DDX Single Interlock Preaction Systems

Single Interlock Preaction Systems are designed for water sensitive areas that require protection from inadvertent water flow into the sprinkler system piping.

At the heart of Rapidrop’s Single Interlock Preaction Systems is the Model DDX Deluge Valve. This deluge valve is a hydraulically operated, straight through design, differential latching clapper type.  System maintenance is simplified since the deluge valve can be reset externally without removing its cover plate. This feature provides a significant system restoration time advantage. The Model DDX Deluge Valve has an intermediate chamber and thereby does not require an inline air check valve. Also, for ease of installation, the deluge valve only requires a single drain connection.

The trim sets for the single interlock preaction systems provide all of the necessary equipment for connections to the Model DDX Deluge Valve’s pushrod chamber inlet and outlet ports, a 1¼” (30 mm) main drain on 2” (50 mm), 2½” (65 mm), 76 mm and 3” (80 mm) valve sizes or a 2” (50 mm) main drain on 4” (100 mm), 165 mm, 6” (150 mm) and 8” (200 mm) valve sizes, alarm devices, air supply, and required pressure gauges. The trim sets are available in individual (loose) parts, in timesaving, segmented assembled kit forms or fully assembled to the Model DDX Deluge Valve (with or without a control valve). The major benefits of a single interlock preaction system, when compared with a wet pipe or deluge system are as follows:

• A fire alarm sounds prior to the operation of a sprinkler head, which may enable extinguishing the fire by handheld means before the actual operation of any sprinklers and subsequent water damage.
• A trouble annunciator signals whenever the integrity of the piping or sprinklers is accidentally or intentionally disturbed; however, no water flow or water damage will occur at that time.
• Speedy detection and an early fire alarm are provided by fire detectors, without the delay associated with water delivery time in the event of a fire. Note that with a wet pipe system, the fire alarm is delayed until after water has begun flowing from an operated sprinkler head.

Sprinkler piping in Wet Pilot and Electric Actuation Single Interlock Preaction Systems can effectively be supervised by means of a Rapidrop Model BSI Air Compressor Panel or Model CSI Air Compressor Panel. Loss of 7 psi (0.5 bar) 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 approximately 4 psi (0.3 bar). Note: Wherever the word “air” is used in this bulletin as a reference to the pneumatic pressure source it shall also mean “air or nitrogen.”

Wet Pilot Line Single Interlock Preaction Systems use a pilot line consisting of a line of closed sprinklers or pilot line detectors (Rapidrop’s Model F1FTR), which are located in the area to be protected. These sprinklers/detectors are more sensitive (lower activation temperature) than the sprinkler heads installed in the fire sprinkler system. The wet pilot line is directly installed to the Model DDX Deluge Valve’s push rod chamber. Wet pilot line sprinklers are detection devices and do not provide any water to aid in the firefighting capability of the fire sprinkler system.