Standard for the installation of sprinkler systems
The National Fire Protection Association (NFPA) publishes the industry standard for automatic fire sprinkler systems. The standard is titled “NFPA 13 — Standard for the Installation of Sprinkler Systems,” and it is a standard maintained by the NFPA Committee on Automatic Sprinklers.
History of fire suppression systems
Legend has it that Leonardo da Vinci designed a fire suppression sprinkler system in the 15th century for a client’s kitchen. The design included a large conveyor oven for a large facility that hosted large banquet parties.
As the story goes, something went wrong during a banquet party. The conveyor oven was operating at capacity, and something that spilled over in the oven caught fire. The conveyor brought the fire out of the oven and into the kitchen, where a worker pulled a manual valve to dump water onto the fire. The fire suppression system worked better than intended. Yet, though it drowned the fire, it flooded the kitchen, ruined all the food and disrupted the banquet.
The first documented sprinkler system was installed in 1812 in the Theatre Royal, Drury Lane in London by architect, William Congreve. He produced a patent drawing dated 1812. The apparatus consisted of a cylindrical airtight reservoir with a volume of water equal to about approximately 25,100 gallons of water (95,000 litres). The system was fed by a 10-inch (250 mm) water main from the tank which branched to all parts of the theatre. A series of smaller pipes fed from the distribution pipe were pierced with a series of one-half inch (13 mm) holes which poured water into the building in the event of a fire. During each performance, someone was positioned in the theatre to be on fire watch, and they would have to be ready to manually open the valve to allow water into the perforated fire suppression piping.
In the United States from around 1852 to 1885, fire suppression systems mostly existed in factories and textile mills to protect the significant investment owners had made in the building and machinery. Most of these early fire suppression systems were accomplished by installing pipes with pre-drilled holes. When a fire was noticed, a fire watchman or employee would go to the main sprinkler valve and open the valve, flooding the entire building and theoretically extinguishing or controlling the fire.
Inventors first began experimenting with automatic fire sprinklers around 1860. The first automatic sprinkler system was patented by Philip W. Pratt of Abington, Massachusetts, in 1872. The earlier fire suppression systems were not automatic systems; a person would have to be physically in the building to witness the fire and then remember to manually open the valve to allow water into the perforated pipe system.
Henry S. Parmalee of New Haven, Connecticut owned a piano factory and was looking for ways to protect his a large building with lots of premium wood. At the time, insurance was not common, and if it was purchased the insurance company was not likely to offer a lower rate for a fire suppression system.
Mr. Parmalee was worried that if he had a fire in his factory, even with one of the open pipe fire sprinkler systems, the activation throughout all floors and areas of the building and subsequent water damage would destroy his factory and pianos. This worry caused many sleepless nights.
Parmalee looked for another way to control a fire in his piano factory that would extinguish a fire and not ruin the pianos and assets within the building. He thought to himself and decided to develop a sprinkler head that would react to heat from a fire, becoming the inventor of the first truly automatic sprinkler head. In 1874, Mr. Parmalee installed the new fire sprinkler system in his piano factory, and he was sure if there was a fire it would not totally destroy his business.
In 1881, Frederick Grinnell improved on Mr. Parmalee's sprinkler with a design close to the modern sprinkler, using metal strips to hold a plug in place, and a small amount of lead solder that would melt away in a fire. Mr. Grinnell went on to make many more improvements and new designs for fire sprinklers and system components.
History of updates to the NFPA Standard for Automatic Sprinklers, published in 1896
Over the years, there have been many significant fires and property losses. The resulting fire investigations have revealed things that have led to improvements in the various NFPA fire protection standards, including the NFPA 13 standard.
With the publication of the 1991 edition of the NFPA 13 standard, there was a significant rewrite and reorganization. They changed the overall format and made it more user-friendly. Substantial changes were made to numerous terms, definitions and descriptions, with additional refinements made in 1994.
