The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
Weston C. Baker Jr. – Senior Engineering Technical Specialist
FM Global, Engineering Standards, Norwood, Massachusetts, USA
With the introduction of the first practical automatic sprinkler in 1874 by Henry H. Parmalee, owner of a piano factory in
New Haven, Connecticut (USA), a major step was taken towards the advancement of industrial fire protection. This
sprinkler, which consisted of a perforated deflector with a water valve that was held shut by a lever attached to a fusible link,
was developed by Parmalee primarily for the intent of lowering the insurance rate for his factory1. Prior to the introduction of
his sprinkler, which allowed for only those sprinklers located directly over the fire to open, sprinkler systems typically
consisted of steel pipes equipped with perforated holes through which water would flow, a system devised in England in the
early 1800’s by John Carey2. In some cases, mill owners would outfit the openings in the pipe with metal caps that would
spray the water outward from the hole opening thus allowing for a larger area of coverage. The drawbacks to these perforated
sprinkler systems were that they (1) had to be manually operated and (2) discharged water through all the holes, as opposed
to just those over the area of fire origin.
Roughly seven years after the introduction of the Parmalee sprinkler, Frederick Grinnell began modifications to the sprinkler
that allowed for it to be more effective and produced at a lower cost3. With the efforts of Parmalee to get insurance
companies to agree to lowering rates for the presence of automatic sprinklers coupled with Grinnell’s improvements to the
sprinkler itself, the installation of automatic sprinkler protection started to become a viable option for industrial buildings in
the late 19th century2. With the majority of building structures at the turn of the century consisting of combustible roof and
floor construction, the deflector of the sprinklers was designed to allow a large portion of the discharged water to be directed
upwards towards the ceiling where it would, in theory, protect it from fire spread and then ricochet down towards the floor
area below.
With the advent of the automatic sprinkler system came guidelines for sprinkler system installations as well as guidelines for
sprinkler system designs. On November 16, 1891, the Associated Factory Mutual Insurance Company (now known as FM
Global) released the first automatic sprinkler system installation guideline entitled, Location and Spacing for Automatic
Sprinklers. In 1896, the National Fire Protection Association (NFPA) published its first installation guideline on sprinklers
entitled, Rules and Regulations of the National Board of Fire Underwriters for Sprinkler Equipments, Automatic and Open
Sprinklers. The design for automatic sprinkler systems became rooted on a pipe schedule basis where the size of the sprinkler
system piping was based on the number of sprinklers located downstream of the pipe. The pipe schedule method was divided
into three categories: light hazard, ordinary hazard and extra hazard pipe schedule. Based on the anticipated hazard of the
occupancy to be protected, the size of the sprinkler system pipe was then determined by the number of sprinklers that were
installed downstream of it. An example of the pipe schedule method is demonstrated in Table 1 for a light hazard occupancy.
References:
1.
Factory Mutual Insurance Company, Prevention (February 1998) pp. 13-14
2.
www.olyfire.com/history.html
3.
www.rpi.edu/dept/NewsComm/sub/frame/inductees/frederickgrinnell.html
Page 1 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
Table 1. Pipe Schedule Requirements for Light Hazard Occupancies4
Nominal Pipe Size
Maximum Number of Sprinklers Fed by Pipe Size
1 in. (25 mm)
2
1-1/4 in. (32 mm)
3
1-1/2 in. (38 mm)
5
2 in. (50 mm)
10
2-1/2 in. (63 mm)
30
3 in. (75 mm)
60
3-1/2 in. (88 mm)
100
4 in. (100 mm)
See Note 1
Note 1: The area supplied by any one 4 in. (100 mm) pipe on any one floor shall not exceed 52,000 ft2 (4,830 m2).
The pipe schedule design method offered a simple means for determining the proper size of a sprinkler system. It, however,
did not take into account the water supply available for the automatic sprinkler system nor did it allow for flexibility when
the occupancy hazard protected by an existing sprinkler system increased. Even with these drawbacks to the pipe schedule
design method, automatic sprinkler systems prior to World War II did an excellent job of keeping fires under control until the
local fire service were able to arrive and manually extinguish the blaze. FM Global loss statistics indicate that roughly 73%
of fire incidents in facilities with automatic sprinkler protection are controlled by the operation of less than ten sprinklers5.
