Det-Tronics C7050 A, C, G, P UV Flame Detector - Manual (Page 10)

produce a count. If the x- or gamma ray flux is sufficient to
produce a count rate higher than the system sensitivity set-
ting, an undesired response of the system can occur.
Data on sensitivity of the C7050 Detector to various x-ray
and gamma radiation intensities is impossible to relate to
a typical detector exposure. The normal precaution
against false actuation due to x-rays or gamma radiation
is to turn off the detection system when sources of high
level radiation are being used in the immediate area.
Caution must be exercised if the detection system is
turned off, since the hazardous area will not be protect-
ed. If the application requires continuous supervision by
the detection system, a “Nuclear Surveillance” system is
needed. Refer to form number 95-8256 or contact Det-
Tronics for complete information.
NOTE
Ultraviolet detectors are very sensitive to arc weld-
ing, and if this type of radiation can be expected, it
must be controlled through proper application.
Successful application techniques include careful
positioning and shielding of the detectors. Some
applications can require a “Remote Surveillance” or
UV/IR system. Contact the Field Support Group at
Detector Electronics for complete information.
Figure 7 shows a composite view of the cone of vision
and the response of a typical detector to a constant UV
source at various relative distances. Depending upon
the intensity of the ultraviolet radiation source, the C7050
can be considered to have a practical application dis-
tance of up to about 50 feet (15 meters). Under certain
controlled conditions, detectors can be used at greater
distances.
SYSTEM SENSITIVITY CONSIDERATIONS
Figure 8 shows the approximate relation between counts
per second (cps) and distance. From this curve it can
be seen, for example, that a 4 ft
2 (0.37 m 2 ) gasoline fire
at 60 feet (18 meters) will normally cause the detector to
generate 20 cps. The same fire at 40 feet (12 meters)
will generate about 50 cps. If a 2 ft
2 (0.18 m 2 ) fire at 20
feet (6 meters) will generate about 100 cps, the same
fire at 70 feet (21 meters) will generate about 8 cps.
Because of the complexity of the combustion process,
the UV tube count rate generated by different size fires
viewed from the same distance is difficult to predict with
a high degree of precision. In general, however, if a fire
doubles in size, the tube count rate is increased by
approximately 60 percent.
NOTE
The count rate of any given detector will depend
upon the sensitivity of the sensor tube, the type and
amount of fuel, the distance between the detector
and the fire, as well as various other factors. Figure
8 illustrates the relative response of a “typical” C7050
to various size gasoline fires based on minimum sen-
sitivity standards for DE1888 UV sensor modules.
Sensor modules with higher sensitivity are available.
Consult the Field Support Group at Det-Tronics for
information or assistance concerning a specific
detector tube type or a specific combustible material.
Selection of controller sensitivity and time delay to be used
in a given application is dependent on the level of hazard
present and the action to be taken in the event of fire. The
adjustable sensitivity and time delay of the R7404 allows it
to meet the requirements of virtually any application.
0°
15°
30°
45°
15°
30°
45°
VIEWING ANGLE
A1288
100
90
80
70
60
50
40
30
20
10
DETECTION
DISTANCE
(PERCENT)
100% REPRESENTS THE MAXIMUM DETECTION DISTANCE FOR A
GIVEN FIRE. THE SENSITIVITY INCREASES AS THE ANGLE OF
INCIDENCE DECREASES.
Figure 7—Detector Cone of Vision
8
260
240
220
200
180
160
140
120
100
80
60
40
20
0
0 10 20 30 40 50 60 70 80 90 100
0 5 10 15 20 25 30
1 (0.09) 2 (0.18) 6 (0.56) 8 (0.74) 10 (0.93) 12 (1.11) 14 (1.3) 36 (3.3) 4 (0.37)
DETECTOR OUTPUT VERSUS DISTANCE
FROM A GASOLINE FIRE AS A FUNCTION
OF SURFACE AREA OF THE SOURCE
DETECTOR OUTPUT – COUNTS PER SECOND
DISTANCE
FEET
METERS
A1487
SQUARE FEET (SQUARE METERS)
Figure 8—Sensitivity of a Typical Detector to a Gasoline Reference Fire