scope:

This standard encompasses the performance requirements for water mist systems for use as fire control and/or extinguishing systems designed and installed per NFPA 750. Examinations are limited to use in the occupancies described sections 1.2.3.1 through 1.2.3.9. Due to the current state of water mist system technology, a comprehensive absolute standard for the testing of water mist system components is not possible. Since each water mist system is unique in its operation and design, the component testing of the water mist system shall be performed on a case-by-case basis. The component testing section is intended to be used as a guideline for the manufacturer as to the scope of the test program that can be expected. While customization of the component testing is necessary, the fire test protocols are generic and required for all water mist systems. The manufacturer's design calculations, stated performance requirements, as well as component functionality and reliability will be verified.

Water mist systems are designed for the protection of specific applications and specific protected area volumes. Extrapolation beyond the volumes which were tested is not permitted except where explicitly noted. The scope of this standard encompasses the following occupancy protection applications:

Protection of combustion turbines in enclosures with volumes up to, and including, 2825 ft³ (80 m³). Combustion turbines included under the scope of this total flooding application shall be protected for a minimum of twice the longest time to extinguish the test fires, turbine rundown time including the time that the turbine surfaces are above the auto-ignition temperature of the lubricating fluid, the time to shut down process equipment, or 10 minutes, whichever is greater. For primary protection consideration; see Section 1.7, (Primary Protection).

Protection of combustion turbines in enclosures with volumes up to, and including, 9175 ft³ (260 m³). Combustion turbines included under the scope of this total flooding application shall be protected for a minimum of to twice the longest time to extinguish the test fires, turbine rundown time including the time that the turbine surfaces are above the auto-ignition temperature of the lubricating fluid, the time to shut down process equipment, or 10 minutes, whichever is greater. For primary protection consideration; see Section 1.7, (Primary Protection).

Protection of combustion turbines in enclosures with volumes exceeding 9175 ft³ (260 m³). Combustion turbines included under the scope of this total flooding application shall be protected for a minimum of twice the longest time to extinguish the test fires, the turbine rundown time including the time that the turbine surfaces are above the auto-ignition temperature of the lubricating fluid, the time to shut down process equipment, or 10 minutes, whichever is greater. For primary protection consideration; see Section 1.7, (Primary Protection).

Protection of wet benches and other similar processing equipment. This application includes tools which consist of ventilated and unventilated compartments, spin rinse dryers, alcohol vapor dryers, chemical and mechanical polishing tools, and step and repeat exposure systems. All hazards included under the scope of this local application shall be protected for a minimum of 10 minutes or double the time needed to extinguish the worst case fire scenario, whichever is greater.

Protection of local application occupancies. Water mist systems which successfully pass the fire scenarios described in Appendix E shall be limited to extinguishing the following types of fires:

A. Ignitable liquid pool fires where the liquid release can be confined to a diked area. The entire surface of the diked area shall be protected by the water mist system.

B. Ignitable liquid channel fires in channels not exceeding the water mist system manufacturer's maximum specified width and with no limit to channel length.

C. Partially obstructed ignitable liquid pool fires where the percentage of obstructed surface is limited to that tested.

D. Spray fires up to 6 MW fueled by ignitable liquids.

E. Spray and pool fire combinations where confined to a diked area.

F. Ignitable liquid residues (ink and paper dust) on printing presses.

Applicants who desire to protect special hazard equipment with ignitable liquids with volatilities less than or equal to those of Heptane will need to conduct the fire scenarios substituting as a fuel, Heptane for diesel where appropriate. All hazards shall be protected for a minimum of twice the longest time to extinguish the test fires, time to shut down process equipment, or 10 minutes, whichever is greater.

Protection of industrial oil cookers. Application of the water mist system is limited to the protection of the industrial oil cookers only, and does not include the protection of other equipment such as exhaust ducts, heaters, heat exchangers, and food processing areas, unless tested for these applications. Consideration of the application and use of nozzle protection caps to prevent or reduce the amount of nozzle contamination shall be given and the use of such caps shall be included in the fire test and nozzle performance test requirement programs. The required extinguishing agent quantity is double the time needed to extinguish the worst case fire scenario, time to shut down heating and process equipment, or 10 minutes, whichever is greater.

Industrial oil cookers are typically non-insulated conveyorized fryers, or occasional batch kettles, used in food processing plants for chicken, fish, potato products (e.g., fries/chips), doughnuts and many other food products. These cookers are extremely different in size, configuration, and construction from standard kitchen or restaurant oil cookers or fryers and require a different type of extinguishment system.

