Circuit with OSSD (SIL 3)
The following figure shows a circuit without OSSD safety device, whilst only safety
directed command devices with forcibly opened contacts in two-channel design are
used. SIL 3 (according to EN ISO 13849-1) is achieved. It is also possible to cascade
several different safe emergency stop devices, position switches or door locks to one
safety circuit.
Circuit without OSSD (SIL 3)
The safety switch device as well as the emergency stop device have to be
certificated as safety devices of at least level SIL 3 to obtain safety level
SIL 3 according to EN ISO 13849-1.
In order to obtain the safety level SIL 3 according to EN ISO 13849-1the
circuit and the layout have been dimensioned according to IEC
60664-1:2008-01. Supporting material according to IEC 60249 covered by a
nonaging protective coat of lacquer according to IEC 60664-3:2003-09 have
been used. The conformity of standard have been tested and approved by
the TÜV-Nord CERT.
13.3 Requirements and Standards
The following parameters are achieved according to the safety case:
▶ according to EN ISO 13849-1:2008-12
─ MTTFd: >100 years
─ DC = 99%
─ Category 4
─ Performance Level e
▶ according to EN 61508-1:2010 and EN 61800-5-2:2014-06
─ PFH = 0
─ SFF = 100 % (if there are PFH values, then SFF<100%)
─ HFT = 0
Safety Circuit / Restart Lock (STO)
W
78 Drive Amplifier SD2B / SD2B plus - Hardware Description
13
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