15
GA0383P02 Rev. C
the generator cooling circuit. In this instance, other site instrumentation should be reviewed
for corroborating indications of generator overheating.
Differential Warning and Alarm — A Differential Warning or Alarm occurs as a result of a
difference existing between Ambient and Generator particle levels. It is an expression of
“Generator less Ambient” and its value cannot equal less than zero.
The Differential Warning and Alarm set points are adjustable, with the factor default being a
30 percent difference for Warning and a 50 percent difference for Alarm. These settings are
adjustable.
In the event of a Differential Warning or Alarm, other site instrumentation should be
reviewed for corroborating indications of generator overheating. The GCM-A’s indication of a
Differential Warning, and particularly a Differential Alarm, is the most serious indication of a
thermal particulation event occurring within the generator’s cooling circuit. Site personnel
are advised to immediately initiate internal procedures for dealing with an acute problem that
could lead to generator failure.
Environment One is sometimes asked whether a GCM-A Differential Alarm should be used
to “trip” a generator off-line. This is not a question that Environment One is in a position to
respond to, as decisions relating to taking a generator off-line involve significant economic
considerations/repercussions and are solely the responsibility of site management.
Environment One can only advise GCM-A end-users that our experience has been that
operators typically reduce load upon a verified alarm in one of our overheat monitoring
instruments. They typically evaluate whether a reduced load changes the alarm condition
and then act in accordance with their established internal procedures. In the event that plant
operators choose to use a GCM-A to trip a generator, the “Differential Alarm” is the only
indication that should be used.
(Typical Responses, cont’d)
To Next Page
Loading...