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flows through the Alarm Port as shown
in Figure 3B at the rear of the Model
DPV-1 Dry Pipe Valve. As the flow
through the Alarm Port exceeds the
drain capacity of the Automatic Drain
Valve, the alarm line is pressurized to
actuate system water flow alarms.
After a valve actuation and upon subse-
quent closing of a system Main Control
Valve to stop water flow, the Clapper
Assembly will latch open as shown in
Figure 3D. Latching open of the Model
DPV-1 Dry Pipe Valve will permit com-
plete draining of the system (including
any loose scale) through the main drain
port.
During the valve resetting procedure
and after the system is completely
drained, the external reset knob can be
easily depressed to externally unlatch
the Clapper Assembly as shown
in Figure 3E. As such, the Clapper
Assembly is returned to its normal set
position to facilitate setting of the dry
pipe sprinkler system, without having to
remove the Handhole Cover.
Accelerator Operation
The Inlet Chamber of the TYCO Model
ACC-1 Dry Pipe Accelerator (Ref. Figure
5), is pressurized via its connection to
the system. The Pilot Chamber is, in
turn, pressurized through its inlet port
which is formed by the annular opening
around the lower tip of the Anti-Flood
Valve. As the Pilot Chamber increases
in pressure, the Differential Chamber
is pressurized through the Restriction.
The Accelerator is in its set position
while it is being pressurized as well
as after the Inlet, Pilot Chamber and
Differential Chamber pressures have
equalized. When in the Set position,
the Outlet Chamber is sealed off by
the Exhaust Valve which is held against
its seat by a combination of the Spring
pushing up against the Lever and the
net downward force exerted by the
pressure in the Pilot Chamber.
Both small and slow changes in
system pressure are accommodated
by flow through the Restriction. When,
however, there is a rapid and steady
drop in system (that is, Inlet and Pilot
Chamber) pressure, the pressure in
the Differential Chamber reduces at
a substantially lower rate. This condi-
tion creates a net downward force on
the Plunger which rotates the Lever.
As the Lever is rotated (see Figure 6),
the Relief Valve is raised out of the
Relief Port and the Anti-Flood Valve
is depressed downward into the Pilot
Chamber Inlet Port, venting the Pilot
Chamber.
The system pressure in the Inlet
Chamber then forces (raises) the
Exhaust Valve off its seat. This contin-
ues the rotation of the Lever into the
0,60
0,50
0,40
0,30
0,20
0,10
0,08
0,06
0,05
0,04
0,03
0,02
0,01
400
600
FLOW RATE IN LITERS PER MINUTE (LPM)
MODEL DPV-1 DRY PIPE VALVE
NOMINAL PRESSURE LOSS VERSUS FLOW
tripped (latched) position (see Figure
6). As the Exhaust Valve is raised off
its seat, system pressure is transmit-
ted to the intermediate chamber of the
Dry Pipe Valve which neutralizes the
differential pressure holding the valve
closed.
Water and any water borne debris such
as silt is prevented from entering the
Pilot Chamber by virtue of the Anti-
Flood Valve having sealed off its inlet
port.
After the accelerator/Dry Pipe Valve
has tripped and the sprinkler system
has been drained, the piping from the
system to the Accelerator must also
be drained and the Accelerator reset/
inspected according to the instructions
given in the Valve Setting Procedure
section.
1000
2000
3000
GRAPH A
The rate-of-flow through the Restric-
tion has been set such that the Model
ACC-1 Dry Pipe Valve Accelerator pro-
vides the maximum practical sensitiv-
ity to a loss in system pressure due to
a sprinkler operation while still being
capable of automatically compensating
for normal variations in system pres-
sure such as are caused by environ-
mental temperature changes. A test for
verifying that the rate-of-flow through
the Restriction is within the range for
optimum Accelerator performance is
given in the Valve Setting Procedure
section.
TFP1090
Page 5 of 26
4000
6000
10000
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