ABB ACX Commissioning Instruction page 44

Cycle Time
Cycle Time Duration
Cycle Time Factory
Setting
Optimum Cycle Time
Setting
Cycle Time Minimum
Value
Event-controlled Start
of the Back-purging
Procedure by Filter
Plugging
44
The cycle time is given as the time interval between two automatic starts of the back-
purging procedure. The higher the dust concentration in the sample gas and the
higher the sample gas flow, the shorter this time interval must be set, to avoid a
blocking of the gas sampling probe filter.
The parameter "Cycle time" is factory-set to 4 hours.
The parameter "Next event time" is factory-set to 08:00 / 12:00 / 16:00 / 20:00 / 00:00
/ 04:00 o'clock.
The cycle time should not be adjusted shorter than needed, because during the back-
purging procedure (approx. ca. 28 sec) and especially during the post-purge time
(factory-set to 150 sec) no measurement can be made. The optimum time will have to
be found out by operational experience.
The cycle time should not be below a lower limit. The back-purging procedure with
cold compressed air causes a cooling of the heated probe filter, and the filter
temperature regulation needs some time to correct this temperature decrease. As the
filter heating regulation is a rather slow control loop, this time will be relatively long.
Therefore the cycle time should not fall below approx. 60 min.
Should despite the time controlled back-purging a probe filter blocking occur caused
by temporary larger amounts of dust, with the result of a sample gas flow decrease
beneath the admissible limit, an additional back-purging procedure is started as a
result, and the probe filter is purged free in between.
ACX Analyzer System Commissioning Instruction CI/ACX-EN Rev. D