NFPA 13 in High-Rise Buildings

NFPA 13 in High-Rise Buildings

Designing and installing fire standpipes and sprinkler systems in modern high-rise buildings properly requires in-depth analysis to ensure occupant safety.

High-rise buildings present several unique challenges not found in traditional low-rise buildings; longer egress times and distance, evacuation strategies, fire department accessibility, smoke movement and fire control.

Nearly 3,700 years ago, the responsibility of the stability of a structure was first bestowed upon building inspectors. The inspectors made sure that building materials were properly cut and made from unflawed components. When the inspectors deemed a stone to be of sufficient quality, they were authorized to affix the king’s seal to the stone. If subsequently a building collapsed and a sealed stone was found to be at fault, the inspector was at fault. This king was, of course, Hammurabi, the inspectors were the progenitors of today’s testing laboratories, and the rationales they used to determine the stone’s quality were the original standards.

High-rise buildings have garnered significant attention in the fire safety world over the years. The multiple floors of a high-rise building create the cumulative effect of requiring great numbers of persons to travel great vertical distances on stairs in order to evacuate the building. The public, code bodies, local, regional and federal governments, as well as the design, build, and ownership communities are all affected by high-rise building safety.

The 42 is a residential skyscraper in Kolkata in the state of West Bengal, India. It is currently the tallest building in India. It is located in Chowringhee, the central business district of the city.

The primary design and installation standard used in most of the U.S. for commercial fire sprinkler systems is NFPA 13 2019: Standard for the Installation of Sprinkler Systems. To properly use this standard to design or install a system, one must be familiar with the standards upon which it is based and those which it references. It is within these auxiliary standards that lurk the minefields that can explode with devastating effect. For example, one of the commonly misunderstood provisions of NFPA 13 is Section 6.1.1., which many believe requires that all materials and devices be listed. It does not.

NFPA 13 recognizes there are eminently acceptable materials, such as pipe, fittings, and valves, manufactured to other long-respected standards promulgated by the American Society for Testing and Materials (ASTM), the American Society of Mechanical Engineers (ASME), and the Manufacturer’s Standardization Society (MSS) of the Valve and Fittings Industry that, when properly selected and applied, will result in perfectly satisfactory strength, durability, and performance. In fact, the materials manufactured to these standards typically have ranges much more appropriate to today’s taller structures than do those listed to the arbitrary and archaic limit of 175 psi found in NFPA 13.

It is therefore important that the engineer designing the fire standpipes and sprinkler systems in modern high-rise buildings properly analyze the needs of the systems, determine the pressures to which the systems will be subject, and, through judicious application of the principles of the ASME Boiler and Pressure Vessel Code provisions found in ASME B31.1 and B31.9, select the pipe, fittings, and valves most suitable for the installation.

An equally important factor in materials selection is the system’s life expectancy. It must be determined, through conversations with the owner, user, and regulatory agencies, what the expectations are for the service life of the systems and their components as well as the building life they are protecting. This, coupled with the engineer’s knowledge of the environment into which they will be placed, allows for selection of materials and corrosion mitigation strategies that will assure an adequate service life, as not all materials are created equal and not all materials used in proximity to each other are compatible.

Blind reliance on listed materials bearing a mark from Underwriters Laboratories (UL) or Factory Mutual Global (FM Global) does not come close to satisfying the standard of care to which an engineer is held, nor does it assure there will not be legal arguments at some future date as to the adequacy of the materials selected. A simple example is the standard commercial riser manifold produced by most of the manufacturers that bears both the FM Global and UL marks and a molded or engraved pressure limit identifier of 175 psi. Upon detailed examination, it can be determined that many of these devices are clearly acceptable for pressures well in excess of 175 psi. However, they are only listed to 175 psi because the UL and FM Global standards under which they are listed arbitrarily chose this number from an oft-repeated pressure in NFPA 13. And, in fact, it is not possible in modern high-rise buildings to limit the pressure of the principal piping systems to 175 psi. Even though recent times have seen the inclusion of products listed at pressures up to 300 psi, such listings do not cover the full catalogue of needs, nor is 300 psi a magic bullet number any more than is 175 psi.

