Through Wall Generator Exhaust Pipe Sealing 2

[Suitcase02]

I have a standby diesel generator located in the basement of a building. The exhaust pipe routes through a building wall (drawings show a through-wall thimble) to the exterior below grade. It then transfers to another larger diameter pipe, continues underground, and eventually exhausts to atmosphere away from the building.

I need suggestions on how to seal between the insulation on the exhaust pipe and the wall. Any suggestions?

 

[EdStainless]

This is fully double walled pipe (tube inside a tube), right? since the gas in is toxic it should be.
Then you can simply grout the outer pipe into the wall at the penetration.

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P.E. Metallurgy, Plymouth Tube

 

[Suitcase02]

EdStainless Thanks for the reply. It is not a double walled tube. Is this a requirement? I haven't come across this in my research.

It is an insulated steel pipe in the interior of the building and penetrates the wall through a thimble (this is shown in the drawing but I can't tell if it is actually installed). The steel pipe stops once it reaches the building exterior and a concrete pipe that butts up against the wall continues away from the building below grade.

I can't access the exterior of the pipe so my plan was to seal between the wall and pipe insulation on the interior using sheet metal around the pipe and caulk the joints. I'm concerned the exhaust heat will transfer through to the plate and damage the interior wall or create a hazard.

Does this sound reasonable or is there a better way?

 

[LittleInch]

This site has an amazing set of options

http://orf.od.nih.gov/PoliciesAndGu...t Penetration through Masonry or Concrete.jpg

This one would seem to match your requirement

http://orf.od.nih.gov/PoliciesAndGu...t Penetration through Masonry or Concrete.jpg

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Suitcase02]

LittleInch Thanks for the response.

 

[dvd]

Do not neglect thermal expansion. If the pipe is reasonably long, there may be significant expansion/contraction which will tear up firmly attached flashing. Let the pipe grow through the wall and through the flashings.

 

[LittleInch]

Also I must admit I'd never heard the term "thimble" before, but it's clear it's a common term for exhaust systems. However it does look like it is designed for an outside wall above ground as it has a lot of holes in for the inlet air to flow into a closed room which has a reciprocating engine in it.

May not be the best idea below ground....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[chicopee]

If the thimble has collars on both sides of the wall, there is no need to seal the insulation. The thimble is used to keep nearby combustible construction material within the wall from getting charred which overtime will catch fire. Such fire occurrence has been prevalent in chimney fires when brick work in chimneys overheated to the point of causing fires in combustible construction material over time of exposure.

 

[MikeHalloran]

Random thoughts:

The noted thimble has holes in its radial elements to reduce conductive heat transfer, and to allow passage of combustion air, so the Diesel doesn't suck the walls in.

Diesels tend to wobble around a little, even if you bolt them down solid, and you might want to include some sort of elastic motor mounts to reduce structureborne vibration transmission from the engine to the building.

It's common to include a flanged metal bellows in the exhaust right near the engine, so the wobble doesn't fracture the pipe, and so that the engine or turbo's exhaust flange is not carrying the weight of the pipe. It would be wise to include a spare with gaskets, and instructions to replace the bellows every few years.
... unless there's room in the building for a big expansion loop, and the loop and its elbows don't push the Diesel over its backpressure limit.

I'm no fan of rock wool, because it tends to come apart and settle over time. This is actually true of all known high temperature fibrous insulation, because the binders that hold the fibers together will burn off in the first few hours of engine operation. Better to have 'exhaust blankets' made to limit the fiber migration, or to use air in annular tubes or thimbles as insulation.

If I saw a concrete pipe abutting the outside of the wall underground, I'd expect it to be quite a bit larger than the actual exhaust pipe inside it, perhaps with some skeletal supports or hangers inside, all arranged so that the pipe proper can be replaced at some future date without major excavation. ... and so that the concrete pipe is not expected to carry the actual exhaust gas.





Mike Halloran
Pembroke Pines, FL, USA