American Fire Sprinkler Association
12750 Merit Dr., Ste 350 * Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
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TECHNICAL UPDATE
OCTOBER 29, 2008
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"Piping is installed and supported by hangers that are 16 to 18 in.
long. A person can reach up and move the system by hand. Is there a
limit to the motion in sprinkler piping when is installed outside
seismic zones? Is "sway brace" synonymous with "seismic brace" only to
be applied in seismic zones?"
We have reviewed NFPA 13, 2007 Edition as the applicable standard. Our
informal interpretation is that the standard does not explicit
indicate that the pipe should be prevented from movement when it is
not required to protect the system against damage from earthquakes.
Regarding the second question, sway bracing is synonymous with seismic
bracing and shall be installed when systems are required to be
protected against damage from earthquakes since both are referenced
under 13:9.3.
To address the first question on pipe motion, the standard does not
address sway or movement for a system that does not require earthquake
bracing. There is an expectation that the piping should remain in
place, but the system piping will move or sway as water flows in the
piping. The use of swivel rings, clevis hangers, and rod lengths
greater than 6 in. will allow the piping to move or sway. There is
little impact on the system performance if the piping were to sway
when upright or pendent sprinklers are used. The pipe will move but
not sufficiently to move the pendent out of the ceiling sheathing,
affect the area of coverage, cause sprinklers to operate from
impacting nearby objects or allows pipe joints to fail. There is more
concern where sidewall sprinklers penetrating sheathing in a wall
where too much movement could cause the head to move behind the
sheathing. This is addressed in 13:9.2.3.6 that indicates wall mounted
sidewall sprinklers be restrained to prevent lateral movement mainly
so the sprinkler does not move behind the wall sheathing. Another area
that addresses pipe movement is when the system piping is laid on the
structural member that it be secured to prevent pipe movement
according to 13:A.9.1.1. Lastly, sprigs that are 4 ft or loner also
have to be restrained against lateral movement according to
13:9.2.3.7. The bottom line is that when the system is supported
according to 13:9.1 and 9.2, it is considered adequate to prevent
excessive movement according to the standard and the piping is
expected to remain in its original location and position for fire
control. It is not the intent of the standard that sway or seismic
bracing be provided for systems outside of areas where protection
against damage from earthquakes referenced in 13:9.3.
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Technical Update is prepared by the Technical Services Dept. of the
AFSA: Vice President of Engineering and Technical Services Roland
Huggins, a PE registered in fire protection engineering; Phill Brown,
a NICET IV certified automatic sprinkler technician and NFPA Certified
Fire Protection Specialist (CFPS) and Tom Wellen, a degreed fire
protection engineering technologist. This is provided with the
understanding that the AFSA assumes no liability for this opinion or
actions taken on it and they are not to be considered the official
position of the NFPA or its technical committees.
Copyright (c) 2008, American Fire Sprinkler Association. All Rights
Reserved
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