Phase alarms in unit modules

Phase Alarms in Unit Modules

The objectives for phase alarms in unit modules are to:

  • Provide alarm annunciation (alarm banner, alarm horn, alarm summary, alarm type event records) when active phases in unit modules have errors or take an unusually long time to complete. In many cases, this relieves operators from having to monitor the execution of batches (or the completion of manually started phases) that normally run unattended.

  • Provide an easy configuration mechanism to enable phase alarms in unit modules.

Unlike other alarms in the DeltaV system, phase alarms are expected to exist for only the period of time the corresponding phase is instantiated. Therefore, a unit module with many phases only carries the alarm parameter and processing overhead for the few phases (maximum of 10) that are instantiated at any point in time.

The following additional properties, which control the behavior of phase alarms in the unit module, are configured in the unit phase table for each phase:

Enable failure alarms on this unit phase - Is a Boolean property. If False, then the values of the other alarm-related properties do not matter. Defaults to True.

Phase alarm name - Is the name that will appear in the alarm details field in the alarm banner when this unit phase has a failure. Must pass the standard parameter name checks (characters, length, no name space collisions, and so on). Defaults to the unit phase name. If the phase class name is changed, the phase alarm name does not change. It remains the same as the original unit phase name.

Unit phase alarm priority - Establishes the initial priority of the unit phase alarm for this phase. Possible values are CRITICAL, WARNING, ADVISORY, and LOG. Defaults to LOG.

TOO_LONG_TIME - Indicates the maximum length of time that a unit phase should take to complete. This is configured as the limit value on the alarm, which is then used to populate the TOO_LONG_TIME parameter. It is an integer with units in seconds. The TOO_LONG_TIME parameter defaults to 0 (not enabled).

When a unit phase is instantiated in a unit module, the following apply:

  • The phase is created as a block in the unit module, with the phase class name as the block name.

  • If failure alarms are enabled, an alarm parameter is created at the unit module level with the configured phase alarm name and alarm priority. The initial alarm state is DISABLED and appears as the first recorded state for the unit phase alarm in the Event Chronicle.

  • While the unit phase is instantiated, the unit module periodically processes the phase alarm to see if the process has been running too long (timeout expired) and processes the alarm parameter based on the failure condition.

While the failure alarm (and its corresponding phase) exists, it operates as a permanent module-level alarm with the following properties:

  • Its fields can be read, can appear on the unit phase detail display, and can be addressed via the unit module.

  • It can be individually acknowledged.

  • It can be disabled or enabled.

  • It can have its priority changed.

  • It is summarized via the ALARMS attribute.