Sprinkler Requirements for Grated Pits

[BatesEngineer]

Hello,

We are designing a welding facility with with multiple large pits (8'W x 41'L x 8'D). These pits will have a fully retractable grated surface to allow the working surface to be lowered to an ergonomic height, and be completely cover by grating when closed. These pits are concrete walls and floors with downdraft ventilation ducts in the walls. This will be a confined space area that will collect steel slag and debris from the work process. There will be no combustible/flammable materials within this pit area and entrance will only be allowed when the pit is fully uncovered. What is the requirement for the fire protection to extend into this area? Please site specific NFPA section for clarification and further discussion.

 

[skdesigner]

NFPA 13-2019 9.5.5.3.1.1 requires sprinklers below open-grate flooring exceeding 4'-0 in width.

A4.3.4 classifies both 'metalworking' and 'machine shops' as ordinary hazard group 2 occupancies, meaning the use of sidewall sprinklers would be permitted.

My solution would be to run a single line of sidewall sprinklers the length of the pit, spraying across. Some kind of a lip or overhang would be necessary, to hang the pipe, shield the pit sprinklers from the roof-level sprinklers above, and provide some kind of protection to the sprinklers from contact with whatever is being lowered into the pit.

 

[cdafd]

Bates

Grates as in open grate??

Does it meet this

1. Openings (in the least dimensions) must be at least ¼” (6 mm) wide.
2. The thickness of the ceiling cannot be more than the minimum opening width.
3. Ceilings have to be at least 70% open.

Or

Is 50 % of the grate open??!

 

[cdafd]

Skd

If open grate,,, would a sidewall activate?

Is there a sidewall listed for this application?

Just asking