10 Optional Functions
92
10
Optional Functions
10.1 Purge Functions
When there is a large amount of dusts in the stack gas, the purge function is effective:
the separate blowback instrument enables the backflush of the dusts collected by the primary
filter using the purge air.
According to the purge time setting, the periodical purge is available.
10.1.1 Principle of operation
When the stack gas contains dusts of high concentration, suction of sample gas for a long
time causes a clogging in the primary filter.
The purge function is a periodical backflush function of the primary filter using purge air
through the analyzer signal. When the purge starts, the sample line closes via the solenoid
valve signal, and the sampling pump of instrument stops. After approximately 5 seconds, the
In-blow line opens to start the in-blow purge of primary filter.
The in-blow line closes after 5 seconds since the set time for in-blow purge is over.
Then the sample line opens, and the sample gas suction starts with the sampling pump
operation. In this process, the sample gas replacement is performed as the DELAY (sample
gas replacement) state until the set DELAY time is completed. During the purge, the
concentration signal output is held, and the contact “in-purge” is output to the external device.
When the automatic calibration (AIC) starts during the purge, the purge sequence is
interrupted. After the AIC completes, the sequence starts from the beginning.
Fig. 66 Principle of operation
Stack
Solenoid valve
IN-BLOW line
Sample line
Primary filter
To analyzer
Purge air
Solenoid valve
F
P
