AFFF System Components

The AFFF system components include the AFFF concentrate tanks, various valves used in the system, and the single agent hose reel.

AFFF CONCENTRATE TANKS.- AFFF concentrate tanks (service or reserve storage) range in capacity from 35 to 3,500 gallons of AFFF concentrate. They are equipped with an externally mounted indicator to show the level of AFFF concentrate in the tank. They are also equipped with access plates for cleaning and inspection. The tanks can be filled quickly from 5-gallon containers, 55-gallon containers, and reserve storage tanks, depending on the type of ship and the AFFF generating system design. Tanks are vented to allow trapped air to escape during filling operations and to relieve any vacuum that occurs as a result of pumping AFFF concentrate out of the tanks. The AFFF concentrate tanks should be fabricated out of 90/10 copper-nickel alloy.

AFFF VALVES.- The AFFF system requires a variety of valves with different capabilities and functions. These valves are described below.

Powertrol Valve.- The powertrol valve (fig. 5-1 3) is a diaphragm-type, hydraulically operated, globe control valve. It is most commonly used as the AFFF control valve. However, some AFFF generating systems use the valve as a water control and AFFF control valve. The AFFF control valve controls the flow of AFFF concentrate. The valve is fitted with an indicator stem (threaded into the main stem) to indicate whether the valve is open or closed. The cover contains a telltale hole to indicate if the diaphragm is ruptured. The

Figure 5-13.-Powertrol valve.

valve is normally held closed by spring pressure acting on the diaphragm, forcing the stem and disk assembly against the seat, thus stopping the fluid flow. Open the valve by pressurizing the operating chamber with fluid. This fluid acts on the underside of the diaphragm, forcing the stem and disk assembly upward, thus overcoming the spring pressure and allowing the fluid to flow.

Powercheck Valve.- The powercheck valve (fig. 5-14) is a diaphragm-type, hydraulically operated, globe control valve. It is used as an AFFF control valve. The valve is essentially a

powertrol valve with check valve features. Powerchecks contain two stems, an upper stem and a lower stem, each of which moves independently of the other. This feature permits flow in one direction only. When flow stops and back pressure develops, the lower stem and disk assembly will be forced downward (lower spring/back pressure) against the seat, stopping the fluid flow. The valve will check even though the operating chamber is pressurized.

Powertrol Valve with Test Connection.-

The powertrol valve with test connection

Figure 5-14.-Powercheck valve. 5-13

(fig. 5-15) is a diaphragm-type, hydraulically sprinkler group unless the fluid flow could be operated, globe control valve. It is essentially a diverted before it is discharged through the powertrol valve with testing capabilities. This sprinkler heads. To make a test, remove the test valve is normally used as a sprinkler group con-connection cap from the bottom of the valve and trol valve. It would be impractical to test a insert a test fitting. The test fitting has an O ring

Figure5-15.-Powertrol valve with test fitting.

Figure 5-16.-Hytrol valve.

to provide a seal between the fitting and the elongated neck on the valve seat. Connect a drain hose to the fitting and place the outlet end of the hose at a suitable location. When the operating chamber is pressurized, the valve opens. Fluid is routed over the top of the seat, diverted through the test fitting and out the drain hose. The valve is successfully tested and the sprinkler groups are dry. When the test is complete, vent the operating chamber, remove the test fitting, and reinstall the test connection cap.

Hydrol Valve.- The hytrol valve (fig. 5-16) is a diaphragm-type, hydraulically operated, globe control valve. It is most commonly used as a water control valve. The water control valve controls the flow of water into the distribution piping or proportioner. Hytrol valves have an indicator stem threaded into the main stem to show whether the valve is open or closed. To close the valve, pressurize the operating chamber with fluid. The fluid acts on top of the diaphragm, forcing the stem and disk assembly downward against the seat, thus stopping the fluid flow. A spring positioned on top of the diaphragm assists in closing the valve. To open the valve, vent the operating chamber. Fluid pressure at the inlet opening will force the disk assembly upward, thus overcoming the spring pressure and allowing fluid to flow.

Hycheck Valve.- The hycheck valve (fig. 5-1 7) is a diaphragm-type, hydraulically operated,

Figure 5-17.-Hycheck valve.

globe control valve. It is used as a water control valve. A hycheck valve is essentially a hytrol valve with check valve features. Hychecks contain two stems, an upper stem and a lower stem, each of which moves independently of the other. This feature permits flow in one direction only. When flow stops and back pressure develops, the lower stem with disk assembly will be forced downward (lower stem spring/ back pressure) against the seat, thus stopping the fluid flow.

Hytrol Valve with Test Connection.- The hytrol valve with test connection is a diaphragmtype, hydraulically operated, globe control valve. It is essentially a hytrol valve with testing capabilities. The testing features of the hytrol valve with test connection are identical to those of the powertrol valve with test connection (fig. 5-15). To use the valve, vent the operating chamber and fluid pressure at the inlet opening. This will act on the underside of the diaphragm to force the disk assembly upward, overcome ^{the spring pressure,} and allow the fluid to flow. The fluid flow will be routed over the ^{top of the seat,} diverted through the test fitting and out the drain hose. When the test is complete, pressurize the operating chamber, remove the test fitting and reinstall the test connection cap.

3-Way Interlock Valve.- The 3-way interlock valve (fig. 5-18) is used in some AFFF generating systems that use a hytrol or hycheck valve as a water control valve. It is used in conjunction with the dry-chemical unit to cause actuation of the AFFF generating system simultaneously with the dry-chemical unit. Some ships use a pressure switch for this purpose. In the open position, the interlock valve will route water out the control

Figure 5-18.-3-way valve. 5-16

outlet port and ultimately to the operating chamber of the hytrol or hycheck valve. To close the interlock valve, pressurize the operating chamber with nitrogen. Nitrogen acts on top of the diaphragm, forcing the disk assembly against the lower seat, securing the water supply. The control outlet port is aligned with the drain port. This allows the operating chamber of the hytrol or hycheck valve to be vented, which, in turn, allows the valve to open. Opening of the interlock valve is caused by venting the nitrogen from the operating chamber through the green ball valve. A spring acts on the underside of the diaphragm, causing the disk assembly to seat against the upper seat. This action closes off the drain port and allows water to flow through the outlet port.

Ultimately, the water flows to the operating chamber of the hytrol or hycheck valve, causing the valve to close.

Manual Control Valve (Closed/Open, Three Port). - This manual control valve (fig. 5-19) is used to actuate the hytrol or hycheck valve. In the closed position, the valve routes the water through the "closed" port and ultimately to the hytrol or hycheck valve operating chamber, thus closing the valve. When the valve is in the open position, water is isolated within the valve and the closed port is aligned with the open port. This vents the operating chamber of the hytrol or hycheck valve, thus causing the valve to open.

Figure 5-19.-2-way 3-port manual control valve.

Figure 5-20.-3-way 3-port manual control valve.

Figure 5-21.-2-way 2-port manual control valve. 5-18

Manual Control Valve (Closed/Neutra/ Open, Three Port). -This manual control valve (fig. 5-20) is used only to actuate powertrol-type valves. When the valve is in the neutral position, water is isolated within the valve. In the open position, the valve routes the water through the open port to pressurize the operating chamber of powertrol-type valves. In the closed position, the valve routes the water through the closed port and to the operating chamber of a 3/8-inch control line powertrol valve, thus causing the valve to open. The control line valve vents the operating chamber of the powertrol-type valve, thus causing the valve to close. To close the control line powertrol valve, set the manual control valve in the neutral position. The operating chamber will vent through an orifice plate that is installed in the control line and eventually close.