Det-Tronics C7050 A, C, G, P UV Flame Detector - Manual (Page 11)

The system can be adjusted to various sensitivity levels
by programming the controller to respond at a pre-deter-
mined detector tube count rate. This count rate is
dependent upon the intensity of the ultraviolet radiation
reaching the detector, which is a function of fuel, flame
size, distance from the detector, and the amount of UV
absorbing vapors that may be present.
Programming the controller to respond to a low count
rate results in high system sensitivity. Conversely, pro-
gramming the controller to require a high count rate
results in low system sensitivity. The presence of UV
absorbing vapors must be examined closely. Some
chemical and petrochemical vapors have very strong UV
absorption characteristics. See Table 2.
Referring to Figure 8 and considering the conditions
described above, the criteria for selecting a correct sys-
tem sensitivity adjustment can be established. For
example, assume that the hazard to be protected is at a
distance of 23 feet (7 meters) from the detector. Assume
that the hazard is gasoline and that it is desired to pro-
duce an alarm signal when a fire with a surface area of 1
square foot (0.09 m
2 ) develops. Reading on the hori-
zontal “Distance” axis of Figure 8, locate the vertical line
at approximately 23 feet (7 meters). Follow this line until
it intersects the “1 square foot” curve. Note that this
occurs at the horizontal line of about 50 counts per sec-
ond on the vertical “Detector Output” axis. This means
that the controller should be adjusted to 48 cps sensitivi-
ty in order to detect this size fire from 23 feet (7 meters).
If the detectors were located 30 feet from the hazard, it
can be seen that it would be necessary to use a more
sensitive (lower cps) setting.
INSTALLATION
IMPORTANT
The installation procedure described in this manual
is intended for wiring and programming the stan-
dard R7404 Controller used with the C7050B
Detector. It is important to note that the R7404
Controller is available with various operating pro-
grams (EPROMs). This can affect the system pro-
gramming and/or terminal configuration of the con-
troller. Since the installation procedure and appli-
cation instructions vary with each model, specific
information is supplied in a separate manual that is
specific to the equipment being installed. When
installing any “special purpose” version of the
R7404 Controller, always use the manual that is
supplied with the controller in conjunction with this
manual. If a conflict arises, follow the procedure in
the manual for the specific equipment involved.
Device Manual Form Number
R7404 with STAR Logic 95-8294
R7404 for Remote Surveillance System 95-8249
R7404 for Nuclear Surveillance System 95-8256
WIRING REQUIREMENTS
The wiring to the detector must be a shielded cable 22
gauge (0.643 mm diameter) minimum, with at least a 600
volt rms rating. If there are two detectors in a zone, they
may share a cable. If the detector leads are run in con-
duit, the conduit must not be used for wiring from other
electrical equipment. Detectors can be located up to
2000 feet (600 meters) from the controller.
Shielded cable is required for the “B” (signal) leadwires.
As with any field device, shielded cable for all wires pro-
vides maximum protection from RFI/EMI sources. In
applications where the wiring cable is installed in con-
duit, the conduit must not be used for wiring to other
electrical equipment.
9 95-8242
Table 2—UV Absorbing Gases and Vapors
The following 38 substances exhibit significant UV absorp-
tion characteristics. These are also generally hazardous
vapors. While generally of little consequence in small
amounts, these gases can restrict UV detection if they are
in the atmosphere in heavy concentrations. It should also
be determined whether or not large amounts of these
gases may be released as a result of a fire-causing occur-
rence.
Acetaldehyde Methyl Methacrylate
Acetone Alpha-Methylstyrene
Acrylonitrile Naphthalene
Ethyl Acrylate Nitroethane
Methyl Acrylate Nitrobenzene
Ethanol Nitromethane
Ammonia 1-Nitropropane
Aniline 2-Nitropropane
Benzene 2-Pentanone
1,3 Butadiene Phenol
2—Butanone Phenyl Clycide Ether
Butylamine Pyridine
Chlorobenzene Hydrogen Sulfide
1-Chloro-1-Nitropropane Styrene
Chloroprene Tetrachloroethylene
Cumene Toluene
Cyclopentadiene Trichloroethylene
O-Dichlorobenzene Vinyl Toluene
P-Dichlorobenzene Xylene
If UV-absorbing gases may be a factor in a given applica-
tion, precautionary measures should be taken. Detectors
can be placed closer to the potential hazard area, and/or
the sensitivity of the detection system can be increased.
Contact the factory for further details.
Substances such as methane, propane, butane, hexane,
camphor and octane are not UV absorbing.