Column Sprinklers in Remote Area in NFPA 409?

6/7/2024

I would like to get your thoughts on the intent of NFPA 409 7.7.3.5 which states "Discharge devices for the protection of columns within the remote area of the overhead sprinkler systems shall be included in the calculations for the overhead system."

When determining the remote area, should it be assumed that the column protection sprinklers are activated?

In the specific case that I am referring to, if column sprinklers are not activated, the remote area of the overhead system does not fall around the columns being protected.

If the column sprinklers are activated, the remote area of the overhead system shifts to fall around the columns being protected.

My thought is that column protection sprinklers should be assumed to be activated when determining the remote area of the overhead system since a fire condition near the column has the potential to activate the column protection sprinklers and the remote area of the overhead system.

If the column protection sprinklers is not included in determination of remote area, this fire condition could cause the system demand to exceed the available supply.

What are your thoughts? Thanks!

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

7 Comments

Dan Wilder

6/7/2024 08:12:59 am

My approach has been to do the hydraulically most demanding area for the overhead, based on the overhead only. Any column sprinkler protection that falls inside that area then is added to the overhead area.

There is a GPM requirement for the wetted surface, but no requirement to keep the same sprinkler type for the columns (7.7.3.2) so change the column protection to not be driving factor.

If your demand calculation is that close to the water supply, does the system still work when a supply calc is performed to verify foam usage (if the system is foam)?

Glenn Berger

6/7/2024 08:53:52 am

Agree with Dan. I am assuming, in this case, that the column sprinklers are on the same system as the overhead and thus they are not activating by remote means.

Jesse

6/7/2024 09:15:07 am

Agree with Dan. I generally calc the most remote area and then add the column sprinklers if needed. I'm presuming this isn't a foam-deluge

Todd E Wyatt

6/7/2024 09:36:06 am

Per the scoping Code (e.g. IBC-2021), the fire-resistance rating (FRR) for the primary structural columns is to be provided by “individual encasement protection by protecting it on all sides for the full column height” or “provided by the membrane protection provided for the wall” or by “Sprayed Fire-Resistant Materials (SFRM).”

There are (3) methods for determining the fire-resistance rating (FRR) of building elements (including FRR for primary structure (e.g. columns)), components or assemblies:

1. 703.2.1 Tested Assemblies
2. 703.2.2 Analytical Methods
3. 703.2.3 Approved Alternate Method

Based on the 703.2, the “703.2.2 Analytical Methods” is to be used “WITHOUT the use of automatic sprinklers or any other fire suppression system being incorporated” so this option is out.

That leaves “703.2.1 Tested Assemblies” or “703.2.3 Approved Alternate Method”.

If the life safety engineer can provide a tested assembly that includes an automatic sprinkler system (ASPS) meeting the requirements of the required FRR assembly for the column, the AHJ may permit it.

However, many AHJs will NOT approve the substitution of a required passive FRR assembly (e.g. encasement, FRR membrane protection of a wall, or SFRM) with an “active system” such as an ASPS. ASPS are not always 100% effective and some AHJs may use the intent of “WITHOUT the use of automatic sprinklers or any other fire suppression system being incorporated” per “703.2.2 Analytical Methods” against the requirements of “703.2.1 Tested Assemblies.”

6/7/2024 09:36:48 am

REFERENCES
IBC-2021
Chapter 7 Fire and Smoke Protection Features

Section 703 Fire-Resistance Ratings and Fire Tests
703.2 Fire Resistance
The fire-resistance rating of building elements, components or assemblies shall be determined in accordance with Section 703.2.1 or 703.2.2 without the use of automatic sprinklers or any other fire suppression system being incorporated, or in accordance with Section 703.2.3.
703.2.1 Tested Assemblies
A fire-resistance rating of building elements, components or assemblies shall be determined by the test procedures set forth in ASTM E119 or UL 263. The fire-resistance rating of penetrations and fire-resistant joint systems shall be determined in accordance with Sections 714 and 715, respectively.
703.2.3 Approved Alternate Method
The fire resistance of building elements, components or assemblies not complying with Section 703.2.1 or 703.2.2 shall be permitted to be established by an alternative protection method in accordance with Section 104.11.

Section 704 Fire-Resistance Rating of Structural Members
704.1 Requirements
The fire-resistance ratings of structural members and assemblies shall comply with this section and the requirements for the type of construction as specified in Table 601. The fire-resistance ratings shall be not less than the ratings required for the fire-resistance-rated assemblies supported by the structural members.
Exception: Fire barriers, fire partitions, smoke barriers and horizontal assemblies as provided in Sections 707.5, 708.4, 709.4 and 711.2, respectively.

704.2 Column Protection
Where columns are required to have protection to achieve a fire-resistance rating, the entire column shall be provided individual encasement protection by protecting it on all sides for the full column height, including connections to other structural members, with materials having the required fire-resistance rating. Where the column extends through a ceiling, the encasement protection shall be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column.
Exception: Columns that meet the limitations of Section 704.4.1.

704.4 Protection of Secondary Structural Members
Secondary structural members that are required to have protection to achieve a fire-resistance rating shall be protected by individual encasement protection.
704.4.1 Light-Frame Construction
Studs, columns and boundary elements that are integral elements in walls of light-frame construction and are located entirely between the top and bottom plates or tracks shall be permitted to have required fire-resistance ratings provided by the membrane protection provided for the wall.

704.13 Sprayed Fire-Resistant Materials (SFRM)

Jack G

6/8/2024 10:59:41 am

I agree that all columns be encased with proper protection. Much better for protection.
If AHJ allows sprinkler protection of the columns ( included in FRR) then the flow should be included in the calculations.
Please see Myers’s Fire July of 2022.

DJT

6/17/2024 09:30:45 am

In my experience, if you are using sprinklers, your design area will include your most remote column sprinklers. The additional flow, fed from the collector main for instance, and pressure demand overcomes a more traditional design area located higher up a roof slope and in between the gridded mains. Your hazard area should dictate at least two columns are required to flow. A taller hangar would be more demanding than one for shorter aircraft on the basis that column protection is a function of column size and height.

Column Sprinklers in Remote Area in NFPA 409?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES