User's Manual

Design
P/N 81-CO2MAN-001 3-27 September 2013
3-6.1.4 QUANTITY OF CARBON DIOXIDE
The quantity of carbon dioxide to be supplied is based on the total calculated rate of discharge
for the hazard and the design duration of liquid discharge. To account for the vapor portion of
the discharge, a vaporization factor of 40% is applied.
(Equation 16)
Where:
= Minimum quantity of agent to be supplied, lb. (kg)
= Total calculated rate of discharge for local application hazards,
lb./min (kg/min)
= Duration of liquid discharge, min
This quantity shall be increased by a sufficient amount to compensate for vaporization of liquid
due to cooling of the discharge pipe. Kidde Fire Systems CO
2
Calculation Software (Part No.
81-190001-XXX) takes this phenomenon into account. NFPA 12 may be referenced for
additional information.
3-6.2 Rate-by-Area Method
The Rate-by-Area application of carbon dioxide is used to suppress fires on flat surfaces or low-
level hazards associated with horizontal surfaces. These include dip tanks, drain boards, fryers,
and floor areas. The basis of this method lies in determining the square footage of the hazard
area. Both the discharge rate and area coverage of the nozzles are based upon nozzle height
above the hazard. Once the nozzle height, discharge rate, and nozzle area coverage has been
established, the nozzle spacing, and consequently, the number of nozzles are determined.
Where deep layer flammable liquid fires are to be protected, a minimum freeboard of 6 in. (152
mm) shall be provided.
3-6.2.1 OVERHEAD NOZZLES
Overhead nozzles are the most common method of applying a rate-by-area local application
system. In this case, Type "S" and Type "M" nozzles are used to suppress fires on liquid
surfaces (e.g., dip tank) or coated surfaces (e.g., drip board).
3-6.2.1.1 Nozzle Coverage and Carbon Dioxide Requirements
Nozzles are selected for their coverage and flow rate to minimize the amount of carbon dioxide
required. Occasionally, hazard conditions may restrict nozzle placements.
Refer to Table 3-4 and Table 3-5 for the height/area coverage/flow rate data, for the Type "S"
and Type "M" nozzles. Extrapolations above or below nozzle approval listings are not
permitted.
The portion of a hazard protected by a single nozzle is based on its "side of square" coverage
and the distance to the protected surface. Generally, the farther the nozzle is from the
protected surface, the larger the area covered and the greater the required discharge rate to
sufficiently penetrate the fire. However, the discharge must also be tempered to prevent
splashing of burning liquid fuels.
The quantity of overhead nozzles needed to protect a hazard may be calculated using
Equations (17) through (19).
W
min
1.4 qt
liq
=
Wmin
q
t
liq