Technical data

15.
1.3.2 Model DDX Type F
The Reliable Type F Double Interlock Preaction system utilizes a Model LP Dry Pilot Actuator down-
stream of a listed, normally closed (de-energized) electric solenoid valve on the outlet of the Model DDX
Deluge Valve push-rod chamber. The dry pilot actuator is held closed with system pneumatic pressure,
and provides a separation between the hydraulically pressurized push-rod chamber and the system
pneumatic pressure. When the programming logic of the release panel has been satisfied, the panel
energizes (opens) the solenoid valve clearing the waterway to the dry pilot actuator. Subsequent loss
of pneumatic pressure from the system due to a sprinkler opening operates the dry pilot actuator which
vents to a drain, relieving pressure from the push-rod chamber and allowing the Model DDX Deluge
Valve to open and flow water into the protected area. The Type F system is described as an electric/
mechanical double interlock preaction system. Two independent conditions must coexist to actuate
the Model DDX Deluge Valve and flow water into the system. These two conditions are (a) activation of
the detection system and (b) loss of pneumatic pressure in the system piping. Detection systems are
more sensitive than sprinklers on the system, and will activate prior to the sprinklers opening. The time
period between fire detection/alarm and opening of the sprinklers allows the building owner a chance
to respond and possibly avoid unnecessary discharge of water into the water sensitive environment. In
the event the alarm is not attended to, the fire will continue to grow eventually fusing one or more sprin-
klers and relieving pneumatic pressure in the system. Loss of pneumatic pressure results in operation
of the mechanical dry pilot actuator. When this second condition (loss of pneumatic pressure) coexists
with the first condition (open solenoid), the Model DDX Deluge Valve operates and allows water into
the protected area. Alarm devices are activated upon the flow of water into the sprinkler system piping.
Pneumatic pressure can be provided from a tank-mounted air compressor, plant air system, nitrogen
cylinders, or nitrogen generator, and must be maintained by a Reliable Model A-2 listed pressure main-
tenance device. Pressure is monitored by a pressure switch* that will notify the owner in the event of
falling pressure due to sprinkler damage, pipe damage, or failure of the compressed gas system. A low
pressure condition in the absence of a detection signal or a detection signal in the absence of a low
pressure condition will NOT result in activation of the main system control valve. The singular condition
can be corrected and the system returned to normal service.
*Note: For Type F systems, system sensor Model EPS 10-2 pressure switch is provided with the trim.
Approvals and technical data for Model DDX Type F Double Interlock Preaction systems can be found
on Reliable Automatic Sprinkler Company Bulletin 751.
Figure 13