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interconnected with minimum 1/2 inch
(15 mm) Schedule 40 steel pipe. The
pilot line is connected to the "Wet Pilot
Detection" connection shown in Figure
D. Minimum clearance dimensions for
the Wet Pilot Actuation Trim are shown
in Figure C.
Wet pilot sprinklers are to be minimum
1/2 inch (15 mm) orifice listed or ap-
proved automatic sprinklers. Manual
Control Stations are to be either the
Model F180 or F184 described in Tech-
nical Data Sheet TD121.
The maximum height of a wet pilot line
above the F470H Valve must not ex-
ceed the limitations given in Graph B
as a function of the minimum water
supply pressure to the F470H Valve
and the length of the pilot line to the
most remote pilot sprinkler.
Provision must be made for installing
a 1/2 inch (15mm) orifice, Inspector's
Test Connection at the most hydrauli-
cally demanding location of a wet pilot
line (usually adjacent to the highest
and most remote wet pilot sprinkler or
manual control station).
To determine the most hydraulically
demanding location of a wet pilot line,
when the choice between two or more
locations is not readily apparent, de-
termine for each location the elevation
above the F470H Valve and the
GRAPH B
WET PILOT LINE DESIGN CRITERIA
equivalent length of fittings plus hori-
zontal pipe from the F470H Valve to
the location. Then, using Graph B, de-
termine the minimum system supply
pressure required for the elevation and
equivalent length of pipe at each loca-
tion. Interpolate between the equiva-
lent length plots as necessary. The lo-
cation requiring the highest system
supply pressure is the most hydrauli-
cally demanding location for the wet
pilot line. (Reference: In no case
should the required system supply
pressure exceed the minimum ex-
pected system supply pressure.)
Operation of a pilot sprinkler or open-
ing of a manual control station results
in a rapid pressure drop in the Dia-
phragm Chamber of the F470H Valve,
and the force differential applied
through the Clapper Latch which holds
the Clapper down in the set position is
reduced to below the valve trip point.
NOTES
Wet Pilot Lines must be maintained at
a minmum temperature of 40°F/4°C.
It is recommended that internally gal-
vanized pipe and cast iron fittings be
used for wet pilot lines.
-4-
Dry Pilot Actuation
(Figure D, Items 1 through 38 plus
Items D1 through D15)
The Dry Pilot Actuation Trim provides
for installation of a detection system
consisting of dry pilot sprinklers (heat
detectors) and manual control stations
interconnected with minimum 1/2 inch
(15 mm) steel pipe. The pilot line,
which is to be pressurized with air or
nitrogen, is connected to the "Dry Pilot
Detection" connection shown in Figure
D. Provision must be made for a 1/2
inch (15 mm) orifice, Inspector's Test
Connection at the most remote loca-
tion from the F470H Valve. Minimum
clearance dimensions for Dry Pilot Ac-
tuation Trim are shown in Figure C.
The Dry Pilot Actuation Trim is pro-
vided with a listed and approved Model
B-1 Dry Pilot Actuator, which is de-
scribed in Technical Data Sheet
TD117W. The Actuator is rated for use
at a maximum pilot service pressure of
50 psi (3,4 bar) and a maximum water
supply service pressure of 175 psi
(12,1 bar).
Operation of a pilot sprinkler or open-
ing of a manual control station, re-
leases pneumatic pressure from the
pilot line. In turn, the Dry Pilot Actuator
opens resulting in a rapid pressure
drop in the Diaphragm Chamber of the
F470H Valve, and the force differential
applied through the Clapper Latch
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