The 100th anniversary edition in 1996 included a significant rework of the requirements pertaining to the application, placement, location, spacing and use of various types of sprinklers. Other changes in the 1996 edition included information on extended coverage sprinklers, and it recognized the benefits of fast-response sprinkler technology controlling a fire in its early stages before the fire generated lots of heat and smoke.
In 1999, NFPA established a technical correlating committee for automatic sprinkler systems and four sprinkler systems technical committees. They also consolidated many of the sprinkler system design and installation requirements, and they implemented numerous technical changes.
In 1999, the scope of NFPA 13 was expanded to address all sprinkler system applications. The 1999 edition contained information on the installation of underground pipe from “NFPA 24 Standard for the Installation of Private Fire Service Mains and Their Appurtenances,” and sprinkler system discharge criteria for on-floor and rack storage of Class I, II, III, IV, and plastic commodities, rubber tires, baled cotton, and roll paper.
Additionally, sprinkler system information for specialized hazards from many other NFPA documents was copied into or referenced in NFPA 13.
A new chapter was also added to address the structural aspects of exposed and buried system piping. A table of cross-references to previous editions and material that was located in other NFPA documents was included at the end of the 1999 edition.
Recently, I have investigated numerous fire main and water main failures, related to mechanical joint restraint fittings with set screws used in lieu of thrust blocks.
Apparently, some mechanical joint salesmen have been telling water utilities and contractors that you do not need to use thrust blocks or piping restraints with their mechanical joint restraints. These joints have published maximum pull-out forces based on a given pipe size, flow velocity and joint type.
I found it interesting that in most cases when you calculate a fire flow condition, the velocity and thrust force exceeds the pull-out force that the mechanical joint can resist by itself. Therefore, these joints will separate. Many buildings have been flooded or water mains separated, causing roadway washouts, physical injuries and other flood-related damage.
If you are not going to take the time to verify the thrust forces involved in your piping system, and consider the significant amount of water damage potential from a separated water main in a tunnel, basement or underground, you should consider including thrust blocks or thrust restraints in the piping system. Especially above ground piping systems. In one case the mechanical joint pull-out resistance force was around 75,000 pounds of thrust resistance force, but the water main had a thrust force approaching 120,000 pounds at a fire flow. You don’t want your water main to fail during testing or a fire.
More specific changes to the 1999 edition of the NFPA 13 document included a new sprinkler identification marking system and the designation of sprinkler sizes by nominal K-factor for flow coefficient factors.
1999 edition of the NFPA 13 included new criteria for the use of steel pipe in underground applications, as well as a new provision to guard against microbiologically influenced corrosion. In 1999, there were new obstruction rules for specific sprinkler types, and rules for locating sprinklers in concealed spaces were revised. New limitations were placed on the sprinkler sizes in storage applications, and criteria for the K-25 sprinkler was added. Additionally, the requirements for protecting sprinklers against seismic events also underwent significant revision.
The 2002 edition of NFPA 13 underwent the typical style formatting and technical revisions. The style formatting was completed to comply with the “Manual of Style for NFPA Technical Committee Documents” and to reorganize many of the requirements in NFPA 13 into unique chapters.
In reorganizing the 2002 edition of NFPA 13, several new chapters, including Chapter 10-13, were created to consolidate requirements.
The 2002 edition of NFPA 13 also made specific technical changes to address several key issues. Three major areas of irregular ceiling were addressed, including: skylights, stepped ceilings and ceiling pockets. The design requirements for early suppression, fast response (ESFR) sprinklers were expanded to allow the user to choose the storage height and then the building height for any allowable arrangement. Design requirements for the protection of storage on solid shelves were added. Requirements for the installation of residential sprinklers were added.
For the 2007 edition, of NFPA 13, definitions were reorganized to locate all of the storage definitions in one area, and several new definitions addressing private water supply terms were added. The definitions and requirements of Ordinary Hazard Group 1 and 2 Occupancies were clarified where storage is present. The requirements for trapeze hangers were clarified and made consistent for all components, and the seismic bracing criteria were updated to ensure that NFPA 13 contains all of the appropriate requirements for installation and design.
