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13-462 INSTALLATION OF SPRINKLER SYSTEMS

Other protection features should be considered to limit the iv.

Pitting, nodules, tubercles, or carbuncles
extent of potential fire damage, including the following: inside piping or valves
(1) Very high density sprinkler systems v. Foreign material in water during drain tests or
(2) Quick-response sprinklers plugging of inspector’s test connection(s)
(3) Early-warning smoke detection vi. Plugged sprinklers
(4) Spacers between carriages or, for automated systems, vii. Plugged piping in sprinkler systems disman‐
automatic park mode to increase flue spaces between tled during building alterations
carriages upon activation of a fire alarm or during idle viii. Frequent false tripping of a dry pipe valve(s)
periods with indications of corrosion inside the
(5) Metal vertical barriers in the middle of the shelf valve(s)
(6) Open-top shelving ix. A 50 percent increase in the time required for
[909:A.9.12.24.4.1.3] water to travel to the inspector’s test connec‐
tion after the valve trips during a full flow trip
A.26.29.1.3.2 The system should be designed to confine fire test of a dry pipe sprinkler system when
growth to the compact storage module of origin or the shelving compared to the original system acceptance
range of origin. [909:A.9.12.24.4.1.4(A)] test
[909: A.9.12.13.3.3]
A.26.29.2.1 Proper pitching is an important element in reduc‐
ing the risk of corrosion. The pitch requirements included in These options are based on those specified by this standard
this standard should be considered the minimum acceptable for applications where water supplies are known to be corro‐
pitch. Where adequate clearance is provided to permit the sive. They are recommended in this code for steel dry pipe and
system to be installed without causing interferences with struc‐ preaction systems because the levels of corrosion found in
tural elements or causing low points, pitches exceeding this these systems are unacceptable for cultural resource facilities.
minimum requirement such as 1∕2 in./10 ft (4 mm/m) should Although this standard also allows the option of treating all
be considered. [909:A.9.12.13.3.1] water that enters the system with an approved corrosion inhibi‐
tor, experience using this option has not been satisfactory in
N A.26.29.2.2 Due to heightened concerns regarding the issues cultural resource facilities due to potential formation of exter‐
associated with corrosion, additional auxiliary drainage is nal crystals on piping and potential reduction in the service life
needed for all preaction systems, regardless of whether or not of gaskets in mechanical couplings. This standard includes the
the protected area is subject to freezing. [909:A.9.12.13.3.2.1] additional option of using a special listed pre-primed preaction
N A.26.29.2.3 A plan to address piping corrosion should include system, in which the piping is normally filled with water.
one or more of the following: [909:A.9.12.13.3.3]
(1) Installation of sprinkler piping that is corrosion resistant
– Galvanized steel piping is not considered corrosion A.26.33.1.11 The quantities and pressure of water for fire
{23188f7b-d887-4151-ae08-bc5f4d1ab905}
resistant for the purposes of this recommendation.
Galvanized coatings can corrode where water and oxygen
extinguishing indicated in 26.33.1.11 are based on limited test‐
ing and should be considered subject to change as additional
are present inside system piping. When galvanized coat‐ data become available. It is recommended that spray coverage
ings fail, the remaining uncoated steel corrodes at an tests be carried out at maximum altitude for manned opera‐
accelerated rate. tions. [99B: A.4.5.2.5.1]
(2) Installation of a special listed pre-primed preaction A.26.34.1.1.1 See 4.3.3 of NFPA 120 for unique requirements
system, filled with water under normal conditions. for protecting this unusual type of occupancy.
(3) Use of a continuous source of dry inert gas for pressure
maintenance. N A.26.34.1.3.3(8) Pipe hangers should be designed to support
(4) Testing of the water supply for corrosivity prior to connec‐ five times the weight of the water-filled pipe plus 250 lb
tion to the sprinkler system. (114 kg) at each point of piping support. Hanger rods should
(5) Equipping any source of compressed air used for pressure be at least 3∕8 in. (9.5 mm) thick for pipe up to 4 in. (102 mm).
maintenance with an air dryer or nitrogen separator. U hooks should be at least 5∕16 in. (8 mm) thick for pipes up to
(6) Implementation of an approved plan for maintaining and 2 in. (50.8 mm). Eye rods should be at least 3∕8 in. (9.5 mm)
monitoring the interior conditions of the pipe at estab‐ thick for pipe up to 4 in. (102 mm). This information is taken
lished intervals and locations, including all of the follow‐ from Chapter 17 of this standard. [120:A.9.4.6.3.2(8)]
ing:
A.26.35.1.2 Underground shaft mines that use diesel-powered
(a) Testing water flow devices between the semiannual equipment generally employ underground diesel fuel storage
tests using a means that does not introduce fresh areas to facilitate equipment refueling. Adit-type mines in the
water into the system western United States can initially locate diesel fuel storage and
(b) Drying system piping before returning systems to refueling facilities on the surface; however, as the active mine
service after trip tests or other incidents that intro‐ workings progress further from the adit portal(s), these facili‐
duce water into system piping beyond the riser ties usually are moved underground. [122:A.11.3.1]
(c) Inspecting for obstructions when any of the follow‐
ing conditions are observed: A common means of fire protection currently found in many
underground diesel fuel storage areas is a fixed water sprinkler
i. Pinhole leaks system. The federal Mine Safety and Health Administration
ii. Frequent operation of system air compres‐ (MSHA) currently approves such systems for this application.
sor(s) The consensus of the committee is that this situation represents
iii. Corrosion on the outside of pipe joints, a significant safety hazard. According to the NFPA Fire Protection
fittings, or sprinklers

2019 Edition