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7.6 Adjustment in heat treatment furnace
• What is the adjustment in heat treatment furnaces?
If, in plant gases to be measured actually, a large amount of other lower-molecular-weigh gases than
nitrogen (N
) such as hydrogen (H
2
nitrogen (N
) such as argon (Ar) are contained, including the measuring components, it is known
2
that the calibration curve (output performance to gas concentration) of gas analyzers will be affected
(pressure broadening).
In such a case, analyzer is adjusted with gases similar to plant gas compositions in manufacturing
(adjustment by scale gas). After this adjustment, the analyzer is checked the calibration curve with
N
balance gas (calibration curve by check gas). Graphs with these calibration curves drawn are at-
2
tached to products to be supplied.
Since measurement in a heat treatment furnace has much gas of such composition, it is considering
as the adjustment for heat treatment furnaces.
In order to perform exact measurement, perform the following span calibration.
Composition of the standard gas for span calibration used for each method and its method are ex-
plained using an example. For the standard gas for zero calibration, use N
zero point will not be affected.
<Example> Assume that a 0-1% CO
in plant gases.
When plant gases are composed of 0.5% CO
N
, either of the following is used as the span calibration standard gas.
2
Standard gas type
Standard gas with the same
1
composition as plant gases (scale gas)
Check gas
2
* A small amount of gas like 0.2% CH
gas.
(1) Method for span calibration by standard gas with the same composition as plant
gas
When using the standard gas with the same composition as plant gases given in 1, calibration can
be performed without correction, as an error in calibration curve does not occur.
1) Set CO
2
2) Perform span calibration by using the operation key.
), or a large amount of other higher-molecular-weight gases than
2
meter of the infrared ray gas analyzer measures CO
2
with little effect on span calibration may be excluded from the standard
4
concentration to span calibration concentration set value.
, 25% CO, 30% H
2
Composition of standard gas
0.9% to 1% CO
, 25%CO,
2
30%H
, remaining N
*
2
2
0.9% to 1% CO
Remaining N
2
74
or Air in any case so that
2
contained
2
, 0.2% CH
and 44.3%
2
4
Method for span adjustment
Perform span calibration
directly.
Perform span calibration
indirectly.
INZ-TN2ZPA-E
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