Det-Tronics Eagle Quantum 95-8470-05, Инструкция по эксплуатации

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V-1 95-8470
Section V
Detector Application
Information
UV DETECTORS
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
For an ultraviolet detector, dust, dirt and other films, UV
absorbing gases or vapors as well as physical
obstructions must not be allowed to come between the
detector and the protected hazard (see Table V-1).
SMOKE
Smoke will absorb UV radiation, and if accumulations of
dense smoke can be expected to precede the
presence of flame, then 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 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 is a partial list of compounds that exhibit
significant UV absorption characteristics. These are also
usually 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 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, hexane,
camphor and octane are not UV absorbing.
Absorption of infrared radiation in the range of 4.2 to 4.7
microns is not a significant problem with most organic
vapors, with the exception of those compounds that have
triple bonds such as acetylene, nitriles, silane, or
isocyanates. Carbon dioxide concentrations higher than
normally present in the atmosphere can also cause
substantial loss of fire detection sensitivity.
Table V-1—UV and IR Absorbing Gases and Vapors