59
6.2.3.2 Can’t resume normal operation after a “Low
Flow” shut down
Possible causes:
Sample probe or internal pump filters need replacement,
sample hose kinked, sample probe and probe assembly
contains fluids.
Solution(s):
Turn off PhD Lite, remove pump, disconnect sample
probe an hose assembly, allow any trapped fluids to
drain; replace filters as necessary, examine hose to
make sure there are no kinks blocking normal flow.
6.3 Sample probe assembly
The sample probe handle contains moisture barrier
(hydrophobic) and particulate filters designed to remove
contaminants that might otherwise harm the instrument.
CAUTION: Never operate the PhD Lite in remote
sampling mode without the sample probe and hose
assembly. The sample probe handle contains
replaceable filters designed to block moisture and
remove particulate contaminants. If the pump is
operated without the probe assembly in place
particulate contaminants may cause damage to the
pump, sensors and internal components of the PhD
Lite.
Particulate contaminants are removed by means of a
cellulose filter. The hydrophobic filter includes a 0.1 µm
Teflon™ barrier which blocks the flow of moisture as well
as any remaining particulate contaminants.
Sample probe filters should be replaced whenever
visibly discolored due to contamination. A spare filter
replacement kit (Biosystems part number 54-05-K0401)
is included with every PhD Lite.
Figure 6.3 PhD Lite sample draw probe
6.3.1 Changing sample probe filters
The threaded sample probe handle is unscrewed (as
shown in Figure 6.3 above) to provide access to the
filters. The particulate filter is held in place by a clear
filter cup. To replace the particulate filter, remove the
old filter and cup, insert a new filter into the cup, and
slide the cup back into place in the probe handle. The
hydrophobic barrier filter fits into a socket in the rear
section of the probe handle. (The narrow end of the
hydrophobic barrier filter is inserted towards the rear of
the handle.)
6.3.2 Changing sample probe tubes
The standard 11.5” long probe tube is held in place by
means of a hex-nut compression fitting and
compression sleeve. The standard probe tube is
designed to be easily interchangeable with other custom
length sections of 1/4” OD tubing, or probe tubes made
of other materials (such as stainless steel).
To exchange probe tubes, loosen the hex-nut
compression fitting, remove the old tube, slide the
compression sleeve into place around the new tube,
insert the new tube into the probe handle, and replace
and tighten the hex-nut.
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