fire extinguishers

[crb7]

hi guys;
I have a petroleum factory which is stored flammable liquids in tanks. There is a table in NPFA10 that tell us the fire extinguisher size and placement for class B fire.

But also there is paragraph which is said:
6.3.2.3 For flammable liquid hazards of appreciable depth, a
Class B fire extinguisher shall be provided on the basis of at
least 2 numerical units of Class B extinguishing potential per
1 ft2 (0.09 m2) of flammable liquid surface of the largest hazard area.

1.May you tell me what does it mean by "flammable liquid hazards of appreciable depth"?
2.Shall I use the above table or 6.3.2.3 sentence?
3.When Shall we use wheeled fire extinguishers?

 

[UFT12]

Be careful what you read. Table 6.3.1.1 applies to spill fires. Par. 6.3.2.3 applies to liquids with considerable depths, a.k.a tanks, collectors etc. Also, although not defined in NFPA 10, IBC provides a determination of the appreciable depth, that is 0.25" (6.4 mm).

As far as concern the wheeled extinguishers, that is depended on how you want to distribute your calculated quantity. There are many factors to take under consideration (see NFPA 10 recommendations) but I would say start by looking how is the rest of the factory equipped (if not all brand new) or whether the insurance carrier clarifies such requirement.

 

[crb7]

tnx UFT12;
There is another clause which is said:

E.4.6:......For fires in flammable liquids of appreciable depth, a Class
B fire extinguisher is provided on the basis of two numerical
units of Class B extinguishing potential per 1 ft2 (0.0929 m2)
of flammable liquid surface for the largest tank within the
area.

there are 6 storage tanks with the same size. As above clause said I have to calculate for 1 of them which is the largest. Am I right?