Emerson Process Management ControlWave EFM 3808 - Manual (Page 212)

F-12 / Appendix F CI-ControlWave EFM
F.5.4.1.3 Ending a Nomination Period
If shut-in on stop mode is in use, the current period will end when the target accumulation
is reached. At this time, the ControlWave EFM attempts to close the control valve. If PID
control is being used, the setpoint is set to 0.0, the current cycle will ramp down
accordingly. When the flow rate reaches 0.0, the current cycle accumulations and the actual
end time are copied into the LAST signals. If the valve fails to close, the volume will
continue to accumulate until the programmed end time. If the shut-in on stop mode is not
in use, the nomination period continues until the programmed end time.
F.5.4.1.4 Changing the Nomination Target
To change the target of the next period, the user should change the NEXT TARGET signal.
F.5.4.1.5 Manually Starting/Ending a Nomination Period
When a Nomination Period is not in progress, the user can immediately begin the NEXT
period by setting the Status signal to the ON state. The current start time will reflect the
time that the user started the cycle. The target and stop times used will be those of the
NEXT period. The user may immediately end a nomination period which is in progress by
setting the Status signal to the OFF state. The current time will be stored as the LAST stop
time.
F.5.5 Flow Control & Valve Control
The Flow Control & Valve Control Web Page (Figure F-9) is accessible via the Flow
Control button. The PID Controller is utilized in the ControlWave EFM for Flow Rate
Control. Sections F.5.5.1 through F.5.5.4 provide information on the four major functions
accessible from the Flow Control & Valve Control Web Page (see Figure F-9).
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,