Industrial oil cookers normally have large cooking surfaces; from 50 ft² (4.6 m²) to several hundred square feet. They contain from a few hundred gallons up to approximately 5000 gallons (18900 L) of cooking oil. Industrial oil cookers (except for some batch kettles) typically have moveable covers, or hoods, that can be hydraulically operated.

The hood is generally in a closed position in a normal operation period; however, the hood can be open from time-to-time as part of a routine maintenance. There are also exhaust stacks connected on top of the hood.

The most severe fire incident involving industrial oil cookers is a fire caused by overheating the cooking oil until it reaches its auto-ignition temperature (AIT). Even though installing an interlocking system to prevent the oil from reaching its AIT is a normal practice in the industry, the AIT fire can, and does, happen due to a system malfunction or simple human error. Thus, all the performance tests proposed in this document require extinguishment of an AIT fire. The AIT fire is particularly challenging because of its rapid spread of flame over the oil surface and its difficulty in extinguishment as it requires flame extinction over the entire surface with simultaneous rapid cooling to prevent re-ignition.

Exhaust air fans shall be interlocked to automatically shut down upon fire detection or operation of the water mist system. Exhaust duct protection is required and shall be so stated in the manufacturer's design, installation, operation and maintenance manual. (Note: Water spray protection for the ducts would be needed if the duct system were required to operate when the water mist system operates. Automatic sprinkler protection is recognized as being an effective alternative to water spray.)

Commonly used cooking oils, their flash points, and AITs are listed in Table 1.2.3.6 as a reference only. Canola oil is considered a representative vegetable oil and shall be used as the testing medium in the Appendix F fire tests. Its nominal density is 7.8 lb/gal (0.93 kg/L) and nominal specific heat is 0.59 BTU/lb ≅°F (2.5 kJ/kg ≅°C).

Protection of continuous wood board presses. Application of the water mist system is limited to the protection of the continuous wood board press only, and does not include the protection of other equipment unless tested for other applications. All hazards included under the scope of this application shall be protected for a minimum of twice the longest time to extinguish the test fires or 30 minutes, whichever is greater.

Protection of ventilated bench-top chemical fume laboratory hoods or enclosures using ignitable liquids. A fire that initiates within a fume hood or enclosure can quickly spread, particularly where there is appreciable use of solvents and/or combustibles, and result in extensive damage to the laboratory and surrounding area. The installation of an integrated water mist system provides an enhanced fire protection strategy to the automatic sprinkler system that can maximize loss prevention and minimize business interruption. All hazards included under the scope of this application shall be protected for a minimum of 10 minutes.

Protection of data center processing equipment rooms/halls which include control rooms, process control rooms, diagnostic equipment, and critical systems and equipment associated with data centers. Forced ventilation is included in the evaluation to a maximum nominal upward velocity of 3.3 ft/s (1 m/s) through perforated floor openings and a maximum 4 ft/sec (1.2 m/s) horizontal airflow from server cabinets. Preaction systems are limited to single interlock configurations with a maximum 30 second water delivery time delay.

For above raised floor protection the water supply shall be capable of supplying 60 minutes of water to the hydraulically most remote nozzles. The design area of the water mist system shall be 6 nozzles or 1.5 times the number of operated nozzles during fire performance testing, whichever is greater. For below raised floor protection the water supply shall be capable of supplying 60 minutes of water to the hydraulically most remote nozzles. The design area of the water mist system shall be a minimum of 6 nozzles for an area of coverage design and a minimum of 4 nozzles for a local application design. For an installation including both above and below raised floor protection the design area of the water mist system shall be based on the most hydraulically demanding protection.

The systems are for the protection of data and power cables with maximum burning rates comparable to those used in the fire performance testing. The systems are not intended to protect data processing equipment with packaging awaiting installation. Packaged equipment is to be located in storage and staging areas separate from data processing equipment rooms (i.e., where fire involving the storage will not expose critical equipment). Where storage and staging areas are not available, limit in-process packaged equipment in data processing equipment rooms to a temporary basis with regular removal of the packaging during the installation.

The systems are tested and listed to provide primary protection of the occupancy. The systems have been proven to extinguish fire involving cables but are not intended to provide equipment protection.

Purpose

This standard states the examination and test requirements for water mist systems for use as fire control and/or extinguishing systems.