Safety Data

These PFD
avg
and PFH calculations are based on the equations from Part 6 of EN 61508 and show worst-case values.

Safety Data for Safe Torque Off

These values apply when Safety Instance is set to ‘Safe Stop Only – No Feedback’.
PFD
avg
and PFH for PowerFlex 755 Drives STO and Times SS1 for SIL 3/PLe (category 4)
Attribute
Frames 1…7
Frame 8
Frame 9
Frame 10
PFD
avg
4.08E-5
1.81E-4
2.73E-4
3.64E-4
PFH (1/hour)
4.77E-10
2.09E-9
3.14E-9
4.19E-9
MTTF
D
years
204.1 (high)
93.3 (high)
69.1 (high)
55.1 (high)
DC
avg
%
97.5% (medium)
97.4% (high)
97.5% (high)
97.5% (high)
HFT
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
Mission time
20 years
20 years
20 years
20 years
PFD and PFH for PowerFlex 755T Drive Products STO and Timed SS1 for SIL 3/PLe (category 4)
Attribute
Frames 5 and 6
Frames 7 and 8
Frame 9
Frame 10
Frame 11
Frame 12
Frame 13
Frame 14
Frame 15
PFD
avg
4.49E-5
2.56E-4
2.82E-4
3.08E-4
3.34E-4
3.60E-4
3.86E-4
4.38E-4
4.90E-4
PFH (1/hour)
5.24E-10
2.96E-9
3.25E-9
3.55E-9
3.85E-9
4.15E-9
4.45E-9
5.05E-9
5.65E-9
MTTF
D
years
187.5 (high)
102.6 (high)
87.8 (high)
76.7 (high)
68.1 (high)
61.2 (high)
55.6 (high)
47 (high)
40.7 (high)
DC
avg
%
97.4% (high)
97.0% (high)
97.0% (high)
97.0% (high)
97.0% (high)
96.9% (high)
96.9% (high)
96.9% (high)
96.9% (high)
HFT
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
1 (1oo2)
Mission time
20 years
20 years
20 years
20 years
20 years
20 years
20 years
20 years
20 years
PFD
avg
and PFH for PowerFlex 755TS Drives  for SIL 3/PLe (category 4)
Attribute
Frames 1…7
PFD
avg
4.12E-05
PFH (1/hour)
4.81E-10
MTTF
D
years
202.2
DC
avg
%
97.5 (high)
HFT
1 (1oo2)
Mission time
20 years

Safety Data for Safe Feedback

Use these values with the PFD
avg
or PFH values above for safety functions that require safe encoder feedback. Safety functions using safe encoder feedback include drive based Monitored Safe Stop 1 and controller-based safety functions SS1, SS2, SOS, SLS, SLP, and SDI.
When using Dual Feedback Monitoring, enable Discrepancy Testing.
PFD
avg
or PFH to Add When Safety Functions Use Safety Feedback
Attribute
Single Encoder Feedback
SIL 2/PLd (Category 3)
Dual Encoder Feedback
(Dual channel values apply with discrepancy checking configured)
SIL 3/PLe (Category 4)
PFD (average)
6.75E-4
4.32E-5
PFH (1/hour)
7.70E-9
4.93E-10
MTTF
D
years
1446.7 (high)
1427.7 (high)
DC
avg
%
90.0% (medium)
99.0% (high)
HFT
1 (1oo2)
1 (1oo2)
Mission time
20 years
20 years
The safe motion-monitoring option can be configured for single feedback or dual feedback to achieve the following safety rating:
  • Single feedback configurations provide up to SIL 2 PLd capability.
  • Dual-feedback configurations provide up to SIL 3 PLe capability when discrepancy testing (either velocity, position, or both) is enabled.
IMPORTANT:
Achievable safety rating depends on each system component. For Safe Feedback, the safety rating of the selected encoders may limit the safety rating of the system.

Safety Data for Safety I/O

The Integrated Safety Functions option module provides four safety inputs and two safety outputs.
PFD or PFH to Add When Safety Functions Use Safety I/O
Attribute
Single Channel Safety I/O
SIL 2/PLd (Category 2)
Dual Channel Safety I/O
SIL 3/PLe (Category 4)
PFD (average)
3.35E-4
2.49E-4
PFH (1/hour)
3.83E-9
2.84E-9
MTTF
D
years
1064.9 (high)
1998.0 (high)
DC
avg
%
96.4% (high)
94.2% (high)
HFT
0 (1oo1)
1 (1oo2)
Mission time
20 years
20 years
IMPORTANT:
Single channel safety I/O is only certified for use in functional safety applications with process safety times greater than or equal to 300 ms; or applications with demand rates less than or equal to 1 demand per 30 second
If single channel safety I/O is used, pulse testing (external pulse testing for safety inputs, pulse testing for safety outputs) MUST be enabled on the single channel I/O points.

Spurious Trip Rate

The Spurious Trip Rate (STR) and Mean Time to Failure Spurious (MTTF Spurious) values for the Integrated Safety Functions option module are calculated according to the ISA TR- 84 method.
STR and MTTF Spurious Values
Attribute
Value
Spurious Trip Rate
3.00E-6
MTTFSpurious (years)
37.0
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