GE Moisture Image 1 Series Service Manual page 97

B. Laboratory
Procedures
Application of the Hygrometer (900-901D1)
If in-line measurements are not practical, then there are two possible
laboratory procedures:
1. The unique ability of the GE Panametrics sensor to determine the
moisture content of a liquid can be used as follows:
a. Using the apparatus shown in Figure A-3 on page A-33,
dissolve a known amount of the solids sample in a suitable
hydrocarbon liquid.
b. The measured increase in the moisture content of the
hydrocarbon liquid can then be used to calculate the moisture
content of the sample.
c. For best results, the hydrocarbon liquid used above should be
pre-dried to a moisture content that is insignificant compared
to the moisture content of the sample.
Note: Since the addition of the solid may significantly change the
saturation value for the solvent, published values should not
be used. Instead, an empirical calibration, as discussed in the
previous section, should be used.
d. A dew point of -110°C, which can correspond to a moisture
-6
content of 10 PPM
sensor sensitivity. The maximum measurable moisture content
depends to a great extent on the liquid itself. Generally, the
sensor becomes insensitive to moisture contents in excess of
1% by weight.
2. An alternative technique involves driving the moisture from the
solids sample by heating:
a. The evaporated moisture is directed into a chamber of known
volume, which contains a calibrated moisture sensor.
b. Convert the measured dew point of the chamber into a water
vapor pressure, as discussed earlier in this appendix. From the
known volume of the chamber and the measured vapor
pressure (dew point) of the water, the number of moles of
water in the chamber can be calculated and related to the
percent by weight of water in the test sample.
c. Although this technique is somewhat tedious, it can be used
successfully. An empirical calibration of the procedure may be
performed by using hydrated solids of known moisture content
for test samples.
or less, represents the lower limit of
W
June 2003
A-35