Foam Mixer (For fixed roof tank)

A foam chamber discharges foam into a fixed (cone) roof atmospheric storage tank. It is mounted on the tank shell near the top, fed by a foam solution line from outside the bund, and directs the foam against the inside of the shell so it runs down and spreads gently across the burning liquid surface rather than plunging into it.

Vapour seal

A vapour seal in the inlet keeps tank vapour out of the foam line while the system is idle. When the system operates, foam solution pressure breaks the seal and foam enters the tank.

Maintenance

• Inspect the vapour seal regularly and replace it if it is cracked or damaged — a broken seal lets vapour into the foam line.
• Keep any air inlet screen clear of debris and nests.
• Test the system at the intervals the governing code sets, and replace the seal after every discharge.