top twelve list of some of the most significant changes in the FM Gl 2

[TravisMack]

Just an FYI on an email I received from NFSA this morning outlining some changes to the FM guidelines:

1. There is no maximum size of system. Instead, the “maximum area of coverage for a sprinkler system is limited only by the hydraulic requirements of the sprinkler system’s design for the occupancy being protected” (2-0:2.4.1.6).



2. All system piping must be arranged to drain back to the system’s 2-inch (50 mm) riser drain or auxiliary drain to a safe area. Even for wet pipe systems, piping must be pitched a minimum of ½ in. per 10 ft (4 mm/m) for all branchlines and ¼ in. per 10 ft (2 mm/m) for all other piping. (2-1:2.5.2.4)



3. Unless recommended in 2-0 or a relevant occupancy-related data sheet, no fluid is permitted in a sprinkler system other than water of specific antifreeze solutions addressed in Section 2.4.7 of the data sheet (2-0:2.4.1.9). While a 30% propylene glycol antifreeze solution is allowed for systems exposed to temperatures as low as 25oF (-4oC), data sheet 2-0 calls for the use of a dry pipe system where temperatures can go lower, or for a “refrigerated-area sprinkler system” where temperatures are consistently maintained below 20oF (-7oC). An exception allows the use of other antifreeze solutions for lower temperatures if specifically FM Approved for a temperature 10oF (6oC) below the lowest expected temperature and if the occupancy-specific data sheet allows the use of an antifreeze solution. A second exception allows the typical NFPA 13 antifreeze solutions where the lowest temperature can be below 25oF (-4oC), but only for protected areas not exceeding 2,000 ft2 (185 m2). (2-0:2.4.7.1)



4. In both 2-0 and 8-9 the terms “control mode density area (CMDA)”, “control mode specific application (CMSA)” and “suppression mode” have been eliminated when dealing with different types of sprinklers. There are now only references to “storage”, “nonstorage” and “special protection” sprinklers. This means that FM Global has essentially abandoned the concept of early suppression that led to the development of ESFR sprinklers twenty years ago.



5. System design requirements (number of sprinklers to be included in the design area and minimum densities, flows or pressures) are not contained at all in data sheet 2-0 but are found in occupancy-specific data sheets like 8-9 and 3-26.



6. Data sheet 8-9 been organized to separately deal with five categories of storage:

· Class 1, 2, and 3

· Class 4 and cartoned unexpanded plastics

· Cartoned expanded plastics

· Uncartoned unexpanded plastics

· Uncartoned expanded plastics



Tables for protection of uncartoned expanded plastics in solid pile/palletized/bin-box arrangements contains criteria for protection using only ceiling sprinklers with ceiling heights up to 40 ft (12 m). All protection tables disregard height of storage, and specify design criteria using sprinkler orifice size, minimum number of operating sprinklers and minimum operating pressure. A minimum 3 ft (0.9 m) clearance must be provided between the top of storage and the ceiling-level sprinkler deflectors. Criteria are more liberal for pendent than for upright storage sprinklers.



7. Where ceiling-only sprinklers are provided for rack storage, all transverse flue spaces must be at least 3 in. (75 mm) in net width and must be provided every 4.5 ft (1.4 m) when their net width is less than 6 in. (150 mm) or when vertical alignment of transverse flues cannot be maintained. For well-aligned transverse flues at least 6 in. (150 mm) in net width, spacing of 9 ft (2.7 m) is permitted. Where in-rack sprinklers are provided, transverse flues are not required in the storage tier directly above any level of in-rack sprinklers. Longitudinal flues are not required in are never required in double-row rack storage but, if provided, must be at least 3 in. (754 mm) in net width. (8-9:2.2.2)



8. Upright storage sprinklers are considered tolerant of objects up to 4 in. (100 mm) wide located directly beneath them at any vertical distance, including the pipe on which they are mounted. (2-0: 2.2.3.5.2) In general, obstruction criteria for storage sprinklers resemble that developed for ESFR sprinklers.



9. No area reduction credit is available for the use of high temperature sprinklers. All of the tables in data sheet 8-9 are based on the use of 160oF (70oC) sprinklers for wet systems and 280oF (140oC) sprinklers for dry systems.



10. Rules relative to ceiling slopes have break points at specific angles such as 10o rather than rise in run dimensions.



11. The traditional FM use of a factor of 1.4 times the square root of the design area for determining the length of branch lines is still found within data sheet 3-0 Hydraulics of Fire Protection Systems, but is only required where roof slope exceeds 5 degrees, with a 1.2 factor allowed for slopes equal to or less than 5 degrees. (3-0:2.1.2.2.3.1).



12. Nonstorage occupancies are divided into four hazard classifications:



· HC-1 – includes office, restaurant seating area, unused attics, etc.

