WATER MOTOR PROPORTIONER (FP- 180).- The FP-180 water motor proportioner (fig. 5-8) consists of a positive displacement water motor that is coupled to a positive displacement rotary gear pump. Inlet and outlet connections for a 2 1/2-inch hose are located on the water motor. There are two connections on the hose selector valve. These are used to connect two 1/2-inch (NPT) AFFF pickup tubes (NPT). The pickup tubes are fitted with a crow's foot. The FP-180 is operated by a water flow that drives the water motor. This causes the direct-connected rotary gear pump to inject a metered amount of AFFF concentrate into the discharge side of the water motor, thus producing the required AFFF/water solution. The rotary gear pump suction is fitted with a hose selector valve with five positions: OFF, PRIME No. 1, HOSE No. 1, PRIME No. 2, and HOSE No. 2. The selector valve allows you to provide the nozzleman with an uninterrupted flow of AFFF/water solution. When the hose selector valve is in the OFF position, only water will be available as a

Figure 5-8.-FP-180 water motor proportioner. 5-7

fire-fighting agent. The FP-180 will proportion AFFF concentrate into the water stream at inlet pressures of 75 to 175 psi, and with flow rates of 60 to 180 gpm. The ideal operating pressure is 125 psig. The general procedure for operating the FP180 is as follows:

1. Connect the supply and discharge hoses to the water motor. A 2 1/2-inch hose or two 1 1/2inch hoses connected to the FP-180 with a wyegate may be used to dispense the AFFF/water solution.

2. Set the hose selector valve handle to the OFF position.

3. Insert each pickup tube into a full container of AFFF concentrate.

4. Station personnel on the discharge hoses.

5. Open the water supply valve slowly.

6. Shift the hose selector valve handle to HOSE No. 1. The valve is designed so a jet of water flows through the pickup tube. This purges the tube of air and ensures immediate priming of the rotary gear pump when the valve is at the intermediate position of PRIME No. 1 or PRIME No. 2.

7. When the FP-180 is operating, the level of AFFF concentrate in the container should decrease. If the concentrate level does not decrease within a few seconds, shift the selector valve handle to HOSE No, 2 position and check the first pickup tube for a blockage or an air leak.

8. When the AFFF container is almost empty, shift the selector valve handle to the appropriate position and replace the empty container immediately.

The FP-180 water motor proportioner requires a certain amount of care and maintenance. After draining the unit of water, squirt a few ounces of light lubricating oil into the water motor through the inlet and discharge openings. Also squirt oil into the hose selector valve and the rotary gear pump. To do this, place the selector valve handle on HOSE No. 1 or HOSE No. 2, pour oil into the appropriate pickup tube, and then turn the extended shaft several revolutions with a wrench to distribute the oil within the proportioner. Check the proportioner periodically for free turning. You can do this by removing the crank opening cover and turning the extended shaft with a wrench. Replace the crank opening cover to prevent the oil from leaking out and foreign matter from getting inside.

IN-LINE FOAM INDUCTOR.- The in-line foam inductor (fig. 5-9) is becoming standard equipment on all naval ships. It is replacing the portable FP-180 water motor proportioner and the Navy pickup unit.

The in-line foam inductor is simple in design, operation, and maintenance. It uses a venturi principle to induct AFFF concentrate into a water stream. As water enters the inlet end of the in-line foam inductor, the velocity of the water is increased by the use of a flow restriction. This creates a negative pressure area in the venturi throat. A pickup tube with a ball check valve and a crow's foot is connected to the venturi throat. The ball check valve stops water backflow when the flow is restricted or when the nozzle is shut off. The pickup tube is placed into a container of AFFF concentrate. Atmospheric pressure forces the concentrate up the tube and into the water stream, thus producing the AFFF/water solution. The AFFF nozzle that is used with the in-line foam inductor must have the same gallonage rating as the in-line foam inductor. If you do not match the nozzle and the in-line foam inductor, you will get either poor quality AFFF/water solution or no solution at all. The in-line foam inductor currently used in the Navy is rated at 95 gpm with a 1 1/2inch hose inlet and discharge connection. The authorized nozzle is a 95-gpm variable-pattern nozzle with a trigger-operated shutoff.

Figure 5-9.-In-line foam inductor.

The in-line foam inductor has several advantages over the FP-180 and the NPU. First, it is lighter in weight and requires simpler maintenance than the FP-180. The weight factor is significant because it allows you to respond to a fire quickly. The efficiency of the in-line foam inductor does not decrease as much as the efficiency of the FP-180 does with age and wear. In addition, the in-line foam inductor does not have to be relocated when the nozzleman moves, as is the case with the NPU. This allows containers of AFFF concentrate to be left at one location away from the scene of the fire. This reduces confusion and gives the nozzleman a greater freedom of movement.

The in-line foam inductor has few disadvantages. A firemain pressure of 100 psig must be maintained to the in-line foam inductor to produce a good-quality AFFF/water solution. This means that only one length of hose (50 feet) may be used between the in-line foam inductor inlet and the fireplug discharge. You can also connect the in-line foam inductor directly to the fireplug. This limits the maximum length of hose authorized between the in-line foam inductor discharge and the nozzle inlet to 150 feet. Finally, you should not operate the nozzle any higher than one deck above the location of the in-line foam inductor.