Servomex DF-310E, Руководство оператора

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Sample Gas Preparation and Delivery DF-310E 35
Ammonia
Argon
Butane
Carbon Monoxide
Ethane
Ethylene
Helium
Hexane
Hydrogen
Methane
Nitrogen
Propylene NH
3
Ar
C
4
H
10
CO
C
2
H
6
C
2
H
4
He
C
6
H
14
H
2
CH
4
N
2
C
3
H
6
Table 3: Gas Scale Factors
6.2.1.1 Disclaimer
The method used to correct the calibration of the DF-310 E Oxygen Analyzer
for measurement in non-nitrogen background gases is derived from a well-
known theoretical mass transfer equation. This equation accounts for the
change in oxygen diffusion rates through different gases.
Although significant empirical work has been done in this field, it is generally
accepted that the equation may be only 85-90 percent accurate. In addition,
there is further error introduced when correcting for a "multi" component
background gas. This may result in up to an additional 3-5% error.
An alternate method when using a non-nitrogen or "multi" component
background gas for spanning is to obtain a certified Calibration standard that
has been prepared in a background gas that models the average process
sample. Care must still be used, however, as certified standards may also have
an inaccuracy associated with them.
Questions regarding the calculation of a background gas correction factor for
a specific application should be directed to the local Servomex Business
Center.
6.3 Sample Flow Rate and Pressure
The analyzer is factory calibrated at a flow rate of 1.0 scfh, in N
2,
and should
be operated at that level for optimal accuracy. However, the Servomex Sensor
is relatively unaffected by gas sample flow rate, within limits. Sample flow
rate should be maintained within the recommended range of 1.0 to 2.0 scfh.
The analyzer can be operated at flow rates outside that range, but it should be
recalibrated at that different flow rate to maintain optimal accuracy.
The analyzer has a small pressure drop (0.2 to 0.5 psi), so relatively small
changes in inlet or outlet pressure causes dramatic changes in flow rate.
Consequently, it is preferable to vent the outlet to atmosphere so that outlet
pressure remains constant, leaving inlet pressure as the only variable to
control.