Safety Reaction And Safe State - Siemens SITRANS F Additional Operating Instructions

SPECIFICATION OF THE SAFETY FUNCTION
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2.5 Safety reaction and safe state

As soon as a failure is detected, the vortex flowmeter reacts safely, by setting the current output
to the low or high failure current (safety reaction). As an additional feature, temporary and
persistent failures can be distinguished:
• A failure current of approximately 3.5 mA is output in case of a transient failure.
• A failure current of approximately 3.35 mA or below, is output in case that a persistent failure
is assumed. A device with a persistent failure will not boot into SIL mode without operator's
interaction (for details refer to
Remarks
• The decision whether a failure is transient or persistent will be made within 30 seconds after
its detection.
• A too low volume flow (below the lower sensor limit) is classified as a typical transient
application dependent failure.
• Some failures will prevent the output of the lower failure current. In such cases, the device
tries to output the high failure current (> 21 mA).
• The fault response time is 30 seconds. Any output older than 30 seconds is correct if the
safety reaction is not triggered due to a safety critical device failure.
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Troubleshooting on page 23).
www.siemens.com/flow
SITRANS FX330
10/2017 - A5E40875009-AB EN