Factory Mutual data sheet 2-0 (the other 13?)

By Samuel S. Dannaway, PE,
President, S.S. Dannaway Associates, Inc., Honolulu

FM Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers, the current edition of which is dated April 2011, was first published in March 2010. This data sheet is dramatically different from the three Data Sheets it replaced, those being:

• Data Sheet 2-2, Installation Rules for Suppression Mode Automatic Sprinklers
• Data Sheet 2-7, Installation Rules for Sprinkler Systems Using Control Mode Ceiling Sprinklers for Storage Applications
• Data Sheet 2-8N, NFPA 13, Standard for the Installation of Sprinkler Systems 1996 Edition

Previously FM sprinkler system installation guidelines used NFPA 13 as a basis for sprinkler installation and modified or added requirements. DS 2-0, which was first issued in March 2010, only refers to NFPA 13 once as noted above. No other references are contained in the document, though NFPA 13 is referenced in companion data sheets.

So, is DS 2-0 a stand-alone sprinkler installation standard? Almost, but not quite. DS 2-0 refers to significant requirements contained in several other companion data sheets, two of the most significant ones are:

• Data Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems
• Data Sheet 3-10, Installation/Maintenance of Private Service Mains and Their Appurtenances

DS 2-0 does not provide occupancy hazard specific design requirements, but rather refers one to the appropriate occupancy-specific data sheets for this information. For those occupancies not covered by a specific data sheet one should refer to DS 3-26 Fire Protection Water Demand for Nonstorage Sprinklered Properties. This document classifies occupancies into three Hazard Categories, HC-1, HC-2 and HC-3, which are roughly equivalent to NFPA 13 occupancies hazard classifications light, ordinary and extra hazard, respectively.

There are several things I find interesting in DS 2-0. The requirements are presented in a straightforward manner and the intent of requirements is provided in many cases. In that sense it is a performance based document. In Section 3.0 Support for Recommendations the goals of this document are clearly stated:

The recommendations in this data sheet are aimed at ensuring the following:

(1) Sprinklers will operate in a timely fashion.
(2) Sprinklers will have an unobstructed water discharge pattern.
(3) Sprinkler system components will function in a reliable manner.

The requirements (or more correctly recommendations) for sprinklers in DS 2-0 are based on one of the three basic sprinkler types recognized by FM, nonstorage sprinklers, storage sprinklers, and special sprinklers.

Now just as we were getting comfortable with the various storage sprinklers FM had provided approvals for, “Control Mode Density Area (CMDA) sprinkler,” “Control Mode Specific Application (CMSA) sprinkler,” and “Suppression Mode (ESFR) sprinkler,” they went on in March of 2010 and eliminated all of these terms, replacing them with the single term of “Storage Sprinkler.”

Special Sprinklers are those sprinklers used in “non-room” applications such as combustible concealed spaces, within ducts, cooling towers, transformers, and exposure protection.

For nonstorage occupancies sprinkler linear spacing and coverage area per sprinkler are a function of the hazard classification (HC-1, 2 or 3), ceiling height, ceiling type, k-factor, sprinkler orientation, and sprinkler response.
For storage occupancies the storage sprinkler spacing and areas for unobstructed ceilings is a function of ceiling height, ceiling type, k-factor, sprinkler orientation, and sprinkler response. There are special provisions for obstructed ceiling construction.

DS 2-0 addresses obstructions to sprinkler discharge with separate requirements for storage and nonstorage sprinklers for 1) avoiding disruption of the development of the sprinkler umbrella spray pattern and 2) avoiding obstruction to the inner core discharge area.

Requirements to avoid disruption of the spray patter are intended to insure that nothing interferes with development of the umbrella spray pattern to a distance of 36 inches below the sprinkler. Requirements to avoid obstruction to the inner core of the sprinkler discharge pattern are intended to deal with large obstructions below and near the sprinkler. There are also obstruction rules for storage sprinklers used in racks.

