Issue 34: Top Ten Changes to NFPA 13 - 2010 Edition
By Kenneth E. Isman, P.E., FSFPE
The 2010 edition of NFPA 131 is now available from the
National Fire Protection Association. In preparing the 2010 edition, the
five committees responsible for NFPA 13 deliberated over more than 850
proposals and comments to change the document. This article will not
attempt to explain the disposition of all those proposed changes.
Instead, the top ten most impactful issues, as voted by the National
Fire Sprinkler Association (NFSA) Engineering Staff, will be discussed
here (with an intention of spreading the discussion out through most of
the chapters of the standard). The top ten changes are:
1) Relief Valves and Air Vents. Concerns over
interior corrosion of wet pipe systems led to recommendations that air
vents be installed to get more air out of all wet pipe sprinkler
systems. Interestingly, these recommendations were made in the annex and
are not mandatory. However, the committee also grew concerned that if
most of the air was evacuated from the sprinkler system, there would be
no air pockets into which water could expand (as the pipes get warmer
during a day or season), so the committee required all wet pipe systems
to have a relief valve. So now, even without an air vent on the system,
it will be necessary to install a relief valve. While they were making
changes, the committee increased the size of the relief valves from 1/4
inch to 1/2 inch (from 6 mm to 12 mm) and also required the relief valve
to be listed. There is no requirement to pipe the relief valve to a
suitable drain, but doing so should be common sense.
2) Ceiling Pockets. Three important clarifications
were made to the ceiling pocket rules that have been in the standard for
several cycles. The first is that a definition of a "ceiling pocket"
was added along with annex text to make it clear that channels formed by
structural members are not ceiling pockets. The second change was to
clarify that the 10 ft (3 m) separation between unprotected pockets only
needs to be provided when the sum of the volume of the pockets exceeds
1000 cubic feet (28 m3). This means that two pockets of 500 cubic feet (28 m3) each, or 10 pockets of 100 cubic feet (2.8 m3)
each, can be unprotected and still do not need to be separated by 10 ft
(3 m). The third change was to clarify how shallow pocket situations
are to be protected where the sprinkler deflector (in the lower ceiling
elevation) is within 12 inches (0.3 m) vertically from the top of the
pocket. Such pockets are considered protected pockets just the same as
any pocket with sprinklers elevated into the pocket itself.
3) Seismic Load Tables. In the 2007 edition of the
standard, tables were added to indicate the maximum load permitted for a
brace to carry in the zone of influence of the brace for schedule 10
and schedule 40 steel pipe, which led everyone to ask, "What about other
types of pipe and tube?" For the 2010 edition, the committee has added
tables for schedule 5 steel, CPVC pipe and type M copper tube. For types
of pipe and tube that do not have a table, the intent of the committee
is to allow that type of pipe to be used with the maximum permitted load
table for the same pipe material with a thinner wall, or to allow the
manufacturer to supply their own load table. So, for schedule 7 steel
pipe (for example) one could use the schedule 5 table, or a table
generated by the manufacturer.
4) Truncated Density/Area Curves. For the last three
cycles of NFPA 13, there has been a spirited debate over whether or not
the density/area curves used to protect storage occupancies should be
eliminated. For the 2010 edition, a compromise was reached that cut off
the top of the curves (above 3000 sq ft - or 280 m2). This
makes sense in that the tops of the curves represented small delivery
density and large operating areas. There has been some concern that
these lower densities might not be capable of controlling a fire, even
if the design area is increased.
5) High Clearance to Ceilings in Storage Occupancies.
The 2007 edition of the standard required that the clearance from the
top of the storage to the ceiling needed to be considered in the
sprinkler system design for Class I-IV commodities. The rule was adopted
that the sprinkler system needed to be designed for a maximum of 20 ft
(6 m) of clearance. So, for example, in a 40 ft (12 m) high building, it
was not possible to design the sprinkler system for 10 ft (3 m) high
storage; one needed to design it for at least 20 ft high storage. For
the 2010 edition, the rules were clarified for rack storage so that the
in-rack sprinkler placement could be better understood.
