Installation And Operation - Honeywell Searchline Excel Open-Path Technical Handbook

MAN0530 Issue 09 October 03
2104M0506
4.2.1 Transmitter
The Cross-Duct Excel Transmitter produces an intense, collimated infrared beam from a Xenon arc
flashlamp. It uses a different optical arrangement compared with the Open-Path Transmitter. This enables
it to produce a beam with a uniform intensity distribution even at the shortest operating range.
Note: The infrared beam is invisible and eye safe.
Compared with the standard Transmitter, the Cross-Duct Transmitter has a larger window heater
to reduce the possibility of condensation.
4.2.2 Receiver
The internal design of the Receiver is the same as that used in the Open-Path versions of
Searchline Excel. Externally the Cross-Duct Receiver has a different front end which fixes onto
the mounting cell. In the Cross-Duct version, the gas reading is automatically converted into a
%LEL (%LEL/m for FM version) measurement, taking into account the path length and the
double pass of the beam across the duct.
4.2.3 Retro-Reflector
Using a retro-reflector panel has a number of advantages for a Cross-Duct gas detector. Because
the infrared beam crosses the duct twice, it will be absorbed twice by any gas present. This
makes the gas detector more sensitive to gas than a single pass gas detector. Sensitivity to
vibration or misalignment is greatly reduced. The retro-reflector can be tilted by up to 15°
before the signal starts to drop. Any positional misalignment does not affect the signals as long
as the beam stays on the retro-reflector. When installing a Cross-Duct Excel, there is no
complex alignment procedure. Provided the retro-panel is mounted opposite the Transmitter
and Receiver gas detector, and perpendicular to the beam, the signals will be sufficient for
normal operation.

4.3 INSTALLATION AND OPERATION

4.3.1 Siting and orientation
Position
Although the Cross-Duct Excel has been designed to tolerate the most severe environmental
and site conditions, for optimum performance care should be taken to avoid areas where the
unit may be affected by:
• Vibration
• Accidental impacts
4. CROSS-DUCT EXCEL
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Searchline Excel