Det-Tronics U7602E Unitized UV Flame Detector/Controller - Manual (Page 4)

The Inspector software (included) can operate on most
Intel
® Pentium ® based computers running Microsoft
Windows 95/98.
The real time clock in the module is furnished with
battery back-up to ensure correct operation in the
event of a power failure. The clock provides second,
minute, hour, day, month and year data.
The detector’s relays and LEDs function exactly the
same as the standard detector; however, the 4 to 20 ma
output is not available.
GENERAL APPLICATION
INFORMATION
In applying any type of sensing device as a fire
detector, it is important to know of any conditions that
can prevent the device from responding to a fire, and
also to know what other sources besides fire will cause
the device to respond.
Windows
Glass and plexiglas windows significantly attenuate UV
radiation and must not be located between the detector
and a potential flame source. If the window cannot be
eliminated or the detector location changed, contact
Detector Electronics for recommendations regarding
window materials that will not attenuate UV radiation.
Obstructions
Environmental contaminants such as dust, dirt and
other films will attenuate UV radiation and should not be
allowed to accumulate on the detector viewing window.
In addition, physical obstructions that can block the
detector’s view must not be allowed to come between
the detector and the protected hazard. It should also
be noted that certain gases or vapors absorb significant
amounts of UV and can adversely affect the detector’s
response time. See Table 1 for a list of UV absorbing
gases.
Smoke
Smoke will absorb UV radiation. In applications where
accumulations of dense smoke can be expected to
precede the presence of flame, ultraviolet detectors that
are used in enclosed areas should be mounted on the
wall approximately 3 feet (1 meter) from the ceiling
where the accumulation of smoke is reduced.
Arc Welding
Electric arc welding is a source of intense ultraviolet
radiation, and care must be taken to ensure that arc
welding is not performed in the protected area without
securing the fire detection system. UV radiation from
arc welding readily scatters and can deflect across
significant distances, even when direct obstructions
exist. Any open door or window can allow nuisance UV
radiation from arc welding to enter an enclosed area.
When x-rays or radioactive substances are present in
the area being protected, the UV system must be
disabled until those sources are removed.
Common Environmental Conditions
The detector is not affected by environmental conditions
such as wind, rain or extremes of temperature and
pressure. It is also insensitive to the ultraviolet
component of solar radiation.
UV radiation generated by periodic lightning or sparks
in the area can be effectively ignored by the detector
using the arc rejection feature or the fire relay time delay.
UV detectors should not be positioned so that their
cone of vision can scan the horizon. Rather, they
should be directed down over the designated
hazardous area to reduce the likelihood of picking up
UV radiation from distant sources.
The following 38 substances exhibit significant UV
absorption characteristics. These are also generally
hazardous vapors. While usually 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 occurrence.
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
application, 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,
camphor, hexane and octane are not UV absorbing.
Table 1—UV Absorbing Gases and Vapors
2