Flowserve DDC-100 Master Station II - Manual (Page 53)

FCD LMAIM5001-00 DDC-100 Master Station II Installation and Operation Manual 53
Flow Control Division
Limitorque Actuation Systems
10.3 Operation
Under normal operating conditions, the Hot processing unit will transmit incremental data updates to the
Standby processing unit via the Ethernet connection.
The Standby unit will also monitor the communication on the network to ensure that the Hot processing
unit is viable.
In the event of a Hot unit failure, the Standby unit will smoothly transition into the Hot role. In addition, a
forced switch may be imposed. The transition period from Hot to Standby and Standby to Hot takes under
20 milliseconds to complete.
Each processing unit is capable of three states: Idle, Standby, and Hot.
Idle state: the processing unit is active, will accept incremental updates from a Hot unit, but will not perform
the Hot unit’s duties nor will the processing unit switch to Hot state should a Hot failure be detected.
Standby state: the processing unit is active, will accept incremental updates from a Hot unit, and will
switch to Hot state should a Hot failure be detected.
Hot state: the processing unit is the Hot unit and will perform the Hot duties of Network polling and
incremental updating of the Standby processing unit.
A state change can occur in any of the following conditions:
Hot Unit Failure: the Hot unit fails to send incremental updates to the Standby unit and there is no
network traffic.
Hot-Standby communication failure: the Standby unit is not receiving incremental update information
from the Hot unit but detects Network traffic. The Standby unit will zero its database and set an alert error.
The HMI will detect this state and will display “Idle” instead of “Standby”.