Foam Chamber is used in one of the most common application to protect vertical fixed roof (cone) liquid storage tanks, with or without internal floating roof with the low expansion foam system. The application of foam is on the basis that the risk comprises the total surface area of the fuel. The foam system design guidelines generally used are in accordance with NFPA-11, standard. Foam Chambers are defined by NFPA-11 as Type II discharge outlets for delivering the foam to the surface of a flammable liquid. The Foam Chambers are widely used with the In-line foam inductor, Balance pressure foam proportioning system, Bladder tank proportioner or Foam tender. MODEL FC SIZE 50, 65, 80, 100 &150 NB inlet WORKING PRESSURE Minimum 2.8 Kg. / sq. cm. (40 PSI) Maximum 7 Kg. / sq.cm. (100 PSI) FLANGE CONNECTION ANSI B16.5 Class 150# APPROXIMATE FC 50- 28.0 Kg. WEIGHT FC 65- 35.0 Kg. FC 80- 52.0 Kg. FC 100- 78.0 Kg. FC 150-108.0 Kg. VAPOUR SEAL 0.7 to 1.75 Kg./sq.cm.(10 PSI TO 25 PSI) RUPTURE PRESSURE Running water/Water foam solution pressure at the inlet of Foam Chamber. MAXIMUM 0.06 Kg./sq.cm. (0.9 PSI) PERMISSIBLE BACK PRESSURE ON VAPOUR SEAL FINISH Red epoxy painted ORDERING a) Model and size INFORMATION b) Inlet pressure. c) Foam solution flow reqd. d) Inlet, outlet flange specification. e) Type of foam concentrate used.
Foam chamber is an air aspirating foam discharge device, covering wide range of flow from 75 to 3600 litres per minute at 2.8 to 7 kg/sq.cm inlet pressure. The foam chamber contains a vapour seal to prevent the entry of vapour into the foam chamber and the foam solution pipe. Each foam chamber is supplied with an orifice plate, designed for the required flow and inlet pressure. The orifice is field replaceable in the event of change in design parameters. The foam is produced by introducing air into the foam solution stream. The inlet of foam chamber is designed to create venturi jet which draws air into the foam solution stream. The air is drawn into the foam solution through the holes located on the foam chamber covered with stainless steel screen to exclude nesting birds and insects. The aerated foam is directed into the deflector for the gentle application of the expanded foam. The deflectors are available in different models. On removal of cover plate from the top of the chamber allows the system to be tested and to draw a sample of the expanded foam, without removing the vapour seal or disconnecting the foam chamber from the tank. Frangible glass bursting disc (vapour seal) can be replaced very easily.
SYSTEM DESIGN REQUIREMENT
The NFPA-11, a standard for low expansion foam, provides the essential requirement of an appropriate designed foam pouring system, which are identified and outlined as below: The Foam Deflector is used with the Foam Chamber. The aerated foam from the Foam Chamber is directed in to the deflector for the gentle application of the expanded foam. The deflector reduces the expanded foam velocity and allows the foam to slide down the tank wall. FOAM CHAMBER MODEL – FC PAGE OF 6 2 a) Number of Foam Chamber The number of foam chambers required is determined by the tank diameter. Where two or more foam chambers are required, they shall be spaced equally around the tank periphery and each Foam Chamber shall be sized to deliver foam at an approximately same rate. Please refer graph to select the unit that will provide the required minimum foam solution application rate at the available operating pressure of the Foam Chamber. For minimum number of Foam Chamber requirement, kindly follow the recommendations as per NFPA/OISD/TAC or as per the governmental codes or ordinances wherever applicable. b) Minimum Foam Solution Application Rate The minimum foam solution application rate is the rate at which the water and foam concentrate in correctly proportioned ratio should be delivered to the surface of a storage tank under protection to control and extinguish the fire. For minimum application rate requirement follow the recommendations as per NFPA/OISD/TAC or governmental codes or ordinances wherever applicable.