GE Moisture Image 1 Series, Service Manual, Page: 71 / 107

Application of the Hygrometer (900-901D1) A-9
June 2003
Corrosive Gases And
Liquids
GE Panametrics M Series Aluminum Oxide Moisture Sensors have
been designed to minimize the affect of corrosive gases and liquids.
As indicated in the
Materials of Construction section of this
appendix, no copper, solder or epoxy is used in the construction of
these sensors. The moisture content of corrosive gases such as H
2
S,
SO
2
, cyanide containing gases, acetic acid vapors, etc. can be
measured directly.
Note:
Since the active sensor is aluminum, any fluid which corrodes
aluminum will affect the sensor’s performance.
By observing the following precautions, the moisture probe may be
used successfully and economically:
1. The moisture content of the corrosive fluid must be 10 PPMv or
less at 1 atmosphere, or the concentration of the corrosive fluid
must be 10 PPMv or less at 1 atmosphere.
2. The sample system must be pre-dried with a dry inert gas, such as
nitrogen or argon, prior to introduction of the fluid stream. Any
adsorbed atmospheric moisture on the sensor will react with the
corrosive fluid to cause pitting or corrosion of the sensor.
3. The sample system must be purged with a dry inert gas, such as
nitrogen or argon, prior to removal of the moisture probe. Any
adsorbed corrosive fluid on the sensor will react with ambient
moisture to cause pitting or corrosion of the sensor.
4. Operate the sample system at the lowest possible gas pressure.
Using the precautions listed above, the hygrometer has been used to
successfully measure the moisture content in such fluids as
hydrochloric acid, sulfur dioxide, chlorine and bromine.