Directed Electronics 3100 Instruções de Operação descarregar pdf (Página 27)

Safety integrity of the hardware for safety-related subsystems

of type B (IEC 61508-2, 7.4.3)

Safe failure fraction Hardware

fault toler-

ance

SFF HFT = 0 HFT = 1 HFT = 2

<60 % not permitted SIL1 SIL2

60 % up to <90 % SIL1 SIL2 SIL3

90 % up to <99 % SIL2 SIL3 (SIL4)

>=99 % SIL3 (SIL4)(SIL4)

9.2 Planning

l The measuring system must be used acc. to the

application

l The application-speciﬁc limits must be maintained and the

speciﬁcations not exceeded.

l Acc. to the speciﬁcations in the operating instructions

manual, the current load of the output circuits must be

within the limits.

l It must be used only in products to which the materials of

the vibrating system are suﬃciently chemically resistant.

Note the following items for use as dry run protection system:

l Avoid buildup on the vibrating system (possibly smaller

proof test intervals)

l Avoid granulation size of the product > 15 mm

For the implementation of FMEDA (Failure Mode, Eﬀects and

Diagnostics Analysis) the following assumptions form the

basis:

l Failure rates are constant, wear of the mechanical parts is

not taken into account

l Failure rates of external power supplies are not included

l Multiple errors are not taken into account

l The average ambient temperature during the operating

time is +40°C (+104°F)

l The environmental conditions correspond to an average

industrial environment

l The service lift of the components is between 8 to 12 years

(IEC 61508-2, 7.4.7.4, rema rk 3)

l The processing unit can interpret "fail low" and "fail high"

failures as interferences and output a suitable fault signal

Genera l instructions and re-

strictions

Assumptions

OPTISWITCH 3100 C - with two-wire output 27

Functional safety

29955-EN-060112

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