Foam concentrate storage quantity

[odelgado]

Greetings everyone,

I am designing a pretty straightforward manual low expansion foam system for fuel storage tanks. According to calculations I need approximately 12,000 gal. of foam concentrate to comply with NFPA 11 requirements. The client is suggesting that the foam concentrate line runs as close to the hazard as possible (190 ft in this case) and that the line is kept filled with concentrate at all times and the volume inside them be considered as part of the required volume so the storage tank is reduced. Is this even possible? I haven't seen anything in the code against it but it is something I had never been asked to do before. Any help with this will be greatly appreciated.

 

[InspGdgt]

I'd look in to the corrosion potential of the concentrate on whatever pipe material you're using. I'm guessing though that if you have the proportioner 190' away from the bladder tank then anything before the proportioner is concentrate, and would be considered as part of the total volume.

 

[cdafd]

A.4.3.2.4.2 Foam concentrates are subject to freezing and to deterioration from prolonged storage at high temperatures. The storage temperature should be monitored to ensure that listed temperature limitations are not exceeded. Concentrates can be stored in the containers in which they are transported or can be transferred into large bulk storage tanks, depending on the requirements of the system. The location of stored containers requires special consideration to protect against exterior deterioration due to rusting or other causes. Bulk storage containers also require special design consideration to minimize the liquid surface in contact with air.

 

[DavidCR]

I´m curious, What type of discharge devices are planned? (foam chambers?). Why so much concentrate?, What type and how many independent proportioning equipment you are planning?.

From NFPA11 you should be sure the pipe material does not affect the quality of the concentrate. So from this, I suppose it is difficult to guarantee that a long pipe is safe for the concentrate, I cannot find an explicit rule neither.

You should include an extra volume to test and star up the system. When you test or start the system up you should leave some time(30-60secs) to make the concentration go steady.