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Page 6 of 20
Operating
Principles
The Model DPV-1 Dry Pipe Valve is a
differential type valve that utilizes a
substantially lower system (air or nitro-
gen) pressure than the supply (water)
pressure, to maintain the set position
shown in Figure 3A. The differential
nature of the DPV-1 is based on the
area difference between the air seat
and the water seat in combination with
the ratio of the radial difference from
the Hinge Pin to the center of the
Water Seat and the Hinge Pin to the
center of the Air Seat. The difference
is such that 1 psi (0,07 bar) of system
air pressure can hold approximately
5.5 psi (0,38 bar) of water supply pres-
sure.
Table B establishes the minimum re-
quired system air pressure that in-
cludes a safety factor to help prevent
false operations that occur due to
water supply fluctuations.
The Intermediate Chamber of the
DPV-1 is formed by the area between
the Air Seat and Water Seat as shown
in Figure 3B. The Intermediate Cham-
ber normally remains at atmospheric
pressure through the Alarm Port con-
nection and the valve trim to the nor-
mally open Automatic Drain Valve
(Fig. 4, 5, or 6). Having the Intermedi-
ate Chamber, Figure 3B, open to at-
mosphere is critical to the DPV-1
Valve remaining set, otherwise the full
resulting pressure of the system air
pressure on top of the Clapper Assem-
bly cannot be realized.
For example and assuming a water
supply pressure of 100 psi (6,9 bar), if
the system air pressure is 25 psi (1,7
bar) and there was 15 psi (1,0 bar)
pressure trapped in the Intermediate
Chamber, the resulting pressure
across the top of the Clapper would
only be 10 psi (0,7 bar). This pressure
would be insufficient to hold the Clap-
per Assembly closed against a water
supply pressure of 100 psi (6,9 bar). It
is for this reason that the plunger of the
Automatic Drain Valve must be de-
pressed during several of the resetting
steps, as well as during inspections,
making certain that the Automatic
Drain Valve is open.
When one or more automatic sprin-
klers operate in response to a fire, air
pressure within the system piping is
relieved through the open sprinklers.
When the air pressure is sufficiently
reduced, the water pressure over-
comes the differential holding the
Clapper Assembly closed and the
Clapper Assembly swings clear of the
water seat, as shown in Figure 3C,
This action permits water flow into the
system piping and subsequently to be
discharged from any open sprinklers.
Also, with the Clapper Assembly open,
the intermediate chamber is pressur-
ized and water flows through the alarm
port (Ref. Figure 3B) at the rear of the
DPV-1 Valve to actuate system water
flow alarms. The flow from the alarm
port is also sufficient to close the oth-
erwise normally open Automatic Drain
Valve in the valve trim.
After a valve actuation and upon sub-
sequent closing of a system main con-
trol valve to stop water flow, the Clap-
per Assembly will latch open as shown
in Figure 3D. Latching open of the
DPV-1 will permit complete 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 un-
latch 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.
TFP1020
Maximum
System Air
Water Supply
Pressure
Pressure,
Range,
psi
psi
20
10
60
15 - 23
80
20 - 28
100
25 - 33
120
30 - 38
145
35 - 43
165
40 - 48
185
45 - 53
205
50 - 58
225
55 - 63
250
60 - 68
TABLE B
SYSTEM AIR PRESSURE
REQUIREMENTS
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