Dewayne,
Per NFPA 13 2013 Edition Section 8.15.19 Return Bends, paragraph
8.15.19.1 states that "Unless the requirements of 8.15.19.3, 8.15.19.4,
or 8.15.19.5 are met, return bends shall be used where pendent
sprinklers are supplied from a raw water source, a mill pond, or
open-top reservoirs."
Paragraph 8.15.19.2 states that "Return bends shall be connected to the
top of branch lines in order to avoid accumulation of sediment in the
drop nipples in accordance with Figure 8.15.19.2." The sediment can be
mud or dirt particles that pass through the strainer easily and forms an
obstruction by building up in the drop nipple.
The "U-bend" was first mentioned in the 1956 edition of NFPA 13 in
section 419 "Where piping on wet pipe systems is concealed with
sprinklers installed in a pendent position below a ceiling, the
sprinklers should be connected, where practicable, to the tops of branch
lines by means of U-bends, in order to avoid accumulation of sediment in
the drop nipples."
In the 1960 Edition of NFPA 13 (National Board Fire Underwriters
(NBFU)-13-1960) Paragraph 4310 RETURN BENDS. Where piping on wet systems
is concealed, with sprinklers installed in pendent position below a
ceiling, U-bends will be required when the water supply to the sprinkler
system is from a raw water source, millpond, or from open top
reservoirs.
In the NFPA 13 - 1985 Edition paragraph 3-8.4 Return Bends. When piping
on wet systems is concealed, with sprinklers installed in pendent
position below a ceiling, return bends shall be used when the water
supply to the sprinkler system is from a raw water source, millpond, or
from open top reservoirs. Return bends shall be connected to the tops of
branch lines in order to avoid accumulation of sediment in the drop
nipples.
In the NFPA 13 - 1991 Edition paragraph 4-4.1.7.20 Return Bends. Return
bends shall be used when pendent sprinklers are supplied from a raw
water source, mill pond, or from open-top reservoirs. Return bends shall
be connected to the top of branch lines in order to avoid accumulation
of sediment in the drop nipples.
Exception No. 1: Return bends are not required for deluge systems.
Exception No. 2: Return bends are not required when dry pendent
sprinklers are used.
I do not know of the configuration of the system but the above noted
paragraphs deal with return bends in sprinkler systems. Need to verify
if systems were installed above a ceiling, if exposed then some judgment
is required.
Have a fire safe day!
Regards
Jim
DAVIDSON ASSOCIATES
Fire Protection Engineering P. O. Box 4010
Code Consultants Greenville, DE 19807-0010
Medical Gas Systems Engineering (302) 994-9500
Fax (302) 234-1781
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-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Dewayne
Martinez
Sent: Monday, March 11, 2013 3:16 PM
To: SprinklerFORUM
Subject: Raw water source
We are doing an addition to an existing building that has a raw water
source as the supply for the fire pump. None of the pendant sprinklers
in the existing building appear to be on return bends. Would the
strainer that is installed on the fire pump allow for the return bends
to be omitted? The original systems were installed in 1988 and 94 so
maybe this requirement was not in the code at that time. Would pendant
heads that are screwed directly into the pipe without any type of drop
be allowed? (ie ESFR pnd sprinkler?)
Thanks,
Dewayne Martinez
Design Build Fire Protection
262-784-7900 (w)
262-784-8401 (f)
414-349-0468 (cell)
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