November 1, 2023 posted in Design and Engineering, Planning
In modern food processing facilities, building codes and insurance companies require automatic sprinklers to protect the lives of the building’s occupants and the property assets.
Plant ambient and evaporator air discharge temperatures must be considered when determining the type of fire protection systems recommended. Typically, processing areas maintained above +40 degrees F can safely utilize conventional wet pipe systems without too much fear of nuisance freeze-up of the system. Areas with temperatures between +32 degrees F and +40°F may utilize dry pendant sprinkler heads fed by a wet pipe system, or more commonly, dry pipe sprinkler systems are used.
Spaces with temperatures below freezing (+32°F) pose special problems for automatic sprinkler systems. For these areas, most HPR (Highly Protected Risk) ensuring agencies require protection via “dry-pipe, double interlocked pre-action” systems. Electronic and pneumatic detection features are utilized to prevent the system pre-action valve from allowing water flow into the piping system, minimizing the possibility of ‘nuisance tripping.’ Should the piping system fill with water, it must be completely drained, dried out, and inspected before normal operations can resume.
The dry-pipe systems in areas below freezing (+32°F) require regular maintenance and inspection for ice plugs that may impair the sprinkler system when needed. To reduce the formation of ice plugs, clean, dry compressed air or nitrogen is required. Often, compressed air packages with desiccant dryers or nitrogen generators producing 95% or greater nitrogen concentration are specified. These systems have the secondary benefit of maintaining an atmosphere within the piping that reduces corrosion and thereby minimizes leaks.
Wet-pipe sprinkler systems most commonly utilize black steel piping; however, dry-pipe sprinkler systems traditionally require galvanized steel piping and fittings. Current ongoing research has shown that when nitrogen is used as the pressurizing gas for dry-pipe systems, in lieu of compressed air, the life cycle of both black and galvanized steel pipe systems is greatly increased. Preliminary results from this research indicate that galvanized steel sprinkler systems, utilizing 98% nitrogen concentration, could extend the life of the piping due to corrosion from 7 to 109 years!
The types of sprinkler heads used within food plants are also important for consideration. Glass must be eliminated in all areas where food products are produced and/or handled because glass cannot be detected if contamination occurs. Most sprinkler heads installed today use a frangible glass bulb as the heat-responsive element for sprinkler activation. Fortunately, sprinkler heads are available that use a metal alloy as the heat-responsive element instead of a glass bulb, which can be detected by the metal detectors commonly used in food production facilities. Realistically, these types of sprinkler heads should be used in all areas of food plants to eliminate any risk of glass making its way into the final product from the sprinkler system.
In addition to eliminating glass bulb sprinklers, there are temperature and material considerations due to production and/or sanitation operations. Sprinklers have a temperature rating at which they operate, with the typical rating being about 160°F. Sprinklers that serve rooms or spaces with ovens, fryers, or other heat-generating equipment will likely require 200°F or even 280°F rated heads to reduce the risk of accidental sprinkler activation. Often, sanitation efforts include hot water washdowns that include cleaning the ceilings. In this case, a minimum of 200°F sprinklers should be considered. Also, harsh chemicals may be used during sanitation that could be corrosive to typical brass or chrome-plated sprinklers, requiring the use of wax-coated, Teflon-coated, or stainless-steel sprinklers instead.
The large size of many new buildings and the increased height of storage racks pose additional challenges to fire suppression systems. Fortunately, developments in sprinkler technology and testing provide adequate protection for these more demanding configurations while reducing or eliminating the need for in-rack sprinklers. In-rack sprinklers are vulnerable to damage from normal warehouse activity, such as pallet handling. They also lack flexibility and portability when re-racking is required and should be avoided if other options exist. If in-rack sprinklers are required, they should always be provided with wire guards and installed to minimize conflicts with normal operations.
Most often, ESFR or “Early Suppression Fast Response” are considered for storage applications, as they were specifically developed to protect rack storage without the need for in-rack sprinklers. However, ESFR heads cannot be utilized with dry-pipe systems. If storage areas are maintained below +40°F, then either Control Mode Density Area (CMDA) or Control Mode Specific Application (CMSA) sprinkler heads must be utilized. There are CMSA sprinkler heads available that will protect some cold storage in buildings to 45 feet in height, with storage up to 40 feet high without the need for in-racks. Protection criteria allow 50 feet of storage with a 55-foot ceiling. However, this condition requires a specialized sprinkler system with very specific building construction requirements.
Employing CMSA and/or ESFR sprinklers necessitates access to a robust water source in terms of flow and pressure. Some installations may require a booster pump and/or a water storage tank due to the hydraulic demands of these sprinkler systems.
Conclusion. The design and implementation of fire protection systems in food and beverage manufacturing plants are crucial aspects that demand careful consideration. The evolving landscape of fire protection in food and beverage manufacturing plants underscores the importance of staying abreast of technological advancements and best practices to ensure the safety of occupants, protect property assets, and maintain the integrity of the manufacturing processes.