TFP910
Page 4 of 20
Operation
When the fire protection system is ini-
tially pressurized, water flows into the
system until the water supply and sys-
tem pressure become equalized, and
the torsion Spring closes the Water-
way Clapper in the Alarm Check Valve.
Once the pressures stabilize, the Alarm
Check Valve is in service and the cen-
trally located groove in the Seat Ring is
sealed. Consequently, with the Alarm
Check Valve set for service, there is
no flow through the alarm port to the
alarm devices (i.e., water motor alarm
and/or pressure alarm switch).
When there is a steady flow of water
into the sprinkler system due to a sprin-
kler operation, the Waterway Clapper
opens as shown in Figure 2. Water is
then permitted to flow into the centrally
located groove in the Seat Ring and
out through the alarm port towards the
Restriction Assembly (Figure 3). When
the flow through the Inlet Restriction of
the Restriction Assembly exceeds the
flow through the Outlet Restriction, the
Retard Chamber (where provided for
systems with variable pressure), begins
to fill.
Subsequently, the Water Motor Alarm
and/or the pressure alarm switch will
be actuated. The alarms will continue
to be actuated as long as the Water-
way Clapper remains open. Water in
the alarm lines will automatically drain
out through the 1/8 inch (3,2 mm) Drain
Orifice in the Restriction Assembly
(Figure 3) when the Waterway Clap-
per closes (due to a stop in the flow of
water into the sprinkler system).
For variable pressure systems, slow
as well as small transient increases in
water supply pressure may continue to
build up in the system (via the Bypass
Check Valve) without opening the
Waterway Clapper.
A transient surge in supply pres-
sure that is sufficient only to open the
Waterway Clapper momentarily will not
cause a false alarm, and a portion of
the increase in pressure will be trapped
within the system, thus reducing the
possibility of another opening. Any
water in the alarm line is automatically
drained, further reducing the possibil-
ity of a false alarm due to a successive
transient surge in supply pressure.
Design
Criteria
In planning installation of the TYCO
Model AV-1-300 Alarm Check Valves,
consideration must be given to the dis-
posal of the large quantities of water
that may be associated with draining
the system or performing a flow test.
Valves installed in the vertical position
must have the flow going up. Valves
installed in the horizontal position must
be positioned so that the drain connec-
tion points down.
The sprinkler system designer must
be aware that the configuration of
the piping network and its tendency
to trap pockets of air (such as in the
case of a peaked-roof gridded sys-
tem) can affect the performance of the
alarm system. Although a slight amount
of trapped air is desirable to prevent
significant pressure increases due to
thermally induced expansion of the
water, a large quantity of trapped air in
a system may result in the possibility of
an intermittent alarm.
The possibility of an intermittent alarm
condition is a consequence of the fact
that the flow out of the system through
the test valve or a single sprinkler is
very small relative to the flow that can
be passed through the valve. This dif-
ference increases with valve size. If the
system were free of trapped air, flow in
would equal flow out and the Waterway
Clapper would always stabilize at some
open position (as needed to accommo-
date the required flow). With trapped
air in the system, however, the Water-
way Clapper first opens wider since the
system initially demands greater flow
until the air pockets are compressed
(back to nearly the supply pressure),
and then it will tend to return closer
PRESSURE
WATERFLOW
ALARM SWITCH
MOTOR ALARM
VALVE
RESTRICTION
(3,2 mm)
OUTLET
ORIFICE
RETARD CHAMBER
BEGINS TO FILL
INLET EXCEEDS OUTLET,
RESTRICTION ASSEMBLY
WHEN FLOW THROUGH
ASSEMBLY
1/8"
CHAMBER
RETARD
INLET
ALARM PORT
RING GROOVE AND
THROUGH SEAT
WATERFLOW
MAIN
DRAIN
ALARM ACTUATE
WATERFLOW PRESSURE
CHAMBER OVERFLOWS,
ONCE RETARD
WATER MOTOR
ALARM SWITCH AND
WATERFLOW
TO SYSTEM
WATERFLOW
TO WATER
7/32"
ORIFICE
(5,6 mm)
UPON SPRINKLER
FLOW, WATERWAY
CLAPPER OPENS
GAUGE
GAUGE
SUPPLY
PRESSURE
PRESSURE
SYSTEM
CHECK
VALVE
ALARM
SCREEN
DRAIN RESTRICTION
WITH 0.125" (3,2 mm)
ORIFICE
INLET RESTRICTION
WITH 0.219" (5,6 mm)
ORIFICE
FIGURE 2
2-1/2, 4, 6 & 8 INCH (DN65, DN100, DN150 & DN200)
MODEL AV-1-300 ALARM CHECK VALVE
OPERATION
FIGURE 3
RESTRICTION ASSEMBLY
(Provided with Alarm Check Valve Trim)
