Using of NFPA Chapter 24 Alternative Sprinkler (25.2EC) 1

[Sittipon99]

Hi i'm designing Extended Coverage sprinkler for warehouse that stored palletized of exposed non-expanded plastic.
Ceiling Height 7.0 m.
Storage Height 3.6 m.
Per NFPA 13 Chapter 24 i did't see using of K25.2EC criteria for exposed non-expanded plastic but FM Data Sheet 8-9 Table 5. said i can use K25.2EC for UUP.
i just curious , Can i use K25.2EC for exposed non-expanded plastic?
Thank you for helping me.

 

[SprinklerDesigner2]

In my opinion yes, you can use the K25.2EC which would fall under the equivalency clause of NFPA #13.

From the 2019 edition of NFPA #13:

1.5 Equivalency.

Nothing in this standard is intended to prevent the use of systems, methods, or devices of equivalent or superior quality, strength, fire resistance, effectiveness, durability, and safety over those prescribed by this standard.

Next we find the Commentary

Section 1.5 provides the user with an option to submit documentation that the proposed alternative or equivalent method of protection meets the equivalent method of design. There are no blueprints on how
to submit an equivalency statement; however, it is generally best to start with solid data. Knowledge of the history of current protection criteria is always a plus in making the case for equivalency. The following are some of the documents (not all are required) to submit when making a case for equivalency:
1. A statement of why (if known) the proposed method is not currently in the standard
2. Test data and a report, preferably from a recognized laboratory (Factory Mutual is a recognized laboratory)
3. Historical data on limitations of or assumptions regarding existing criteria in the standard
4. A report on why the proposal provides equivalent or superior protection to that prescribed in the current standard
5. Special listings or approvals from recognized laboratories (The K25.2 EC is listed by FM Global)
6. Data or supporting documentation from a manufacturer
The authority having jurisdiction has the right of approval for all equivalent methods. It is advisable for authorities having jurisdiction to reach out to industry experts for opinions and support on equivalency proposals outside their level of expertise.
1.5.1 Technical documentation shall be submitted to the authority having jurisdiction to demonstrate equivalency

Thing you need to recognize is you can go to FM Global and if you do then you follow EVERYTHING in the data sheets and not jump back and forth to whatever is most convenient or cost saving.

That all said be careful because some AHJ's don't understand the equivalency clause.

 

[SprinklerDesigner2]

IMO one of the most stupid rules in NFPA 13 is the maximum size of the system.

52,000 sq ft for light and OH but 40,000 sq ft for EH and storage.

Why, where did these magic numbers of 52,000 and 40,000 sq ft come from? Did it come from testing and why are we still required to follow it?

Well, to find the answer go back in time well before you were born. About 100 years ago systems weren't limited by size but by number of heads.

The magical number of heads on any system was 400.

Everything was pipe schedule and the maximum spacing for OH was 130 sq ft so 400x130=52,000 sq ft. For extra hazard it was 100 sq ft so 400x100=40,000 sq ft.

That's it, no studies or tests it was numbers of 100 years ago pulled right out of thin air. There's really no reason behind this other than the rules of 100 years ago.

Why not limit the system to 100,000 sq ft?

The argument is if you had a system down if it only covers 50,000 sq ft instead of 100,000 sq ft then you would have two systems with a 50% chance that in the event of a fire the system covering the area would discharge. Sound good but....

FM Global did a world wide survey and not once did they ever run into a situation where a building was saved because there were two smaller systems but one down while the other was on. Never happened. The industry has spent BILLIONS of dollars over the years for something that never happened. Brilliant!

 

[TravisMack]

SD2,

I believe you will find in addition to what you state,

FM Global did a world wide survey and not once did they ever run into a situation where a building was saved because there were two smaller systems but one down while the other was on. Never happened.

they also found that one of the most common reasons for system failures was a closed control valve.

I believe this is why FM has removed the system area size limitations. It is rather a self limiting item such as velocity. If the systems get too big, the friction losses start becoming an issue. You are going to make 4 "smaller" systems of say 4" mains and 2" lines than 1 massive system with 4" lines and 8" mains.

Travis Mack, SET, RME-G,
MEPCad, Inc
AutoSPRINK | AutoSPRINK FAB | AutoSPRINK RVT

 

[SprinklerDesigner2]

Travis,

From what I had heard in some CEU classes I have attended the NFPA 13 committee has attempted to bring forth a change is system sizes but every time it has been brought up the biggest fighters against it are our manufacturers.

Why sell one alarm valve when you can sell three?

Today, in Georgia and Florida, all control valves must be monitored by a central station alarm company so chances of an accidental valve closure are more remote.

 

[Sittipon99]

Thank you for your helping SprinklerDesigner2.

IMO for the area limitation in FM Stardard it depending on time. (60 sec alarm after trip inspector's test connection) is that right?