General Description
Reliable Single Interlock Preaction Systems are de-
signed for water-sensitive areas that require protection
from inadvertent water flow into the sprinkler system pip-
ing.
Sprinkler piping in single interlock systems can effec-
tively
be supervised by means of a Reliable Model A-2
Pressure Maintenance Device and a tank-mounted air
compressor. Loss of supervising pneumatic pressure,
due to a damaged sprinkler or sprinkler pipe will not
cause water to flow through the Model DDX Deluge
Valve and into the system piping. A significant loss of
pneumatic pressure will activate a trouble-annunciating
device when the system pressure falls below a predeter-
mined pressure level.
When one electrical detector senses the presence of
fire, the electrical releasing control panel activates fire
alarm devices and energizes the two redundant, nor-
mally-closed solenoid valves in the open position (
Note
:
Arranging detectors in a cross-zoned pattern will require
operation of two detectors before the solenoid valves
can open). These solenoid valves, when closed, retain
sufficient AIR pressure in the Model LP Pilot Line Actua-
tor, which in turn preserves sufficient WATER pressure in
the push rod chamber of the Model DDX Deluge Valve in
order to maintain it closed.
Energizing the solenoid valves relieves the air pressure
in the Model LP Dry Valve Actuator (see Fig. 8), thereby
releasing the water pressure that it was retaining. This is
turn relieves the pressure in the push rod chamber of the
Model DDX Deluge Valve. Venting this push rod cham-
ber will open the Model DDX Deluge Valve and allow wa-
ter to flow into the sprinkler system.
T
o fully operate a cross-zoned single interlock system,
two electrical detectors must activate and a sprinkler
head must open. During the early stages of a fire, smoke
or heat activates the first detector, which causes the con-
trol panel to produce a local alarm and an alarm at the
main fire alarm panel. Electrical relays inside the releas-
ing control panel can be used to shut down airmoving
equipment or activate security doors and other electrical
devices. Subsequent activation of a second, nearby or
adjacent detector will cause the panel to energize the
solenoid valves open and release water into the sprinkler
system piping. Water flowing into the sprinkler system
piping will simultaneously produce water pressure that
causes the transfer of contacts in the pressure switch
mounted in the trim. This pressure switch can electrically
initiate the shutdown or startup of equipment, such as
computers or other second alarm devices. This flow of
water into the sprinkler system piping effectively con-
verts the dry system into a wet pipe system. In the event
that the fire subsequently produces sufficient heat to op-
erate a sprinkler head, water will flow from that sprinkler,
controlling or suppressing the fire.
The major benefits of a single interlock preaction sys-
tem, when compared with a wet pipe (deluge) system
are as follows:
A.
A fire alarm sounds prior to the operation of a
sprinkler head, which may enable extinguishing
the fire by handheld means before the actual oper-
ation of any sprinklers and subsequent water dam-
age.
B.
A trouble annunciator signals whenever the in-
tegrity of the piping or sprinklers is accidentally or
intentionally disturbed; however, no water flow or
water damage will occur at that time.
C.
Speedy detection and an early fire alarm are
provided by fire detectors, without the delay asso-
ciated with water delivery time in the event of a fire.
Note:
with a wet pipe system, the fire alarm is de-
layed until after water has begun flowing from an
operated sprinkler head.
At the heart of Reliable’s Single Interlock Preaction Sys-
tem is the Model DDX Deluge Valve. This Deluge Valve is
a hydraulically operated, straight-through-design, differ-
ential-type valve (see Fig. 1). System maintenance is
simplified since priming water is not required and the
deluge valve can be reset externally without cover re-
moval. This is accomplished by pushing in and turning
the external reset knob at the rear of the deluge valve
(see Fig. 1). This feature provides a significant sys-
tem-restoration time advantage.
The Reliable Single Interlock Preaction System trim set
(see Fig. 2) provides all of the necessary equipment for
connections to the Model DDX Deluge Valve’s pushrod
chamber inlet and outlet ports, the 2” (50mm) main
drain, alarm devices, air supply, water supply, and re-
quired pressure gauges. This trim set is available in indi-
vidual parts, in time-saving, segmentally assembled kit
forms, or fully assembled to the Model DDX Deluge
Valve.
Listing & Approvals
The
4” (100mm), 6’ (150mm) and 165mm Single Inter-
lock Preaction Systems shown in this bulletin must only
be used in the combination described herein to be Loss
Prevention Certification Board (LPCB) approved. Instal-
lation of these systems must be according the require-
ments of Technical Bulletin TB21:1994:1.
The
majority of the system’s components are individu-
ally Listed by Underwriters Laboratories Inc. and Fac-
tory Mutual Approved.
2.
Summary of Contents for Single Interlock Preaction System
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