Full Line 061411_Full line Brochure - Reliable Automatic Sprinkler Co.

Special Hazards/Special Systems
Preaction systems contain no water in the sprinkler piping under normal operating
conditions. The piping either contains air at atmospheric pressure (i.e., unsupervised
systems) or a low pressure compressed gas, such as air or dry nitrogen, for the purpose of
supervising the integrity of the sprinkler piping. Usually, supervision of the sprinkler piping
is done at a pressure of either 2 to 10 psi (0,1 to 0,7 bar) , or 10 to 26 psi (0,7 to 1,8 bar),
depending on the type of preaction system being used. Areas typically protected by
preaction systems include computer rooms, museums, libraries, and freezers.
Single Interlock Preaction Systems
Single interlock preaction systems are designed for water sensitive environments in heated
areas that require protection from inadvertent water flow into the sprinkler system piping as
a result of damaged sprinklers or sprinkler piping; or, during a fire event, where water is
required at the sprinkler as soon as the sprinkler operates. Preaction systems can also
replace dry pipe systems, providing cost advantages except for storage occupancies in the
hydraulics of the system (i.e., 1500 ft 2 (139.4 m 2 ) design area vs.1950 ft 2 (181.1 m 2 )
design area for dry systems) and where dry system piping capacities exceed volume
limitations imposed by the applicable standards, where water delivery performance is
adversely affected.
Automatic (closed) sprinklers are attached to a piping system containing 2-10 psi (0,1 –
0,7 bar) supervisory pressure, and a supplemental electric fire detection system is installed
in the same area protected by the sprinklers. This detection system is used in conjunction
with an approved releasing control panel. Preaction systems may also be activated by
mechanical means using either wet pilot or dry pilot line sprinklers or fixed temperature
release pilot line detectors.
When one detector activates in the event of a fire, the deluge valve opens allowing water to
enter and fill the sprinkler system piping. Water then stands ready at the sprinkler and will
immediately discharge once the sprinkler operates, acting like a wet pipe sprinkler system.
Water will only discharge from those sprinklers that have been operated by heat over the
fire. Loss of supervisory air pressure as a result of damaged sprinklers or damaged system
piping will only activate a supervisory alarm and not cause the deluge valve to open.
For more detailed information including approval data, please refer to the technical bulletin specified.
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