Contaminants; Non-Conductive Particulates - GE Moisture Image 1 Series Service Manual

Contaminants

Non-Conductive
Particulates
Application of the Hygrometer (900-901D1)
Industrial gases and liquids often contain fine particulate matter.
Particulates of the following types are commonly found in such
process fluids:
•
carbon particles
•
salts
•
rust particles
•
polymerized substances
•
organic liquid droplets
•
dust particles
•
molecular sieve particles
•
alumina dust
For convenience, the above particulates have been divided into three
broad categories. Refer to the appropriate section for a discussion of
their affect on the GE Panametrics moisture probe.
Note: Molecular sieve particles, organic liquid droplets and oil
droplets are typical of this category.
In general, the performance of the moisture probe will not be
seriously hindered by the condensation of non-conductive, non-
corrosive liquids. However, a slower response to moisture changes
will probably be observed, because the contaminating liquid barrier
will decrease the rate of transport of the water vapor to the sensor and
reduce its response time.
Particulate matter with a high density and/or a high flow rate may
cause abrasion or pitting of the sensor surface. This can drastically
alter the calibration of the moisture probe and, in extreme cases,
cause moisture probe failure. A stainless steel shield is supplied with
the moisture probe to minimize this effect, but in severe cases, it is
advisable to install a Teflon® or stainless steel filter in the fluid
stream.
On rare occasions, non-conductive particulate material may become
lodged under the contact arm of the sensor, creating an open circuit. If
this condition is suspected, refer to the Probe Cleaning Procedure
section of this appendix for the recommended cleaning procedure.
June 2003
A-5