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7.3 Cycling an Ex nA solenoid valve
In this example a BA374NG is required to cycle a
Zone 2 Ex nA solenoid valve such that it is opens 4
times for 10 minutes at 15 minutes intervals. Once
all 4 solenoid valve cycles have been completed a
remote “sequence complete” lamp is illuminated in
the safe area until the reset push button is operated.
If, during the sequence, power is lost the control
outputs are to remain de-engergised when power is
restored. The timer is to recommence operating
from the last known point when the start push button
is pressed.
When the start button is operated control output 1
closes which opens the solenoid valve and the Timer
times-down
for 10 minutes. When the elapsed time
equals zero, control output 1 opens thus closing the
solenoid valve. The timer then counts down the 15
minute delay which is shown on the lower display
(display 2). When the delay equals zero, control
output 1 closes again for a second 10 minutes, the
whole cycle being repeated such that the solenoid
valve opens and closes 4 times. After the solenoid
valve has closed for a forth time control output 2
closes which illuminates a “Sequence Complete”
lamp indicating that the whole operation is finished.
The lamp remains illuminated until the reset push
button is operated (Reset is shown in the display) at
which point control control output 2 is de-energised
which turns the lamp off.
Operating the stop button at any time during the
timing cycle will pause the cycle. The cycle can be
resumed by operating the start button or abandoned
by operating the reset button.
Note:
Both the timer (display 1) and delay (display 2) will
count down – but the cycle display counts
up
towards its target.
Fig 15 Cycling an Ex nA solenoid valve
Summary of Contents for BA374NG
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