Ground Support/Rotorcraft Engineering 1

[Mr_Detail]

Hello Gentlemen;
I have been tasked to see what I can find out regarding insulating some 316 Stainless Steel pipe from 1,150 degrees of hot air inside.
I work on both the Chinook and V-22 programs in the rotorcraft business. I am also in what is known as the "Ground Support" group which
basically supports the aircraft in the hangar and shipboard. This particular piece of equipment I am asking about is called a "Pneumatic
Valve Test Stand". The pipe is no longer than 2 feet and the largest piece of pipe is about a 3.00" in diameter. Let me know if anyone
might have some ideas for me as to which way might be the best way to go for insulating this pipe. Thanks much!

 

[3DDave]

Are you trying to protect the pipe or protect what is near the outside of the pipe?
Is this degrees F or degrees C?

 

[Mr_Detail]

We are trying to protect the surrounding area of the pipe or as you put it, what is near the outside of the pipe.
It would be degrees Fahrenheit.

 

[3DDave]

Depending on the total need for protection, adding a cage could be enough. One example is visible on truck exhaust pipes where a perforated sheet metal is mounted on standoffs, about an inch, significantly cuts the risk of setting fires. The perforations allow hot air to exit. Unlike fibrous material it cannot collect water which might flash to steam.

It may be beneficial to put a second barrier to reduce it from a likely burn to reduce that.

One consideration is that the attachment not be rigid. The pipe will expand as it heats, but the barrier pipe will ideally not heat and therefore not expand. One temptation is to weld the standoffs both parts - depending on how often the temperature cycles it will bend the standoffs back and forth and eventually break them. A good solution is to use slots in the outer item and jam nuts so the outer item is free to move.

 

[Mr_Detail]

Sir;
I believe I have led you in the wrong direction. My lead engineer wants to prevent the heat from leaving the outer surface of the pipe altogether. In other words, what about some sort of wrap around the outer diameter of the pipe or spray on deterrent? The protection is for the surrounding area hardware and fittings. We really don't want to re-design the pipe itself.

 

[IRstuff]

If the objective is to get below about 55C, then you'll need a multilayer insulation, where the innermost layer will likely be ceramic, and the outer layer some sort of styrofoam or urethane. Since you now have a surface temperature to work with, you can calculate the convective loss to the air, which gives you the heat load that the insulation must minimize given the internal and surface temperatures.

You need to get below around 65C to ensure that you don't incur instantaneous contact burns.

https://ameriburn.org/wp-content/uploads/2017/04/scaldinjuryeducatorsguide.pdf

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[Mr_Detail]

Mr. IRstuff;
Since you mentioned the 131 degrees Fahrenheit temperature as a goal to achieve so that one might not incur instantaneous burns, would there be another forum or topic on this site that might address my next step in purchasing the proper ceramic wrap and/or Styrofoam and urethane?

 

[3DDave]

At this point - contact a pipe insulation company.

 

[Sparweb]

You might want something like firesleeve:

https://www.firesleeve.com/product/aerospace-firesleeve/

Fiberglass with silicone jacket.

http://www.sparweb.ca

 

[Mr_Detail]

SparWeb, that "firesleeve" initially looks good but after checking your web link it looks like it can only protect to 500 degrees F continuously. We need 1,150 degrees.

 

[WKTaylor]

AMS3679 ceramic fiber insulation batting against the pipe with a 'plain fiberglass woven cloth or wide-tape' jacket MIL-Y-1148, seams stitched with fiberglass yarn or 'glued' with VHT [ceramic] adhesive...

… or molded ceramic fiber insulation jacket... Ceramic fiber infused with ceramic adhesives/resinous matrix

or molded/wrapped ceramic paper, etc... there are creative solutions.

I am 'most familiar with'...

Unifrax family of materials

https://www.unifrax.com/industry/aerospace/

Morgan Advanced materials 'Alphawool® Unifelt or Kaowool batting or felt...

http://www.morganthermalceramics.com/

Regards, Wil Taylor

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