GAA610-M
ADVANCED EMISSION GAS MONITORING SYSTEM | OI/GAA610-M-EN REV. B
41
Filter unit backpurging sequence
Step
Duration
Function
Sample gas valve
−Y60
Probe tube
backpurging valve
−Y61
Filter backpurging
valve −Y62
Display
Status signal
1.
12 h*
Measuring
Sample gas
Closed
Closed
Measure
off
2.
2 s
Switch over
Ambient air
Closed
Closed
Probe purging
Maintenance
3.
8 s
Back-purging probe filter Ambient air
Closed
Open (pulsed)
Probe purging
Maintenance
4.
12 s
Back-purging probe tube Ambient air
Open (pulsed)
Closed
Probe purging
Maintenance
5.
90 s**
Post-purging
Sample gas
Closed
Closed
Probe purging
Maintenance
6.
12 h*
Measuring
Sample gas
Closed
Closed
Measure
off
* Cycle time factory-set to 12 hours, can be adjusted.
** Post-purging time factory-set to 90 s
Switch over
At first the sample gas valve
−Y60
is switched over to position
‘Calibrate zero / Ambient Air’. This separates the sample gas
conditioning system and the analyzer system from the sampling
system and protects it against the back-purging pressure.
At the same time the status ‘Maintenance mode’ is activated and
all analog outputs and limits are set on hold.
• The display reports ‘Probe purging’.
• The Modbus signal ‘Sample line1 in purging’ is set to ‘1’.
• The Modbus signal ‘Line 1 in operation’ is set to ‘0’.
• The lamp ‘Line1 Measuring Status’ is off.
Back-purging probe filter
The back-purging procedure continues with the back-purging of
the probe filter. To increase the cleaning effect, the compressed
air is applied not continuously but by two 2 s pressure impulses
alternating with a 2 s interval each.
Back-purging probe tube
After this the probe tube is purged back in the same way with
two pressure impulses. A single pressure impulse of 4 s is
followed, to blow out the remaining dust from the tube.
Post-purging period
The calibration valve switch back to position ‘Measure’ will not
finish the back-purging procedure, because first the actual
sample gas must flow through the pneumatic system to purge it,
and the analyzer must adjust to the new actual measuring value.
A purge time of 90 s is factory-set.
End of the back-purging procedure
The back-purging procedure is not finished until the purge time
has expired. Now the analog outputs and limits are set free
again and they will take over the actual values. The message
‘Purge back active’ in the display as well as the status signal
‘Maintenance mode’ will vanish.
