Understanding the NFPA 13-2022 updates

An overview of the adopted changes of NFPA 13 offers insights into what changes are imminent

By Jarron Gass May 26, 2022
Courtesy: CDM Smith

 

Learning Objectives

According to NFPA, its first published document in 1896 was called the Rules and Regulations of the National Board of Fire Underwriters for Sprinkler Equipments, Automatic and Open Systems. Now known as NFPA 13: Standard for the Installation of Sprinkler Systems, this document has been continuously updated and revised over the past 125 years to help guide acceptable practices for the design and installation of fire sprinkler systems.

The latest edition of NFPA 13 is for the 2022 code cycle and had an effective date of issue by the NFPA Standards Council of Sept. 15, 2021. According to NFPA, the standards development process is an open, consensus-based process for each of the more than 300 codes and standards published. The typical revision cycle can take up to two years to complete and includes opportunities for input by both technical committee members, interested individuals or members of the general public. NFPA 13 is traditionally on a three-year revision cycle.

NFPA 13-2022 updates

It is imperative for users of the various codes and standards to understand the revisions, additions or deletions that have been incorporated in each revision cycle. Even if the current edition isn’t immediately adopted in one’s area, the adopted changes can provide insights into what changes are imminent, as well as provide valuable alternatives to present challenges.

The first modification within NFPA 13 is the modifications for design approaches, located in Chapter 19 of the Occupancy Hazard Fire Control Approach for Spray Sprinklers. NFPA has labeled this change to the traditional density/area curves used for design as a philosophical change. This change moves away from permitting the selection of a design density anywhere along the curve for new systems, to only allowing the use of two specified points. Table 19.2.3.1.1 from NFPA 13 describes the new specified design points listed for the traditional light ordinary and extra hazards.

Figure 1: Small diameter backflow preventer for residential fire sprinkler system was damaged due to freezing conditions in the mechanical space. Courtesy: CDM Smith

A vast majority of systems previously designed with standard criteria would use the smallest area along the curve with the higher density, with a minor number of systems designed to a larger area with lower density to take advantage of water supply conditions for a given site. The new criteria mandate the single point for systems, with the alternate point being directed to requirements for combustible concealed spaces. The traditional density/area curves are still maintained for the evaluation or modification of existing systems (see Figure 19.2.3.1 in NFPA 13).

Figure 2: Early suppression fast response pendent fire sprinkler shown in proximity to several potential obstructions. Building structural elements, other conduits and light fixtures all present potential obstructions to the discharge of ESFR sprinklers. Courtesy: CDM Smith

This fundamental shift in the application of design densities is a large departure from previous precedence. Development of the older curves had not been proven at all points along the curve. Support for the older curves was largely derived from those that could see the value of a sliding curve based on available water supplies.

At the time the older curves were created, however, there was not the abundance of sprinklers that are currently available. Today, sprinklers come in different k-factors orifice sizes, response types and spray pattern developments for more occupancy or area specific uses.

Another change that was made to the updated version was the addition of the following language, found in section 16.4.1.1.1:

“The weather temperature used to determine if an unheated portion of a system is subject to freezing and required to be protected in accordance with 16.4.1.1 shall be the lowest mean temperature for one day, obtained from an approved source.”

NFPA defines “approved” as being acceptable to the authority having jurisdiction. There is no additional guidance in the annex regarding this section.

This single sentence found in section 16.4.1.1.1 will likely now compel more areas of the country to apply this section of the standard with a greater focus. Firstly, it would be consequential to identify adequate sources that are likely to be approved by the authorities having jurisdiction. This process could be as simple as a Google search for relevant data.

Figure 3: Nitrogen generation as a means of replacing compressed air in dry systems can be beneficial for the life expectancy of dry sprinkler systems. Delayed corrosion of dry system piping helps reduce the ongoing expenses of maintaining these systems. Courtesy: CDM Smith

Alternatively, jurisdictions might require something more substantial such as data from the National Weather Service, Climate.gov or another reputable public source. The lack of specific direction on how to implement this change could lead to uneven implementation across different jurisdictions, with varying requirements for whether or not a dry or pre-action type system might be required or other alternative protection for vulnerable parts of a system. This could also trigger a greater need for evaluation, even for existing installations, to provide more significant alternatives for items that are subject to freezing temperatures.

Figure 4: Dry pipe valves are to be located in a heated enclosure to ensure that the water-filled portion of the system is not subjected to freezing conditions. Courtesy: CDM Smith

ESFR sprinkler system criteria

Early suppression fast response — known as ESFR — sprinkler system criteria and obstruction rules have been updated in Chapter 14 to further align with the testing and research that was done by the NFPA Fire Protection Research Foundation in its recent report on Obstructions and Early Suppression Fast Response Sprinklers.

