Aerotech Automation1 XC2, Hardware Manual, Page: 55 / 96

2.4.1. STO Standards
Table 2-26 describes and specifies the safety requirements at the system level for the Safe Torque Off
(STO) feature of the XC2. This assumes that diagnostic testing is performed according to Section 2.4.4.
and Table 2-27 .
Table 2-26: STO Standards
Standard Maximum Achievable Safety
EN/IEC 61800-5- 2:2016 SIL 3
EN/IEC 61508-1:2010 SIL 3
EN/IEC 61508-2:2010 SIL 3
EN ISO 13849-1:2015 Category 4, PL e
EN/IEC 62061:2005 with Amendments SIL 3
Table 2-27: STO Standards Data
Standard Value
EN ISO 13849-1:2015
MTTF
D
> 1000 years,
DC
AVG
99%
Maximum PL e, Category 4
EN ISO 13849-1:2015
EN/IEC 61508
Lifetime = 20 years
No proof test required
Interval for manual STO test:
l
Once per year for SIL2/PL d/category 3
l
Once per three months for SIL3/PL e/category 3
l
Once per day for SIL3/PL e/category 4
EN/IEC 61508
SIL3
PFH < 3 FIT
SFF > 99%
XC2 Hardware Manual 2.4. Safe Torque Off Input (STO)
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