HALON 1301

The Halon 1301 system is a relatively new fire-extinguishing system (fig. 5-45) used aboard naval ships. For most fires, a Halon concentration as little as 5 to 7 percent can extinguish a wide variety of flammable liquids and surface-burning solid fuels. It can also control deep-seated fires in flammable solids.

HaIon 1301 systems distribute a 5- to 7-percent concentration evenly throughout the space upon complete discharge of the agent. This concentration should be held in the space for a minimum of 10 minutes. Furthermore, this fast-acting, colorless, odorless, electrically nonconductive, heavier-than-air gas is just the thing to use as a last resort against most class A, class B, and class C fires.

In addition, Halon is low in toxicity, does no damage to property, and leaves no mess to clean up. As a matter of fact, the National Fire Protection Association recognizes Halon 1301 as the only gaseous agent acceptable for use in occupied areas. Because of its speed in extinguishing fires, it can even stop fire while you are exiting the space! It has been used in closed spaces for over 30 years without a single reported injury resulting from exposure to its vapor. Furthermore, the heat decomposition products of Halon (for example, hydrogen bromide and hydrogen fluoride create a lesser hazard than the decomposition products from the fire itself, especially carbon monoxide, smoke, heat, and oxygen depletion. In most fire situations where 1301 is used, Halon by-products are often barely detectable by the nose. When the by-products are at harmful toxic levels, you will notice a noxious and irritating odor.

HaIon 1301 has NOT been found to be effective on the following burning materials:

1. Certain chemicals or mixtures of chemicals, such as cellulose nitrate and gunpowder, that are capable of rapid oxidation in the absence of air

2. Reactive metals such as sodium, potassium, magnesium, titanium, zirconium, uranium, and plutonium

3. Metal hydrides

4. Chemicals capable of undergoing thermal decomposition, such as certain organic peroxides and hydrazine

The term Halon was first used in 1948 by the U.S. Army Corps of Engineers as a convenient means of identification. Halon is a shortened version of halogenated hydrocarbon. The U.S. Army devised a numbering system and, in 1948, chose Halon 1301 as the ideal extinguishing agent. It proved to be safe, fast, and clean. The Navy used Halon 1301 on ships in the early 1970s on a test basis.

The major purpose of Halon is to extinguish disastrous fires in machinery spaces. By 1978, ocean minesweepers (MSOs) and new construction ships were equipped with HaIon 1301 systems. Many of the older naval ships have since been equipped with these systems. Halon 1301 complements the total shipboard fire-fighting system. It is used as the final line of defense after other alternatives, such as portable extinguishers and the twin agent system, have been considered. In machinery spaces, HaIon 1301 used in conjunction with AFFF is quite effective against class B fires.

The Halon 1301 systems are located in three major types of spaces-machinery spaces, flammable liquid and flammable gas storerooms, and Versatile Avionic Shop Test (VAST) spaces. Three types of systems are available-modular, manifold banked, and central storeroom. HaIon in VAST spaces is stored in a spherical container, with piping going to multiple nozzles and an actuation system. Therefore, VAST HaIon may be classified as a modular system. Storerooms for flammables typically are equipped with the modular systems. Manifold banked systems are found in most machinery spaces. The major exception to this is the minesweepers. They use a central storeroom Halon setup. In machinery spaces, such as engine rooms or firerooms, you may find Halon 1301 in one or more cylinders piped to discharge nozzles located at the overhead of the space. The discharge nozzles and piping

take on different configurations, depending on Manually operated Halon systems may be litwhat type of Halon system is installed. off with either local or remote pneumatic actuators (small CO2 cylinders). These CO2 cylinders also

The type of Halon system you are likely to have a rupture disk feature. Their bursting range encounter varies according to the type of ship. is also between 2,650 psi and 3,000 psi at 70F. Regardless of the type or location, all Halon is Actuation is triggered from within the space or stored in liquid form in nonshatterable steel outside and next to each main access to the space. storage cylinders. With the help of super Actuation stations for machinery spaces are pressurized nitrogen, the Halon is expelled as a located inside each main machinery space, gas. In machinery spaces, Halon cylinders are fireroom, and engine room. Stations are also super pressurized with nitrogen to 600 psi at 70 located at the outside entrance to each main access "F. Nitrogen acts as a booster, ensuring rapid trunk on the damage control deck. Other safety and complete discharge of all the extinguishing features of the system include automatic agent. If Halon in one of the cylinders exceeds ventilation shutdown, actuation of local and 240F (or 2,650 psi to 3,000 psi at 70F), the remote predischarge alarms (such as a red rotary rupture disk will break. This is a built-in safety beacon light and a loud horn), a 60-second feature that prevents cylinders from exploding. discharge time delay, and a discharge alarm.

3.164

Figure 5-46.-P-250 pump.

WARNING

Do not reenter the space where Halon has been used to extinguish a fire unless you are wearing an oxygen breathing apparatus (OBA). Wear the OBA until the atmosphere is certified safe. Anyone suffering from the toxic effects of Halon 1301 vapor should immediately move, or be moved, to fresh air.

A soaking period of at least 15 minutes is required to ensure that the space has cooled and the fire will not reflash upon reentry of personnel. Oxygen that is let into the space when a hatch is opened or the ventilation system is restarted will dilute the concentration while the fuel is at or above ignition temperature.

Halon, however, is far from perfect. Battle damage or other events allowing air into the space can result in loss of Halon from the space. There is no cooling effect associated with Halon. Therefore, as long as hot surfaces or smoldering materials are present, reflash is possible. Another limitation is that Halon cannot be replenished during operation. Boiler fire extinguishment poses a danger of flashback or explosion within the boiler. Finally, the presence of Halon decomposition products adds to the already dangerous toxic substances in the space, even though the danger from the Halon itself is minimal.

Halon 1301 systems are the only systems that combine effective fire control with personnel safety. Also, Halon 1301 has the lowest toxicity levels of all the Halons currently in use. Very little of the agent is needed to put out most fires. When properly used, it is safe.

P-250 PUMPS

The P-250 pump that has been in service for some years is being replaced by the P-250, Mod 1. Both pumps are discussed below.