Det-Tronics X5200 UVIR Flame Detector with Pulse Output User Manual

Page 7

95-8547

7.1

FaLSE aLaRM SOURCES

: The UV sensor is solar blind to the ultraviolet

component of solar radiation. However, it will

respond to sources of UV besides fire, such as

electric arc welding, lightning, high voltage corona,

x-rays and gamma radiation.

: The detector has been designed to ignore steady

state infrared sources that do not have a flicker

frequency characteristic of a fire, however, it should

be noted that if these steady state infrared sources

are hot enough to emit adequate amounts of infrared

radiation in the response range of the IR sensor

and if this radiation becomes interrupted from the

view of the detector in a pattern characteristic of a

flickering flame, the IR sensor can respond.

Any object having a temperature greater than

0° Kelvin (–273°C) emits infrared radiation. The

hotter the object, the greater the intensity of the

emitted radiation. The closer the infrared source is

to the detector, the greater the potential for a false

alarm. The IR sensor can respond to IR radiation

sources that can meet the amplitude and flicker

requirements of the detector such as vibrating hot

objects.

Although the detector is designed to reduce

false actuations, certain combinations of ambient

radiation must be avoided. For example, if IR

radiation with an intensity that exceeds the fire

threshold of the IR sensor should reach the detector

as a flickering signal, and if at the same time

an electric arc welding signal also reaches the

detector, an alarm output will be generated.

NOTE

Radiation generated by false alarm sources such
as periodic lightning or sparks in the area can be
effectively ignored by the detector using the arc
rejection feature or time delay.

FaCTORS INHIBITINg DETECTOR RESpONSE
windows
Glass and Plexiglas windows significantly attenuate

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 radiation.

Obstructions
Radiation must be able to reach the detector in order

for it to respond. Care must be taken to keep physical

obstructions out of the line of view of the detector. In

addition, UV or IR absorbing gases or vapors must not

be allowed to accumulate between the detector and

the protected hazard. See Table 2 for a list of these

substances.

Smoke
Smoke will absorb radiation. If accumulations of

dense smoke can be expected to precede the

presence of a flame, then 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.

Detector Viewing windows
It is important to keep the detector viewing windows as

free of contaminants as possible in order to maintain

maximum sensitivity. Commonly encountered substances

that can significantly attenuate UV and/or IR radiation

include, but are certainly not limited to, the following:

–

Silicones

–

Oils and greases

–

Dust and dirt buildup

–

Paint overspray

–

Water and ice