Typical Operating Conditions
The Controller is calibrated at the factory for flow rates to deliver gas in sccm units. The following table summarizes the typical operating conditions:
Table 1 Typical Operating Conditions
Condition | SCD | NCD |
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Detector Pressure (Torr) | ||
Dual Plasma Controller | ||
Pressure (Torr) |
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Burner Temperature (°C) | 800 | |
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Hydrogen Flow Rate (sccm) | ||
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Oxidant Flow Rate (sccm) | ||
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|
Background Noise (mV) | ||
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|
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*
Thermocouple lifetime at 950 °C is diminished.
The recommended conditions should yield satisfactory results for most applications and should be used as a typical starting point for any method development. Like any detector, however, there are optimum conditions which may very somewhat from the recommended conditions. In optimization of conditions for the Dual Plasma Burner and Controller the following guidelines should be considered:
High flow rates of hydrogen and oxidant can release enough heat at high temperature to vaporize combustion tubes and cause blockages downstream where the materials condense. High flow rates will eventually cause the pressure in the Burner to exceed its fault
A higher hydrogen to oxidant ratio may initially show higher response but later yield a reduced response because of the accumulation of contaminants, such as soot or other active species, that reduce the Detector response.
Operating the Burner at higher temperatures will place more demand on the heater, thermocouple and seal materials, effectively shortening their lifetime.
In general, when making any parameter change, keep in mind that the system may require time to reach equilibrium.
Operation and Maintenance Manual | 75 |
