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GA0383P02 Rev. C
Typical Responses to GCM-A Warning & Alarm Indications
This section addresses what a power plant may consider as reasonable actions in response
to particular GCM-A indications. It does not purport to cover all instances.
The GCM-A provides information for plant personnel to use in making operational decisions.
The information provided is often validated by other I&CS. Plant management is encouraged
to consider the relationship of the GCM-A to other systems installed on site. By considering
these relationships, plant management will be in the best position to maximize the utility of
the GCM-A to the plant’s efficient operation.
In the event of:
GCM-A System Trouble — Select SHOW FAULTS LOG from the <LOG MENU>. If no
faults are indicated, then the operator may have disabled monitoring. If faults are indicated,
see the section “About the Faults Log” for interpretation.
Ambient Warning and Alarm — The Warning point is typically selected based on an initial
examination of the normal, or typical, background particle level at the site. Standard practice
is to allow a GCM-A run for several days to determine the highest nominal background
particle level at the site and then select a Warning point that is marginally above that. The
Alarm set point is similarly arrived at; the Alarm point must always higher than the Warning.
When Ambient particle levels rise above the Warning and possibly to the Alarm threshold, it
is reasonable to ask whether this is a short-term condition or whether the nominal
background particle level has changed due to the introduction of another environmental
factor.
In the event of an Ambient Warning or Alarm, examine the operating environment for the
presence of particle generation sources that are not common to the normal operating
environment (excessive exhaust or a fire is a good example of an extraneous source). If
there is such a temporary extraneous event, site personnel should consider whether it
can/should be eliminated/anticipated in the future and make adjustments to Warning and
“Alarm” set points as necessary.
If additional equipment has been installed at the plant site since the GCM-A’s installation
date, an Ambient Warning or Alarm may result from that equipment’s impact on nominal
background particle levels. In such an instance, site personnel may need to consider
increasing the Warning point to a level that is above the highest anticipated nominal particle
level. Essentially, the GCM-A is an environmental monitor; therefore, if the nominal
background particle level has changed because of the introduction of a sustained particle
generating source, reassessment of Warning and Alarm points is required.
Generator Warning and Alarm — The Generator Warning and Alarm points are selected
similarly to the Ambient points (see above). Therefore, a change in the nominal Ambient
particle level could be expected to cause a similar particle level increase in the Generator
signal, insofar as the Ambient air represents the same air as the air contained within the
generator’s cooling circuit.
If a Generator Warning or Alarm occurs and it is not accompanied by an Ambient Warning
or Alarm, site personnel are advised to consider that overheating may be occurring within
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