Oil Insulated Transformer Containment Pit - Fire Flow Volume

[engjg]

In design of a containment pit for an oil insulated transformer NFPA 850 5.5.2 states the "...should be sized to accommodate...(2)maximum expected number of fire hose operating for a maximum of 10 minutes"...an older version of NFPA 850 included this note (500 gpm operating for a minimum of 10 minutes) which as I understand it would give you 5000 gpm assuming you anticipate only one hose needed to fight fire for typical transformer....this provision seems to have been removed. I have another engineer citing the fire flow volume (which containment should accommodate) is based on 0.3 gal/sf/min for 10 minutes. I can not find the basis of this?

 

[7anoter4]

In my opinion, if the art.5.5.2 states:
5.5.2* The provisions for drainage and any associated drainage facilities should be sized to accommodate all of the following:
(2) The maximum expected number of fire hose operating for a minimum of 10 minutes
and art.6.2.1 states:
6.2 Water Supply.6.2.1*:
The water supply for the permanent fire protection installation should be based on providing a 2-hour supply for all of the following:
(2) The hose stream demand of not less than 500 gpm(1890 L/min). then the maximum expected number of fire hose water flow it has to be NOT LESS then 500 gpm.
If an open pit is used then:
5.5.6.2 Open Pits. Where an open pit is used, one of the following forms of protection should be provided:
(1) Automatic sprinkler or water spray protection should be provided for the pit area designed to a discharge density of 0.15 gal/min•ft2 (6 mm/min) over the area of the pit.