system. There are three types of 4.4 FOAM SYSTEMS systems :- 4.4.1 Types of Foam i) Fixed ii) Semi-Fixed Foams are classified by producing iii) action of generation and expansion. Foam concentrate to be used shall (i) Foam System conform to IS:4989 2006/UL-162 or Equivalent Standard (Annexure Fixed foam conveying system – IV) comprises of fixed piping for water supply at adequate pressure, foam 4.4.2 Types of Low Expansion Foam concentrate tank, eductor, suitable proportioning equipment for drawing For combating large hydrocarbon foam concentrate and making foam fires particularly in a contained area solution, fixed piping system for like storage tank, foam has proved onward conveying to foam makers useful for its inherent blanketing for making foam, vapor seal box and ability, heat resistance and security foam pourer. against burn-back. Aqueous Film Forming Foam (AFFF) compound is (ii) Semi-Fixed Foam System technically superior and compatible with other fire fighting agents. Semi-fixed foam system gets supply of foam solution through the mobile Efficient and effective foam delivery foam tender. A fixed piping system system is a vital tool for its connected to foam makers cum usefulness in controlling the fire. vapor seal box in case of cone roof tanks and foam maker and foam The process of adding or injecting pourers in the case of floating roof the foam concentrate to is tanks conveys foam to the surface called proportioning. The mixture of of tank. water and foam compound (foam solution) is then mixed with air in a (iii) Mobile System foam maker for onward transmission to burning surface. Mobile system includes foam producing unit mounted on wheels 4.4.3 CONVEYING SYSTEMS which may be self propelled or towed by a vehicle. These units The system consists of an adequate supply foam through monitors/foam water supply, supply of foam towers to the burning surface. concentrate, suitable proportioning equipment, a proper piping system, (iv) Sub-surface foam injection foam makers and discharge devices designed to adequately distribute This system is for protection of the foam over the hazard. fixed roof storage tanks. It comprises of high back pressure Conventional systems are of the foam generator connected through open outlet type in which foam product lines or separate lines near discharges from all foam outlets at the bottom of the tank. the same time, covering the entire hazard within the confines of the (v) Under the Seal Foam application
4.4 FOAM SYSTEMS 4.4.1 Types of Foam Foams are classified by producing action of generation and expansion. Foam concentrate to be used shall conform to IS:4989 2006/UL-162 or Equivalent Standard (Annexure – IV) 4.4.2 Types of Low Expansion Foam For combating large hydrocarbon fires particularly in a contained area like storage tank, foam has proved useful for its inherent blanketing ability, heat resistance and security against burn-back. Aqueous Film Forming Foam (AFFF) compound is technically superior and compatible with other fire fighting agents. Efficient and effective foam delivery system is a vital tool for its usefulness in controlling the fire. The process of adding or injecting the foam concentrate to is called proportioning. The mixture of water and foam compound (foam solution) is then mixed with air in a foam maker for onward transmission to burning surface. 4.4.3 CONVEYING SYSTEMS The system consists of an adequate water supply, supply of foam concentrate, suitable proportioning equipment, a proper piping system, foam makers and discharge devices designed to adequately distribute the foam over the hazard. Conventional systems are of the open outlet type in which foam discharges from all foam outlets at the same time, covering the entire hazard within the confines of the system. There are three types of systems :- i) Fixed ii) Semi-Fixed iii) (i) Foam System Fixed foam conveying system comprises of fixed piping for water supply at adequate pressure, foam concentrate tank, eductor, suitable proportioning equipment for drawing foam concentrate and making foam solution, fixed piping system for onward conveying to foam makers for making foam, vapor seal box and foam pourer. (ii) Semi-Fixed Foam System Semi-fixed foam system gets supply of foam solution through the mobile foam tender. A fixed piping system connected to foam makers cum vapor seal box in case of cone roof tanks and foam maker and foam pourers in the case of floating roof tanks conveys foam to the surface of tank. (iii) Mobile System Mobile system includes foam producing unit mounted on wheels which may be self propelled or towed by a vehicle. These units supply foam through monitors/foam towers to the burning surface. (iv) Sub-surface foam injection This system is for protection of fixed roof storage tanks. It comprises of high back pressure foam generator connected through product lines or separate lines near the bottom of the tank. (v) Under the Seal Foam application
Std-117AUG2007.docx