Nortec Industries Airfog Series - Manual (Page 21)

10-10
Page 14
2008-04-11
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 sub-components. As illustrated
in Figure 9 Vacuum Valve Interfaces. First, the safety valve interfaces directly with
the primary water supply to open or close on command from the control panel.
Loss of pilot air pressure (below 10 psig) will automatically close this valve to
prevent water proceeding beyond this point. In series with, and downstream of the
safety valve, is the water regulator. The water regulator is used as the first stage
of water pressure reduction. The water regulator reduces the supply water
pressure to a range between 5 and 10 psig. This is set manually at time of
installation. Please note that system performance is not sensitive to the exact
setting as long as the pressure is within this range.
(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