Instruction Manual
748262-M
May 2002
2-2 Installation Rosemount Analytical Inc. A Division of Emerson Process Management
Model 400A
2-4 FUEL AND AIR REQUIREMENTS
WARNING
INSTALLATION RESTRICTIONS
Fuel, air and calibration gas cylinders are
under pressure. Mishandling of gas cylin-
ders could result in death, injury or prop-
erty damage. Handle and store cylinders
with extreme caution and in accordance
with manufacturer's instructions. Refer to
General Precautions for Handling and
Storing Gas Cylinders, page P-4.
During normal operation, the analyzer uses
fuel and air to maintain the burner flame. Cri-
teria for selection of these gases are given in
Sections 2-4a (page 2-2) and 2-4b (page 2-2).
In addition, the analyzer requires suitable
standard gas(es) for calibration. Refer to Sec-
tion 3-1a (page 3-3).
Each gas used should be supplied from a tank
or cylinder equipped with a clean, hydrocar-
bon-free, two-stage regulator. In addition, a
shutoff valve is desirable. Install the gas cylin-
ders in an area of relatively constant ambient
temperature.
a. Fuel Gas
The standard analyzer is equipped to use
only mixed fuel, i.e. 40% hydrogen/60%
nitrogen or helium. Such blends are sup-
plied by many gas vendors specifically for
this use, with a guaranteed maximum to-
tal hydrocarbon content of 0.5 ppm,
measured as methane (THC < 0.5 ppm).
This specification should be used when
buying such mixtures.
When the analyzer is equipped with the
optional hydrogen fuel kit, P/N 622576,
100% hydrogen fuel is to be used. This is
also supplied by many gas vendors spe-
cifically for this use, with the same guar-
anteed total hydrocarbon content (THC <
0.5 ppm) which, again, should be speci-
fied when buying the gas.
NOTE:
Always assure the sample flow is pre-
sent when using the 100% hydrogen
fuel option. Absence of sample flow
can result in burning of detector tip
when using 100% hydrogen.
b. Air
Burner air should also be relatively free of
hydrocarbons in order to assure a low
background signal. Several grades of air
are supplied by various gas vendors for
this use. A maximum total hydrocarbon
content of less than 1 ppm (THC < used
as a zero standard).
An alternate source of pure air for burner
and zero gas can be provided by a dia-
phragm pump and heated palladium
catalyst which effectively removes mod-
erate amounts of both hydrocarbons and
carbon monoxide from normal ambient air
on a continuous basis.
2-5 SAMPLE HANDLING
CAUTION
BYPASS GAUGE PROTECTION
When applying sample pressures greater
than 5 psig, insure that the bypass regula-
tor is fully open to protect the bypass
gauge.
Operating range for the internal sample pres-
sure regulator is 4 to 5 psig (28 to 35 kPa) for
an analyzer using 100% hydrogen fuel, and
1.5 to 5 psig (10 to 35 kPa) for an analyzer
using mixed fuel. With either fuel, sample and
calibration gas(es) must be supplied to the
sample inlet at a pressure slightly, but not ex-
cessively higher than the desired setting on
the internal sample pressure regulator. The
criterion for correct supply pressure is that the
gas flow discharged from the by-pass outlet
must be between 0.5 and 3.0 liters/minute to
operate within the control range of the sample
pressure regulator, and preferably should be
between 2 and 3 liters/minute to minimize
system response time.