Emerson Process Management ControlWave XFC - Manual (Page 114)

F-12 / Appendix F CI-ControlWave XFC
Users are cautioned to test the regular override controller actions to verify correct valve
movement for all expected conditions.
F.5.5.1 Nomination
Function
The Nominations Function provides for enabling/disabling the nominations feature (see
Section F.5.3). If this signal is set to the disable state, no nomination will be performed.
Status
The Status signal is an output of the nominations algorithm that indicates whether there is
currently a nominations period in progress. The user may change the state of this signal to
end an in progress nomination immediately, or to start the next period immediately (see
Manually Starting/Ending a Nomination Period in Section F.5.3).
F.5.5.2 Flow Control
Enable
Pressing the button to the right of Enable will allow the operator to toggle between PID
Flow Control Enabled and Disabled. It is recommended that GAIN, INTEGRAL and
DERIVATIVE adjustments be checked before turning a controller ON.
Warning
Do not enable PID Flow Control without first checking the external process control
loop. The initial values displayed on the PID Menu may drive some critical
processes beyond the extremes of safe limits. This could result in fire, explosion,
property damage, and injury to persons. When setting the WebBSI Web Page
parameters, make sure the associated process is observed and protected.
Setpoint (x1000)
This field contains the operating point at which the flow rate is to be controlled. Set-point
units are MSCFH with a default setting of 1000 MSCF per Hour. To change the Setpoint
value, right click on the field and select Change Signal Value.
Gain
Gain controls the amount of output change resulting from a change of the measured
variable. The default value of 1.00 is typically used as a starting point; final gain is usually
less. To change the Gain value, right click on the field and select Change Signal Value.
Integral
Integral determines the time it will take the PID to correct an error in the measured
variable. The number of times the output is adjusted in a given time period is specified in
seconds. An entry of 60 seconds can be used as a starting point; this would provide one (1)
repeat per minute. To change the Integral value, right click on the field and select Change
Signal Value.
Derivative
Derivative compensates for a rapidly changing measured variable. The time is specified in
seconds (SECS) and most applications will use a setting of zero (0). To change the
Derivative value, right click on the field and select Change Signal Value.