In General; Components For Automatic Back-Purging Procedure - ABB ACX Commissioning Instruction

Gas Sampling with Automatic Back-Purging

In General

Filter Plugging
Pump Suction Increase
Filter Cleaning

Components for Automatic Back-Purging Procedure

Components for
Automatic Back-
Purging Procedure
Control of the
Automatic Back-
Purging Procedure
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During operation of the ACX 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 longer.
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-purging procedure with
compressed air. To control this procedure a function block program is used.
To carry out the automatic back-purging of the filter unit, components are integrated
in the ACX analyzer system as follows:
• the PFE2 filter unit with valves combination for back-purging or
• the PFE3 filter unit and separate back-purging unit with integrated compressed-air
conditioning components and
•
the control program.
The back-purging procedure is integrated into the main control program of the ACX
analyzer system. The manual handling is carried out with softkeys on the system's
display and control unit.
ACX Analyzer System Commissioning Instruction CI/ACX-EN Rev. D