BERTHOLD TECHNOLOGIES LB4710-050, User Manual

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Chapter 3 Functional Safety
Mini-Switch LB 471
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3.2
Safety Function
The safety function of the measuring system comprises the detec-
tion and indication of changes in the count rate of the detectors
caused by the presence of product being measured in the measur-
ing path between radiation source and measuring system.
The safe status is dependent on the mode of operation:

Maximum level (overflow protection): Product between radia-
tion source and detector -> low count rate

Minimum level (protection against running dry): No product
between radiation source and detector -> high count rate
3.3
Safety Requirement
Safety integrity
level
Operating mode with
low demand rate
Operating mode with high
or continuous d emand rate
SIL PFD
avg
PFH
4 ≥10 -5 to <10 -4 ≥10 -9 to <10 -8
3 ≥10 -4 to <10 -3 ≥10 -8 to <10 -7
2 ≥10 -3 to <10 -2 ≥10 -7 to <10 -6
1 ≥10 -2 to <10 -1 ≥10 -6 to <10 -5
Safe failure fraction Hardware fault tolerance
SFF HFT = 0 HFT = 1 HFT = 2
none: <60% not allowed SIL 1 SIL 2
low: 60% to <90% SIL 1 SIL 2 SIL 3
medium: 90% to <99% SIL 2 SIL 3
high: ≥99% SIL 3
3.4
Project Planning

Please make sure that the measuring system will be used in
accordance with its designated function.

The application-specific limits have to be observed and the
specifications must not be exceeded. See also the technical da-
ta and ambient conditions in the User’s Manual.

The fault tolerance time of the overall system must be greater
than the reaction time of the measuring system.

The relay contacts have to be protected by a 1A fuse.

The digital inputs 1 and 2 must not be closed in case of a safe-
ty-related application.
General instructions and
restrictions