Rockwell Automation Publication 2198-UM001I-EN-P - May 2019 173
Kinetix 5500 Safe Torque-off - Hardwired Safety Chapter 9
Probability of Dangerous
Failure Per Hour
Safety-related systems are classified as operating in a High-demand/continuous
mode. The SIL value for a High-demand/continuous mode safety-related
system is directly related to the probability of a dangerous failure occurring per
hour (PFH).
PFH calculation is based on the equations from IEC 61508 and show worst-
case values. Table 68
provides data for a 20-year proof test interval and
demonstrates the worst-case effect of various configuration changes on the
data.
Table 68 - PFH for 20-year Proof Test Interval
Safe Torque-off Connector
Data
The 10-pin connector consists of two parallel 5-pin rows for cascading safety
connections from drive-to-drive in multi-axis configurations.
Figure 75 - Pin Orientation for 10-pin Safe Torque-off (STO) Connector
Table 69 - Safe Torque-off (STO) Connector Pinouts
IMPORTANT Determination of safety parameters is based on the assumptions that
the system operates in High-demand mode and that the safety function
is requested at least once every three months.
Attribute Value
PFH (1e-9) 0.35
Proof test (years) 20
Pin 1
SB+
SB-
S1
SC
S2
STO Pin Description Signal
1
Safety bypass plus signal. Connect to both safety inputs to disable the STO
function.
SB+
2
Safety bypass minus signal. Connect to safety common to disable the STO
function.
SB-
3 STO input 1 (SS_IN_CH0). S1
4 STO input common (SCOM). SC
5 STO input 2 (SS_IN_CH1). S2
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