Emerson VILTER MicroVission Operation And Service Manual page 242

Appendix D • Compressor Sequencing Setup
Compressor Sequencing Menu Setup
The compressor loads and unloads itself based on the
control settings that are set in Compressor Sequencing
Setpoints (see Figure D-2) and Compressor Control
Setpoints menu (see Figure D-3).
Page 2 of the compressor sequencing menu (see Figure
D-2) allows the operator to view and adjust settings
which are used for compressor sequencing. The pres-
sure / temperature control setpoints, Start/Stop offset
and Start/Stop timers to accomplish sequencing control
are defined here:
1. Suction Pressure / Process Temperature Setpoint
2. Start Offset
3. Start Timer
4. Stop Offset
5. Stop Timer
6. Compressor Sequencing Control Mode
Suction Pressure / Process Temperature
• Compressor Sequencing
Compressor Capacity to maintain the Suction
Pressure / Process Temperature at this value.
D − 2
Algorithm modifies
Figure D-2. Compressor Sequencing Control Setpoints
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
Start Offset
• Defines the offset from pressure/temperature con-
trol setpoint to start Compressor. If suction pressure
/ process temperature goes above start offset set-
point and highest priority compressor is loaded fully
then sequencing algorithm allows starting of second
highest priority compressor according to Start Timer
and load to cater increasing load requirements. The
lead (highest priority) compressor should not wait to
meet this condition (i.e should bypass this settings).
Start Timer
• Provides delay to start the next compressor in se-
quencing. In start/load sequence when suction pres-
sure/ process temperature goes above start offset
then it will be monitored for start Time period.
Stop Offset
• Defines the offset from control setpoint to stop com-
pressor. If suction pressure / process temperature
goes below this setpoint value, then it will allow stop-
ping of compressor if it is not the highest priority
compressor. The lead (highest priority) compressor
should not stop in the sequencing if suction pres-
sure/ process temperature drops below (setpoint –
stop offset).