GE RSTi-EP, Руководство по функциональной безопасности

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Chapter3 . Safety
GFK-2956A November 2017 7
Warning
EXPLOSION HAZARD - SUBSTITUTION OF COMPONENTS MAY IMPAIR
SUITABILITY FOR CLASS I, DIVISION 2.
WHEN IN HAZARDOUS LOCATIONS, TURN OFF POWER BEFORE REPLACING
OR WIRING MODULES; AND
DO NOT CONNECT OR DISCONNECT EQUIPMENT UNLESS POWER HAS
BEEN SWITCHED OFF OR THE AREA IS KNOWN TO BE NONHAZARDOUS.
2.3.1 ATEX Zone 2
The module must be mounted in an enclosure certified in accordance with EN60079-15 for use in
Zone 2, Group IIC and rated IP54. The enclosure shall only be able to be opened with the use of a tool.
2.3.2 ATEX Marking
II 3 G Ex nA IIC T4 Gc
Ta: -20°C ... +60°C
2.4 Notes on Functional Safety
2.4.1 Safety Integrity Level (SIL)
The safety requirements necessary for the safety functions of an application are determined in a risk
analysis. Here, the probability of failure of the safety functions is important. In an operating mode
with a high rate of demand or continuous demand, the probability of dangerous failure per hour
(PFH) must be taken into consideration, whereas in an operating mode with a lower rate of demand,
the probability of dangerous failure on demand (PFD) must be taken into consideration.
According to IEC 61508 and IEC 62061, the safety requirements are graded by the failure limit values
as follows:
Safety Requirements by Failure Limit Values
PFD PFH
SIL3 < 10
-3
< 10
-7
SIL2 ≥ 10
-3
to < 10
-2
≥ 10
-7
to < 10
-6
SIL1 ≥ 10 -2 to < 10 -1 ≥ 10 -6 to < 10 -5
2.4.2 Performance Level (PL)
According to DIN EN ISO 13849-1, the degree to which a safety function contributes to risk
minimisation is defined as the performance level. A distinction is made between the five levels PLa to
PLe with an increasing contribution to risk minimisation.
2.4.3 Safety Categories
Safety categories according to DIN EN ISO 13849-1 describe a minimum level of applicable safety
and to what extent monitoring is required.