The FPRF report focused on obstructions to ESFR sprinklers that were caused by primarily structural elements, such as bottom chords of bar joists. Testing was performed to analyze spray pattern development for varying K-factor ESFR sprinklers with various size obstructions to refine the existing criteria.

The result was to provide additional guidance in Section 14.2 of the standard that will allow for more flexibility in the installation of ESFR systems that maximize system hydraulics, minimize overage in flow characteristics. This will allow for more cost-effective designs that need less fire sprinkler heads and potentially smaller piping. Additional guidance was provided for obstructions as small as 1½ inches. Another guide was also added for obstructions up to 6 inches wide or less. This additional guidance will further assist designers on the front end of projects, as well as the installers during construction.

Figure 5: This image depicts typical sprinkler main piping with various branch line piping and upright fire sprinkler heads. Courtesy: CDM Smith

Using nitrogen in dry systems

Another update to highlight in the latest edition of NFPA 13 is the additional guidance and provisions for the use of nitrogen in dry systems. Chapter 8.2.6.9, in conjunction with Table 28.2.4.8.1 from the plans and calculations chapter, now allows for the Hazen-Williams C-factor to be increased to 120 for dry systems using nitrogen with the use of either black or galvanized steel piping.

The caveat for this increase in the C-factor is that the nitrogen must be from a listed and permanently installed nitrogen generator capable of providing 98% nitrogen concentration throughout a system at a minimum leakage rate of 1.5 pounds per square inch per hour, with a visual means of verifying the actual nitrogen concentration. As always, the nitrogen generator must be installed in accordance with the manufacturer’s listing requirements.

This increase in C-factor value will allow for systems to be designed with a more favorable friction loss, matching that of traditional wet systems using steel pipe. Depending on the size of a dry system that is being installed, the potential savings from smaller pipe diameters and smaller fittings will contribute to offsetting the additional cost of sizing and installing the nitrogen generation system. Nitrogen generators have shown through short-term and long-term testing to increase the usable life of a dry system well beyond that of systems using traditional compressed air.

Traditional compressed air injects a mix of moisture with the warm compressed air and fosters an environment that allows for corrosion. This addition to the standard provides a reasonable step forward in the nitrogen approach that is rapidly becoming more mainstream for the installation of dry pipe sprinkler systems.

Figure 6: A typical service entrance setup, in this case, depicting three separate risers with a backflow prevention device. On the wall, you can observe a spare head cabinet, including spare dry type sprinklers mounted to the wall along with a sprinkler system zone map. Courtesy: CDM Smith

Small temporarily occupied enclosures

One last change was the addition of language to address small temporarily occupied (permanently installed) enclosures. Found in Chapter 9.2.10, this section states that sprinklers shall not be required in small isolated temporarily occupied enclosures that do not extend to the ceiling and are less than 24 square feet. Annex language explains that these areas would be similar to a hearing testing booth, lactation room, phone booth or other pods that are not used for storage. They can contain miscellaneous furniture, wastebaskets or other nonstorage items.

The annex further clarifies that the word “isolated” is intended to mean that units should not be located adjacent to each other and should be physically separated. While this is not a massive change, it does help to facilitate the installation of these units and implies that lacking excessive combustible loading, these pods should be protected by the presumed existing overhead sprinkler system within the overall space. This effectively treats these small pods similar to a large piece of movable furniture (such as a conference table) and provides flexibility for these types of units to be relocated as needed to accommodate whatever occupancy they are present in.

Figure 7: This image depicts typical sprinkler branch line piping and upright fire sprinkler head. Courtesy: CDM Smith

Figure 8: Area/density curves for evaluating existing systems. Courtesy: CDM Smith

The future of sprinkler standards

This has touched on just a few of the changes that were made in the recent 2022 edition of NFPA 13. There are many other changes embedded in the current edition of the standard. Some changes might be more substantial than the ones listed here. Other changes may be more an aligning of language or definitions with other standards, with a minimal change to the actual intent.

While this edition was published in September 2021, the standard keeps moving on, getting ready for the next revision cycle. The standard keeps preparing to change and adapt for the next need, the next type of new technology or the next type of building or architectural feature that does not currently have a code-prescribed solution for protection.

This leaves the industry pondering what will be addressed in the next edition. It may be related to the emergence of electric vehicles that drive the need for new protection criteria in parking garages. Or it may be that high-piled storage facilities can be constructed taller, with storage higher than is currently available in the criteria. These answers will be ultimately revealed in three years, in the next edition.

 

CDM Smith is CFE Media content partner.


Jarron Gass
Author Bio: Jarron Gass is fire protection discipline leader at CDM Smith. He focuses on fire suppression and alarm design and analysis and water supply analysis.