Gas Sampling With Automatic Back-Purging; In General - ABB GAA330-M Operating Instructions Manual

Gas sampling with automatic back-purging

In general

Filter plugging
Pump suction increase
Filter cleaning
GAA330-M EMISSION MONITORING SYSTEM
During operation of the analyzer system the dust which is contained in the
sample gas will accumulate in the probe filter of the gas sampling system.
This is uncritical if dust concentration is low and only requires a cleaning of
the filter periodically in longer time intervals.
But if the dust concentration is high, the dust accumulation in the filter will
cause an increasing pressure loss, and the gas feed of the sample gas pump
decreases and also the sample gas flow, and finally the filter is blocked in an
extreme case.
At first this effect can be compensated by occasional adjustment of the
sample gas flow, which increases the suction of the sample gas pump.
The pump is strong enough, but if the fouling continues, the needed suction
for keeping up the required gas flow will increase to such a high value, that
several unfavorable effects will emerge and can finally be accepted no long-
er.
If the suction exceeds a limit of about 300 mbar (accordingly the absolute
pressure falls below 700 mbar), the sampling system filter has to be cleaned.
The PFE2 and PFE3 filter units can be cleaned automatically by a back-purg-
ing procedure with compressed air. This procedure is controlled by the
AC500.
| OI/GAA330-M-EN REV. C 45