
CMC TECHNICAL REFERENCE MANUAL
1X36003 Version 2.52
1996-1999 Ingersoll-Rand Company
Date of Issue: 18-Oct-1999
77
Compressor Operating States
Turbine Driven Packages
Stopped
+
Waiting
Not Ready
Ready
Compressor
+
+
Rotating
Starting
Accelerate-1
Accelerate-2
Slow Rolling
Loading
Unloaded
MinLoad
Loaded
Full Load
MaxLoad
A-D Unloaded
Surge Unload
Unloading
Coasting
Surge Control
All surge related issues are identical to motor driven units with the exception of the detection
methodology.
How Surge is Detected
The CMC senses surge when the rate of change in last stage discharge pressure is greater
than the surge sensitivity setpoint value. The difference between this and motor driven units
is that the motor driven units uses rate of change in motor amps also.
Compressor Operating Methodology
Comparing the chart to the right for
Turbine driven compressor and Motor
driven compressor, the only state
differences are the addition of the first
three states under Rotating. These are
Accelerate-1, Accelerate-2 and Slow
Rolling.
Accelerate-1
This state is provided to give the operator
five minutes from the time the Start button
is pressed to get enough steam to the
turbine to get the speed above the Zero
Offset Speed. This speed is defaulted to
15 rpm. If this speed is not achieved in this
time period, the event message
“Accelerate-1 Fail” will appear and the
controller will trip the compressor. As
always, the compressor must be “Ready”
before the start button is pressed. The
reason for the five-minute limitation is to
prevent the compressor from being ready
for an indefinite period of time. This
prevents the operator from forgetting that
the compressor is ready to accelerate.
“Accelerate-1” could also be explained as
“accelerating to zero speed offset” or
“waiting for compressor rotation”.
Accelerate-2
After the transition to Accelerate-1 is complete, this state is initiated when rotation is
detected and the turbine has not reached the low trip speed. This state may be bypassed if
the turbine accelerates very quickly.
Once in this state, a sixty (60) second timer is initiated. If the speed does not get to the
minimum slow roll speed within this time period, the event message “Accelerate-2 Fail” will
appear and the controller will trip the package. This state is limited sixty (60) seconds to
prevent bearing damage from rolling the compressor at too low a speed. The bearing design
requires a minimum speed to form the oil film thickness required for proper bearing