Table of Contents
Advertisement
RESPONSE TO HOT REFRACTORY
Although the infrared amplifier will not respond to steady
radiation, as produced by hot refractory, be careful to protect
the infrared detector from hot refractory radiation because of
shimmer
two possible conditions,
a. Shimmer-Turbulent hot air, steam, smoke, or fuel
spray in the combustion chamber can reflect, bend, or
block the steady infrared radiation emitted by a hot
refractory. These conditions can change the steady
radiation from a hot refractory into a fluctuating radia-
tion. If these fluctuations occur at the same frequency
as that of a flickering flame, they will simulate flame
and will hold in the flame relay after the actual burner
flame has been extinguished.
b. Radiation saturation--Steady hot refractory radiation
can become strong enough to mask the fluctuating
radiation of the flame. This is similar to the effect of
holdingupacandleinfrontofthesun-thelightofthe
sun is so strong that the candle light cannot be seen. If
radiation saturation is extreme, the flame relay will
drop out, and the system will shut down as though a
flame failure has occurred.
Both of these problems will be minimized by aiming the
detector at a portion of the refractory that is:
as cool as possible.
l
as far from the cell as possible.
l
as small as possible reduce the field of view, see Figs.
l
Refractory temperatures in the combustion chamber will
vary with combustion chamber design but generally, the end
wall of the chamber will be the hottest point. It will normally
be best to aim the detector at the side wall of the refractory
(Fig. 4), at a point above the refractory (Fig. 5), or at the floor
of the combustion chamber (Fig. 6).
SIGHTING SUMMARY
When sighting the detector, two important factors to
consider are: (1) proper sighting of the flame being detected
(normally the pilot/main Rame junction), and (2) avoiding
hot refractory sighting.
A typical sighting arrangement is shown in Fig. 4. The
detector is aimed at the intersection of the pilot and main
flames, and at a relatively cool side of the combustion
chamber. The detector, in this case, would be located as close
as possible to the burner to sight the maximum depth of the
pattern.
The detector can also be sighted from a point below and
close to the burner with the line-of-sight above the refractory
(Fig. 5).
The third method is to aim the detector from above the
burner, sighting a portion of the refractory floor (Fig. 6). This
type of application requires that the pilot flame be carefully
sighted from the side. The detector should not be sighted
the shoulder
of the pilot because the chances increase of
a
sighting
pilot too small to satisfactorily light the main flame,
as possible and consistent with proper sighting of the flame.
Refer to Figs. 2 and 3 for methods of reducing the ama of hot
refractory sighted.
raa'iation saturation.
and
over
7
Fig. 4--C7015A infrared Flame Detector aimed
at side wall of combustion chamber.
_-
AREA VIEWED BY C7015A
I
I
.
.
Fig. 5-C7015A Infrared Flame Detector aimed
at a point above refractory.
BURNER
FACEPLATE
I
AND MAIN FLAME
I
I
Fig. 6-C7015A Infrared Flame Detector aimed
at floor of combustion chamber.
I
I
,
REFRACTORY FLOOR
I
INSTALLATION
MAIN BURNER FLAME
-
-
-
-
--
I
,
,
ABOVE TH
-
-
. .
. .
CENTER LINE
60-2306-5
Advertisement
Table of Contents
