Sprinkler Protection of Storage Facilities Goes Green
Fire sprinkler systems have been “green” throughout their long existence. They use less water for fire suppression and control than the manual methods used by the responding fire department. They save the structure and the commodities, which equates to less materials and energy usage required for rebuilding and replacement of products.
With the worldwide concern over diminishing water supplies for domestic and industry usage, the fire protection industry is now looking at new technology to further reduce the designed water demand for sprinkler systems and the amount of water that needs to be stored when municipal water services cannot provide sufficient water flow.
With a new generation of storage sprinklers and the applicable use of early suppression fast-response (ESFR) sprinklers, we are able to use less water, fewer sprinklers, and lower pressures for protection of storage warehouses.
Previous Storage SprinklersIn the past we have designed storage systems using two basic sprinkler categories: control mode density area (CMDA) and early suppression fast-response (ESFR).
Control Mode Density Area Sprinklers. The various building heights, types of building construction, commodity types and heights, storage configurations, and less restrictive obstruction requirements allow these sprinklers to be used for virtually all storage applications.
The penalties for using CMDA sprinklers come with the addition of in-rack sprinklers when the height of the existing storage exceeds: approved limits, hose stream demands of 500 gpm, water supply duration of up to two hours, and increased system demand versus ESFR or CMSA sprinklers.
Extended Coverage, Control Mode Density Area Sprinklers (EC CMDA). There are also now three extended coverage spray sprinklers (two pendents and an upright) that may be used for control mode density area storage applications. The K factors are 16.8 and 25.2 for these sprinklers.
They may be installed with protection areas up to 196 square feet per sprinkler. The K-25.2 EC sprinklers are also approved for use under a category called Special Designs of Storage Protection. This allows their use in certain retail stores with special shelf and rack configurations.
Even though these are extended coverage, control mode sprinklers, their application and installation are limited only by those limitations imposed by NFPA 13 and FM Global on control mode sprinklers.
Using extended coverage CMDA sprinklers may not reduce the total water demand but they will reduce the amount of piping, fittings, and hangers required for installation - and this makes them greener than standard coverage sprinklers.
Early Suppression Fast-Response Sprinklers. Developed by the Factory Mutual Group to protect higher rack storage without in-rack sprinkler protection, the ESFR is the only suppression sprinkler. Because higher challenge fires can be suppressed without the use of in-rack sprinklers, building owners were able to be more flexible in their rack arrangements and eliminate the risk of mechanical damage inherit to in-rack sprinkler piping and sprinklers.
The ESFR has had the green advantage in the past with a hose stream demand of 250 gpm versus 500 gpm for most control applications. The duration of the water supply was also one hour, while control sprinklers required 1.5 to 2 hours.
Current SprinklersControl Mode Specific Application Sprinklers. With a large variety of K factors to choose from, CMSA sprinklers have been developed to accomplish the main benefit of the ESFR: eliminate the use of in-rack sprinklers in high challenge storage applications. The difference is control versus suppression.
These spray sprinklers are listed at a minimum operating pressure and with a fixed number of calculated flowing sprinklers for a defined storage scheme and/or a type of commodity. There is no interpretation of curves or charts to decide on the density or design area. Limitations of building height, storage height, commodity type, storage arrangement, sprinkler temperature rating, sprinkler spacing, etc., are all specified in the listing or approval of the product. Fire testing is conducted for the exact approvals desired.
Current approvals for CMSA sprinklers include: Class I-IV, cartoned unexpanded plastics in solid piles, palletized, shelf or bin box, open frame racks, and solid shelves with certain limitations.
The manufacturer’s engineering data sheets must be followed exactly for commodity approval, restrictions of maximum and minimum spacing, clearance to commodity, obstruction requirements, hose stream allowances, water supply duration, deflector distance to ceiling, sprinkler temperature requirements, and any other design and installation criteria.
NFPA 13 for 2007 refers to these sprinklers as Specific Application Control Mode Sprinklers. For the 2010 edition of NFPA 13, the terminology will change to Control Mode Specific Application, and new tables referencing CMSA design criteria will be added. The industry is already using the term Control Mode Specific Application.
