6. 2 Power plant installations utilizing long sample lines can
experience significant sampling problems. New sample lines
noLally require longterm conditioning. Iron oxides and other
deposits accumulate in slow flowing horizontal sample lines
and can develop chromatograph-like retention of ionic species,
resulting in very long delay times. Precautions are described in
Section 9. _
6.3 Cell and flow chamber surfaces will slowly leach trace
ionic contaminants, evidenced by increasing conductivity read-
ings with very low or zero flowrate. There must be sufficient
flow to keep these contaminants from accumulating to the point
that they affect the measurement. The high and convoluted
surface area of platinized cells precludes their use for high
purity measurements for this reason.
6.4 Capacitance of the cell and extension leadwire, espe-
cially in high purity ranges can add significant positive error to
conductance readings (negative error to resistance readings).
The measuring instrument must be designed to accommodate
cell and leadwire characteristics in high purity water as
described in 7.1.1 and Annex Al. In addition, the instrument
manufacturers’ recommendations on cell leadwire must be
carefully followed.