SECTION 2
THEORY OF OPERATION
2.1
The basic principles of operation of the system are illustrated in Figures 2-1 through 2-4.
2.2
Air samples are continuously drawn from each protected space through the CO2 system distribution piping, with
individual lines to each detecting module at the main cabinet. The air samples are continually inspected for the
presence of smoke as a result of being drawn through a darkened space in each module. A light beam is directed
into the darkened space in such a manner that it does not fall on the sensitive photoelectric cell (Figure 2-1).
2.3
When smoke is present in the air sample, it causes the light to scatter, permitting some light to reach the
photoelectric cell (Figure 2-2). At a factory calibrated level, the electric circuitry will cause the module to lock into
the alarm mode, originating the specified audible and visual alarm signals.
2.4
For most spaces on the vessel, the smoke detector piping is also used for the discharge of CO2 (Figure 2-3)
Manually operated 3-way valves are supplied on the CO2 system manifold to provide an interconnection from the
accumulator in the protected area to the individual detector module.
2.5
The 3-way valves permit carbon dioxide to be discharged into the selected space without penetrating the smoke
detection system (Figure 2-4).
2.6
NOTE:
The 3-way valves may be used to isolate the smoke detection cabinet from spaces causing false alarms
caused by abnormally dirty ambient air conditions or the presence of smoke known not to be dangerous.
2.7
CAUTION:
If this step has been taken and an actual fire condition develops, all 3-way valves other than those on
lines to the fire areas must be returned to normal prior to discharging the CO2 system.
2.8
NOTE:
It is necessary to operate the 3-way valve to discharge into the smoke detector unit through any of the
lines at any time.
2.9
Details of the installation and operation of the CO2 system are covered in the Kidde CO2 system manual.
2-1
