Dynamic enabling and disabling of SPM alarms

Situations may exist where the monitored point is deliberately being operated outside its normal operating range, or the process may be starting up or shutting down, or the process may be transitioning from one operating regime to another. During those times it may be desirable to disable alarms so operators don't experience nuisance alarms. The CALC block has logic for dynamically enabling and disabling alarms at run-time. The logic does this by changing the HI_ENAB and LO_ENAB parameters of the AI blocks (RMT_SPM_HART) or the Alarm blocks (RMT_SPM_FF). There are two separate criteria used to enable and disable alarms. One is by an external reference, and the other is by operating the process outside configured PV or Mean limits.

Alarm Management by external reference

The ALARMS_ENABLED configuration parameter in the template is used to link the control module to an external reference used to toggle the SPM alarms between the enabled and the disabled states. The value of this external reference can be modified by a process parameter, or by an operator action. The external reference is generally a logic statement in another control module. A logic result of 0 (zero) disables alarms. A logic result of 1 (one) enables alarms. A single external reference can be used to enable or disable the alarms from a single or multiple instances of SPM modules.

The ALARMS_ENABLED configuration parameter enables and disables the HI and LO alarms of all AI Blocks (AI1, MEAN, STDEV, CV). The parameter does NOT enable or disable AI1 HIHI (HI_HI_ALM), AI1 LOLO (LO_LO_ALM), or PV_BAD alarms.

Alarm management by PV or Mean

The PV_LIM_MODE parameter disables and enables StDev or CV alarms based on the PV or MEAN exceeding the HI or LO limit. The parameter FP_VAR_1 (described in Faceplate variables) determines whether the PV or Mean limits are used to enable or disable StDev and CV alarms.