2.3 Safety loop
The safety loop, to which the AC500-S Safety PLC belongs, consists of the following three parts: sensors,
Safety PLC and actuators.
~35 % of safety loop PFH
~1
5 % of safety loop PFH
~50 % of safety loop PFH
Safety loop
Safety PLC
Sensor
Safety CPU
Module
Safety Input
Module
Safety Output
Module
Actuator
Fig. 3: Typical safety loop with AC500-S Safety PLC
For the calculation of the PFH/PFD values of an examplary safety system, a maximum of 15 % is assumed
for the Safety PLC. The detailed values of PFH for AC500-S Safety modules and PFH/PFD of the Safety
PLC Loop can be obtained on request.
2.4 Safety values
Table 1: The following safety values can be used for AC500-S safety modules:
Type
Description
SIL
(1)
PL
(2)
DC
(3)
PFHd
(4)
MTTFd
(5)
T1
(6)
SM560-S (-XC)
Safety module
3
e
≥ 95 %
< 3.0E-09
> 100 years 20
AI581-S (-XC)
Safety Analog Input
Module
3
e
≥ 95 %
< 3.0E-09
> 100 years 20
DI581-S (-XC)
Safety Digital Input
Module
3
e
≥ 95 %
< 3.0E-09
> 100 years 20
DX581-S (-XC) *
Safety Digital Input/
Output Module
3
e
≥ 94 %
< 3.0E-09
> 100 years 20
(1)
- according to IEC 62061 and IEC 61508 ed. 2 (continuous and high demand mode)
(2)
- according to ISO 13849-1
(3)
- Diagnostic Coverage (see ISO 13849-1)
(4)
- Probability of dangerous failure per hour according to IEC 61508 ed. 2 (Continuous and high demand
mode) and IEC 62061
(5)
- Mean Time To Failure (years) dangerous according to ISO 13849-1
(6)
- Proof Test Interval - Mission Time - Lifetime Years
* - See the danger note below
Overview of AC500-S Safety PLC
Safety values
30.03.2017
AC500-S
20
