6 MAINTENANCE
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6.4.7 MALFUNCTIONS OF THE MONITOR
These may produce many effects after calibration, some of which produce the
following:
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Abnormal slope % values - see Section 4.2.
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Display alternates between (value) and “out”. A very large offset from
the sensor takes the reading beyond the range of the monitor.
The standard or Buffer solutions may cause unpredictable problems. If you
question the integrity of these solutions, replace them with freshly prepared
solutions in the early stages of the faultfinding investigations. The conditions
of all of the solutions involved, one or more of which could be incorrect,
control the monitor’s accuracy.
Note
. If the Buffer becomes completely exhausted, the reading may be very
erratic due to the lack of ionic strength adjustment of the high purity sample.
Systematically check mechanical components involved with liquid handling
for leaks or blockages—these problems change the chemical conditions
around the sensor. Most problems are found in the solution chemistry and in
the liquid handling section.
REPLACEMENT OF PLASTIC TUBING
Over time, certain sections of plastic tubing require replacement as leaks,
blockages, or poor conditions occur. To avoid this occurance, refurbish the
liquid handling panel every twelve months including the replacement of all
plastic tubing. Use only the correct size and type of tube.
Two specific sections of tubing
are critical
:
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The tube found between the constant head unit and the entrainment
“T”. The tube should be taut; any changes to this tube interfere
with the flow and self-starting characteristics.
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The tube found between Buffer container and entrainment “T”. It
must be a polyethylene-lined tube, which has good chemical
resistance to the Buffer.
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