Vigilantplant TDLS8000, User Manual

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<Appendix 6 Maintaining Good Transmission>
App.6-1
IM 11Y01D01-01EN
Appendix 6 Maintaining Good
Transmission
l
High dust application
Depending on the measurement location, the process may include large amounts of
contamination, dust, and particles. In such conditions, the amount of laser beam that reaches the
SCU decreases.
Normally, such information should be conveyed to Yokogawa through the process information
questionnaire of the Application Data Sheet and assessed in the TDLS8000 design, engineering,
and specification determination stages before TDLS8000 installation. However, depending on
the process, the contamination, dust, and particle conditions may change (e.g., waste disposal
sites, thermal oxidation).
To improve transmission in a high particulate concentration process, you must reduce the
process optical path length and perform process window purge correctly and thoroughly.
Ø190.5
Ø190.5
Ø127 RF
44.5
23.4 RF to RF
305
41
48.3
ANSI Class 150-3B 316LSS flange
Unit: mm
5/8 inch 11 UNC
1-1/2 inch schedule 40
Hastelloy-C276
Figure 1 Example of Insertion tubes
For high dust concentration applications, please consult with Yokogawa. If it is deemed that
reducing the process optical path length can significantly improve the transmission level (or
at least to within the tolerance of the TDLS8000 capacity), we will discuss with you the special
insertion tube specification requirements. In many cases, insertion tubes are made of materials
compatible with the process medium. In applications that include acidic or corrosive gas,
Hastelloy C276 or Monel 400 is used.
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Handling process nozzle clogging problems
If dust accumulates repeatedly in process flanges or insertion tubes, try the following measures.
• Increase the flow velocity and pressure of the process window purge gas
• Use a process nozzle or insertion purge tube with small opening.
• Keep the process nozzle warm to prevent condensation or solidification
• Combine the above methods
• In the worst case, move the TDLS8000 to a cleaner measurement location (e.g.,
downstream side of ESP, knockout drum, filter scrubber).
3rd Edition: Jun. 10, 2016-00