Fire Sprinkler Hazard Classification

I'm Looking for opinions out there on a fire sprinkler hazard classification per NFPA 13 2002 edition chapter 5. Given a CFC 2007 regulated repair garage S-1 occupancy that is required to be protected with fire sprinkler system. Now the operation is capable of servicing 9 motor vehicles, no hot welding, but tune up, tires, and lube/oil changes performed. My question has to do with evaluating the correct hazard classification for water supply to the fire sprinkler system One of the operations in the pit 1000 square foot area is approx 1000 gallon tank of class III combustible liquid, connected to two hose station dispensing units above floor in a repair area. The system is pressurized at 300 psi. Based on this combustible liquid and pressurized amount, would it be appropriate to classify the area protection as extra hazard group 1 instead of ordinary group 2? The annex of 13 does have as examples for ord 2 listed repair garages, but eh1 has combustible hydraulic (under pressure) fluid use areas. I also read some information in the applicable 13 handbook advising the EH1 areas would be areas with systems utilizing combustible liquids under pressure. As an AHJ, we want to ensure reasonable protection design, and I understand that the generic mention of repair garage does not mean every repair garage is immediately a ordinary group 2 design, but all combustible content, quantity, specific operations, must be evaluated to provide the correct amount of water minimum to control a fire involving the hazard. Any opinions or advise out there please reply!

thank you,

Daniel
Original Post
I'm surprised at the 300 psi - that sounds like a very high pressure for what you have described to be a typical oil-change bay - If that is the correct pressure, I wonder why they would need it to be that high just to move oil from the tank into the car?

At any rate, I normally would classify a repair garage as O.H. Group 2, but given the installation of a pressurized oil system with that much pressure, I'd be inclined to ask for E.H. Group 1.
I agree with Mr. Humberson, that sounds pretty high.

Your best bet is to get a fire protection engineer to evaluate the hazard, and then protect the area with the pressurized liquid protected for the specific hazard in that area. It could be that a water based fire protection system is not adequate

Also, note that the EH1 refers to combustible hydraulic fluid. Motor oil, and grease are different than hydraulic fluid in that hydraulic fluid under pressure can be explosive under the right circumstances. Make sure you are comparing apples to apples.
All, thanks for your replies. The oil pump and dispense design is a 5:1 ratio and based on the number of runs, the system designer is stating that 300psi is present in the hose between the dispense nozzles and the tank when nozzle is closed. The sprinkler designer is proposing a ordinary group II sprinkler density in the repair area where the hose stations for dispensing are and an open pit area where a 750 gallon tank is for motor oil and 500 gallon tank and dispensing for ATF. The designer states it's based on the annex NFPA 13 listing repair garages under possible occupancy for ordinary group 2.

My position is that based on NFPA 13 section 5.1.2 and some expanatory application material in the handbook NFPA 13, this hazard combustible liquid under pressure, and the area used is more suitably designed as EH1 minimum to control a fire in the event of ruptured hose, leak in pipe or fittings resulting in a fine spray discharging causing a rapid spreading intense fire that Ordinary 2 would not control. I believe this hazard falls under the NFPA 13 section 5.4.1 and it just happens to be in this particular repair garage. Not all repair garages are the same, and some pose more fire hazards based on operational processes and combustible content.

Does anyone have any suggestions for mitigation? I was thinking maybe a shunt trip shutting off the dispense system and the pressure tanks and relieving pressure under activation of fire sprinkler or fire alarm system. Any ideas? Thanks,

Daniel
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