Heat Detector Locations

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TLBryant

TLBryant

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West Virginia
The attachment shows a diagram of an airplane hanger. The owner wants to install a foam fire suppression system. The system is to be activated by rate compensating heat detectors installed throughout the hanger.

Taking spacing reduction into account for the ceiling height; should the detectors be installed at location "A" on the decking between the steel beams or at location "B" under the bar joists?

If this was for a fire alarm system I would have the EC install the heats at location "A". Since these detectors are activating a suppression system, my thought is to have the detectors as close to the heat source as possible.

Any one ever run into a similar scenario?
 
The bottom of the bar joist is wrong. See Nfpa 72 spacing requirements for sloped ceilings.

You would have to hope the heat would stratify to putnin on the bottom,:D which is something that occurs with smoke in large spaces.

The bar joist is the lazy mans way, a lot of people do it that way. It's not that it is lazy is dangerous.

The preaction system you are using is for EARLY detection, so put it where it will work!!!
 
With suppression, how about both ? You should have an A and a B zone and program that both zones must trip for the releasing agent to fire. With suppression, eliminate all false alarms, it's an expensive proposition.
 
Stallzer said:
With suppression, how about both ? You should have an A and a B zone and program that both zones must trip for the releasing agent to fire. With suppression, eliminate all false alarms, it's an expensive proposition.
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That would defeat the purpose of a PREaction deluge sprinkler system.
 
we installed a bunch of hangar fire alarms. fwiw, the aircraft were protected by flame detectors on the perimeter, which initiated a countdown which the duty officer had to inhibit to prevent automatic foam activation. There were smokes/heats up at the hangar roof, but I don't recall if they just rang the alarm or were tied in to foam activation. Of course, there was also manual foam switch. There's some info on the web which discusses some of the problems with using the overhead heat detection. I found this article which discusses a solution using video smoke detection (similar in some ways but also very different in others from using flame detectors)

http://bssme.com/royal.pdf

the hangars we did were similar to this specification for deluge systems (which I also found on the web):

http://www.wbdg.org/ccb/NAVFAC/INTCRIT/fy05_01.pdf
 
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