Rockwell Automation 21G PowerFlex 750 Series Safe Torque Off - Manual (Page 12)

12 Rockwell Automation Publication 750-UM002F-EN-P - July 2013
Chapter 2 Safety Concept
PFD and PFH Data PFD and PFH calculations are based on the equations from Part 6 of IEC 61508.
This table provides data for a 20-year proof test interval and demonstrates the
worst-case effect of various configuration changes on the data.
PFD and PFH for 20-year Proof Test Interval
Safe State The Safe State encompasses all operation that occurs outside of the other
monitoring and stopping behavior defined as part of the Safe Torque Off Option
module.
If a Safe State Fault is detected, the safety option goes to the Safe State. This
includes faults related to integrity of hardware or firmware.
Safety Reaction Time The safety reaction time is the amount of time from a safety-related event as
input to the system until the system is in the Safe State.
The safety reaction time from an input signal condition that triggers a safe stop,
to the initiation of the configured Stop Type, is 10 ms (maximum) for drive
Frames 1…10.
Attribute Value
Drive Frames 1…7 Drive Frame 8 Drive Frame 9 Drive Frame 10
PFD 3.29E-5 1.73E-04 2.65E-4 3.56E-4
PFH 3.75E-10 1/hour 1.99E-9 1/hour 3.04E-9 1/hour 4.09E-9 1/hour
SIL CL 3 3 3 3
PL e e e e
Category 3 3 3 3
HFT 1 (1oo2) 1 (1oo2) 1 (1oo2) 1 (1oo2)
PTI (Proof Test Interval) 20 years 20 years 20 years 20 years
IMPORTANT An input signal condition that is present for less than the reaction time may not
result in the safety function being performed. Repeated request of the safety
function for less than the reaction time may result in a spurious detection of a
fault.