Automatic Sprinkler System Design for the Year 2000 and Beyond
The 1999 edition of the Standard for the Installation of Sprinkler Systems (NFPA 13) was released in mid-1999. The new version was acted on by the National Fire Protection Association during its Spring Meeting in Baltimore last May. The Standards Council issued the standard on July 22, 1999 and it became effective on August 13, 1999.
There have been more than 50 revisions and amendments to the standard since the Rules and Regulations of the National Board of Fire Underwriters for Sprinkler Equipments, Automatic and Open Systems was first adopted in 1896. Substantial changes have been made to the provisions for sprinkler system design in the past eight years, which include the latest four editions.
The 1991 edition incorporated a new format intended to make the standard more user-friendly and contained major changes for numerous terms, definitions and descriptions. The 1994 edition continued the effort to make it easier to utilize the standard and included expanded provisions regarding extended coverage sprinklers, protection in electrical equipment rooms and elevator shafts, and seismic protection. The 1996 edition contained a major reformatting of the chapter on sprinkler installation requirements, including positioning and spacing rules and area of coverage provisions for each type of sprinkler. New material regarding fast-response sprinkler technology was also added to the standard.
The 1999 edition of NFPA 13 has broadened its scope to address all sprinkler system applications. As a result, the number of pages in the new document doubled that of the previous edition. The standard now includes requirements for the installation of underground pipe, sprinkler system discharge criteria for general and rack storage of Class I, II, III, IV Commodities, along with plastics, rubber tires, baled cotton and roll paper. Information for special hazards from over 40 NFPA documents have either been incorporated into NFPA 13 using NFPA's extract policy or specifically referenced.
This article does not attempt to cover all of the revisions to the standard. This would be impossible in the allotted space considering the Report on Comments (ROC) and Report on Proposals (ROP) contain more than 500 pages of material regarding proposed changes to the automatic sprinkler system design and installation requirements. However, some of the specific revisions to NFPA 13 include:
- A new sprinkler identification marking system.
- A new designation system of sprinkler sizes using nominal K-factors.
- New criteria for the installation of steel pipe in underground applications.
- Revised provisions for obstruction rules for specific sprinkler types.
- Revised requirements for sprinkler locations in combustible concealed spaces.
- Revised provisions for protecting sprinkler piping against seismic events.
- New limitations on the sprinkler sizes for storage applications.
- New provisions to protect against microbiologically influenced corrosion.
Chapter 1: General InformationThe scope of NFPA 13 (Section 1-1) was revised to include the installation of private fire service mains, which used to be covered in NFPA 24. Aside from some minor revisions to general definitions, subsections were added for numerous definitions related to private water supply piping, general storage, rack storage, rubber tire storage, baled cotton and roll paper.
Chapter 2: Classification of Occupancies and CommoditiesThis is a new chapter in NFPA 13 and contains information regarding the classifications of occupancies that was previously located in the "Definitions" section of the 1996 edition. Aside from editorial changes, the committee has also added and revised some language to clarify their intent of certain provisions. For example, the Extra Hazard Classifications (Groups 1 and 2) have been clarified with respect to the amounts of flammable and combustible liquids that can be present.
New to the standard is the inclusion of Commodity Classifications from NFPA 231, NFPA 231C and NFPA 231F. Sections 2-2.1 through 2-2.5 include descriptions of Commodity Classes (Class I through IV), classifications of Plastics, Elastomers and Rubber (Groups A, B & C) and classifications of Roll Paper Storage (Lightweight, Mediumweight, Heavyweight & Tissue).
Chapter 3: System Components and HardwareAs more and more varieties of sprinklers are being manufactured, a new system was developed to minimize confusion for sprinkler identification. Section 3-2.2 requires all sprinklers manufactured on or after January 1, 2001, to be permanently marked with a one- or two-character manufacturer symbol, followed by up to four digits. The purpose of this is to identify a model of a sprinkler for each orifice size or shape, deflector characteristic and thermal sensitivity. The sprinkler manufacturers and listing laboratories have both agreed to this new identification system.
The Committee felt that the best way to move forward in the area of orifice size categories is through the use of nominal K-factors. To facilitate this, the table for Sprinkler Discharge Characteristics Identification (Table 3-2.3.1) was reformatted. Nominal K-factors now range from 1.4 to 28.0 gpm/psi1/2 to reflect new listings.
An exception was added to Section 3-3.5 regarding usage of other types of piping and tubing. The exception allows any piping or tubing that is listed for Light Hazard Occupancies to be installed in Ordinary Hazard accessory rooms of a Light Hazard Occupancy. These accessory rooms must be less than 400 sq. ft.
