Use of monel rivets in gas turbine exhaust stream

[Boathouse]

Does anybody have evidence of the detrimental effect of longtime exposure to exhaust plume from a gas turbine engine on monel rivets. We have divided opinions within our engineering community but with no real empirical data to back up either "pro" or "con" claims.

Thanks in advance

 

[hacksaw]

By exhaust plume are you implying a unconfined exhaust 400-500 deg F?

Low sulfur fuel, etc.?

 

[Boathouse]

Yes, this is core flow from an APU so it could well be around 1100 deg F before it starts to mix with entrained compartment flow. Fuels used, run the gamut of normal fuels, Jet A, JP 4 etc.

Any help would be useful since we only have non-documented experience rather than documented lessons learned and unfortunately thats what the customer wants !!

 

[TVP]

The best information that I can provide is that this would be a questionable application. Monel alloy 400 (SAE AS7233 rivet material) begins to lose strength when temperatures exceed 800 F. I don't have any data on resistance to sulfidation at those kind of temperatures. I would review the available information on the Special Metals website and contact them for specific data. A link to the website is below:

http://www.specialmetals.com/products/publication/tech_bulletin_400.pdf

 

[Michael996]

The APUs I have worked with generally have exhaust temperatures ranging from a min of 900° F to 1400° F. With failure modes that can provide 1700° F. I believe I had to Inconel fasteners.

Be sure of your mixing temperatures.

Allied Signal ( I think they are Honeywell now) publishes an APU installation design handbook.

 

[jlight]

Boathouse, I was wondering if you found any information for monel rivets. I have a monel rivet failure in an exhaust ejector assembly.