IRIS S55XX SERIES VIEWING HEADS APPLICATION MANUAL
PAGE 7
Purge air will help reduce conducted heat
through the sight pipe and flange. A heat insu-
lating ultem nipple (IRIS part R-508-12) will
reduce will reduce this conducted heat, but
direct radiation can cause housing case tem-
perature to exceed limits. If the ambient heat
(direct radiation) is excessive, then a fiber op-
tic extension should be considered. This uses
a fiber optic cable between the sight pipe and
the viewing head, allowing the viewing head
to be placed further away form the heat source.
Refer to the Fiber Optic Manual, or the IRIS
web site for more information.
The model S550 and S55XB series of viewing
heads have in place a sensor for sensing the
internal temperature of the head. To access
the reading of the viewing head temperature,
press the “Reset” and the “Down” arrow key
at the same time. The temperature reading will
be displayed in the four-digit readout. The
reading (indicated in °C) will disappear and
the normal reading will continue after several
seconds.
VIBRATION:
Do not install the viewing head
where it could be subject to vibration. A vi-
brating IR sensing viewing head can simulate
flame when viewing a glowing background.
Provide an anti-vibration mount if excessive
vibrations are present.
CLEARANCE:
Make sure there will be suffi-
cient room to remove the viewing head hous-
ing for servicing.
SIGHT PIPE
A minimum two inch diameter black iron pipe togeth-
er with a swivel mount is recommended for use with
all IRIS viewing heads. IRIS manufactures a range of
swivel mounts, both pipe thread or flange mounting.
See the IRIS ACCESSORY CATALOG on the User
Manuals CD, or view it on the IRIS web site.
PURGE AIR
Use a flexible air supply line, to allow for reposition-
ing of the viewing head and sight pipe until a final and
permanent position has been decided. A continuous
flow of air must be maintained in order to keep the
viewing cool and the sight pipe clean. At least three
CFM at approximately eight inches of water column
above windbox pressure is recommended for each
viewing head. The air supply must be clean, free of
oils and water, and preferably cool.
VIEWING HEAD SIGHTING
The sighting of the viewing head should be parallel
to the center line of the burner in the direction of the
flame. The sight pipe should be mounted as close to
the center line as possible, the idea is to sight along
the flame rather than across the flame. This will help
prevent drop outs of the flame under changing load
conditions. See figures 4 and 5 on page 15
Utilizing a sighting or the sight pipe aimed at the root
of the flame (where the turbulent combustion air mix-
es with the flame) is a good starting point for optimiz-
ing the sighting. Using a swivel mount to “zero-in” on
the highest signal will assure maximum performance.
A typical viewing head installation using a swivel
mount is shown in figure 7 on page 16.
The sight pipe diameter should be large enough to
allow a reasonable field of view, and to allow for ad-
justment of the swivel mount angle. The S550B has
two angles of view, one for the IR detector, which is
1.0
°
and one for the UV detector which is about 3.0
°;
this translates into a circle of view that varies with the
viewing distance as shown in the following table.
Distance Distance
Diameter of
IR View
Diameter of
UV View
ft
inches
inches
inches
2
24
.64
1.3
3
36
.73
1.9
6
72
1.45
3.8
12
144
2.9
7.6
18
216
4.35
11.4
Detecting flame in a sulfur recovery unit can present
a challenge for flicker type flame monitors. The IR
detector will detect natural gas used for the warm-up
of the reactor. Usually the combustion air is turbulent
enough to cause a good flicker signal.
When the sour gas is introduced and the natural gas is
shut down, the flame signal may drop off or drop out
entirely. The reason for this is that there is a complete
change in the flicker content for the existing viewing