ETL 1110-3-484
26 Sep 97
In order to achieve this, branch lines may have to be run through open-web steel joists. If
necessary, branch line segments can be coupled between sprinklers in order to permit getting
piping between closely-spaced joists. This is preferable to using sprigs, particularly where such
would have to be several feet in length. If the use of sprigs is unavoidable, provide for individual
bracing of sprigs longer than about 1 m (3 ft).
10.3.7.2 Auxiliary Drains. Connect branch lines running down roof slopes to a common manifold
or ganged drain at the low points. This will permit simultaneous draining of several branch lines
through one drain valve.
10.3.8 Relief Valves. Provide relief valves or auxiliary air reservoirs on gridded wet-pipe foam
water sprinkler systems in accordance with NFPA 13. Note: Wet-pipe systems with branch lines
manifolded into gang drains are considered to be gridded.
10.4 Nozzle Systems.
10.4.1 General. Nozzle systems are often provided for rapid application of foam to combat fuel
spill fires that threaten irreparable damage to aircraft. For fixed-wing aircraft, the area where the
wings connect to the fuselage are particularly vulnerable to damage from a fuel spill fire.
Consequently, applicable design criteria will often require nozzle systems for certain fixed-wing
aircraft but not helicopters. Nozzle systems can effectively minimize damage to the aircraft of fire
origin and prevent fire spread to adjacent aircraft. Such fire control will indirectly protect the
hangar facility from catastrophic damage. The decision of whether or not to provide nozzle
systems will be based upon various factors as addressed in MIL-HDBK-1008C or supplemental
design criteria of the pertinent DoD agency involved.
10.4.2 Nozzle Placement and Alignment. Experience has shown that nozzles are often
susceptible to failure due to being blocked by moveable equipment used in a hangar.
Consequently, nozzle placement is extremely critical. The designer must consider all factors that
can adversely affect nozzle effectiveness. This includes hangar size and configuration, aircraft to
be housed, proposed and possible aircraft parking positions, equipment proposed for use, and
other factors known by the facility user. To maximize nozzle performance, provide multiple
nozzle locations. The number of locations will vary with the size and configuration of the facility.
Aim nozzles toward designated or assumed aircraft parking locations. Where possible, direct
discharge toward hangar doors. Locate nozzle assemblies, including control valves, along walls
as necessary to avoid obstruction from equipment that can or will be used in the hangar. If
permitted by facility configuration and use, locate nozzle assemblies away from walls to afford
protection against obstruction. In such cases, provide pipe trenches in concrete floors for routing
of piping. Provide concrete-filled pipe bollards to protect nozzle assemblies from physical
damage.
B-13
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