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Instruction Manual Rev B
Section 2 Installation Considerations
Regulatory/Process Considerations
The EPA has established the following guidelines for choosing an opacity/dust density monitor installation site:
1) Locate the transmitter across a section of a duct or stack that will provide a particulate matter flow
through the path of the transmitter beam representative of the duct or stack flow.
2) Ensure the transmitter location is down-stream from all particulate control equipment.
3) Locate the transmitter as far from bends and obstructions as practical.
4) If a transmitter is to be located less than 4 duct diameters downstream from a bend, install the
transmitter in the plane defined by the bend, as shown in the figure below.
5) Ideally, locate the transmitter eight to ten stack diameters upstream from the stack exit and three
to five diameters downstream from any bends, junctions, or other constrictions in the stack or
duct.
For best results, mount the transceiver and retro reflector modules so the light beam is exactly perpendicular to
the stack or duct and the beam goes through the center. Do not install the transmitter downstream of a wet
scrubber. The water droplets introduced to the gas stream by such equipment will interfere with the opacity
readings. For an accurate measurement under these conditions, choose a location upstream from a wet
scrubber or a location downstream from the scrubber where the
water droplets are vaporized by the reheating of the gas. The
stack exit correlation is especially important to verify. If possible
all dimensions should be verified by actual measurements.
Measure and record inside stack dimensions at the measuring
point and at the stack exit, and compute the Optical Path Length
Ratio (O.P.L.R.). Check that the calculated and the O.P.L.R. found
in the Factory OPLR Check step found further in this section are
within +/- 2%.
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