Technical data

5.
1.1.2 Model DDX Dry Pilot Line Trim
Where freezing conditions exist, or where height/distance limits of wet pilot lines are exceeded, a dry
pilot line can be used. Closed sprinklers or fixed-temperature-release pilot line detectors are installed
throughout the protected area on small diameter piping that contains pressurized air or nitrogen. A
Model LP Dry Pilot Actuator is installed on the outlet of the Model DDX Deluge Valve push-rod cham-
ber. This device provides a separation between the hydraulically pressurized push-rod chamber and
the pneumatically pressurized pilot line. The dry pilot line is a pneumatic extension of the push-rod
chamber pressurizing piping. Upon activation of a pilot line sprinkler or pilot line detector, pneumatic
pressure is released from the piping allowing the dry pilot actuator to vent and release hydraulic pres-
sure from the push-rod chamber. This allows the Model DDX Deluge Valve to open and deliver water to
the open sprinklers, nozzles, or other discharge devices in the protected area. Alarm devices are ac-
tivated upon the flow of water into the sprinkler system piping. Pneumatic pressure in the dry pilot line
can be provided from a tank-mounted compressor, plant air system, or nitrogen cylinders, and must be
maintained by a Reliable Model A-2 listed pressure maintenance device. To prevent accidental system
activation, pneumatic pressure is monitored by a pressure switch* that will initiate a signal in the event
of low pressure due to sprinkler damage, pipe damage, or failure of the compressed gas system.
*Note: System Sensor Model EPS 40-2 pressure switch is provided with the dry pilot trim.
Approvals and technical data for Model DDX dry pilot deluge systems can be found on Reliable Auto-
matic Sprinkler Company Bulletins 516 through 519.
Figure 3