Standard Coverage CMSA Sprinklers. The manufacturer’s engineering data must be used, and not all CMSA sprinklers have the same height and commodity approvals.
As of this writing, there are three standard coverage (100 square feet) CMSA sprinklers approved for storage applications: Tyco’s upright Ultra K17 (K-16.8), Viking’s pendent VK592 (K-19.6), and Victaulic’s pendent LP-46 (K-25.2).
Extended Coverage CMSA Sprinklers. NFPA 13 and Factory Mutual Global allow the installation of storage sprinklers that have been tested and approved for up to a maximum coverage area of 196 square feet or 14-ft. x 14-ft. spacing. These sprinklers must provide the same level of protection of a standard coverage CMSA sprinkler, while providing for a reduction in the total number of sprinklers installed in a system.
Reliable’s N252 EC CMSA (K-25.2) pendent sprinkler is FM approved for coverage areas up to 196 square feet or 14-ft. x 14-ft. spacing for building heights up to 30 feet in height with storage up to 25 feet. They are also approved for coverage areas up to 144 square feet or 12-ft. x 12-ft. spacing for building heights up to 35 feet in height with storage up to 30 feet.
The total system water demand is also lower than the ESFR and standard coverage CMSA sprinklers for buildings of 30 feet and 35 feet in height with Class I-IV and cartoned plastic storage. This is the “green” sprinkler for these storage applications, because fewer sprinklers mean less pipe, fittings, hangers, fabrication expense, shipping expense, field labor and design time. All of this adds to the “green” benefit.
Which Sprinklers Provide the Lowest Water Demand for Storage Protection?All flows referenced in Tables 1-4 (see link to pdf below) are for comparison only. The actual flows will typically be higher based upon friction loss in the piping.
The tables are for Class I-IV and cartoned unexpanded plastics in solid-piled, palletized, shelf, or bin-box and single, double, or multiple-row open shelf rack storage without in-rack sprinklers.
Other Considerations for ESFR or CMSA InstallationSmoke and heat vents may be required when using control mode sprinklers for high piled storage protection. FM Global does not desire or require their use. Fire testing for storage applications are not conducted using any type of ceiling openings.
Draft curtains are required for use with ESFR systems to separate the storage protection areas from control mode sprinkler systems that are used to protect manufacturing or other non-ESFR areas. CMSA sprinklers are by definition control mode sprinklers and draft curtains should not be required.
The Industry and New Storage Sprinkler TechnologyBeginning in early 2010, FM Global will have a category called Storage Sprinklers. As the name implies, this will consolidate all storage sprinklers (CMDA, ESFR, and CMSA sprinklers) into a single document. In addition, FM Global will also be changing to a set pressure and number of sprinklers to be calculated based upon protection requirements and the storage sprinkler to be installed. Fire testing has provided them with data on existing control mode sprinklers of K-11.2 and larger. This eliminates the potential for incorrect interpolation of all the various design factors.
These factors should move the industry to develop storage sprinklers that are specific to the hazards to be protected, help to eliminate the potential for inaccurate interpretation of the standards, and lessen the improper installation of fire sprinklers.
For NFPA 13 - 2010, some of the CMSA sprinklers will be included in new tables for storage applications. To use any CMSA sprinkler that receives UL or FM Global approval under NFPA requirements, the following paragraphs in NFPA 13, 2007 apply: 188.8.131.52.2, Definition of a Specific Application Control Mode Sprinkler; 1.6.1 and 1.6.2: New Technology; and 8.4.9 Specific Application Control Mode Sprinklers.
Paragraph 8.4.9 is the most important. Specific application control mode sprinklers (now CMSA sprinklers) must be installed in strict accordance with their listing. You must use the manufacturer’s engineering data, as it supersedes any NFPA requirement.
Sprinkler manufacturers will continue to develop new CMSA sprinklers that may protect storage applications with fewer sprinklers, less water demand, and lower pressures. Applications such as sloped ceiling approvals and improvements for dry and preaction systems will all be researched. However, nothing will eliminate the need to provide reliable sprinkler protection for storage applications: Sprinklers that have been thoroughly tested and approved for the actual storage situation.