European Safety Systems Ltd.
Impress House, Mansell Road, Acton, London W3 7QH
www.e2s.com
Tel: +44 (0)208 743 8880
Document No. D156-00-621-IS
Issue 1
27-10-22
Sheet 8 of 15
12) SIL 2 Instruction Safety/Manual
Figure 11: The SIL 2 Module monitors the Beacon and interfaces to the customer plant.
Warning
–
To maintain the integrity of the SIL 2 units the system must be installed, commissioned and used within the
parameters outlined in this manual. Failure to comply could result in an unintended unit operation or function.
Warning
–
The unit must be powered in either Standby or Active modes to comply with the SIL 2 approval requirement. If the
power is disrupted the unit must be allowed to go through the commissioning cycle to reset. Failure to complete the
commissioning cycle and continued disruption in the power supply will generate a fault state which will require the
beacon to be reset (see section 15-4).
SIL 2 System Description
The SIL 2 module monitors the function of the device and
provides feedback to the control panel. A fault condition can
be communicated by two methods:
•
4 wire installation can be seen as per section 15-1.
A SIL 2 system wiring for fault detection in standby
and active mode with independent fault contacts.
•
2 wire installation can be seen as per section 15-2.
A SIL 2 system by the introduction to the monitoring
circuit and linking in an end of line resistor can only
register the fault in standby mode.
13) SIL 2 System Terms and Function
The SIL 2 Beacon Unit Monitors:
•
Standby mode and Active mode
•
Health status of power supply
•
Beacons correct function and flash pattern
The SIL 2 beacon operates as part of a SIL 2 system.
The beacon will after commissioning remain powered in
Standby mode
(reverse polarity) until the beacon is required
to operate. When the signalling device is required to operate
beacon the polarity is changed back to normal supply and the
beacon will go into
Active mode
where it will start to
function/flash. When periodically testing the system and
beacons, operation is put into
Active mode
.
The system panel or PLC will control whether the system is in
either of the main two operational modes.
Standby Mode
–
This is where the power supply polarity is
reversed so negative (
–
ve) is fed to the positive (+) beacon
terminal and positive (+) is fed to the negative (
–
ve) beacon
terminal.
In Standby mode the beacon will not flash but the SIL 2 unit
is monitoring power supply and is set-up ready to go to Active
(alarm) mode.
Power relay RLY1-1 will be open whilst SIL 2 relay RLY1-2
will be closed contact between terminals 1 & 2.
If power is disrupted the SIL 2 unit will go into
Fault mode
, in
fault mode the Power relay RLY1-1 will close whilst SIL 2
relay RLY1-2 will become an open circuit between terminals
1 & 2.
Active Mode
–
This is where the power is in normal polarity,
positive (+) supplied to the positive (+) beacon terminal and
negative (
–
ve) is supplied to the negative (
–
ve) beacon
terminal.
In Active mode the beacon will output the selected flash
pattern. The SIL 2 module checks for the correct flash pattern
output and the functionality of the flash signal generation
process.