6) Back-to-Back Shelf Storage. The rules for shelf
storage have always defined a shelf as "up to 30 inches (0.8 m) wide".
But the rules have never been clear on whether aisles needed to be on
both sides of the 30 inch (0.8 m) wide shelves or if the shelves could
be back-to-back. The committee finally solved the problem by creating a
new category of storage called "back-to-back shelf storage" and defining
new protecting criteria for the sprinklers.
7) Record Storage. People who attended the 2006 NFPA
Annual Meeting will remember that the committee tried to move forward
with new rules for protecting records storage (class III commodities in
specially arranged racks with specific dimensions and catwalks up
through the racks) that were not acceptable to the record storage
industry. The folks from the record storage industry showed up in large
numbers to vote in favor of removing these new rules from the 2007
edition of the standard, and they were successful at convincing the NFPA
membership to do so. In the intervening years between the development
of the 2007 and 2010 editions of NFPA 13, the records storage industry
worked with the NFPA Sprinkler System Discharge Criteria Committee to
run full-scale fire tests aimed at developing better rules. These better
rules now appear in the 2010 edition and appear to be acceptable to the
record storage industry.
8) Compact Storage. Compact storage modules consist
of record storage shelves or bins on movable rails where there is only
one aisle. The shelves or bins are moved on their rails to create the
aisle where it is needed to get to any particular record. Full scale
fire tests conducted with the Fire Protection Research Foundation2
led to the development of criteria under which these filing systems
could be used with light hazard fire sprinkler systems. In order to be
used with light hazard, the files cannot exceed 8 ft (2.4 m) in height,
only paper records can be stored (up to 5% plastic are allowed for file
tabs and other miscellaneous items) and the 18 inch (0.5 m) clearance
needs to be maintained for the sprinkler deflector over the top of the
storage unit. Additional rules also concern the construction and size of
the compact storage modules, which need to be provided with metal
longitudinal and transverse barriers and cannot exceed 250 sq ft (23 m2) in area in order to use the light hazard rules. Section 20.6 of NFPA 13 provides all of the specific rules.
9) High-Bay Record Storage. High-bay record storage
is a combination of the last two items - high-bay record storage that
uses a mobile module that slides on rails to open a single aisle where
the records need to be stored. But instead of being 8 ft (2.4 m) high
like the compact storage discussed above, these modules can be up to 34
ft (10 m) high. The criteria in NFPA 13 is based on full-scale test data
that was submitted to NFPA.
10) Hydrostatic Tests. NFPA 13 has always required a
200 psi (1.4 MPa) hydrostatic test, and for years has said that the
pressure is measured during the test at the lowest elevation. Some
people have interpreted this as meaning that 200 psi (1.4 MPa) is
measured at the lowest elevation. Others believed that the intent was to
expose every piece of pipe to at least 200 psi(1.4 MPa), so that meant
measuring a higher pressure at the lowest elevation to make up for
elevation head loss. The NFPA committee clarified for the 2010 edition
that the former interpretation is correct. This means that in a building
with a 30 ft (9 m) riser, the hydrostatic test is conducted with 200
psi (1.4 MPa) at the base of the riser and the pressure will only be 187
psi (1.29 MPa) at the piping at the top of the riser.
Kenneth E. Isman, P.E., FSFPE, is with the National Fire Sprinkler Association.
NFPA 13, Standard for the Installation of Sprinkler Systems, National Fire Protection Association, Quincy, MA, 2010.
Schirmer Engineering Corporation, "Compact Mobile Shelving System Fire
Testing Project," Fire Protection Research Foundation, Quincy, MA,
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The Society of Fire Protection Engineers (SFPE) was established in 1950 and incorporated as an independent organization in 1971. It is the professional society representing those practicing the field of fire protection engineering. The Society has over 4,600 members and 100 chapters, including 21 student chapters worldwide.