There is simply no substitute for doing an appropriate engineering analysis of system needs and specifying materials and devices that will meet the demands of that analysis. Mere reliance on the obvious provisions within NPFA 13, the listing directories of UL and FM Global and manufacturer’s catalogues written to satisfy the requirements of those documents is not adequate.

In preparing specifications, the engineer must be careful to specify only that which he needs and intends to enforce. Clauses such as “Comply with all applicable federal, state, and local codes and standards” don’t cut it. First, few engineers know what constitutes “all” of those applicable federal, state, and local codes and standards as they each have internal references to and adoptions of yet more codes and standards. Second, even fewer engineers have “all” of those codes and standards on their shelves; most of those who do have them are not aware of what is in them. And what is in Code A is not always compatible with the requirement of Standard B, though both are applicable and the more stringent will apply.

For example, NPFA 13 requires that to fully equip a building, sprinklers must be installed in all places that a fire could occur. An elevator machine room is such a space. However, ASME A17.1 Rule 102.2: Safety Code for Elevators and Escalators requires that electrical power to the equipment be shut off prior to the application of water. There is no direct connection between the response time and temperature rating of a heat detector and that of a sprinkler. The response time index (RTI) of a sprinkler is determined by what is known as the plunge test; there is no similar or equivalent test for a heat detector. Therefore, there is no way to reasonably comply with Section 21.4.1 of NPFA 72: National Fire Alarm and Signaling Code, which requires a heat detector be provided to respond appropriately prior to sprinkler activation. Feasibility requires a much more complex solution, especially when the intent of the code is taken into consideration.

One method of accomplishing the intent of these seemingly incompatible codes and standards would be to install a double interlock pre-action system within the elevator machine room and to require that one of the events necessary for the double interlock to release be the completion of the timing sequence for elevator recall. As elevator manufacturers will not permit direct monitoring of elevator circuitry to determine the initiation and status of recall, one must rely on a predetermined time and initiate that timer based on either smoke or heat detection within the elevator machine room. In the event of an actual fire, the other portion of the double interlock, the fusing of the sprinkler and consequent reduction in air pressure within the air-supervised pre-action system, will assure the presence of water in a timely manner when the electrically held valve is opened by the timing sequence.

Consulting or specifying engineer has a statutory first duty to preserve the public safety and a fiduciary duty to his client, normally the owner, it is an abrogation of those duties for the engineer to delegate responsibility to the design/build contractor, who is only required to comply with the lawful mandate of the local inspection authorities and has a fiduciary duty only to its ownership, by means of that all-too-commonly used bailout, “Contractor to provide and install a system complying with all applicable codes and standards.”

Ref: NFPA.org

Our Follower firesafetypunjab ask below question.
As discussed, NFPA 13 is an installation standard and does not specify which buildings or structures require a sprinkler system. NFPA 13 specifies how to properly design and install a sprinkler system using the proper components and materials after it has been determined that a sprinkler system is required. The administrative authority for requiring sprinklers within buildings rests with any of the following: the local building code; NFPA 5000, Building Construction and Safety Code; NFPA 101, Life Safety Code; International Building Code; or insurance regulations that typically specify which buildings and structures require sprinkler systems.

If you are using the strategies of the NFPA 101, Life Safety Code for an existing building, section 31.3.5.12 has an application for high-rise buildings.

Excerpt from 2015 NFPA 101 Existing Apartment Occupancies

Here are the references for the standards for installation:

Its most interesting that the building code deals with new construction not existing occupancies. Therefore the AHJ that is dealing only with the building code will naturally require new construction for renovations.

I can not speculate what the local building codes and regulations are for automatic sprinkler system.

Thanks to Milt Werner for correction.