IRIS MODEL P522 APPLICATION MANUAL
Note that both the SIG and SIG GND circuits are switched. However, this can cause a lockout condi- tion if the transfer of the viewing heads is done dur- ing the dark period. This problem can be avoided by changing channels when switching heads (i.e., by wiring the two terminal blocks V.H. SEL and CHAN SEL together in parallel). This will inform the P522 that the viewing heads are being transferred, and the pulses counted during the dark period will be ignored.
In this way, the flame signal can be optimized by adjusting the viewing head to the target at the end of the pipe.
SELECTING THE PIPE
We recommend a black iron pipe to provide reliable flame sensing. The viewing head is tapped for a one- inch national pipe thread (NPT) threaded pipe. Any diameter
DETERMINING SIGHT PIPE SIZE | MOUNTING HOLE | |
In order to determine the proper sight pipe, it is im- | Cut a hole for the sight pipe in the burner front | |
portant to understand how the viewing head “views” | windbox at the selected location. The hole should | |
the flame. The viewing head employs a | be large enough in diameter to allow adjustment of | |
vex lens in front of the photodetector that focuses | the sighting angle. If register vanes interfere with | |
the flame radiation on the surface of the detector. | the desired line of sight, trim the interfering vanes to | |
The active photodetector element is quite small, and | ensure an unobstructed view of the flame. | |
its diameter and the focal length of the lens deter- | MOUNTING OF SIGHT PIPE | |
mines the angle of view. For the S509 viewing head, | ||
After cutting the pipe to the desired length, thread | ||
this angle of view is about 2.8 degrees. For the S512, | ||
the angle is slightly less. | one end of the pipe to fit the viewing head flange or | |
To understand what this means, imagine a circular | required coupling (see Figure 20). Insert the other | |
end of the pipe into the mounting hole, align the pipe | ||
target of flame radiation, one inch in diameter, 24 | ||
to the desired sighting angle, and tack weld it in place | ||
inches away from the lens: this is the maximum field | ||
to allow further sighting adjustments. Make sure | ||
of view the detector sees. In other words, a | ||
the tack weld will support the weight of the detector | ||
diameter sight pipe two feet long will allow maxi- | ||
when it is installed. Once the final position has been | ||
mum signal to be detected. A | ||
determined, weld the sight pipe in place. | ||
sight pipe four feet long presents the same target. | ||
INSTALLING THE VIEWING HEAD | ||
Actually, a | ||
an immeasurable signal attenuation, so you can use | The | |
a | inch NPT threaded pipe (see Figure 20). Use a cres- | |
signal attenuation. | cent wrench to tighten the flange onto the sight pipe. | |
The angle of view for the S511 viewing head is 1.1 | PURGE AIR | |
degrees. This translates into a | Use a flexible air supply line, allowing reposition- | |
get 52 inches away from the lens. In other words, a | ||
ing of the sight pipe until the permanent detector | ||
position has been verified. A continuous flow of air | ||
inch diameter sight pipe eight feet long) will allow | ||
must be maintained in order to keep the head cool | ||
maximum signal to be detected. | ||
and the sight pipe clean. We recommend that at least | ||
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For a detailed explanation of how the angle of view | three CFM at approximately eight inches of water | |
is derived, refer to section ANGLE OF VIEW OF | column above windbox pressure be provided for each | |
VIEWING HEAD. | viewing head. The air supply must be clean, free | |
If a long sight pipe is required, then we recommend | from oil and water, and preferably cool. | |
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that a swivel mount be used to overcome any optical |
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misalignment that might be present (see Figure 20). |
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| Page 15 |