However, after the end of World War II, changes in industrial practices were starting to demonstrate the limitations of the
pipe schedule design method. Prior to World War II, most buildings were constructed of heavy wooden timbers or, better yet,
reinforced concrete. However, during and after World War II came the introduction of steel supported building structures.
The use of steel, which was of lighter weight and higher strength compared to wooden beams, allowed buildings to be built
higher than before and helped to reduce the combustible loading of the building structure itself. However steel itself weakens
after a relatively short timeframe when exposed to temperatures over 1,000°F (538°C). Industrial fires generally exceed
1,000°F (538°C) thus creating a condition where a building structure could possibly collapse due to the failure of a steel
column even when automatic sprinkler protection was provided at ceiling level.
Other changes in industrial practices soon after World War II that had measurable affects on automatic sprinkler protection
were the introduction of the fork-lift truck as well as plastic materials. Prior to World War II storage areas in industrial
facilities were typically only about 6 to 8 ft (2.0 to 2.4 m) high, or as high as a person could lift the stored item over their
head. In addition, most commodities maintained in storage areas consisted of metal, glass or wooden type materials. With the
combustible loading of the stored materials being relatively low coupled with the relatively low storage and ceiling heights
maintained in warehouse areas, existing sprinkler systems were able to provide control when fires did originate. Fire control
is achieved from an automatic sprinkler system by discharging a sufficient amount of water during a fire event that (1) keeps
the ceiling area cool enough to open only those sprinklers directly over the area of fire origin, and (2) discharges enough
water to pre-wet surrounding combustible materials so that the fire is incapable of spreading much horizontally beyond the
point of fire origin.
References:
4.
FM Global, Hydraulics Tables Seventh Edition (April 2004) page 48
5.
FM Global, Understanding the Hazard, Lack of Automatic Sprinklers (February 2003) page 1
Page 2 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
After World War II the introduction of the fork lift truck allowed for the heights at which storage was maintained within
warehouse areas to dramatically increase above what was previously the norm. The use of steel in the storage racks also
allowed for larger loads to be maintained within the rack structure. The introduction of plastic materials also greatly increased
the fire hazard in industrial facilities after World War II. The heat of combustion of ordinary combustibles (e.g., wood or
paper) generally ranges between 6,000 and 8,000 Btu/lb (13,960–18,600 kJ/kg). The heat of combustion for plastics generally
ranges between 12,000 and 20,000 Btu/lb (27,910-46,520 kJ/kg). The burning rate of a commodity is dependent on many
things, but plastic materials generally exhibit higher maximum burning rates than similarly arranged ordinary combustibles.
This difference can be two to three times higher for many plastic products6.
Loss statistics at FM Global indicate that in the 1950’s, a number of uncontrolled fires took place at industrial facilities
equipped with what was thought to be adequate automatic sprinkler protection. Research at FM Global in the 1950’s led to
two major changes in the world of fire protection. The first major change was the introduction of the standard spray
automatic sprinkler. Prior to this change the sprinkler deflector of an upright sprinkler allowed a significant amount of the
water discharge to be directed upwards; such sprinklers are commonly referred to today as conventional sprinklers. The
deflector of the standard spray upright sprinkler was modified so that nearly all of the water discharge from the sprinkler was
directed downwards in a parabolic shape, commonly referred to as an umbrella discharge pattern.
