GE Moisture Image 1 Series, Service Manual, Page: 88 / 107

June 2003
A-26 Application of the Hygrometer (900-901D1)
B: Special Case (cont.)
Note: If the saturation concentration at the desired ambient
temperature can not be found for any of these special case
hydrocarbons, the value at any other temperature may be
used, because K is constant over a large temperature range.
3. Find the moisture content in hexane, at an ambient temperature of
10°C, if a dew point of 0°C is measured with the GE Panametrics
hygrometer.
a. From the literature, it is found that C
S
for hexane at a
temperature of 20°C is 101 PPM
W
.
b. Using a straightedge on Figure A-2 on page A-32, connect the
101 PPM
W
saturation concentration with the 20°C ambient
temperature and read the Henry’s Law Constant of 5.75 on the
center scale.
c. Using the straightedge, connect the above K value of 5.75 with
the measured dew point of 0°C, and read the correct moisture
content of
26 PPM
W
where the straightedge crosses the
moisture content scale.
4. Find the moisture content in an unknown organic liquid, at an
ambient temperature of 50°C, if a dew point of 10°C is measured
with the GE Panametrics hygrometer.
a. Either perform a Karl Fischer analysis on a sample of the liquid
or obtain a dry sample of the liquid.
b. Either use the PPM
W
determined by the Karl Fischer analysis
or add a known amount of water (i.e. 10 PPM
W
) to the dry
sample.
c. Measure the dew point of the known test sample with the GE
Panametrics hygrometer. For purposes of this example, assume
the measured dew point to be -10°C.
d. Using a straightedge on the nomograph in Figure A-2 on page
A-32, connect the known 10 PPM
W
moisture content with the
measured dew point of -10°C, and read a K value of 5.1 on the
center scale.
e. Using the straightedge, connect the above K value of 5.1 with
the measured 10°C dew point of the original liquid, and read
the actual moisture content of
47 PPM
W
on the left scale.