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E-25-7-E
9
8.4 Confirming the Two-stage Valve Opening and Closure
You can confirm the valve opening and closing in two stages by one of the following two approaches:
Once set the initial and final setpoint at “0,” choose a batch setpoint somewhere above “” and press
START
▲
and
STOP
ROT.
key to verify proper shutoff valve actuation.
If simulated pulses (from OVAL pulse checker PC2201, for example) are available, you can confirm
proper batch operation of the shutoff valve by setting the initial and final setpoint at any point, pressing
START
▲
key, and then feeding a simulated pulse train.
NOTE:
The target batch setting should be greater than the sum of the initial and final setting.
8.5 Description of Batch Operation
NOTE: Operation can best be understood by referring to the operation time chart in Fig. 8.2 below.
Upon depression of
START
▲
key, the valve opens to a predetermined position (initial flowrate). When a
predetermined quantity (from point A to point B) has been delivered, the valve opens fully; when metering
has reached point C, the valve automatically throttles the flow and maintains a predetermined valve
position (final flowrate).
At point D, a closure signal is generated. However, due to a time lag in valve actuation, inherent to the
type of valve used, the valve actually close at point E. If an overshoot, or overmeasurement, exceeds a
predetermined quantity, the controller produces an alarm.
Safe and accurate measurement is thus achieved. In this connection, valve positions A
→
B and C
→
D
must be preselected on the part of the valve.
Fig. 8.2 Operation Time Chart
Valve
control
signals
Partial flow signal
(Partial open signal)
High limit
flow signal
(Full open signal)
High limit flow open
(MV: LCD 1 comes on.)
Partial flow open
(SV: LCD 1 1comes on.)
High limit flowrate
Flow
rate
Initial flowrate
Initial partial flow
(Initial setting)
START
signal
STOP
signal
Time
Final flowrate
Overshoot
End of batch
Batch setting
(Target quantity)
Final partial flow
(Final setting)
•
•