Yokogawa In-Situ Gas Analyzer TDLS200 - Manual (Page 128)

9-3
IM 11Y01B01-01E-A 6th Edition :Feb 13, 2013-00
<9. TROUBLE SHOOTING>
• Adjust Analyzer Alignment. Adjusting the alignment will ensure the analyzer has not physically changed
to the point where the laser beam is off center (at detect unit). While monitoring transmission % adjust
the alignment in all directions (by a small amount) until you see the transmission increase. Fine tune the
adjustment to ensure maximum alignment.
•
Initiate On-Line Validation (if fitted). On-line validation will provide an indication of whether the analyzer
is responding to gas changes. During this step, manually record the amount of analyzer reading
change. detector.
•
Record Results. Download data files from the analyzer for e-mail to Yokogawa.
• SPECIAL NOTE – Parts removal (if necessary) should be done so with great care! There are
electrostatic sensitive devices (such as the Laser Diode Module!) that can be damaged if not handled
correctly.
DO NOT CUT WIRES TO REMOVE ANY ITEMS PARTS!!!
• THE LASER DIODES MODULES AND DETECTOR MODULES ARE ELECTROSTATIC SENSITIVE –
IMPROPER HANDLING CAN CAUSE PERMANENT DAMAGE AND SUBSEQUENT REPLACEMENT
Of PARTS.
9.1.1. Trouble Shooting Procedure for Lost and/or Low Transmission
For a TDLS analyzer to function correctly there must be a suitable amount of the laser light reaching
the detector. There are several factors (or combinations of) that can affect the amount of light that
is detected:
• Alignment:
The mechanical alignment of the laser beam with the detector unit
o The beam not directed at the detector window
o The detector not aligned with the incoming laser beam
o Miss-aligned flanges and/or nozzles
• Plugging:
The quality of the ‘clear aperture’ through which the beam travels
o Physical obstructions inside the nozzles and/or piping
o Dirt or residue fouling of the process windows
o Mechanical obstructions
• Particulate:
The process gas optical clarity
o Excessive smoke density/opacity and/or particulate matter that prevents sufficient light from
reaching the detector
• Weak Laser:
The output power of the laser module itself
o Weak or dead laser diode source not outputting sufficient light
This procedure will help new and existing installations with respect to troubleshooting situations that incur lost
and or low (or even none) transmission. Transmission is a relative value for light power received at the detector.
Typically, a functional analyzer with clean windows mounted on an off-line calibration cell the transmission will
be anywhere from 90 to 100% (sometimes a little over 100%). Additional isolation windows can further reduce
transmission, typically by an additional 30% for Sapphire isolation windows and by up 20% for BK-7 windows
(BK-7 not typically recommended by isolation flanges – pending process conditions).