Foam Maker is used in one of the most common application to protect tank seal in vertical liquid storage tank with internal floating roof with low expansion foam system. The application of aspirated foam is on the basis of the risk comprising the area in the annular ring between the rim of the floating roof and the tank shell. The Foam system design guidelines generally used are in accordance with NFPA 11 standard. The Foam Makers are defined by NFPA 11 as Type II discharge outlets for delivering the low expansion aspirated foam to the seal. The Foam Makers are widely used with the Inline foam inductor, Balance pressure foam proportioning system, Bladder tank system or Foam tenders.
Foam Maker is an air aspirating foam generator connected to the foam pourer to deliver the aspirated foam gently into the tank seal area. Foam maker covers wide range of foam solution rates from 75 to 1200 litres per minute at 2.8 to 7 kg/sq.cm inlet pressure. Each foam maker is supplied with an orifice plate, designed for the required flow at 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 maker is designed to create venturi jet which draws air into the foam solution stream. The air is drawn into the foam solution through holes located on the foam maker covered with stainless steel screen to exclude nesting birds and insects. The aerated foam is directed into the pourer for the gentle application of the expanded foam. The pourers are available in different models.
SYSTEM DESIGN REQUIREMENT
For essential requirement of appropriately designed foam pouring system for storage tanks refer NFPA-11 / OISD-117 / TAC / Governmental codes or ordinances wherever applicable. a) Minimum Number of Foam Makers The maximum spacing between two foam makers shall be 24.4 metres for foam dam height of 610mm and 12.2 metres for foam dam height of 305mm. ( Refer NFPA-11 ) When two or more foam makers are required they shall be spaced equally around the tank periphery and each foam maker shall be sized to deliver foam at the same rate. As per reference to OISD-117 standard maximum spacing between two foam makers shall be 24 metres of shell perimeter based on 600mm foam dam height and minimum of two Foam Makers are to be provided.