System Diagnostics
and Testing
“The best laid plans o’ mice an’ men gang aft agley” (Robert Burns). Loose transla-
tion: In spite of your best efforts, some things just go wrong.
This book focuses on selecting the proper air pollution control equipment for a
given application. What happens if, however, you are “stuck” with what you have?
Perhaps you dont need to replace it (or can delay replacing it). Maybe a repair or
upgrade is in order.
Readers of the rst edition of the Air Pollution Control Equipment Selection
Guide requested that a chapter be added on problem solving for one of the most
popular pieces of gas cleaning equipment, wet scrubbers. Sometimes the best of
designs simply fail to work properly. Sometimes the process changes. Sometimes
the economy changes and there simply arent enough funds to make a change. The
pressure drop may be too high or the efciency too low, chemical may be wasted,
or assorted miscellaneous problems could arise. How does one go about correcting
these problems? In this chapter, some proven ways of diagnosing and correcting
some common and not-so-common problems with wet gas cleaning systems will be
discussed. Many techniques mentioned also apply to dry scrubbers and may also be
instructive for the reader.
24.1 TOOLS
First of all, you need the right tools.
To diagnose most scrubber problems, you could need any or all of the following:
1. Copy of operating manual (or, lacking that, a copy of the purchase order
and quotation for the equipment)
2. Copy of any and all stack tests on the system (particularly the most recent ones)
3. Copy of operating records, charts, datalogger output, etc.
4. Name and contact information of the person(s) operating the system
5. Name and contact information of the person(s) maintaining the system
6. A Dwyer Magnehelic™ gauge, or equal, of a range greater than the total
differential pressure of the system (see Figure24.1)
7. A pitot tube (such as the type S) and manometer (see Figures24.2 and 24.3)
8. A pH probe and meter
9. An oxidation reduction potential (ORP) probe and meter if it is an odor
control system
10. A 4–20 ma signal injector or calibrator if the system uses a 4–20 ma con-
trol loop
222 Air Pollution Control Equipment Selection Guide
FIGURE 24.2 Type S pitot tube for gas volume measurement (Dwyer Instruments, Inc.).
FIGURE 24.3 Manometer for velocity pressure measurement (Dwyer Instruments, Inc.).
FIGURE 24.1 Dwyer Magnehelic for pressure measurement (Dwyer Instruments, Inc.).

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