Rosemount Analytical NGA 2000, Руководство пользователя

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I
NSTALLATION
748332-D Rosemount Analytical June 1997 2-3
NGA Non-Dispersive Infrared Analyzer
(in the rear of the manual) specifies a background gas, use this as a zero gas. If a
background gas is not specified, use dry nitrogen.
Span gas should be between 75% and 100% of fullscale span. Flowing reference (if
used) should be dry nitrogen.
F
LOW
R
ATE
Recommended sample flow rate is 1 to 2 SCFH (500 TO 1000 cc/min). A lower flow
rate will not affect readings but may result in an undesirable time lag. Excessive flow
can produce increases cell pressurization and reading error.
At higher cell pressures, the nonlinearity of the calibration curve increases. Therefore,
the calibration curve should be redrawn for higher flow rates. Also, the effect of
increased cell pressurization can be negated if the same flow rate is used for sample,
zero and span gases. But, if flow is high enough to cause elevated pressure, careful
control (tighter tolerance) of flow rate is required to avoid errors.
If low is kept at or below 2 SCFH (1 L/min), sample and instrument temperatures
reach equilibrium regardless of stream temperature (within specifications; 0 to 55
°
C).
At extremely high flow rates, this may not be true, although no such effect has been
noted up to 18 SCFH (9 L/min).
See Table 2-1 for cell purging times at atmospheric sample pressure.
S
AMPLE
P
RESSURE
/F
ILTRATION
Sample should be introduced to the Analyzer Module at a maximum 690 hPa-gauge
(10 psig). Pressurized applications are available, which require pressurized cells and
careful control of flow rates, consult factory for these applications. Sample should be
filtered for particulates down to two microns.
L
EAK
T
EST
The Analyzer Module is completely tested at the factory for gas leakage. The user is
responsible for testing for leakage only at the inlet and outlet fittings on the rear panel.
The user is also responsible for internal leak testing periodically and if any internal
pneumatic components are adjusted or replaced (with a test procedure chosen by the
user).
2.4.2 C
ONNECTIONS
(See Figure 2-3) Connect inlet and outlet lines for sample/zero/span and flowing
reference (if applicable) to appropriately labeled fittings on the rear panel. All four
connections are 1/4 inch ferrule-type compression fittings.