In considering the application of the detector it is important to know of any conditions that may
prevent the detector from responding. The detector provides reliable response to Hydrocarbon
flames within its field of view, and insensitivity to common false alarm sources. Solid obstructions
or a direct view of intense light sources may result in a reduction in the coverage and/or a
reduction
in the detector sensitivity. Scaffolding or tarpaulins in the detector’s field of view may
reduce coverage. Contamination of the detector window may result in a reduction in sensitivity.
The detector has a 90° conical field of view. The location and orientation of the detector in
relation to the protected area determines the actual footprint.
Achieving the desired coverage
depends on congestion within the protected space, the location
of the detector(s) and the
distance of the detector from the hazard. It may be necessary to install
more than one detector
within an area to achieve adequate coverage.
The detector sensitivity, expressed as fire size at a distance, is determined by the radiant heat
output of the fire. This is a function of the fuel source, how it is released and distance from the
detector to the fire.
In common with other forms of flame detection the detector’s sensitivity is reduced and
potentially blinded by dense obscurants such as smoke, fog and other airborne particulates.
The detector is insensitive to arc welding; however, this should not be conducted within 10m of
the
detector.
5.1 Positioning Requirements
The following guidelines have been based on operational feedback, reflecting commonly
experienced problems which can be traced to a failure to observe the following:
• Ensure the mounting position is free from vibration or movement.
• Prevent accidental knocking or forcing out of alignment.
• Isolate as far as possible from local electrical interference sources.
• Ensure sufficient detection to achieve adequate coverage for all likely hazards.
• Minimise exposure to contamination of the detector face plate.
• Ensure ease of maintenance access to detector (i.e. direct ladder or scaffold
access).
• Do not allow the FDS303 to have direct view of hot surfaces.
• Ensure that the FDS303 has no direct view or reflected view of a friendly fire.
• The detector should be aimed downward by at least 10
o
to 20
o
.
All these issues are of crucial importance to a successful installation and they should be afforded
great attention during the detailed design, construction and commissioning phases of the work.
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