CMC TECHNICAL REFERENCE MANUAL
1X36003 Version 2.52
1996-1999 Ingersoll-Rand Company
Date of Issue: 18-Oct-1999
37
b) Switch to the System Folder Page 1 and press the Enter Key to enable edit mode.
c) Use the horizontal navigation keys to select the bypass valve.
d) Increment the value to position the valve to 100 percent.
4. Load the compressor by pressing the Load Key.
5. Find the throttled surge point.
a) Slowly decrement the bypass valve position until the last stage discharge pressure
equals the pressure setpoint.
b) Allow the system to stabilize at MinLoad. It the system does not stay at MinLoad,
slightly decrement the valve position to force the machine to throttle to MinLoad.
c) Decrement (MinLoad) 2%.
d) Verify the last stage pressure equals the pressure setpoint and adjust the bypass
valve position if necessary.
e) Repeat 5.2-4 until the compressor surges.
6. Increase MinLoad by five percent.
7. Exit MinLoad editing by pressing the Enter Key.
8. Unload the machine.
9. Disable manual valve control by unchecking the manual check box.
Setting MinLoad Surge Index Increment
When Surge Indexing is enabled (MinLoad Surge Index Increment is greater than zero), the
Index Increment value is the amount added to the MinLoad Control Setpoint upon a surge.
The MinLoad Control Setpoint will stop being incremented when and if the value reaches
MaxLoad.
Setting Surge Sensitivity
The Surge Sensitivity setting should be set sensitive enough to detect a surge, yet not
trigger on spurious noise in the system. To set the surge sensor the machine is forced to
surge by running the machine at MinLoad and the MinLoad setpoint is dropped until the
machine audibly surges. The process is repeated until the correct setting is found.
1. Before continuing this procedure, verify the following:
a) The plant can tolerate a pressure disturbance when the machine surges.
b) Surge Indexing (by placing MinLoad Surge Index Increment to zero) is disabled.
c) Surge Absorber is disabled.
d) The pressure setpoint is set to the pressure at which the machine is going to
operate.
e) The machine is running unloaded.
2. Set the initial Surge Sensitivity setting to 9.
a) In the Settings Folder, select the Edit Data cell for Surge Sensitivity.
