Yokogawa IR400 - Manual (Page 20)

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IM 11G02N01-01E
Analyzer without O
2
measurement
N
2
gas
Gas with concentra-
tion of 90% or more
of full scale
Analyzer with external zirconia O
2
sensor
Dry air or atmospheric air (Note)
Gas with concentration of 90% or
more of full scale
1 to 2% O
2
Zero gas
Span gas other
than for O
2
measurement
Span gas for O
2
measurement
3.4 Sampling
3.4.1 Conditions of sampling gas
1. Dust contained in the sampling gas should be completely removed with a filter. For the final
stage filter, use a filter that allows removing dust particles of 0.3mm.
2. Dew point of sampling gas must be lower than the ambient temperature to avoid occurrence
of drain in the gas analyzer. If vapor is contained in the sampling gas, dew point should be
lowered to 0
°
C by using a dehumidifier.
3. If SO
3
mist is contained in the sampling gas, use a mist filter or cooler to remove SO
3
mist.
Other mists should be removed by using a mist filter or cooler.
4. Corrosive gases such as Cl
2
, F
2
and HCl, if they are contained in the sampling gas in consid-
erable amounts, will shorten the life of instruments.
5. Temperature of sampling gas should be within 0 to 50
°
C. Provide a means that prevents
entry of hot gas directly into the instrument.
3.4.2 Sampling gas flow
Flow of sampling gas should be 0.5
±
0.2L/min.
Avoid flow fluctuation during measurement.
Observe the flow reading by a flowmeter provided as shown in the example of the sampling
system configuration (Item 3.4.6).
3.4.3 Preparation of standard gas
Routine calibration is required by standard gas for keeping this instrument under normal operation
condition (once a week). Prepare a standard gas cylinder for zero calibration and span calibration.
3.4.4 Reduction of moisture interference
NO and SO 2 measurement is subject to moisture interference.
As shown by the configuration example on the next page, provide a device for humidifying zero
calibration gas, thus controlling the moisture content at a constant level (moisture content in
sample gas should also be controlled here) in configuring a sampling system. That allows the
same moisture content as in the case of measurement to be contained in zero gas for calibration.
3.4.5 Purging of instrument inside
The inside of instrument need not be purged generally except for the following cases.
1. A combustible gas component is contained in sample gas.
2. Corrosive gas is contained in the atmospheric air at the installation site.
3. The same gas as the sample gas component is contained in the atmospheric air at the installa-
tion site.
In such cases as above, the inside of analyzer should be purged with the air for instrumentation
or N
2
. Purging flow rate should be about 1L/min.
If dust or mist is contained in purging gas, it should be eliminated completely in advance.
Analyzer with built-in O
2
sensor
N
2
gas
Gas with concentration of
90% or more of full scale
Gas with concentration of
90% or more of full scale or
atmospheric air (21%)