Specifications

748414-A
August 1999
8
Heated Flame Ionization Detector Analyzer Module
Rosemount Analytical NGA 2000
2
INSTALLATION
CAUTION: PURGE AIR REQUIREMENTS
The front panel LEDs of the Analyzer Module, as installed, are not visible, the
user should provide an indicator for the safety system as per ANSI/NFPA 496
standards.
2.4.3 S
PECIFICATIONS
Fuel Gas
Standard analysis usually requires mixed fuel, i.e., 40% ±2%) hydrogen and 60% helium.
H2/He mixed fuel is recommended over H2/N2 fuel because of better linearity in
concentration output. Such blends are supplied by many gas vendors specifically for this
use, with a guaranteed maximum total hydrocarbon content of 0.5 ppm, measured as
methane. This specification should be used when obtaining these mixtures.
NOTE
The fuel restrictor is marked with a red dot, and the sample capillary is marked with a
red or green dot for mixed fuel applications.
Burner Air
In order to ensure a low background signal, burner air should contain less than 1 ppm
maximum total hydrocarbon content. An alternate source for burner air and zero gas (see
CALIBRATION GASES below) is a combination diaphragm pump and heated palladium
catalyst. This process continuously removes moderate amounts of hydrocarbons and
carbon monoxide from ambient air.
Purge Air
Instrument quality air or nitrogen is required for the safety purge system.
Regulated Air
Instrument quality air or nitrogen is required. The air should contain less than 2 ppm
maximum total hydrocarbon content.
Calibration Gases
Calibration method and gases depend on the operating range, and the desired
measurement accuracy. In all methods, zero and span gases are used, and are introduced
through the sample inlet at the rear of the module.
Zero Gas - Analysis is affected by the background gas of the sample. Therefore, it is
recommended to use zero gas with as close to the background composition of the sample
as possible. Normally less than 0.5 THC as CH
4
is sufficient.