The DeltaV SIS CHARMs Smart Logic Solver (CSLS) executes extensive self-testing on a continuous basis to detect potential faults. This section presents an overview of fault detection, how the DeltaV Safety Instrumented System (SIS) responds to a detected fault, and what you should do if a fault occurs. Although the presence of a fault is expected to be uncommon, it is important to have a fundamental understanding of the topic.
Faults detected by logic solver diagnostics are generally related to hardware failures in the logic solver, but can also be associated with field devices and field wiring, or other conditions not related to hardware. Some faults have the potential to prevent the appropriate response to a process demand, some do not. The CSLS response and the recommended action depend on the type of fault detected.
The terms fault and error are used interchangeably. Not all diagnostic conditions detected and annunciated by the CSLS are faults or errors. Some merely cause an advisory alert such as a reminder that a proof test of the CSLS is due soon.
The CSLS responds to a detected fault by initiating a shutdown; a DeltaV SIS alarm occurs.
Reasons for a fatal error include, among others, a processor has failed and does not arm the hardware watchdog, a processor has detected that a critical task did not complete in a timely fashion, or the main processors have calculated different output values. An alarm occurs following a fatal error, but the particular alarm depends on whether the CSLS is simplex or redundant.
A DeltaV SIS alarm occurs when the CSLS detects a fault; the CSLS continues providing its protection function.
The CSLS has detected a non-fatal condition. An alarm occurs because the condition requires an operator action such as initiating maintenance or taking steps to clear the condition. When a non-fatal condition is active, the CSLS is still able to respond to a process demand.
DeltaV SIS software logs an event record when the CSLS detects a fault; the CSLS continues providing its protection function.
The CSLS has detected a non-fatal condition, but no alarm occurs because immediate action is not necessary. An event record is added to Event Chronicle, which may be of interest in a future investigation. DeltaV SIS software creates event records for all annunciated conditions in addition to these event-only conditions.
Hardware alerts due to failures of LS CHARMs are not reported under the CSLS. They are a part of SIS Controller hardware alerts and are under the SIS controller name (to which the CSLS is assigned).
HART device alerts on LS HART CHARMs are not reported under the CSLS. They are under the HART device container name.