Chapter 5 Explanations
Mini-Switch LB 471
High gas pressure
If the container is under gas pressure
during operation, empty calibration
also has to be carried out under this
gas pressure. If this is not possible,
then empty calibration may also be
carried out without gas pressure, and
then it has to be compensated for au-
tomatically using the entries in:
Code 33 (container diameter) and
Code 34 (gas density).
Cooling or heating jacket
Cooling or heating jackets have to be
filled for calibration. In order to pre-
serve the density of the cool-
ing/heating liquid, it should have the
same temperature as under operating
conditions.
5.2.1 External Empty Calibration
Wall deposits and caking may trigger false alarms.
If these deposits build up slowly and their layer thickness changes
only gradually, you can ensure the safe function of the measure-
ment by carrying out regular empty calibrations. A digital input
(terminals 22a/c) allows automatic empty calibration directly from
the control room. If the terminals are short-circuited, empty cali-
bration is performed followed by an automatic calibration. Pre-
requisite is that the level of filling is below the monitoring
level.
A measuring system using a Co-60 source is less sensitive to wall
deposits than one with a Cs-137 source.
Figure 11:
Container with
gas pressure
Figure 12:
Container with
cooling or
heating jacket
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