Common Problems - GE PM880 Operations & Installation Manual

Common Problems

If the PM880 measurement readings seem strange, or they do not
make sense, there may be a problem with the probe or a
component of the process system. Table 9-2 below contains some
of the most common measurement problems.
.
Table 9-2: Troubleshooting Guide for Common
Possible Cause
Symptom: Accuracy of moisture sensor is questioned.
Insufficient time for
system to equilibrate
Dew point at sampling
point is different than
the dew point of the
main stream.
Sensor or sensor shield
affected by process
contaminants (refer to
Appendix A).
Diagnosis and Troubleshooting
Problems
System
Response
Probe reads too Change the flow rate. A change in
wet during dry dew point indicates the sample sys-
down condi- tem is not at equilibrium, or there is a
tions, or too dry leak. Allow sufficient time for sam-
in wet up con- ple system to equilibrate and mois-
ditions. ture reading to become steady. Check
for leaks.
Probe reads too Readings may be correct if the sam-
wet or too dry. pling point and main stream do not
run under the same process condi-
tions. The different process condi-
tions cause readings to vary. If
sampling point and main stream con-
ditions are the same, check sample
system pipes, and any pipe between
the sample system and main stream
for leaks. Also, check sample system
for adsorbing water surfaces, such as
rubber or plastic tubing, paper-type
filters, or condensed water traps.
Remove or replace contaminating
parts with stainless steel parts.
Probe reads too Clean the sensor and the sensor
wet or too dry. shield as described in Aluminum
Oxide Probe Maintenance on
page A-9 in Appendix A. Then rein-
stall sensor.
August 2003
Action
9-5