generator exhaust pipe running close to/touching concrete beam overhead

[srm01]

I was at a jobsite yesterday and the generator exhaust pipe was running close to/touching the concrete beam overhead. See attached pictures. There is maybe 1/2" thick insulation wrap around the pipe. I have reviewed the Florida Building Code and NFPA37 for guidance on this and the most applicable statement I could find is from NFPA37 which states "Exhaust pipes and ducts shall have clearances of at least 9 in. to adjacent combustible materials...". However, concrete is not combustible and there is no mention of clearance to non-combustible materials. The generator max exhaust temp is 920F.

I am not concerned about the beam catching fire, but what about the heat transfer into the beam and potential adverse effects from that and thermal cycling? Has anyone encountered this and is it addressed anywhere?

The beam is 33"H x 36"W.

Thank you in advance for your input!

 

[MotorCity]

If the temp of the steel reinforcement reached 920F, I would be concerned but I think its a non issue here because:

1. The generator is probably not emitting its max exhaust temp under general operation or for long periods of time (if ever)
2. The pipe is insulated, so even if its poorly insulated, the surface temp of the insulation is probably not 920F.
If it was, I would think there would be other preventative measures in place to prevent someone from coming in contact
with it if its in a generally accessible area. Did you touch the insulation?
3. If the temp is not affecting the metal hanging rods or strap, I would not be worried about the steel reinforcement in the
beam under a few inches of concrete cover (even though concrete is an extremely poor insulator).

 

[Brad805]

Looks like a question for the architect. I suspect they may have an issue with this.

 

[BridgeSmith]

I think Motorcity is correct that the exhaust pipe won't change the temperature of the concrete significantly, but if there's a concern, a $20 non-contact thermometer will tell you what kind of temperature rise there is in the concrete.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[srm01]

Thank you for the responses so far.

MotorCity, the generator is a backup generator so it was not running at the time of the site visit. A little more background, they need to replace the piping through the wall of the building (block wall) and outside since the pipe is completely corroded outside. The building is next to the ocean and it is an old building probably from the 80s. They probably repurposed the space from parking garage to generator room at some point in the last few years.

What happens if there is a hurricane and the power to the building is out for a prolonged time? The generator will need to run continuously to provide emergency lighting, probably conditioned fresh air to the common areas, and support any other emergency systems. Would there be concerns with the concrete seeing prolonged exposure to high temperatures? I agree with you, probably not the max, but let's say 700F. What if power is out for 3-4 days? The fuel tank is very large.

 

[phamENG]

These sorts of generators have to do maintenance runs to ensure they'll perform in an emergency. Contact building maintenance and let them know you want to be present next time they do one. Bring a non-contact thermometer and measure the temperature of the concrete. As long as it doesn't exceed 212[sup]o[/sup]F, I wouldn't be worried.