before discharge. Hot piping causes excessive
vaporization of carbon dioxide and a resultant
delay in effective discharge.
Pressure relief devices or valves that prevent
entrapment of liquid carbon dioxide may be in-
stalled on sections of piping that can be closed
off. On high-pressure systems, relief devices
usually operate at 2,400 to 3,000 psi, and, on low-
pressure systems, at 450 psi.
Nozzles are of various designs and discharge
patterns. Two common types are shown in figure
8-32. Nozzles are marked with a code number in-
dicating the diameter in 1/32-inch increments of
a single orifice standard nozzle having the same
flow rate. A No. 5 nozzle, for example, has the
same flow rate as a 5/32-inch-diameter standard
orifice. A plus sign ( + ) after the number indicates
a 1/64-inch larger size. Decimals are sometimes
used to indicate sizes between the whole numbers.
TOTAL FLOODING SYSTEMS
Total flooding systems are used for rooms,
ovens, enclosed machines, and other enclosed
spaces containing materials extinguishable by
For effective total flooding, the space must be
reasonably well enclosed. Openings must be
arranged to close automatically and ventilation
equipment to shut down automatically, no later
than the start of the discharge. Otherwise,
additional carbon dioxide must be provided to
compensate for the leakage.
Automatic closing devices for openings must
be able to overcome the discharge pressure of the
carbon dioxide. Conveyors, flammable liquid
pumps, and mixers associated with an operation
may be arranged to shut down automatically on
actuation of the protection system. A typical
arrangement of a total flooding carbon dioxide
system is shown in figure 8-33.
Figure 8-33.Total flooding carbon dioxide system installation.