VEGA VEGATROL 10 Ex 1 - Manual (Page 4)

VEGATROL 10 Ex 1 4
2 Technical Information
2.1 Product description
General
The described fail-safe overfill protection VEGATROL 10
consists of a VEGASWING 83 W5 Ex vibrating level switch
and VEGATOR 526 W Ex signal conditioning instrument.
The application range comprises stationary vessels acc. to
the pressure vessel regulations for storing liquid gas acc.
to DIN 51 622:
- in individual vessel plants
- in liquid gas plants
- in distribution plants
- in plants with several vessels
each of group A, B, C and D.
When used in distribution plants up from group C min. two
separate overfill protections must be installed acc. to the
requirement of TRB 801, no. 25. Even in these cases one
VEGATROL 10 is sufficient due to the VdTÜV-approval to
meet with the TRB-requirement.
In plants with several vessels VEGATROL 10 can be used
as continuous monitoring and locking system.
Function
The level is detected by a vibrating level switch
VEGASWING. Its tuning fork is piezoelectrically energized
and vibrates at its mechanical resonance frequency. A
second piezoelectric element measures this resonance
frequency. If the tuning fork is covered by the liquid gas,
the resonance frequency changes proportional to the
degree of covering. The oscillator in VEGASWING detects
continuously the resonance frequency and converts the
value into a current to the signal conditioning instrument.
When the switch point is reached an erratic increase of the
current signal is triggered. The level relay in the signal
conditioning instrument de-energizes.
Fail-safe / Self-monitoring
A special feature of the overfill protection of VEGATROL
10 is the integral self-monitoring. It is based on a redun-
dant microprocessor system in the signal conditioning
instrument and includes the whole measuring chain from
the tuning fork via the oscillator, the two-wire line as well
as the signal conditioning instrument.
The self-monitoring includes two routines:
-
the permanent monitoring
- the cyclical selftest.
During the permanent monitoring the signal conditioning
instrument causes the oscillator of the sensor to trigger a
test cycle in 960 msec. cycle. Defined test signals are
transmitted via the two-wire line to the signal conditioning
instrument. Possible failures in the sensor electronics as
well as line break, short-circuit and mechanical damage on
the tuning fork are signalled via these test signals. During
the cyclical selftest security relevant components and
procedures (e.g. level relay, CPU, memory, time reaction)
are checked in the signal conditioning instrument in a very
tough time pattern. The function test of the level relays is
made without interruption of the circuit of connected
systems.
If during the self-monitoring a failure is detected, the level
relays and the fail safe relay de-energize.
Due to the above mentioned measures a reliable and
correct function of the overfill protection is ensured without
any staff involved for control tasks.
2 Technical Information