Special Conditions to Comply with SIL-
2 Requirements
74
SafEye
TM
Open Path Detection System User Guide
A.4.2
Alarm Operation Using the 4
–20mA Signal Current
•
The connected controller has to monitor the 4
–
20mA signal current for
on page 24).
Mode
Normal
Warning
Alarm
Continuous current with low
sensitivity (Full Scale: 5 LEL*m)
4 mA
(0 LEL*m)
7.2 mA
(1 LEL*m)
13.6 mA
(3 LEL*m)
Continuous current with high
sensitivity (Full Scale: 2 LEL*m
4 mA
(0 LEL*m)
7.2 mA
(0.4 LEL*m)
12 mA
(1 LEL*m)
Discrete current
4 mA
14 mA
19 mA
•
The connected controller has to monitor the 4
–
20mA signal current for
values below 4mA and above 20mA.
A.4.3
Alarm Operation Using Relay Outputs
•
Low Demand
:
Only 1 alarm relay is needed
•
High Demand
:
The accessory relay has to be configured as the
second alarm relay. The contacts of both alarm relays have to be
connected in series.
•
The fault relay error message has to be monitored by the connected
controller.
•
The relay contacts must be protected with a fuse rated at 0.6 of the
nominal specified relay contact current.
A.5
Miscellaneous
•
The complete functional performance of the gas detector has to be
verified every 6 months (gas detection, fault detection, performance of
the 4
–
20mA signal current and the relays), gas alarms On and Off.
•
The HART and RS-485 interface may not be used for the transmission
of safety-related data.
