Introduction User
Manual
October 2015
QCL-MAN-CT2211-Aerosol-Leak-Detection-System-Rev F
Introduction
6
The power supply (not shown) for the sensor is also mounted outside the explosive
environment.
The Venturi (not shown) is powered by compressed air and mounted in the exhaust
line below the sample cell. It is used to draw air from around the aerosol cans via the air
extraction arch.
The 3-phase blower (not shown) is powered from the control cabinet and mounted in
the exhaust line below the sample cell. It is used to draw air from around the aerosol
cans via the air extraction arch.
The Venturi air status pressure switch (not shown) signals a third party controller if the
air pressure drops below that required by the Venturi.
Gas concentrations are measured using mid-infrared optical absorption spectroscopy.
The light sources are quantum cascade lasers, which are operated to produce
wavelength sweeps that cover the absorption lines of the gases.
The lasers are mounted in the leak detector, and light is directed into the sample cell,
where it is partially absorbed by the gas from the stack. The reflected light from the
cell is detected by a receiver in the leak detector. The variation in the intensity of the
light in the vicinity of the absorption lines is measured, and the concentration is
determined using a comprehensive spectral fitting routine.