The second major change was the introduction of the density/area design concept, which indicated a specified flow rate per
sprinkler, depending on the sprinkler’s area spacing, for all sprinklers operating within an indicated area. Coupled with this
design requirement from the ceiling level sprinklers was an allowance for fire service hose application as well as a timeframe
(i.e. duration) that the sprinkler system requirements were needed for. This concept took the idea of the pipe schedule design
method one step further; it still looked at the occupancy hazard to define the protection needed for the automatic sprinkler
system, however with the density/area design method it now based the protection needed on the water supplies ability to
deliver a minimum volume of water from the operating sprinklers. Although the density/area design method nowadays
(February 2010) are commonplace, it took roughly two decades before this design method became more prevalent than pipe
schedule design methods. With the density/area design method sprinkler contractors would have to mathematically
demonstrate that their proposed sprinkler system lay-out would be adequate whereas with the pipe schedule design method
they did not. It wasn’t until hand-held calculators and eventually computer programs specifically designed for sprinkler
system calculations came along that the density/area design method truly took foothold in the fire protection community.
In the late 1970’s, research at FM Global lead to the development of a new sprinkler that was specifically targeted for the
protection of storage occupancies; it became commonly referred to as the “large-drop” sprinkler. The size of the orifice was
0.64 in. (16 mm) in diameter and discharged approximately twice the volume of water when compared to a ½ in. (13 mm)
orifice sprinkler. With this advancement in sprinkler performance also came a new design format; the large-drop sprinkler
used a design format based on an indicated minimum pressure at the sprinkler while simultaneously flowing a given number
of sprinklers. A decade later FM Global used the knowledge gained from the large-drop sprinkler program coupled with
another project from the 1970’s that helped develop the quick-response thermal element to develop the sprinkler concept that
would eventually lead to the development of the “early suppression fast response” sprinkler, or ESFR for short. The design
format for the ESFR sprinkler was also based on an indicated minimum pressure at the sprinkler while simultaneously
flowing a given number of sprinklers.
References:
6.
FM Global, Data Sheet 8-1, Commodity Classification (May 2004) page 6
Page 3 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
By the start of the twenty first century the single sprinkler initially produced by Parmalee and further refined by Grinnell had
grown in magnitudes that no one could possibly have foreseen back at the start of the twentieth century. Sprinklers were now
commercially available in various sizes starting as small as K2.8 (K40) and currently available in sizes as big as K25.2
(K360). Sprinklers come in various orientations, such as pendent, upright or sidewall, nominal temperature ratings,
commonly 160°F (70°C) but many other temperature ratings are available, and finishes, such as brass, chrome, paint and
paint for decorative purposes or a finish such as wax for corrosion resistance purposes. Even the area spacing of the
sprinklers has changed over time. Sprinklers historically were installed such that the area of coverage that each sprinkler had
to protect was roughly 100 ft2 (9.3 m2). The deflectors of some sprinklers have been designed to discharge water in such a
way that they can now protect as much as 196 ft2 (18.2 m2) for storage occupancies and up to as much as 400 ft2 (37.2 m2) for
non-storage type occupancies.
Over time the fire protection community has come to group sprinklers into three categories know today by the terms Control
Mode Density Area (CMDA), Control Mode Specific Application (CMSA) and Suppression Mode (formerly called ESFR)
sprinklers. The first two categories group sprinklers by an assumed performance during a fire event (i.e. control of a fire) with
their design format and the method by which they are approved and/or listed being the main differences between the two
categories. The third category also groups sprinklers by an assumed performance during a fire event (i.e. suppression of a
fire), which allows for a reduced number of sprinklers in the design format (typically 12 sprinklers) as well as a reduced hose
stream allowance (250 gpm [950 lpm]) and sprinkler system duration (1 hour).
Automatic sprinkler protection is the best line of defense against fire within an industrial facility; in fact FM Global statistics
show that an industrial facility equipped with automatic sprinkler protection can be expected to have roughly 17% of the
amount of monetary loss when compared to such a facility without automatic sprinkler protection7. However, since the
release of the first installation and design guidelines back in 1891, the requirements for automatic sprinklers have become
much more complex. Present day installation guidelines from FM Global, which are outlined in three data sheets, FM Global
Data Sheet 2-2, Installation Rules for Suppression Mode Automatic Sprinklers, Data Sheet 2-7, Installation Rules for
Sprinkler Systems Using Control Mode Specific Application (CMSA) Ceiling Sprinklers for Storage Applications, and Data
Sheet 2-8N, NFPA 13 Standard for the Installation of Sprinkler Systems, 1996 Edition, encompass a total of 344 pages
whereas the design guidelines for typical warehouse occupancies are covered in FM Global Data Sheet 8-9, Storage of Class
1, 2, 3, 4 and Plastic Commodities, which consists of 123 pages.
