Emerson Process Management 760004-A - Manual (Page 23)

Instruction Manual
760004-A
February 2002
Rosemount Analytical Inc. A Division of Emerson Process Management Description and Specifications 2-3
Model NGA 2000 HFID
b. Pneumatic Connections
WARNING
HIGH TEMPERATURES
The Sample In, Sample Bypass Out, and
Burner Exhaust Out gases and fittings can
reach temperatures of up to 250
°C. Make
connections to these fittings when the oven
heater is disabled or the module is powered
down.
(See Figure 2-1) Connect inlet and outlet
lines for sample, burner fuel and air, ex-
haust, bypass, regulated air, and purge to
appropriately labeled fittings on the rear
panel. All connections are 1/4-inch fer-
rule-type compression fittings except the
PURGE AIR IN and OUT connections,
which are 3/8-inch compression fittings. The
Burner Exhaust is a 3/8-inch connection.
It is recommended that no connection be
made to the PURGE AIR OUT port. If, how-
ever, the analyzer's location requires inter-
connection with a venting system, the 3/8"
O.D. line should be kept as short as possi-
ble, and no longer than four feet.
CAUTION
POSSIBLE INSTRUMENT DAMAGE
No connection should be made to the
PRESSURE RELIEF VALVE fitting. Doing so
may cause damage to the instrument.
CAUTION
PURGE AIR REQUIREMENTS
The front panel LEDs of the Analyzer Mod-
ule, as installed, are not visible, the user
should provide an indicator for the safety
system as per ANSI/NFPA 496 standards.
c. Specifications
Fuel Gas
Standard analysis usually requires
mixed fuel, i.e., 40% ±2%) hydrogen
and 60% helium. H
2/
He mixed fuel is
recommended over H
2
/N
2
fuel because
of better linearity in concentration out-
put. Such blends are supplied by many
gas vendors specifically for this use,
with a guaranteed maximum total hy-
drocarbon content of 0.5 ppm, meas-
ured 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 dia-
phragm pump and heated palladium
catalyst. This process continuously re-
moves moderate amounts of hydrocar-
bons and carbon monoxide from
ambient air.
Purge Air
Instrument quality air or nitrogen is re-
quired for the safety purge system.
Regulated Air
Instrument quality air or nitrogen is re-
quired. 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