AFFF SPRINKLER SYSTEM

Sprinkler systems are a convenient and quick method for the fire party to apply AFFF/water solution or water to large areas of burning fuel. The system consists of a large header pipe with smaller branch connections and attached sprinkler heads. A sprinkler group control valve (powertrol or hytrol with test connection) will control the discharge flow to the sprinkler heads. The group control valve may be actuated by an SOPV or a manual control valve. Some sprinkler systems are activated by a manually operated cutout valve. Actuation controls for the group control valves may be located in primary flight control, the navigational bridge, helo control, a conflagration station, locally at the AFFF generating station, and at various locations throughout the ship, depending on the sprinkler system installation and type of ship. An AFFF sprinkler system is a subsystem of AFFF generating systems. Some of the different types of sprinkler systems aboard naval ships are listed below:

The bilge sprinkler is located in the main and auxiliary machinery spaces with the sprinkler heads installed below the lower level deck plates.

The overhead sprinkler system is installed in the overhead of helo and hangar bays, well decks, vehicle cargo holds, and fuel pump rooms. Some diesel-powered ships have the overhead sprinkler system installed in the main machinery space.

The flush-deck system uses the countermeasure washdown flush-deck nozzles to discharge AFFF/water solution during flight deck and helo deck fires. This capability is currently available to all aircraft carriers, helicopter carriers, and some auxiliary and combatant ships.

. The deck-edge sprinkler sprays AFFF/water solution over the flight deck of aircraft carriers, helicopter carriers, and battleships. The system consists of spray nozzles that are positioned at the deck-edge combing of the port and starboard sides on helicopter and flight decks. The nozzles project the AFFF/water solution across the deck in an arc pattern to spray over the top of the burning fuel and aircraft.

AFFF TRANSFER SYSTEMS

AFFF generating stations use large volumes of AFFF concentrate during fire fighting. The service tank alone may not contain enough concentrate to combat a conflagration-type fire. Transfer capabilities are available to replenish the AFFF concentrate service tanks.

The installed system consists of a reserve transfer pump (positive displacement, sliding vane or centrifugal), reserve storage tanks, and associated piping and valves. The transfer system can deliver AFFF concentrate to on-station service tanks via a transfer main, The transfer main consists of a large pipe, with smaller branch connections interconnecting the AFFF service and storage tanks. This feature gives the on-station concentrate pump the capability of delivering AFFF concentrate into the transfer main. Once the transfer main is pressurized, either by the reserve pump or by the on-station pump, all AFFF generating station service tanks can be replenished. On-station pumps used in conjunction with jumper hoses and hose connection valves may be used to transfer AFFF concentrate. Some ships can replenish the service tanks with 55-gallon containers located near the generating station. They do this with an installed hand-operated pump or air-regulated transfer system. The airregulated transfer system may be used to replenish reserve storage tanks. Ships may replenish service tanks or storage tanks by manually dumping AFFF concentrate from 5-gallon containers via a fill connection.

AFFF TESTING EQUIPMENT

AFFF concentrate and AFFF/water solution must be tested periodically to ensure that the fire party has an effective agent to combat class BRAVO (B) fires. To accomplish the test, you must have a basic understanding of the equipment used during the test. The following paragraphs will discuss the hand refractometer and the quantab chloride titrator strip.

Refractometer

The hand refractometer gives accurate readings of total dissolved solids in aqueous solutions, If an AFFF generating system is tested according to procedures, the refractometer reading will show the percent of solids present. For the readings to be meaningful, you must draw samples from the same water source and AFFF concentrate service tank that were used to generate the AFFF/water solution. If a ship has 20 AFFF generating systems, then you must take 20 AFFF concentrate samples and 20 AFFF/water solution samples. Use the refractometer to determine the percent of solids present in the aqueous solution samples. Once you have the readings, you can determine the percent of AFFF concentrate that is being proportioned with water by using the following formula:

Quantab Chloride Titrator

Quantab chloride titrator strips are used to measure salt (chloride) in aqueous solutions. Seawater contains approximately 20,000 ppm (parts per million) of chloride. The allowable limit for chloride contamination of AFFF concentrate is 2,000 ppm, which is equivalent to a 10 percent contaminant ion. All approved AFFF concentrates have been subjected to 10 percent seawater contamination tests and have passed corrosion tests for metals approved in AFFF generating systems. Contamination above the 10 percent limit by seawater causes two problems: First, AFFF generating system components will corrode; second, improper AFFF/water solutions will result in an ineffective fire-fighting agent.

If contamination exceeds 2,000 ppm, the source of contamination must be identified and corrected before dumping the contents of the AFFF concentrate tank. Clean all AFFF concentrate components before replenishing the service tank. Carry out all AFFF testing procedures in

accordance with the planned maintenance requirements.