To help reduce the complexity of automatic sprinkler installation and design, FM Global is embarking on a new method of
classifying automatic sprinklers starting in April of 2010. Instead of categorizing sprinklers based on an assumed
performance during a fire event, FM Global will categorize sprinklers based on intended application. Based on the FM
Global Approvals website, sprinklers are currently categorized based on three main headings: (1) Control Mode sprinklers,
(2) Suppression Mode sprinklers and (3) Residential sprinklers. While the last category is based on an intended application,
the first two categorizes are based on an assumed performance. Starting in April of 2010, FM Global will categorize
sprinklers based on the following three headings: (1) Storage sprinklers, (2) Non-Storage sprinklers, and (3) Special
Protection sprinklers. The intended application of Storage sprinklers is for the protection of storage type occupancies as well
as other occupancies where high heat release rates can be expected. The intended application of Non-Storage sprinklers is for
the protection of non-storage occupancies, such as offices as well as manufacturing and other moderate heat release rate type
occupancies as defined by the occupancy-specific FM Global data sheets. The intended application of Special Protection
sprinklers is for the protection of occupancies not generally covered by the other two categories, such as residential areas, the
inside of cooling towers as well as the inside of combustible ductwork, to name a few.
References:
7.
FM Global, Understanding the Hazard, Lack of Automatic Sprinklers (February 2003) page 1
Page 4 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
Although this new method of classifying sprinklers may seem like a rather minor change in the overall scheme of fire
protection, it actually creates a new approach where the design of a sprinkler system can be based on the actually
performance of a sprinkler as opposed to an assumed performance or, in the case of the density/area design method, the
performance of the least efficient sprinkler.
Based on this new approach, FM Global will be taking the three data sheets that currently address the installation
requirements for automatic sprinklers, Data Sheets 2-2, 2-7 and 2-8N, and combine them into a single document entitled Data
Sheet 2-0, Installation Guidelines for Automatic Sprinklers. The installation guidance provided within this new document
will be formatted to address the specific requirements for Storage sprinklers, Non-Storage sprinklers or Special Protection
sprinklers coupled with the installation guidelines that are common to all three types of sprinklers. It will also provide
guidance to contractors as to what documentation FM Global needs in order to properly review a plan submittal as well as
guidance on conducting a sprinkler system acceptance test.
Also as a result of this new approach, the next version of FM Global Data Sheet 8-9, which is scheduled for release in April
of 2010, will reference the use of FM Approved Storage sprinklers at ceiling level and, when needed, as in-rack sprinklers. In
addition, the designs offer in Data Sheet 8-9 will be based on five attributes associated with a sprinkler which are in
alphabetical order:
1.
K-factor
2.
Orientation
3.
Response Time Index (RTI) Rating
4.
Sprinkler Spacing
5.
Temperature Rating
The sprinkler’s K-factor is dependent on the orifice diameter of the sprinkler and is based on the amount of flow that the
sprinkler can discharge at a given pressure. The orientation of a sprinkler is simply a relationship between the sprinkler pipe
and the location of the sprinkler’s deflector; although sidewall is an orientation used with light hazard type occupancies, only
pendent and upright orientation is addressed in Data Sheet 8-9. The Response Time Index (RTI) rating looks at how fast a
sprinkler’s thermal element will react once it has been exposed to its temperature rating; FM Global currently uses the ratings
of either quick-response or standard-response. The area spacing of sprinklers in most applications can range from as low as
64 ft2 (5.9 m2) to as high as 400 ft2 (37.2 m2) depending on the sprinkler chosen. Within Data Sheet 8-9 the area spacing of
“regular” sprinklers will range between 64 ft2 (5.9 m2) and 100 ft2 (9.3 m2) however “extended coverage” sprinklers, which
will be represented by an “EC” suffix after the indicated K-factor number, will range between 100 ft2 (9.3 m2) and 196 ft2
(18.2 m2). Lastly, the (nominal) temperature rating of a sprinkler within Data Sheet 8-9 will be linked to the type of sprinkler
system that the sprinkler will be installed on. If the sprinkler system is to be a wet system then the recommended nominal
temperature rating of the sprinkler in Data Sheet 8-9 will be 160°F (70°C); if the system will be dry then the nominal
temperature rating of the sprinkler will be 280°F (140°C).