The requirements for storage were further reorganized and divided into separate chapters addressing general requirements for storage.
For the 2010 edition of NFPA 13, many of the major changes related to the requirements for storage protection. First is the combining of large drop sprinkler and the specific application control mode sprinkler requirements, and revising the terminology to now identify them as control mode specific application sprinklers (CMSA). Next, new criteria for use of smoke vents have been added to Chapter 12. The density/area curves in the storage chapters have been reduced to a maximum 3000 square feet operating area; this is a significant reduction of some curves that had extended up to 6000 square feet.
Changes to rack storage in this edition include a new method to calculate the rack shelf area. Finally, the provisions for back to back shelf storage have been added to the storage chapters.
Criteria for the protection of three new special storage arrangements have been added to Chapter 20. These include protection of carton records storage with catwalk access; compact shelving of commodities consisting of paper files, magazines, books, and similar documents in folders and miscellaneous supplies with no more than five percent plastics up to 8 feet high; and protection of high bay record storage.
In Chapter 9 of the 2010 NFPA 13, a number of changes occurred regarding sway bracing of sprinkler systems including the introduction of new zone of influence tables for Schedule 5 steel pipe, CPVC and Type “M” copper tube. Also, the means for calculating the loads in the zone of influence have been modified to correlate with the American Society of Civil Engineers and the structural Engineering Institute’s standard titled: “ASCE/SEI 7 - Minimum Design Loads for Buildings and Other Structures” and a new Annex “E” describes this calculation.
Other areas of change in 2010 included requirements for listed expansion chambers; clarification of ceiling pocket rules; and clarification of the formulas used in calculating large antifreeze systems.
In 2016, there were revisions to the commodity classification tables in NFPA 13. The changes to the commodity classification table upgrades were the most significant update to the tables since the 1988 edition.
Updated classification tables in NFPA 13 Chapter 5 Annex, based on today’s materials, help sprinkler system designers avoid common errors in classifying commodities. The new tables improve accuracy and reduce the risk for mistakes that could prove catastrophic in a fire.
Corrosion has become an increasing problem as thin-wall piping and microbiologically induced corrosion (MIC), combined with air trapped in systems, has led to a significant number of corrosion related leaks.
Recently, a task group addressed the costly problem of corrosion in piping. Changes related to this task group’s recommendations include a major change. The 2016 NFPA 13 adds a new requirement that a single air vent be installed at the top of each wet sprinkler system to help reduce potential corrosion activity due to trapped air.
The task group concluded that venting the trapped air in a wet system can decrease water delivery time, reduce alarm ring delay, reduce water flow alarm cyclic ringing and reduce corrosion activity.
I have witnessed and videotaped a water-flow alarm resetting itself with one sprinkler flow test valve open. The air that was trapped in the upper piping was compressing and recoiling, causing the flow switch to reset. Thus, never notifying the fire department or the local alarm panel of a water flow condition. This is because most flow switches have a delay built in to eliminate false alarms from city water pressure surges. Eliminating air in the top of the system is crucial for eliminating this problem.
There were many other changes in the 2016 edition of NFPA 13 that provide more design options for sprinkler designers. The changes include:
- More options for protecting exposed bay plastics in racks in Chapter 17, in response to the potential for serious fires.
- New language in Chapter 8 allows sprinklers to be omitted above certain cloud ceiling configurations based on research done by the Fire Protection Research Foundation.
- Listed window sprinklers are required to be used where glazing assemblies are used as an alternative to fire-resistance-rated construction.
- There are changes that address the use of concrete anchors in Chapter nine.
- An alternative storage protection scheme has been added for certain storage arrangements.
You can order a copy of the NFPA 13 2016 edition standard at the NFPA website.
Ron George, CPD, is president of Plumb-Tech Design & Consulting Services LLC. He can be reached at: office 734-322-0225; 755-1908; and at www.Plumb-TechLLC.com.