166 Performing Routine Maintenance
Trident Planning and Installation Guide
Output Voter Diagnostics (OVD)
Output voter diagnostics (OVD) is a set of tests that detects failures in the output
voting circuitry of DO Modules only. OVD runs without operator intervention or
awareness and enables the Trident controller to continually verify its own integrity.
!
CAUTION
OVD may affect a controlled process! For this reason, Triconex provides special
instructions for disabling OVD on selected DO points from TriStation. For more
information, see the TriStation 1131 Developer’s Guide.
If OVD is disabled, you should verify that the output voter circuitry is working
properly by enabling OVD every three to six months. All DO Modules can be
tested simultaneously.
To enable and disable OVD, use the appropriate system attribute in your TriStation
project. Leave OVD enabled for several minutes. When testing is done, disable
OVD.
Verifying Spare Modules
The controller automatically tests all modules installed in the system. The only
action needed to guarantee the integrity of a spare module is to periodically install
it in an online system.
Spare I⁄O modules should be installed as hot spares. The controller automatically
tests these modules by shifting control between the active and hot-spare modules
as follows:
• Periodically, approximately once an hour
• After a power failure
• After an MP re-education
Spare MPs and I⁄O modules that cannot be used as hot spares should be periodically
rotated into an online system to ensure the integrity of spare inventory. A rotation
schedule should be established so that a spare is not allowed to sit on the shelf more
that six months.
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