Page 5 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
By going to the concept of a Storage sprinkler within Data Sheet 8-9, the design format for this sprinkler will now be
consistent throughout the document and based on an indicated minimum pressure at the sprinkler while simultaneously
flowing a given number of sprinklers. This means that the design format of density/area will be eliminated from Data Sheet
8-9 as well as other FM Global design-based storage protection data sheets in 2011. To many in the fire protection
community this may appear illogical as sprinkler systems that have been installed using the density/area design format have
performed very well since the design concept was introduced in the 1960’s when looking at lost history in general. However,
FM Global does consider the use of density as a design format to be limited benefit to fire protection designs due mainly to
the manner that current protection tables using density must base the design indicated in the tables off the performance of the
least effective sprinkler listed for the table. For example, if a protection table indicates that the design required for a given
storage arrangement and commodity hazard is a 0.45 gpm/ft2 density (18 mm/min) over a 2,500 ft2 (232 m2) area, then all
sprinklers that are listed as acceptable for this design must be able to meet it.
To prove this point based on actual full-scale fire test conditions conducted at FM Global’s Research Campus, consider the
open-frame rack storage of cartoned unexpanded plastics to 20 ft (6.1 m) high under a 30 ft (9.1 m) high ceiling with an 8 ft
(2.4 m) wide aisle provided between storage racks. Protection at ceiling level was based on a 0.80 gpm/ft2 (32 mm/min)
density from ceiling-level sprinklers. In one fire test the ceiling was equipped with K11.2 (K160) standard-response upright
160°F (70°C) nominally rated sprinklers on 10 x 10 ft (3.0 x 3.0 m) spacing. In the other test the ceiling was equipped with
K16.8 (K240) standard-response upright 160°F (70°C) nominally rated sprinklers on 10 x 10 ft (3.0 x 3.0 m) spacing. In both
tests all conditions were identical except for the K-factor of the sprinklers as well as the discharge pressure of each sprinkler
in order to maintain a 0.80 gpm/ft2 (32 mm/min) density. At the conclusion of the K16.8 (K240) sprinkler test a total of 15
sprinklers opened8, however at the conclusion of the K11.2 (K160) sprinkler test a total of 29sprinklers opened9, nearly twice
the number of the K16.8 (K240) sprinkler test even though both tests were at the same density. Using today’s density/area
design concept, the design for both sprinklers would be the same and would have to be based on the results of the K11.2
(K160) sprinkler, which had the poorer performance in this particular test.
The test comparison outlined above is representative of many of the tests that FM Global has conducted over the decades
when the comparison is based strictly on K-factor. In summary, sprinklers with larger nominal K-factor values provide better
performance than sprinklers with smaller nominal K-factor values when all other test conditions are maintained the same.
