Exhaust System Design

[SME456]

I've read several of you posts regarding this issue and found them very helpful. I'm current working on some noise issues for off-highway equipment and am working with a supplier to design a new muffler. With the new muffler I'm forced to design a new 5in. dia. tube to run between the turbo and muffler. Because of component locations the tube requires a 90 deg bend located about 15in from the engine. As long as I'm in the design phase I'd like to investigate using a laminated pipe for that section. Do any of you know of a supplier I could work with on this?

 

[MikeHalloran]

Pipe, laminated from what?

It has to resist ~1000F for a Diesel, more for gasoline engines.



Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

There's two sorts I know of. The expensive stufff is twin wall tube. Don't know where to get that. The cheap stuff is pressed tin cladding with something or other between the downpipe and the tin. Don't know where to get that either. Which were you thinking of?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

I thought about making some.

Yacht owners like the mirror polished finish that's obtainable on, and the cool exterior surface that's typical of, a water jacketed pipe. They don't like replacing the pipe every couple of years because the water eats them. They don't like the bulk or the appearance of any of the suitable forms of dry insulation.

So, there's a potential market for a double walled exhaust pipe with dry insulation between the pipes and a polished outer pipe. The challenges have to do with putting a thermal break in the joint between inner and outer pipes (at the ends), and preventing the assemblies from cracking.

But there's not so much of a market that anyone said, "Try it for the first time on _my_ boat." No matter; the job evaporated.

I think I've seen double wall tube advertised in the SAE house rag. I suspect you have to save a lot in material costs to pay for the difficulty of making true double wall tube.




Mike Halloran
Pembroke Pines, FL, USA

 

[Rob45]

The principal mfr of laminated pipe in this country is AK Tube in Columbsu, Indiana. Your contact there would be Brian Huelskamp.
To my knowledge, they're not at present making tube as large as 5", but with enough interest, they might.
I think right now the largest they're producing laminated is 3.5".
I had requested they prototype several pieces of 5" tubing, but the prototypes couldn't readily be bent by our usual suppliuers, so that program fell through.
Brian probably still has several pieces approximately 40" long lying around, and I still think those could be bent using a press bender and filling the tubes with an incompressible material, e.g., core sand or iron shot.

For a production ag application, I'd recommend looking at a laminate of T1 aluminized outside/carbon steel (uncoated) inside.
Let me know if you learn they're producing 5"!
Regards,
- R

 

[profozone]

Don't know if this will help, but there is an aftermarket manufaturer that sells double walled exhaust pipes for Harley Davidsons (to prevent the blueing seen on many chromed motorcycle exhaust pipes). Shouldn't be hard to find them with a search. Maybe they can help or lead you to someone who could.

Good luck.

 

[Rob45]

"Double-walled" as used by Harley-Ferguson means "air-gap" which is not at all what SME456 had in mind, I don't think.
There's little noise benefit to using an air-gap pipe, and the forming and bending of these is an order of magnitude more expensive than for the laminated pipe.

(PS: Please excuse the numerous spelling errors in my previous post; I too often fall victim to the "flying fingers" syndrome.)