Honeywell C7061A1020 Manual page 7

IMPORTANT
When installing the detector, make sure it does not
respond to ignition spark.
Single burner requirements
The detector must have an unobstructed view of the flame it is
supervising under all firing conditions. This implies a proper
sighting angle and the minimization of screening effects.
Sighting angle
The first 30 percent of a flame (the root) radiates the most intense
ultraviolet energy. The low angle sighting permits the detector to
view a greater depth of the flame root, thus reducing the effects of
irregularities in the flame pattern. The best sighting angle is nearly
parallel to the axis of the flame, as shown in Figure 3.
NOTE: When possible, it is desirable to tilt the detector and sight
pipe downwards to prevent the build-up of soot in the pipe
or on the viewing lens.
In most installations, the detector will need to respond to
pilot flame alone, then to the pilot and main burner flame
together and finally to the main burner flame alone. The detector
must meet all sighting requirements which apply:
-
1. Pilot flame alone the smallest pilot flame that can be
detected must be capable of reliable ignition the main
burner.
2. Pilot and main burner flame together
sight the junction of both flames.
-
3. Main burner flame alone the detector must sight the most
stable part of the flame or all firing rates
Fig. 3. Sighting angle
Screening effects
Smoke, fuel mist, dirt and dust are masking agents that absorb
ultraviolet radiation from the flame. They create a screen that
reduces the amount of ultraviolet radiation reaching the detector
and may cause flame signal deterioration resulting in a shutdown.
The adverse effects of Screening may be minimized by proper
burner adjustment, increasing the detector viewing area (shorten
sight pipe and/or increase its diameter).
Multifuel requirements
In addition to meeting the requirements for a single burner, a
multiburner installation also requires flame discrimination.
Flame discrimination may be defined as the location of all flame
detectors such that each detector responds only to
produced b y the burner it is supervising.
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the
-
the detector must
the flame(s)
7
Multiburner requirements
In multiple burner systems, not every detector can be positioned
so its line of sight does not intercept flames from other burners.
This situation occurs in front-fired boiler furnaces having more than
one row of burners, or in multi- level opposed-fired furnaces where
the burners face each other. When planning such an installation,
locate each flame detector so that it has the best possible view of
the root of the flame(s) it is supervising and the worse possible
view of all other flame.
Fig. 4. Critical detector application problem
Figure 4. illustrates a critical detector application Problem
requiring flame discrimination.
accomplished by detector 1 by reducing its sensitivity until the
flame relay (in the flame safeguard control) does not respond to
flame 2. Note that detector 1 is aimed at the
where UV (ultraviolet) energy is most intensive. Although it sights
flame 2 is not aimed at the
detector 1 is reduced to
sensitivity to flame 1 while rejecting flame 2. similarly, detector 2 is
adjusted to ensure maximum sensitivity to flame 2 while rejecting
flame
If the sensitivity control on a detector is set at its minimum position
and flame discrimination cannot be achieved, insert an orifice plate
in the sight pipe. An orifice of the proper diameter will reduce the
ultraviolet radiation reaching the detector so that the sensitivity
can be adjusted to effect flame discrimination.
Parallel flame detectors
Two C7061A/F detectors can be connected in parallel to the same
flame signal amplifier and still provide independent sensitivity
adjustment. This capability is particular useful for multiburner,
multifuel applications.
Shifting flame patterns, commonly encountered on burners with
wide turndown ratios, may require parallel detectors
the flame at the highest and lowest firing rates.
one detector supervises the pilot (interrupted) and both detectors
supervise the main burner flame. During the main burner "run"
period, either detector is capable of maintaining system operation.
In addition to assuring more reliable flame detection, parallel
detectors facilitate maintenance during burner operation.
Each detector can be removed in turn without shutting down the
supervised burner. However, a flame simulating failure occurring in
the flame signal amplifier or in either detector will cause a
shutdown.
Flame discrimination
root of Flame 1
root of flame 2. The sensitivity of
a point that ensures maximum
to prove
In this case,
EN1C-0015 R2105
is