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Old 09-26-2022, 12:06 PM   #1
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Exhaust to ceiling clearance

I had a new exhaust built and installed. The exhaust is shrouded in wire laced lagging. The engine room ceiling and walls are covered in perforated aluminum covered wall board. The insulated riser actually touches the ceiling and turned the “wallboard” a dark color.
I have googled to find how much space is required between an insulated exhaust pipe and ceiling tile to no avail.
Looking at the build it appears there is a lattice structure of 2x4’s which are sandwiched between the upper flooring and engine room ceiling panels.
My thought is to remove a section of ceiling panel which will give a 3 to 4” clearance between the exhaust and flooring substrate.
The hot spot is directly above a seam in the insulation and I can put my finger in that seam. My plan is to remove the wire fastened lagging and wrap that seam area with some exhaust insulating tape and then resecuring the lagging.
I will then attach a quarter inch thick aluminum plate to the floor substrate as not only a heat shield but a point I can take temp measurements when running.
Your thoughts will be appreciated. Also what is a safe clearance distance for this exhaust?
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Old 09-26-2022, 12:47 PM   #2
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Some good photos would help.

Be very carefull about removing any of that wire laced blanket. Is it the grey stuff with what looks like glass fiber inside? It is quite effective at containing the heat in the pipe. I know because I have dry exhaust system and even the blanket gets hot but without it the engine compartment would be totally intolerable. Even though that blanket may be hot the pipe inside will be blazing hot in comparison and the loss of that insulation will toss heat into the engine compartment at a far higher rate then what you have now..

Personally a piece of aluminum will be the wrong material for your isolation. ALuminum is a very good heat conductor so it too will be very hot and will simply transfer that heat to the other surface to be radiated at the floor..

Rather, I would seriously consider a piece of polished SS. SS is a relatively poor heat conductor, compared to aluminum, so won't transfer nearly the quantity of heat through itself. The polished surface will reflect heat back into the engine room rather than transferring it through the metal.

Have you contacted the guys that did the work. Personally, from your description they goofed and should make good on it. THere should have been at least two or so inches between the piping and the floor underside and with a metal, SS, heat shield on standoffs.

Just my opinion.
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Old 09-26-2022, 02:26 PM   #3
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You could try a ceramic/fiber heat shield barrier.

https://www.fortluft.com/fortluft-al...-x-23-00584mm/
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Old 09-27-2022, 07:17 AM   #4
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The exhaust guys were probably trying to get as much lift as possible to avoid back flooding the engine. I’d rather have more lift and make the clearance at the floor/ceiling like you’re planning.
I’d just be careful how much sound proofing I was removing. As mentioned, a stainless heat shield stood off a half inch or so, or better yet, with a heat blocking fiber behind it will protect the ceiling.I would think an inch or two away from the exhaust would do it. As long as the wood structure isn’t getting above 200 degrees or so, you’re ok.
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Old 09-27-2022, 10:13 AM   #5
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Update

Thank you for all the feedback.
I pulled the blanket and the issue is not as bad as I first believed.
The black mark on the ceiling was mostly carbon from an exhaust leak at the flange. It appears the blanket anchors indented the blanket just enough for the exhaust to travel up the blanket and exit a small gap between two blankets.
I believe now the forward plan will be to address the exhaust leak and be certain the blanket segments are snug to each other to prevent heat from escaping.
I measured 1.5” clearance between the bare pipe and ceiling so I am still going to raise the ceiling in that spot to give me 2.5 inches. That particular spot is beneath the galley fridge and cabinet so I do have room to add some insulation if needed.
I found a high temp sensor with alarm . I will place the thermal coupler just above the exhaust and the readout and alarm in the galley. Probably not necessary but will give me piece of mind on longer passages.
The leak is bothersome. We filed and cleaned the turbo surface prior to installing the new exhaust. We also added a gasket between the two flanges and replaced the v-clamp . Today I will separate the flanges and see what went wrong.
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Old 09-27-2022, 10:20 AM   #6
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Pictures of project
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E479166D-7DB1-47DF-8EFD-9C489511B59C.jpg   3B74DA74-57F4-4AC5-8A69-307B6DA75787.jpg   4152B5E7-DD1D-434C-B0EE-4B457FB20744.jpg  
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Old 09-28-2022, 08:55 AM   #7
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Yes, the black coating is soot from a leak from the photos. Check for pinholes in the welds. I had to reweld a few spots in my system due to pinholes. Since that time no more sooting.

Ask if the fabricator can supply small blankets to cover the joins in the main blanket pieces. That will contain the escaping heat from those butt joints.

When my system was done there was a small blanket used for exactly that purpose.

Otherwise from what I can see it looks ok. You just have t deal with the overhead where the system appears to be to close to the overhear sole.
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Old 09-28-2022, 11:08 AM   #8
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Thank you for the suggestion about blankets at the joints. I plan to wrap the joint areas before reinstalling fabricated blankets. The exhaust was originally wrapped but I did not like not being able to remove it easily to inspect. I am going to pull the exhaust today to check the mating surfaces and install a new gasket.
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Old 09-28-2022, 11:14 AM   #9
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Pictures of wrap to be used
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Old 09-29-2022, 09:02 AM   #10
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That is very similar to my setup. I also added the "titanium" wrap underneath because my custom lagging is worn on the inside. I should look into how much new lagging would cost. As to what metal to use for a heat shield, aluminum would be a better choice than stainless because it is more heat conductive. Stainless can get a hot spot and stay hot, consentrating the heat and sending the heat through rather than outward. Aluminum quickly transfers the heat away from what would be a hot spot. 8" x 8" x 1/8" thick with a quarter inch space would handle a direct exhaust leak for long enough to smell the exhaust problem.
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Old 09-29-2022, 09:15 AM   #11
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The heat shield I referenced earlier has self adhesive backing and is available on Amazon for just under $30.

https://www.amazon.com/FORTLUFT-Alum...0979XTF11?th=1
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Old 09-29-2022, 10:21 AM   #12
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Quote:
Originally Posted by Larry M View Post
The heat shield I referenced earlier has self adhesive backing and is available on Amazon for just under $30.

https://www.amazon.com/FORTLUFT-Alum...0979XTF11?th=1
Looks like a good product. Cheap and easy to try. Why overthink it?
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Old 10-02-2022, 04:18 PM   #13
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Divealot,

Be sure to wear heavy rubber gloves when working with that fiberglass tape. I used thin nitrile gloves and that didn't seem to be enough. Something like dishwashing gloves would be better. And a mask.
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Old 10-02-2022, 04:19 PM   #14
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Also wetting the tape with water first will help keep the dust to a minimum.
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