Rockwell Automation Publication 1444-UM001D-EN-P - June 2018 229
Configure Alarms Chapter 8
Fail-Safe
The voted alarm fail-safe definition is not used by the voted alarm (logic).
Rather, it is inherited by any relays that reference the alarm (see Relay Page
on
page 203).
When defined as fail-safe, the coil of the relay is energized when not in an
alarm condition, and de-energized when it is in the alarm condition. This
provision is to make sure that upon loss of power that the relay moves to its
“safe” condition, which is assumed to be its position when in alarm.
Relays
Relays are the final element of the 1444 series Alarm Management System.
While the voted alarm can act as a “virtual relay”, it cannot switch off power to
a motor. Also, the voted alarm cannot route power to a light or other
annunciator, or control a solenoid valve that can trip a turbine.
Also, in applications that require API-670 compliance, relays are the only
approved interface between the monitor system and the emergency shutdown
system or final actor when used to initiate a forced shutdown.
See Relay Page
on page 203 for an overview on how to use relays in the 1444
series system.
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