Inconel 800H @ low temperature - allowable stress question 1

[timsch]

I am trying to find the allowable stress value for Inconel 800H @ -49F. For ferrous materials, there is General Note (e) for table 1A in II-D.

"(e) Stress values for -20°F to 100°F are applicable for colder temperatures when the toughness requirements of Section III,VIII, or XII are met."

I don't see a corresponding note for Table 1B. I'd assume that the same would apply, in that impact testing is required, and the same rules would apply, where the allowable stress from -20 - 100F is used.

Where do I find info on this?

 

[SnTMan]

timsch, not sure what Code you are working to, but in Sec VIII, Div 1, Part UNF, UNF-23(a) states that for colder temperatures allowables for -20 to 100 shall be used. Part UNF-65 states that your alloy (Table UNF-23.3) may be used to -325 F without impact testing. I assume other Codes would have similar rules.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[timsch]

Thanks, SnTMan. I am working to Sec VIII, Div 1, so that's just what I needed.

 

[SnTMan]

Very good

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

Will your material see high temperature service also?
If so then you may want to be a bit cautious about impact toughness.
With large grain size and heavy carbides the ductility goes down a lot.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[timsch]

Design temperature is 1150F, so it's getting up there. I work for a designer and manufacturer of temperature sensors, typically for refinery applications. We design according to their specs, and they are the ones who choose the material for their processes.

This thermocouple pipewell is a unique one for us to have a specifically high temperature alloy with a MDMT this low. They also want this PWHT'd, which we've also not seen before. I don't have the material knowledge to understand the ramifications of these material decisions on their end (wish I did....)

 

[XL83NL]

They also want this PWHT'd, which we've also not seen before. I don't have the material knowledge to understand the ramifications of these material decisions on their end (wish I did....)

I’m sure some here can provide more guidance in that. We’ve PWHT-ed vessels under VIII-1, and also 1 piping system. The latter was due to a client spec, the former is just an VIII-1 code requirement. B31.3 also had a record some time ago to get this in the code, but it didn’t pass iirc since some (committee members) were in understanding that PWHT does not add or contribute to 800H piping design.


Huub
- You never get what you expect, you only get what you inspect.

 

[weldstan]

Is the item really experiencing low temp operation at pressure or is this merely a conservative design issue? What is the actual low temp operating condition?

 

[timsch]

I only have the design conditions. It's possible that this low temperature could be a potential startup temperature in some northern climate, but that's mere speculation.

 

[weldstan]

When low temp startups are required, low temp startup protocols should be developed and rigorously followed.