Building Design and Construction Handbook - Merritt - Ventech!

14.60 SECTION FOURTEEN
14.29.2 Sprinkler Piping
There are numerous types of sprinkler piping currently accepted for the installation
of sprinkler systems. In all cases the piping specified for a sprinkler system must
be installed and used within the parameters of its U.L. Listing.
Most sprinkler piping specified today is black or galvanized, welded and seamless
steel pipe. Normally smaller pipe sizes are specified as Schedule 40 and larger
sizes as Schedule 10 black steel pipe. The joining methods for sprinkler pipe include
the use of flanged fittings, prefabricated welded outlets, cast or malleable iron fittings
or mechanical grooved fittings. In all cases, sprinkler pipe and fittings must
be capable of withstanding pressures of 175 psi. For further details NFPA 13 and
pipe manufacturer catalogs should be consulted.
Areas Protected by Sprinklers. To provide a fully sprinklered building, which is
the intent of most building codes and insurance industry sprinkler requirements, all
areas of a structure, with few exceptions, must be provided sprinkler protection.
Generally, all spaces that are accessible, combustible or intended for storage or
occupancy require sprinkler protection. The guidelines for permissible sprinkler
omissions in fully sprinkled buildings are contained in NFPA 13. Except for void
spaces in walls and noncombustible concealed spaces there are few exceptions and
where exceptions do exist they are extremely specific with respect to accessibility,
construction and dimensions.
With respect to individual sprinkler spacing requirements, the maximum area
protected by one sprinkler should not exceed the area specified for the specific
sprinkler as indicated in the manufacturer’s specification sheets. Standard spray
sprinklers are listed for light hazard, ordinary hazard and extra hazard occupancies
for 225-, 130- and 100- 2 protection areas, respectively.
In most installations, the area or coverage of each sprinkler is usually less than
the maximum areas listed.
14.29.3 Sprinkler Position
In areas where construction is unobstructed, sprinkler deflectors should be parallel
to and within 12 inches of the ceiling. Where construction is obstructed sprinklers
must be within 22 inches of the roof deck above. In all cases, when locating sprinklers
the maximum expected ambient temperature of the area being protected must
be considered such that unwanted sprinkler activation does not occur.
Undesirable sprinkler water spray obstructions must also be considered when
locating sprinklers. Where obstructions such as ducts are greater than 4 feet wide
and are located below sprinklers, additional sprinklers should be added to spray
below the obstruction. Furnishings such as tables are not considered obstructions
unless they are within 18-inches, measured vertically of a sprinkler. When locating
all sprinklers NFPA 13 and the sprinkler manufacturer’s guidelines must be followed
to prevent unwanted water spray obstructions.
Sprinkler System Layout. A sprinkler system is generally laid out as a ‘‘Tree’’,
‘‘Loop’’ or ‘‘Grid’’ type system. Whatever the case, sprinklers are attached directly
to pipes called branch lines. Branch lines, normally the smallest of sprinkler pipes,
are supplied water from cross mains or feed mains which are directly connected to
the system riser.
The riser, configured to control the water supply and monitor water flow and
valve position, may support a single sprinkler system or if manifolded, many sys-