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5.5 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 that
2
the calibration curve (output performance to gas concentration) of gas analyzers will be affected (pres-
sure 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 attached 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 explained
using an example. For the standard gas for zero calibration, use N
will not be affected.
<Example> Assume that a 0-1% CO
plant gases.
When plant gases are composed of 0.5% CO
either of the following is used as the span calibration standard gas.
tandard gas type
tandard gas with the same
1
composition as plant gases (scale gas)
Check gas
2
* A small amount of gas like 0.2% CH
(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
concentration to span calibration concentration set value.
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
2
Composition of standard gas
0.9% to 1% CO
30%H
, remaining N
2
0.9% to 1% CO
Remaining N
2
with little effect on span calibration may be excluded from the standard gas.
4
- 76 -
or Air in any case so that zero point
2
, 23% CO, 30% H
, 0.2% CH
2
Method for span adjustment
, 25%CO,
Perform span calibration
2
*
directly.
2
Perform span calibration
indirectly.
2
contained in
2
and 44.3% N
,
4
2
INZ-TN2ZSVS-E
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