A new section on underground piping was added (Section 3-4). Most of the material was extracted from NFPA 24. A new table references 24 American Water Works Association (AWWA) piping manufacturing standards.
Chapter 4: System RequirementsThe requirements for the arrangement of supply piping and valves for antifreeze systems were modified. Two subsections of Section 4-5.3 address different scenarios, one with a backflow prevention device and one without.
It was determined that the control valve and small solution test valves are not necessary when a backflow preventer is provided. The five-foot drop was deleted from Figure 4-5.3.2, which now shows a more simplified arrangement. The section was also revised to require that pre-charged air pressure be provided. This was added to ensure that the expansion chamber is pre-charged with the appropriate amount of air pressure in order to be effective.
Chapter 5: Installation RequirementsSection 5-18.104.22.168 requires quick-response sprinklers to be used in all new Light Hazard occupancies, except when residential sprinklers are permitted by Section 5-4.5. When an existing system (in a Light Hazard occupancy) having standard response sprinklers is modified or when individual standard response sprinklers are replaced, standard response sprinklers can be used.
Section 5-4.6.4 contains a new provision for areas having ESFR sprinklers adjacent to standard response sprinklers. A 24-inch noncombustible draft curtain must be provided between the two areas. In addition, a minimum four-foot aisle centered below the draft curtain must be maintained to separate the areas.
Two exceptions were added to the combustible concealed space provisions (Section 5-13.1.1). In a sprinklered attic, sprinklers are not required in the space below insulation that is directly on top or within the ceiling joists. In addition, sprinkler protection is not required in pipe chases less than 10 sq. ft. that are formed by studs or wood joists, as long as the chases are firestopped at each floor.
Chapter 6: Hanging, Bracing and Restraint of System PipingIn the 1996 edition of NFPA 13, provisions for hangers and supports were found in two different areas. A subsection of the System Components and Hardware chapter contained requirements for the types of hangers that could be used and installation requirements were covered in a separate chapter.
The new chapter on hangers and supports consolidates the provisions and contains more than 12 pages of requirements. There were numerous revisions made, including provisions regarding seismic protection of sprinkler piping.
Chapter 7: Design ApproachesA requirement was added for buildings having two or more adjacent occupancies that are not separated by a barrier capable of delaying heat from a fire in one area from activating sprinklers in the adjacent area (Section 7-1.2). The sprinkler design criteria required for the more demanding occupancy must extend 15 feet beyond its perimeter. The section does not specify a minimum fire resistance rating for the barrier.
The table for Hose Stream Demand and Water Supply Duration Requirements for Hydraulically Calculated Systems (Table 7-22.214.171.124) was expanded to include the Commodity Classifications for general and rack storage applications.
Chapter 8: Plans and CalculationsThe information required to be shown on working drawings (Section 8-1.1.1) was expanded to include:
- Structural member information on full height cross sections.
- The nominal K-factor of sprinklers.
- Size and location of standpipe risers and monitor nozzles.
- Size and location of hydrants; the flow and pressure hydrants used in the flow test must be identified.
- Size, location and piping arrangement of the fire department connection.
A new subsection (Section 8-2.2) was added regarding water supply information. For areas with water supplies that have contributed to microbiologically influenced corrosion of sprinkler piping, the type of condition that requires treatment, type of treatment and details of the treatment plan must be indicated.
The calculation procedure was revised for situations where ESFR sprinklers are installed above and below obstructions (Section 8-4.4.4). Now up to two sprinklers from one of the levels must be included in the calculations, along with the sprinklers on the other level.
AppendicesTwo new appendices were added to the standard. As with previous editions, the material in any of the appendices is not considered part of the standard; it is provided for informational purposes only.
Appendix D identifies portions of the Life Safety Code (NFPA 101) that pertain to sprinkler system design and installation. A note indicates that the material is not intended to provide complete information regarding all aspects of fire protection addressed in the Life Safety Code.
Appendix E includes information regarding rack storage applications. The material covers results of actual fire test data and procedures that led to the development of sprinkler system discharge criteria.
A new useful feature is the 24 pages of cross-references to previous editions. It is found in the back of the standard and contains cross-references between the new sections of NFPA 13 and material from previous editions of NFPA 13, NFPA 24, NFPA 231, NFPA 231C, NFPA 231D, NFPA 231E and NFPA 231F. This index also indicates whether a section was extracted from another NFPA document, revised or not revised, deleted or new.