NOZZLES AND APPLICATORS

The Navy all-purpose nozzle, shown in figure 5-5, comes in two standard sizes: 2 1/2 inches and 1 1/2 inches. The valve on the nozzle can be set in one of three positions-SHUT, FOG, or OPEN.

Fog is generated either by a low-velocity fog head or by a high-velocity nozzle tip. A number of small outlets are drilled at converging angles in the head or tip. The water stream is broken up into fog particles when the small streams impinge upon each other. The size, design, and placement of the outlets determine the velocity with which the fog particles emerge from the nozzle. Control of this velocity is important, since low-velocity fog is better for some fires and high-velocity fog is better for others.

If you want high-velocity fog, leave the highvelocity nozzle tip in place in the fog outlet on the nozzle. If you want low-velocity fog, remove the tip and place an applicator equipped with a low-velocity fog head in the fog outlet on the nozzle. A bayonet joint holds the high-velocity tip or the applicator in the nozzle. The highvelocity tip is permanently attached to the nozzle with a short piece of chain. Thus, the tip is always readily available.

There are three standard sizes of applicators. The 4-foot and the lo-foot applicators will fit only in the 1 1/2-inch Navy all-purpose nozzle. The 12-foot applicator will fit only in the 2 1/2-inch Navy all-purpose nozzle. The size of pipe used and the angle of bend at the low-velocity fog head

Figure 5-5.-All-purpose nozzle.

for each of the three applicators are shown in figure 5-6.

AFFF SYSTEMS

Aqueous film forming foam (AFFF) is one of the most familiar and widely used fire-fighting agents. It is used in conjunction with water or dry chemical to fight class B fires throughout the ship. AFFF is delivered through both portable and installed equipment. You need a basic understanding of the different kinds of AFFF systems and the equipment and components within those systems. Different ships use different AFFF setups. Once you understand these basics, you should be ready to understand and use the AFFF systems aboard any Navy ship.

AFFF GENERATING EQUIPMENT

AFFF generating equipment is located most often in main machinery spaces, JP-5 pump rooms, on flight decks, and in hangars and helo bays. These are the places where class B fires are most common. AFFF is used in both portable and installed generating equipment, both of which are covered in the following pages.

Portable AFFF Equipment

The portable AFFF equipment used to deliver AFFF/water solutions includes the Navy pickup unit (NPU), the FP-180 water motor proportioned, and the in-line inductor. However, both the NPU and the FP-180 units are being

Figure 5-6.-Standard applicators.

Figure 5-7.-Navy Pickup Unit (NPU) nozzle assembly. 5-6

replaced by the in-line inductor in all Navy ships.

NAVY PICKUP UNIT (NPU) NOZZLE.- The NPU nozzle (fig. 5-7) consists of a piece of flexible, wire-reinforced rubber hose with a metal discharge end. A 1 1/2-inch female hose connection is located at the inlet end. This allows the NPU to be connected to a 1 1/2-inch fire hose. A 3/4-inch pickup tube is also connected to the inlet end of the NPU. The pickup tube transfers the AFFF concentrate from 5-gallon containers into the water stream of the NPU nozzle. Four protruding metal tabs are located on the inlet end of the pickup tube. These four tabs are known as a crow's foot. The crow's foot prevents the pickup tube from taking a suction of the AFFF container's bottom. To operate the NPU nozzle, use the following procedures:

1. Connect the inlet end of the nozzle onto a

1 1/2-inch fire hose.

2. Have someone man the NPU nozzle.

3. Open the water supply valve slowly.

4. Insert the pickup tube into a container of AFFF concentrate.

5. When the container is nearly empty, transfer the pickup tube to a full container. A 5- gallon container of AFFF concentrate will only last about 1 1/2 minutes.