Compressor Performance Plot

Open the Compressor Performance Plot window to view a graphical representation of compressor data and gage the efficiency with which the compressor is operating.

The Compressor Plot window displays the following data:

• The current performance curves (speed vs. efficiency) for a specified compressor. These performance curves are based on data supplied by the manufacturer of the compressor.

• Alarm limits (surge control, surge warning).

• A plot of current or historical operating points (head pressure vs. flow rate), superimposed on the speed vs. efficiency curves.

  Note: When you first open the Compressor Plot window, it displays the current operating points.

Other information, such as flow conditions status, is displayed graphically through plot symbols. The age of the operating point is indicated through color.

Note: The data quality of an operating point is not shown in the Compressor Plot window.

However, data quality is available through the Current Data Summary window. For more information, refer to Open the Current Data Summary window

You can use the Compressor Plot window as a guide to running the compressor efficiently. It indicates the efficiency with which the compressor is running, given the pressure ratio or head across the compressor and the current flow rate and compressor speed.

You can also use the Compressor Plot window to prevent compressor damage. For a centrifugal compressor, surge conditions must be prevented. Surge occurs when there is insufficient flow into the compressor, causing the compressor to run backwards until enough head is produced to compress the gas to discharge pressure, potentially causing damage. The Compressor Plot window may also show the operating point reaching stonewall, the maximum flow capacity for the compressor. Alarms alert you when a compressor may be approaching an undesirable state.

Historical data can be used to detect compressor degradation and to derive the locus of the compressor operating point with respect to time.

Usually, the four most recent operating points appear on the plot. The symbols used to display the operating points indicate flow conditions, and the colors of the operating points indicate the age of the data. For more information, refer to View the legend The plot is updated automatically when a new operating point is sampled or calculated.

If the performance curve set has been recently reassigned, you may not see the expected number of operating points. This is because plotted data does span a time range in which two different curve sets were assigned to a compressor. Similarly, if you try to plot data from a time period in which the current curve set was not in use, no data will be plotted.

If the compressor is off-line, the operating point data displayed may not be valid and thus may not be plotted within the range of the x and y (flow and head) axes.