The approach to categorizing obstruction rules is similar to that of NFPA 13, but the figures and tables in DS 2-0 are far more user friendly, especially the diagrams showing the umbrella patterns.

A few of the notable differences between DS 2-0 and NFPA 13 are as follows

• Ceiling Construction. The definitions of obstructed and unobstructed ceilings are different. In DS 2-0 obstructed ceilings are simply those that do not meet the definition of an unobstructed ceiling.

• Clearance Below Sprinklers. DS 2-0 requires a minimum clearance below sprinklers of 36 inches for both storage and nonstorage applications. In NFPA 13 the general minimum requirement is 18 inches with several conditions requiring at least 36 inches.

• Though not contained in DS 2-0, sprinkler design densities and design areas tend to be greater than those required by NFPA 13.

• Ceiling Slope. Chapter 12 of NFPA 13 indicates that storage design criteria is limited to facilities with ceiling slopes that are 2 in 12 or less. For other than storage applications there are no general limitations on slopes though there are several limits on application for slopes exceeding 2 in 12 for specific sprinklers. In DS 2-0 for nonstorage sprinklers there are limitations on ceiling slope with several exceptions allowing slopes to exceed 4 in 12. For storage sprinklers ceiling slopes are limited to 2 in 12 except that is one uses standard response sprinklers in conjunction with in rack sprinklers a maximum 4 in 12 slope is permitted. The document also notes that occupancy specific data sheets may permit varying slope conditions also.

The limitations in both NFPA 13 and DS 2-0 on ceiling slopes is an issue that needs more research as the slope limitations are driving building design. DS 2-0 comes right out and recommends a flat ceiling be installed to solve the problem (The architects will just love that).

Now the most interesting difference between 13 and DS 2-0 (to me anyway) is that in the most recent edition of DS 2-0 the maximum area of coverage for a sprinkler system is no longer limited by a firm floor area. The area covered by a single sprinkler system is limited only by the hydraulic requirements of the system and/or the maximum time permitted for activation of water flow alarm when a sprinkler activates (which is 60 seconds). Again, this is a performance based approach. Now, one can argue that this increases risk because a closure of a single valve will shut off protection to a very large area. I believe the approach that FM uses here is one of providing proper valve supervision combined with a philosophy of “the fewer control valves the better” the chances that protection will remain in place. It is noted that NFPA 13 has a requirement for an audible alarm be sounded with 5 minutes of start of sprinkler flow.

So is FM Data Sheet 2-0 better than NFPA 13? In my opinion, it depends. I would use an analogy comparing private secondary schools to public secondary schools. DS 2-0 would be the private school and NFPA 13 would be public school. FM can take this relatively simplified and direct approach to sprinkler installation because of the controls they have in place for “FM Approved” systems. Namely that one must use FM approved components, comply with the installation quality control requirements, acceptance testing provisions, and operations and maintenance requirements. In other words FM to a certain extent and depending on the market, FM can pick whom they protect, similar to a private school attracting the better students, while NFPA 13, like a public school, has to serve the needs of the entire range of students.

SFPE Note: Organized in 1950, the Society of Fire Protection Engineers (SFPE) is the professional organization that represents engineers engaged in fire protection worldwide. Through its membership of more than 5,000 professionals and 65 international chapters, SFPE advances the science and practice of fire protection engineering while maintaining a high ethical standard. SFPE and its members serve to make the world a safer place by reducing the burden of unwanted fire through the application of science and technology. Thinking about membership? Visit www.sfpe.org.

 

Samuel S. Dannaway, PE, is a registered fire protection engineer and mechanical engineer with bachelor’s and master’s degrees from the University of Maryland Department of Fire Protection Engineering. He is past president and a Fellow of the Society of Fire Protection Engineers. He is president of S. S. Dannaway Associates Inc., a 15-person fire protection engineering firm with offices in Honolulu and Guam. He can be reached via email at SDannaway@ssdafire.com.