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 installed 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

Nozzles are of various designs and discharge patterns. Two common types are shown in figure 8-32. Nozzles are marked with a code number indicating 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 carbon dioxide.

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.