G.VACUUM VALVE
(1)The vacuum valve must be centrally located so there are approximately an equal number of nozzles being fed from each of its two output ports (one on the left side and the other on the right side). There is a mounting bracket supplied with each vacuum valve. Figure 9 Vacuum Valve Interfaces illustrates the plumbing interface details. Elevation of the valve is very critical, as is the positioning of the nozzles. The maximum height above the nozzle supply line the valve should be installed is 12” (30 cm). Never install the vacuum valve lower than the nozzle water feed lines.
(2)The water flow rate through this valve is limited to 24 GPH, which limits the number of AFE nozzles it can supply to 16. If more than 16 nozzles are to be installed, then the system must be broken into zones using multiples of 16 (or less) nozzles with each zone controlled by its own vacuum valve. One control panel can control multiple zones by “T” ing off the single control panel air pilot output.
(3)Air pressure from the control panel is used to open the water safety valve permitting water to enter the vacuum valve, which controls the water feed to the nozzles. Figure 8 Vacuum Valve Operation explains the operation of this water regulator. The vacuum valve assembly has three
(4)The second stage of water pressure reduction is the vacuum diaphragm, which drops the pressure to ambient (0 psig). Output is through two exit ports on the underside of the vacuum valve. This permits the nozzle to draw water from the supply as required rather than having pressure force it into the nozzle. The siphoning action of the nozzle is controlled by the pilot operated air regulator.
(5)On top of the vacuum valve is a thumb wheel adjustment for adjustment of the AIRFOG droplet size. The adjustment changes the volume of water to the nozzles. A reduction in available water for a constant air flow results in smaller droplets and a finer spray. This adjustment can be used to reduce the water throughput if there is a problem with water droplets reaching the floor.
H.PILOT OPERATED AIR REGULATOR
(1)The pilot operated air regulator controls the air supply to the nozzles and is illustrated in Figure 11 Pilot Air Regulator. The pilot regulator is modulating flow controller rather than a simple On/Off valve. The greater the pilot air pressure, the greater the air pressure fed to the nozzle supply network. This means that the Control Panel is able to request a proportional opening of the Air Regulator simply by varying the pilot pressure. There is a linear 1:1 relationship between the pilot pressure and the output pressure drop. A pilot air pressure of 25 psig (172.5 kPa) will drive the air regulator to have an output of 25 psig (172.5 kPa). A pilot pressure of 50 psig will drive the air
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