43
Capacity Control
C
APACITY
C
ONTROL
on a RECIP compressor is performed by adding or removing stages. Loading the
compressor adds stages which increases the compressor capacity and Unloading the compressor
removes stages which decreases the compressor capacity. A stage can consist of one or more Loaders
which energize to add pistons, or Unloaders which de-energize to remove pistons. Capacity Control can
be performed manually or automatically depending on the mode of operation.
C
APACITY
SETPOINTS
there is a Max Time at 0% capacity which is a timer that is intended to NOT
allow the compressor to run too long at 0% capacity. The timer is activated in automatic and remote
modes. If the compressor runs at 0% capacity longer than the allowed time then the compressor will
perform a “Normal” stop and a log entry will be documented. When Auto Start/Stop is enabled then the
compressor will restart when the suction pressure rises above the cut-in setpoint. The compressor may
restart immediately, when two cases occur. Case #1- When the capacity ramp start delay is programmed
lengthy and a low max time is at 0% capacity, it is possible that the Max 0% capacity timer will expire
before the capacity ramp allows the machine to load. If, the suction pressure is above the cut-in setpoint
and auto start/stop is enabled, compressor will restart immediately. Case #2- When the suction pressure
is above cut-in and discharge pressure is above the limit/unload may be holding the compressor at 0%
capacity so the 0% capacity timer will expire and the compressor will restart immediately.
Manual Capacity Control
In
M
ANUAL
mode, the capacity is adjusted using the keypad on the Viltech. The up-arrow is used
to add stages and the down-arrow is used to remove stages. Each time an arrow key is hit, one
stage is added or removed until the compressor is fully loaded or unloaded. Manual capacity
control can only be performed when viewing the Main Status screen.
Automatic Capacity Control
A
UTOMATIC
C
APACITY
C
ONTROL
is accomplished by adding or removing stages to load and
unload the compressor in response to changes in the control parameter (suction pressure or process
temperature). Capacity changes are achieved using a time proportional control strategy with
setpoints for Control Deadband, Normal Bandwidth, Normal Stage Delay, and Fast Stage Delay.
Separate setpoints are provided for loading and unloading the compressor so that the operator may
tune the system differently for increasing or decreasing load conditions.
The operator can also define up to four Control Groups which consist of Cut-In, Cut-Out, Control,
Low Alarm, and Low Failure setpoints. The active control group can either be selected manually by
using the active group screen or automatically through setpoint scheduling. The operator can also
define a minimum capacity value which is used to limit capacity changes at the lower limit.
Summary of Contents for Vilter VilTech
Page 1: ...VILTech micro controller Operation and service manual ...
Page 2: ...2 ...
Page 10: ...10 Notes Page ...
Page 11: ...11 ...
Page 16: ...16 ...
Page 18: ...18 ...
Page 29: ...29 ...
Page 38: ...38 ...
Page 53: ...53 ...
Page 88: ...88 ...
Page 138: ...138 ...
Page 142: ...142 ...
Page 145: ...145 ...
Page 147: ...147 ...
Page 153: ...153 ...
Page 154: ...154 Alarm and Failure Data ...
Page 155: ...155 Alarm and Failure Data Continued ...
Page 156: ...156 Alarm and Failure Data Continued ...
Page 158: ...158 Compressor State Table ...
Page 159: ...159 Last RECIPStart Status Table ...
Page 172: ...172 ...
Page 173: ......