with an FID,
turn off the supply of hydrogen (or nitrogen) gas and the combustion air as well.
(7) Remove the cover or insulator attached to LSV, if any.
(8) Remove the four couplings connected to the outside of the isothermal oven. When removing
the couplings, label them for ease of identifying the connections later.
(9) Turn the locknut to LSV counterclockwise with the coil over wrench for LSV to remove it.
Slowly pull off the cylinder of LSV.
(10) Remove the seal unit. When it is diffi cult to remove the seal unit, fi rst remove the four
screws on the locknut-clamp fi tting.
(11) Install a new seal unit. Then reinstall the cylinder part in the reverse order of step (9).
Note
• If any deposit cannot be removed from the stem, replace the stem with a new one.
• Take care not to damage the stem.
• Disc springs of the spring assembly should be stacked face-to-face.
• Manually fasten the locknut of LSV. Then give it a 1/4 clockwise turn with the coil over
wrench for LSV.
(12) Reconnect the pipes in the reverse order of step (8).
(13) Perform a leak test on the piping.
Note
After the isothermal oven temperature become stable at the preset level, rotate the locknut by
another 1/8 turn to fasten it.
2nd Edition : May 11, 2012-00
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