Rockwell Automation Publication 2198-UM001M-EN-P - November 2022 161
Chapter 9 Kinetix 5500 Safe Torque Off - Hardwired Safety
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 shows worst-
case values. Table 72
provides data for a 20-year proof test interval and
demonstrates the worst-case effect of various configuration changes on the
data.
l
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
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.
Table 72 - PFH for 20-year Proof Test Interval
Attribute Value
PFH (1e-9) 0.35
Proof test (years) 20
Table 73 - Safe Torque Off (STO) Connector Pinouts
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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