4 molybdenum converter option, 5 external desiccant canister option, 6 alternate bypass flow orifice option – Teledyne 9110AH - Nitrogen oxides analyzer User Manual
Page 87: 7 external converter option

TELEDYNE Model 9110AH NO
X
Analyzer Operator Manual, 01620, Rev. F
6-5
6.4 Molybdenum Converter Option
The Molybdenum Converter is used in applications where the NO
2
concentration will not be
expected to exceed 5 ppm. In these applications it exhibits very high conversion efficiencies,
thus enabling the accurate measurement of low concentrations of NO
2
. Operating the Converter
where the concentrations exceed 5 ppm will cause lower efficiencies and will shorten the life of
the converter.
6.5 External Desiccant Canister Option
This Option is located between the PermaPure Dryer and the ozone flowmeter. See Figure 2-2
for location and Figure 8-5 for pneumatic schematic. It is mounted external to the analyzer. It
should be used at extremely humid sites, or where the –70 C dewpoint air produced helps in
reducing reaction cell contamination and window clouding.
6.6 Alternate Bypass Flow Orifice Option
The standard bypass flow is 250 cc/min. For those applications requiring a higher sample flow,
this option provides a 500 cc/min bypass flow. The overall sample flow is 550 cc/min with this
option installed. The orifice is located in the vacuum manifold at the rear of the instrument see
Figure 2-5.
6.7 External Converter Option
The M9110AH can be ordered with an External Thermal Converter. Its conversion performance
is very similar to the Mini HiCon. The advantage of this converter is that it is less prone to
plugging because it is constructed of larger diameter tubing, also the conversion efficiency is
very high because the thermal converter is followed by a molybdenum converter. Since the
converter is external to the M9110AH the response of the instrument is considerably slower if
operated in the NO/NO
x
switching mode. This is due to the larger internal volume that must be
purged during the NO/NO
x
measurement cycle. This effect is less noticeable if the M9110AH is
being operated in the NO
x
only mode.
The External Thermal Module contains 2 converters, a high temperature stainless steel and a
molybdenum converter. While this combination produces very high conversion efficiencies, the
life of the moly must be considered. If high levels of NO
2
are expected in the sample stream,
the high temperature converter converts only about 90 % of the total NO
2
, the moly must
convert the rest. Since the moly operates by reacting the molybdenum metal with the NO
2
, its
lifetime can be quite short if high levels (>50 ppm) of NO
2
are present.
In instruments that have the external converter option, the Mini HiCon housing assembly
contains only the catalytic ozone killer and a heater to keep the ozone catalyst temperature at
200 C. Its temperature is monitored in the TEST function O3KL.