We also use this at my company for tendering and planning purposes.
Here's a good reference on estimating: Link
Page 124 should be of interest for you, if you think it is worth the money.
Even the redacted preview on their website gives you a general idea on the methodology.
Have a look at this, particularly pg 5, "Dissimilar Pumps in Parallel":
http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/TEH-1109A.pdf
I don't know about NFPA, but in Europe, EN 12845 for automatic sprinklers does give a limit of 10 m/s in pipes and 6m/s through valves, flow meters and strainers.
I believe fire fighting design is based on the "area of operation". This is the area where you expect a fire may break out, and the maximum area a fire fighting system is designed for.
This implies that your most unfavourable area of operation as described above may not always coincide with...
We really need more info about the application. The more details you give, the better advice you'll get.
If it is fine to seal it permanently, why not simply weld it? It should be more that enough for an unpressurized container.
You mention contamination, so I'm guessing corrosion might be an...
