M&M RWB series User Manual

Standard Screw Compressor - RWB Series
3-12
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Network Control
When the Network Communications option is enabled, and the compressor is in the
Auto-Remote mode, capacity control is performed using Automatic Capacity Control.
The control setpoint is selected using setpoint messages from a remote computer.
Sequenced Capacity Control
While in the Sequenced mode, Automatic Capacity Control is used to adjust the slide
valve as documented above. When a sequenced compressor is on-line, one of the follow-
ing three commands will be sent from the master sequencer controller.
• Trim When the trim command is sent from the master sequencer, the CCS
will start the screw compressor. The Control Parameter and Control
Setpoint will be also be sent from the master, and the compressor will
begin making slide valve adjustments using Automatic Capacity Con-
trol. Once the compressor is started, the status area will display
RUN-TRIM indicating that the trim command was received.
• Full Load When the Full Load command is sent from the master sequencer, the
CCS will force and hold the slide valve at the fully loaded position.
When the Full Load command has been received, the status area will
display FULL LOAD.
• Seq-Stop When the Seq Stop command is received from the master sequencer
the CCS will stop the screw compressor automatically and leave it
on-line for sequenced operation.
Low Alarm and Failure Setpoints
When Sequenced mode is enabled and the compressor is online or running, the local
low alarm and failure setpoints are replaced by the Sequencer low alarm and failure
setpoints. This is true for both Suction Pressure and Process Temperature operation.
The local sensor is still used to generate the alarm or failure condition.
Running in Trim Mode
When the trim command is sent from the master sequencer the CCS receives the
System Control Parameter, System Control Setpoint, and the sequencer load and
unload deadband and bandwidth parameters. These new control parameters are
used instead of those defined on the CCS itself. The compressor’s local long-pulse,
short-pulse, and update time are used for slide valve movement.
The main status page will identify the control setpoint group as SY indicating that it is
the System Control Setpoint. Automatic Capacity Control is used to adjust the slide
valve while in Sequenced mode. The System Control Parameter, System Control set-
points, and Low Alarm and Failure setpoints are sent to the compressor periodically
by the master sequencer to ensure that the compressor is always using current data.
All automatic starting and stopping of the screw compressor is controlled by the mas-
ter sequencer. The local screw's Cut-In and Cut-Out controls are also disabled. When
the screw compressor is fully loaded, limited, or forced to unload due to high Motor

M&M RWB series Specifications

General

Brand	M&M
Model	RWB series
Category	Controller
Language	English