Alarm processing

Surge alarms warn operations personnel of undesirable and potentially costly operating situations.

The following conditions cause alarms to be generated:

• The operating point is past the surge warning limit.

• The operating point is past the surge control limit.

• The operating point has returned to within the normal operating range.

  In comparing the operating point to surge alarm limits, Compressor Performance Monitoring (CPM) uses a linear approximation of the surge control line from the slope configured in the curveset record.

  The surge control and surge warning lines are initially defined as part of the curveset record. Once the curve set has been loaded, you can modify alarm limits and inhibit alarms and events for each compressor individually. This functionality is available to both the Controller and Administrator. For more information, refer to the Compressor Performance Monitoring user documentation for Controllers and Compressor Row Edit: Alarming tab.

Surge Control and Surge Warning Alarms

Surge control alarm processing is similar to the high-low alarm processing provided with AVEVA Enterprise SCADA. With surge control alarming, CPM compares the current operating point to the surge control and surge warning limits. A sample compressor performance curve showing surge control and surge warning lines is shown in the "Sample Rated Speed Curve" figure.

• If the current operating point is to the left of the surge control line, then the operating point is deemed to be in an alarm state, and an alarm is presented to the Controller. After the Controller acknowledges the alarm, it remains in the Alarm Summary until the operating point returns to a normal state (to the right of the control line and outside of the warning limit deadband). The alarm deadband is used when the operating point is in an alarm state to prevent nuisance alarms.

• If the current operating point is to the right of the surge control line but within the warning limit, then the operating point is deemed to be in an alarm state, and an alarm is presented to the Controller. When the Controller acknowledges the alarm, it remains in the Alarm Summary until the operating point returns to a normal state (to the right of the control line and outside of the warning limit deadband).

• If the current operating point is to the right of the surge control line and outside of the warning limit, then the operating point is deemed to be in a normal state. If the point was previously in an alarm state, then a return-to-normal alarm is presented to the Controller. When the Controller acknowledges the alarm, it is removed from the Alarm Summary.

As the current operating point may not appear exactly on the compressor performance curves defined, the CPM application uses linear interpolation and the Fan Law to determine if the operating point is to the left or right of the defined surge control line.

The surge control line is defined for each compressor curve set as described in Curve set configuration.