· HC-2 – includes parking garages, schools, casinos, etc.

· HC-3 – includes plastics processing, interior loading docks, etc.

· HC-4 – heavily loaded nonstorage areas



Minimum sprinkler orifice sizes are based on the hazard classification and ceiling height. For example, K-5.6 (Km80) sprinklers can be used in HC-1 occupancies with ceiling heights up to 30 ft (9 m), but K-11.2 (Km160) sprinklers must be used if ceilings are 30-60 ft (9-18 m) in height, and K-25.2 (Km360) sprinklers for higher ceilings. (3-26:2.1)

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[spkreng]

Travis, there is a video explaining this on the FM Global website for viewing, also you can sign up for automatic updates from them.
tom

spkreng, CET

 

[NJ1]

Man this is good stuff.

 

[firepe]

Travis,

Honorable Mention:

The requirement to include additional ESFR heads (installed due to obstructions) in hydraulic calculations has gone away.

Fire Sprinklers Save Lives.
Can You Live Without Them?

 

[TravisMack]

Firepe:

Do you know where that is shown. I am working on a job right now where that information would be very beneficial. It would just save me some searching.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[desnov74]

In statement #1 when they refer to "hydraulic requirements", do they mean that they defer to the area limitation of NFPA or that they are all out the window and to be just calculated to make the hydraulics work? Seems to conflict with #9.

(ie. 52000 sqft on any floor served by a riser;or 100, 130 225 for xtra, ordinary, and light etc. etc.)

Seems scarry when the hydraulics can be made to "work" with a little massaging by many a masseuse turned sprinkler designers.

 

[TravisMack]

It is my understanding that FM is not requiring systems to be limited by 40k or 52k sq ft any longer. If the pressure is available for a system, you could do one system for 400k sq ft. It may be like velocity in that it is some what self limiting.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[NJ1]

I just have one question. I know these changes have being made by FM but have they being approved by the NFPA committee?
I am just asking since I would like those changes incorporated in the standard rather than other agencies. It only make sense unless you are designing a system to be evaluated by FM.

 

[desnov74]

NJ1~
I don't think NFPA has say so on FM. When they are both on a project's specs, I've gone with the more stringent. Recall(as you already know I'm sure) the code is a minimum.

 

[pipesnpumps]

NFPA 13, Section 1.5, Equivalency states it is up the AHJ to accept..

So a system designed for 400,000 sq ft can still meet NFPA 13 as long as the AHJ accepts the FM approach..

I'm not too familiar with NFPA, but offhand I'd guess it will take NFPA much longer to mull this over, maybe it will be in the 2013 revision cycle.. maybe not.

 

[Cidona]

Seems that the criteria in NFPA and FM is so different now, with the recently revised FM Datasheets, that if both are stated on a spec, then a phone call is needed explaining to the client's representive the differences and consquenses between the 2 and getting written clarification on the details of that conversation as a revision to the spec from the project EOR.
If a section of one is to be used in a given respect (e.g. elimination of restriction of system size other than per calculations (new FM)), but otherwise per NFPA, then I would get those specifics entered into the contract documentation.
The pitching of pipe in certain racks is pretty difficult (impractical). This pitching requirment also limits certain design options, e.g. In locations that are not subject to freezing conditions, it was common to install unistrut tight to the bottom of purlings with the branchline on top with pendent sprinklers. Certain situations where that will not be posible to do that anymore. (long branchlines where allowable section of purlin for anchor is limited). In general it prevents being able to 'find a layer (elevation), to run pipe perpendicular to service, especially when dealing with a retrofit.
The elimination of K115 sprinklers in storage occupancies can make a big difference to calcs and pipe sizes.
The biggest problem I have with the new FM Datasheet is the new requirments for obstruction to sprinkler discharge. Now in needing sprinklers under obstructions in excess of 2' instead of 4'. If the obstruction is 4' wide (storage), you need 2 rows of sprinklers, and if the obstruction doesn't have a flat, solid bottom then you're restricted to 4' spacing. Seems a bit extreme, and expensive. Not to mention while as a layout technician, my scope is merely to apply the Standards/specs, I would have concern with the concept of having all these additional sprinklers, and them not needing to be calculated. I mean it helps the calc for pipe sizes but if there ever was a fire in the area, quite a few of these are lightly to open and could have massive effect of the actual discharge flow and pressre versus the designed.
All storage sprinklers needing to comply with the new obstruction criteria which is more similar to ESFR criteria is a major change. For retrofits where other services are not being altered as part of the project scope can make meeting this new criteria next to imposible without adding twice as many sprinklers under the obstruction as as at the ceiling. (Which again, I have to imagine can't be a great idea when all these additional sprinklers are not calculated as part of the layout).