For the comparison of upright sprinklers and pendent sprinklers, consider a full-scale fire test series that was conducted at
FM Global’s Research Campus consisting of open-frame rack storage of cartoned expanded plastic commodities to 15 ft (4.6
m) high under a 30 ft (9.1 m) high ceiling with an 8 ft (2.4 m) wide aisle provided between storage racks. Protection at
ceiling level in one test was based on a K11.2 (K160) standard-response upright 160°F (70°C) nominally rated sprinkler
installed on 10 x 10 ft (3.0 x 3.0 m) spacing whereas in the other test the sprinklers at ceiling level were K11.2 (K160)
standard-response pendent 160°F (70°C) nominally rated sprinklers also installed on 10 x 10 ft (3.0 x 3.0 m) spacing. The
flow from the upright sprinklers was arranged to discharge at a 1.00 gpm/ft2 (40 mm/min) density whereas the flow from the
pendent sprinklers was arranged to discharge at a 0.60 gpm/ft2 (24 mm/min) density. Based on our current concept of density
one would expect the upright to well out perform the pendent since it was given 67% more water to apply to the fire, however
at the conclusion of the fire tests the test involving the pendent sprinklers opened a total of 10 sprinklers10 whereas the test
involving the upright sprinklers opened a total of 32 sprinklers11.
References:
8.
Full-scale fire test conducted at FM Global Research Campus on July 27, 2005
9.
Full-scale fire test conducted at FM Global Research Campus on April 20, 2007
10. Full-scale fire test conducted at FM Global Research Campus on February 27, 2009
11. Full-scale fire test conducted at FM Global Research Campus on December 19, 2008
Page 6 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
Full-scale fire testing at FM Global over the past 40 years has demonstrated that the amount of water that is discharged from
ceiling level sprinklers in terms of an applied density is not nearly as important as the amount of water that is actually
reaching the fire area, which can be thought of as an actual delivered density. What helps increase the actual delivered
density during a fire event can be found in the aforementioned attributes of a sprinkler, namely orientation, K-factor, RTI
rating, temperature rating and, in some degree, sprinkler spacing. As a result FM Global will be using these five attributes to
define the protection required for storage arrangements defined by Data Sheet 8-9 using the design format of an indicated
minimum pressure at the sprinkler while simultaneously flowing a given number of sprinklers. An example of one of the new
protection tables in Data Sheet 8-9 is shown below in Figure 1 and addresses the protection requirements of Class 1, 2 and 3
commodities maintained in either solid-piled, palletized, shelf or bin-box storage arrangements.
Figure 1. Example protection table from FM Global Data Sheet 8-9, Storage of Class 1, 2, 3, 4 and Plastic Commodities
Note that all of the protection options previously covered under the separate categories of CMDA sprinklers, CMSA
sprinklers and Suppression Mode sprinklers are now listed in a single table as opposed to three tables in previous versions of
Data Sheet 8-9.
By making the step to the new categorization of Storage sprinklers, FM Global has created a new method by which the hose
stream allowance and the duration of a sprinkler system is determined. FM Global is taking an approach that the hose stream
allowance and the required duration of a sprinkler system can be reduced as the efficiency of a sprinkler system increases,
which can be measured by the number of sprinklers that can be expected to open at ceiling level. Simply stated, as the
number of sprinklers in the ceiling design increases the hose stream and duration requirements will also increase. You will
note that some of the protection options shown in Figure 1 are highlighted with a green background. What these highlighted
options represent are options that require only a 250 gpm (950 lpm) hose stream allowance and a duration of only 1 hour, the
minimum value for each requirement.
With this new approach to categorizing sprinklers FM Global has created the platform by which future testing and research
can help build upon and improve the guidelines provided for both the installation and design of automatic sprinklers. Future
projects at FM Global will include exploring the possibility of using the five sprinkler attributes currently used for defining
design requirements for Storage sprinklers and applying them to the designs utilized for Non-Storage sprinklers. In addition,
FM Global will embark upon a project to evaluate in-rack sprinkler protection schemes that will determine how the
performance of ceiling and in-rack sprinklers can be improved while at the same time reducing the cost of such an
installation.
Page 7 of 8
The Evolution of Automatic Sprinkler Protection and the Introduction of the New FM Global Data Sheet 2-0 and the Revised
Version of FM Global Data Sheet 8-9
With these changes, coupled with anticipated future changes in both FM Global Data Sheets 2-0, 8-9 and other design-based
data sheets, FM Global is poised to provide the most effective installation and design protection options, which are aimed to
be simpler to understand, cheaper to install, but a more sustainable choice.
Page 8 of 8