Okay, compare beam/purlins with wood joist construction. The wood
joist
spacing is closer than the purlin spacing. But there is a
restriction of 40
feet for the span. If the span was more than 40 feet, it is not
obstructed
construction. So clearly the "box" effect has to be considered. In
the case
of beam/purlins, there is no box. So UNOBSTRUCTED CONSTRUCTION.
Tony
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ray
Vance
Sent: October 18, 2007 2:28 PM
To: [email protected]
Subject: RE: purlins
As a follow up, here is an informal interpretation from NFSA on
this type of
issue from the March 13th E-Tech Alert.
Question 3 - Beam and Girder Pocket Limitations for Obstructed
Construction
In NFPA 13 (annex section A.3.7.1(1) in the 2002 edition), the
definition of
beam and girder construction as a type of Obstructed Construction
calls for
"beams spaced 3 ft to 7-½ ft on center". However the definition
does not
provide a maximum square footage for the beam and girder pocket. We
have a
building that has steel I-beams spaced 7'-6" apart but these beams
sit on
larger trusses, thus creating an air gap above the two ends above
the truss.
This being said, can we consider this Obstructed Construction?
Answer: Yes. As described, the trusses are perpendicular to the
beams and
provide their support. If the tops of the beams are at the ceiling
and the
trusses are below then the beams should be considered the primary
ceiling
structure. The sprinklers' ability to collect heat and distribute
a spray
pattern is going to be affected most by the structural members
directly
below the ceiling. As you have noted, beam type construction
spaced 3 to
7.5 feet on center is obstructed construction. There is no
requirement that
the beams frame into the trusses or that a maximum size of pocket be
provided. The location of the trusses with regard to sprinkler
spacing must
be considered so that they do not create obstructions to sprinkler
discharge
patterns.
In older editions of NFPA 13, beams that framed into other beams to
form
pockets less than 300 sq. ft. were given special consideration as
"panel
construction". Sprinklers were permitted to be placed further
below the
ceiling due to the greater capacity of panel construction to bank
heat.
While this type of construction is still defined in annex section
A.3.7.1(4), there is no allowance for greater sprinkler deflector
distances
below the ceiling. This annex section can be used, however, to justify
obstructed construct ion deflector distances even where members are
spaced
more than 7.5 ft on center provided the ceiling pocket criteria is
met. This
can be useful in situations where there are multiple adjacent ceiling
pockets.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ray
Vance
Sent: Thursday, October 18, 2007 3:50 PM
To: [email protected]
Subject: RE: purlins
To All:
The proper definition, in my humble opinion is still beam and girder
construction, therefore obstructed contruction.
Girder, by definition, is "a strong horizontal beam used as a main
support
inside a building" ie, the support beam system (girder) on which
the purlins
sit.
There are no length nor volume limitations imposed by NFPA on this
type of
construction, nor does it classify any type of "panel"
configuration be
maintained.
The determining factor is that the SPACING between the purlins
"framed into
or on" the girder must be between 3 ft to 7 1/2 ft on center.
If the beam/purlin spacing exceeds 7 1/2 ft on center, then you can
still
classify it as PANEL construction, provided the 300 sq.ft. "panel"
limitation is met.
With typical purlin depths of 8" to 10", the following scenarios
tend to
play out:
(1) If you classify it as unobstructed, your deflector distance
will be 1"
to 12" below the deck or insulation (with standard spray sprinklers).
(2) If the purlins are 12" in depth, you can still install the
sprinklers
with the deflectors even with the bottom of the purlin and meet the
deflector and obstruction rules.
(3) If you classify it as obstructed, your deflector will be 1" to 6"
below the purlins not to exceed 22" below the deck or insulation.
(4) Or you can install the sprinklers with the deflector even with the
bottom of the purlins and meet the deflector and obstruction rules.
(5) If ESFR sprinklers are considered, then your main concern is if
the
purlins are more than 12" deep, you must install ESFR's in every
bay formed
by the purlins.
As to the "open space" formed by the purlins sitting on the girder,
the
volume of opening created at each end of the span will not
typically create
a large enough concern to warrant a change in the construction
definiton, in
my opinion.
I would think that NFPA would have given direction on this if it
was of a
major concern.
Thanks,
Ray Vance
Chief Engineering Tech.
Wayne Automatic Fire Sprinklers, Inc.
www.waynefire.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Greg
McGahan
Sent: Thursday, October 18, 2007 3:07 PM
To: [email protected]
Subject: RE: purlins
Based on what? It clearly does not fall into panel construction due
to the
space above the beam. They are not girders.
I am not fighting for or against, I just would like a conclusive
answer.
Is there not a manufacturer or committee member there that could
enlighten
us? I would think that the tests run on these storage heads and
such would
have forced a definition for the manufacturers.
Greg
Living Water Fire Protection, LLC
1160 McKenzie Road
Cantonment, FL 32533
850-937-1850
Fax: 850-937-1852
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Todd
Williams
- FPDC
Sent: Thursday, October 18, 2007 1:59 PM
To: [email protected]
Subject: RE: purlins
Up here, it usually goes beams, purlins above (on) the beams, steel
deck on
the purlins. The insulation goes in between the purlins. Is the
insulation
going on the metal deck roof?If the insulation comes to the bottom
of the
purlin, it will create a fairly flat ceiling and I would consider it
unobstructed. If there is no insulation, I would think it would be
considered obstructed.
At 02:51 PM 10/18/2007, you wrote:
No, above them. A typical warehouse.
Living Water Fire Protection, LLC
1160 McKenzie Road
Cantonment, FL 32533
850-937-1850
Fax: 850-937-1852
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Todd
Williams
- FPDC
Sent: Thursday, October 18, 2007 1:50 PM
To: [email protected]
Subject: Re: purlins
Is there insulation between the purlins?
At 02:45 PM 10/18/2007, you wrote:
Poll:
Are typical 8" and 10" purlins spaced 4-5' apart with open space
above the beams where the purlins rest considered OBstructed or
Unobstructed construction?
Living Water Fire Protection, LLC
1160 McKenzie Road
Cantonment, FL 32533
850-937-1850
Fax: 850-937-1852
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email
to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email
to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email
to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email
to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email
to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
Wayne Automatic Fire Sprinklers, Inc.
2006 Inductee into "The Players Hall of Fame"
at The Great Games of Business
Wayne Automatic Fire Sprinklers, Inc. "Best Places to Work"
Rated #1 in 2006
Large Business Category
by Orlando Business Journal
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email to:Sprinklerforum-
[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email to:Sprinklerforum-
[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email to:Sprinklerforum-
[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
