Active Control Mode; Load Limiting - Emerson VILTER MicroVission Operation And Service Manual

Section 5 • Compressor Control

Active Control Mode

This drop-down box gives the operator the ability to
change the type of Active Control Mode such as Suction
Pressure, Process Temperature or Discharge Pressure.
The operator can also switch from Setpoint 1 (SP1) and
Setpoint 2 (SP2) for each control method. The options
for drop-down box will depend on the number and type
of control selected in the configuration screen. This
drop-down box will not be available from selection when
compressor is running in Auto-Seq or Auto Seq Stand-by
run mode.
I/O Based Setpoint Control
This checkbox when enabled, monitors the Remote
Setpoint #1/#2 Digital Input (10th Digital Channel on
Multi IO Board). The selection of Active Control Setpoint
depends upon the state of Remote Setpoint #1/#2
Digital Input. When Remote Setpoint #1/#2 Digital
Input is Energized, Active Control Mode will be Setpoint
2. When Remote Setpoint #1/#2 Digital Input is De-
Energized, Active Control Mode will be Setpoint 1.
Figure 5-9. Compressor Control Screen – Active Control Mode - I/O Based Setpoint Control
5 – 10

Load Limiting

The stop load and force unload feature's primary pur-
pose is an attempt to prevent the compressor from trip-
ping off due to instrument reading. For example, if the
suction pressure drops very low, the compressor will trip
off for safety reasons. However, the stop load and force
unload algorithm recognizes the potential trip and ei-
ther stops the compressor from loading up or even un-
loads the compressor step-by-step to prevent the trip.
Stop Load Setpoints
High Suction Pressure
• When the suction pressure value is equal to or
greater than this setpoint, algorithm will not allow
loading of the compressor. However, if the suction
pressure value drops below this setpoint, algorithm
will allow loading of the compressor.
High Discharge Pressure
• When the discharge pressure value is equal to or
greater than this setpoint, algorithm will not allow
loading of the compressor. However, if the discharge
pressure value drops below this setpoint, algorithm
will allow loading of the compressor.
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3