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Dry Pipe Sprinkler Systems
A Dry Pipe Sprinkler
System is one in which pipes are filled with pressurized air or
nitrogen, rather than water. This air holds a remote valve,
known as a dry pipe valve, in a closed position. Located in a
heated space, the dry-pipe valve prevents water from entering
the pipe until a fire causes one or more sprinklers to operate.
Once this happens, the air escapes and the dry pipe valve
releases. Water then enters the pipe, flowing through open
sprinklers onto the fire.
Under Irish and European Design Codes for Automatic Sprinklers
Systems it is possible to use and Alternate "Wet and Dry"
Systems.
Dry pipe sprinkler systems provide automatic protection in
locations where freezing is possible. Typical dry pipe
installations include unheated warehouses and attics, outside
exposed loading docks and within commercial freezers.
The alternate wet and dry system is used where the sprinkler
pipes may be subjected to freezing temperatures at certain times
of the year, when the system is used 'dry'. When freezing
temperatures do not occur, the system is used 'wet'.
The sprinkler pipe work of a dry or alternate system is
installed with a gradual fall to permit drainage of the system
when it is changed from 'wet' to 'dry'. Drain valves at all low
parts of the installation are opened periodically on 'dry' to
allow drainage of any condensation.
Many people view dry pipe sprinklers as advantageous for
protection in water sensitive areas. This perceived benefit is
due to a fear that a physically damaged wet pipe system will
leak while dry pipe systems will not. In these situations,
however, dry pipe systems will generally not offer any advantage
over wet pipe systems. Should impact damage happen, there will
only be a mild discharge delay, i.e. 1 minute, while air in the
piping is released before water flow.
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