6
Sensitivity to Refrigerants
The system is sensitive in varying
amounts to all of the halogen-based
refrigerants,
those
containing
molecules of fluorine, chlorine or
both. As part of the initial setup, the
specific refrigerant to be monitored is
entered into the system. The control
electronics compensates for the
differing sensitivities, resulting in a
true ppm reading for the refrigerant
specified.
Factory Calibration
The IR-SNIF-1,2,3 is calibrated at
the factory prior to shipment. The
system maintains accuracy through
automatic rezeroing. Periodically,
the system switches to the fresh air
inlet, and reestablishes a reference
signal to which it compares sample
air. This process eliminates the
potential
variations
caused
by
changes that develop in electronics
as components age. If a change in
infrared energy or detection of the
infrared
energy
develops,
that
change will be first measured in the
reference signal, then also in the
sample. The ppm level is based on
the ratio of the sample to the
reference. This ratio eliminates the
effect
of
any
variations,
and
eliminates the need to periodically
calibrate a monitor in the field.
PPM vs. Leak Rate
The relationship between the actual
amount of product lost and the
resulting ppm level refrigerant in the
air is complex. There is no direct
relationship between the amount of
refrigerant
leaking
and
the
concentration being measured. The
size of the room, the location of the
pick up point, the location of the leak
and airflow in the room will all affect
the actual concentration at the inlet.
However, by judicious location of the
inlets (see installation section) and
maintaining the alarm set points at a
level not too far above ambient,
leaks
should
be
detected
substantially before they otherwise
would be noticed. See Appendix B
for a detailed discussion of room
volume
considerations.
This
appendix will help to provide a
correlation
between
pounds
of
refrigerant lost over a given period to
the ppm level measured. This
correlation can be developed for a
specific application.
Содержание IR-SNIF-1
Страница 50: ...47 05 20 2008 ...
