Foam-Water Sprinkler Systems
Foam-Water Sprinkler Systems
Foam-Water Sprinkler systems use foam to extinguish fires. NFPA 16 Standard for Installation of Foam-Water Sprinkler and Foam-Water Spray Systems is most commonly used for designing these systems. Foam-Sprinkler systems are used in control and extinguishment of fires by foam, wherein foam is preferred extinguishing agent.
Foam Sprinkler system typically consists of open type foam discharge devices “Foam-Water” Sprinklers, to have an effective distribution of foam in areas to be protected. The system is usually controlled by automatic deluge valve, which is actuated by one of the detection devices, also installed in the same area as Foam-Water sprinklers. As soon as there is detection of fire, The Foam-Water sprinkler immediately discharge foam for the complete area. These systems can also be used for discharging water for some initial period followed by foam discharge for longer period. For these applications, foam bladder tank proportioners are very commonly used for effective proportioning and supply of foam solution. In-line inductor may not be suitable because it is a fixed flow device and if in case few foam-sprinklers get clogged/blocked due to some reason, then effective foam induction will not take place at the inline inductor due to lower flow. Typically, the proportioning device, foam concentrate and foam sprinklers are UL Listed or FM Approved together with each other as a complete system. As per NFPA foam brands or types should not be mixed or interchanged in foam-sprinkler systems.
The quantities of foam concentrates required is based on Flow Rate and Duration of discharge, which is given in NFPA 16. The foam discharge density given in NFPA is minimum 6.5mm/sq.m (0.16 gpm/sq.ft). While foam sprinkler is recommended to cover maximum of 9.3 sq.m (100 sq. ft) area with spacing between two sprinklers not more than 3.7 m (12 ft). Foam sprinklers are always located at the roof (ceiling area). The Foam-Water Sprinklers are designed to operate at a minimum of 2.1 and a maximum of 4.2 Bar pressure. For example, HD Foam-Water Sprinkler with K-42 will deliver about 61 LPM foam at 2.1 Bar pressure. The foam solution shall be designed to be discharged for a period of minimum of 10 minutes over the entire area to be protected with the simultaneous operation of all foam sprinklers. While as per NFPA, water supplies for the system should be designed such that it is enough for at least 60 minutes.
Foam-Sprinkler systems are commonly used in places that are considered high hazard areas, such as chemical storage and handling areas, LNG manufacturing and storage areas, power plants, aircraft hangars, warehouses, elevator and machine rooms, generator rooms, etc.