VEGA VEGATROL 20 Ex - Manual (Page 19)

VEGATROL 20 Ex 19
4 Supplement
4.3 General instructions for the use of
overfill protections
Application of a liquid gas overfill protection (ÜFS) is to
monitor the level of the liquid gas stage and to interrupt
the filling procedure when the permitted level in the vessel
is reached and to trigger an acoustic or optic alarm.
The configuration as well as the operation of such an
overfill protection must always meet with the requirements
of an overfill protection as well as the special conditions of
the VdTÜV-regulation "overfill protection 100".
This furthermore requires that the filling of a pressurized
vessel for liquid gas is only possible if it is ensured that the
overfill protection works interferencefree and correctly. At
least before each filling procedure the whole measuring
system of the overfill protection must be checked.
Normally this test of overfill protections is triggered by a
manually triggered test key. In case of failure the filling
must be suppressed by a locking circuit.
Due to the self-monitoring, this test is not necessary with
VEGATROL.
The overfill protection always operates discontinuously
and can be planned and operated independent from the
function of the continuous level measurement. The
continuous level measurement is not subjected to the
special requirements to the functional reliability of the
overfill protection.
However both have to be included in an alarm system as
follows:
-
the continuous measurement generates the pre-alarm
signal and controls an acoustic or optic warning system
or interrupts the filling procedure
- the overfill protection triggers a main alarm signal and
stops the system
Criteria for dimensioning:
-
triggering pre-alarm, e.g. at 83 % to filling (dependent
on the vessel geometry)
- triggering main alarm, generally at 85 % filling
- tolerance of the switch point of the overfill protection:
±
1 %
The pre-alarm is adjusted such that there is sufficient time
to avoid response of the overfill protection.