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Project planning information > Electrical connection > IC 40
Feedback signalling
The feedback signal function (relay contact) possible with
the outputs may not be used on its own for fail-safe
signalling of the status or of the position.
Please refer to the relevant Directives and Standards as
to
whether and when a fail-safe signal is required.
As defined in European Standard EN 746-2 for instance,
gating of two non-fail-safe sensors (signals) must be
considered as a fail-safe equivalent array if the two
sensors detect different physical variables.
Example 1:
A fail-safe equivalent array for the ignition position of the
butterfly valve for air may be series connection of a
pressure switch signal with the feedback signal of the IC
40.In this application, the pressure switch monitors the
maximum permitted air pressure so as to restrict the
maximum permitted start fuel flow rate using the air/gas
ratio control GIK.
Example 2:
VAS..N
VAS 1
One other option of fail-safe limitation of the start fuel flow
rate is utilization of a bypass in the gas circuit. A bypass
valve can limit the amount of gas in fail-safe manner
owing to its nominal cross-section. The maximum possible
gas pressure must be allowed for when selecting the
nominal cross-section.
At all events, the plant operator is responsible for
assessing installation safety. Elster Kromschröder can, in
this case, only provide its own estimates and resultant
recommendations which do not reflect the individual
situation of the particular
installation.
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