Safety Considerations Guide for Trident v2 Systems - TUV ...

40 Chapter 3 Fault Management
Digital Output Module Alarms
Digital output module faults are reported to the control application and can be used to increase
availability during specific multiple-fault conditions. Loss of field power or logic power is
reported to the control application.
The inability of a digital output module to control an output point is reported to the control
application as a Load/Fuse alarm. This condition can result from a loss of field power or a field
short condition. The alarm can be used to modify the control strategy or direct effective
maintenance action.
Pulse Input (PI) Module
The pulse input module points use a combination of comparison and reference diagnostics.
Under system control, each channel is independently compared against the measured value of
all channels. If a mismatch is found, an alarm is set. Each channel’s measured values are also
compared against the channel’s internal references. These diagnostics are executed
independently by each channel, thus assuring nearly 100 percent fault coverage and fail-safe
operation under all single-fault scenarios, and most common multiple-fault scenarios.
Pulse Input Module Alarms
Pulse input module faults are reported to the control application. These alarms can be used to
increase availability during specific multiple-fault conditions. Loss of logic power is reported to
the control application.
Solid-State Relay Output (SRO) Modules
Solid-state relay output module points are not intended for safety-critical applications. The
diagnostics used by the solid-state relay output points cannot detect faults in the relay contacts.
Solid-State Relay Output Module Alarms
Solid-state relay output module faults are reported to the control application.
Safety Considerations Guide for Trident v2 Systems