Nicky,
My understanding is that this arrangement makes up the entire ceiling. With
that, my first stab at this is to suggest that the proposed arrangement is o.k.
I think the sprinklers will operate just fine if placed in these 2" (50mm)
gaps.
As to what to calculate. You need not flow sprinklers above and below the
ceiling at the same time. You may want to do a calc for both scenarios to
verify which is the most demanding (which will be dependent on configuration of
drops, etc.). The possible exception may come from insurance company
requirements - some have required including sprinklers both above and below
obstructions in calculations. My personal feeling is that in this particular
case those insurance companies would be overly conservative. I don't foresee
the 50mm gaps being large enough to allow enough heat above the ceilings to
active sprinklers above - at least not prior to the sprinklers below or in any
significant numbers.
One last note: you should include water shields above the pendent sprinkler in
the event a roof level sprinkler does operate before the sprinklers between the
clouds.
Mark A. Sornsin, P.E. | Karges-Faulconbridge, Inc. | Fire Protection Engineer |
Fargo, ND | direct: 701.552.9905 | mobile: 701.371.5759 |
KFIengineers.com<http://www.kfiengineers.com>
From: Sprinklerforum [mailto:[email protected]] On
Behalf Of Nicky Marshall
Sent: Thursday, May 26, 2016 11:30 PM
To: [email protected]
Subject: Cloud ceilings & sprinklers in gaps
I would appreciate if anyone has some thoughts on this arrangement:
~4m (13ft) high roof, ~3.5m (11.5 ft) high ceiling. Both slope 3 degrees.
The 'ceiling' is to be made up of many Autex acoustic panels 1.1 x 2.3m (3.6 x
7.5 ft), non-combustible, suspended with 50mm (2 in) gaps around them.
There will be sprinklers in the roof space because there are cable trays with
loads of combustible cables.
They architect wants to put the sprinklers in the 50mm gaps to avoid cutting
holes in the acoustic panels.
Whilst we are designing to NZS 4541, this code is silent on cloud ceilings or
anything like this, so I am looking for guidance from other sources.
I note NFPA 13:2016 clause 8.15.24 gives some guidance and it seems to indicate
our ceiling arrangement would not require sprinklers above the clouds or have
any specific sprinkler location requirements.
I am also aware of the Fire Protection Research Foundation report on cloud
ceilings. This seemed to suggest that each cloud must have its own sprinkler -
but doesn't test with such small gaps - and recommends further study in this
area where coverage can be achieved without sprinklers in every cloud.
Three questions:
Are the gaps small enough to just call this a ceiling - not a cloud ceiling
(what size gap affects the plume flow enough to make a difference)?
Is it acceptable to locate the sprinklers within the small gaps, or will this
location significantly affect their operation?
Do we have to cumulatively flow sprinklers above and below the ceiling, or
since NFPA permits this arrangement to not have roof space sprinklers
(suggesting heat flow into this space is not significant?), this would not be
required?
Kind regards
Nicky Marshall
Southern Regional Manager
PROTECH DESIGN LIMITED
Specialist Fire Protection Consultants
Phone: +64 (0)3 579 5577 Mobile: +64 (0)21 433 488 Email:
[email protected]<mailto:[email protected]> Skype:
nicky-marshall Web:www.protechdesign.co.nz
Address:105A Alabama Rd, Redwoodtown, Blenheim 7201, NZ Postal: PO Box 4022,
Redwood Village, Blenheim 7242, New Zealand
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