Instruction Manual
760000-C
November 2002
3-40 Operation Rosemount Analytical Inc. A Division of Emerson Process Management
Model NGA2000 CLD
An apparent subnormal efficiency can be
due to a problem external to the Analyzer
Module, perhaps located either within the
test setup or between it and the Analyzer
Module. Check the following:
1. Leakage.
2. Loss of NO
2
between test setup and
Analyzer Module. Such loss can oc-
cur by reaction with a rubber dia-
phragm in a pressure regulator or
flow controller. Stainless steel dia-
phragms are preferred. Loss can
also occur during passage through
filter media.
d. Replacement of Converter
If the subnormal conversion efficiency is
real, and not due to measurement error
introduced by the test setup, the converter
must be replaced. See Section 4-4, page
4-1.
The usual cause of converter failure is
destruction of a large part of the catalytic
material by excessive heat. This is due ei-
ther to an excessively high temperature
setpoint or failure of the converter tem-
perature control circuitry.
e. Capillaries
Replacement vent and pump capillaries
should be installed finger-tight. Use of a
wrench can constrict capillaries, thus
changing flow rate. Sample capillary is
metal; use a wrench for tightening.
f. TEA
Scrubber
The presence of NO
2
in the NO cylinders
can cause inaccurate converter efficiency
values. The TEA Scrubber accessory
(P/N NL635741) can be used to remove
residual NO
2
from the NO cylinders. Use
of this accessory allows an NO
2
-free NO
calibration gas.
