Allowable stress for SA-789 (UNS S32750) tube material of size 1.25"

[mandarkardekar]

Subject data is not available in ASME IID, also no size limitation in ASME Sec IIA.

What allowable values can be used for these tubes?

IS it ok if we use values for 1"size tubes?

or chaning the tube size to 1" from 1.25"is the only option?

 

[XL83NL]

Its not fully clear to me what the background of your question is. Is this about a vessel design?

Since SA789 UNS S32750 is limitied to less than or equal to 25 mm, you cant use these stress allowables for a 1.25" tube.
See II-D, subpart 1 "Stress Tables", 5th indent.

IS it ok if we use values for 1"size tubes?

Nope

or chaning the tube size to 1" from 1.25"is the only option?

No; the other option is to write a code case.

 

[mandarkardekar]

thank you for response..

yes i am concern about design of tubes as per ASME Sec.VIII Div 1 ...

i am also curious about supply of tubes of this size in this material...

 

[EdStainless]

Well then back up.
How can you design something when you don't know if it is even available?
I know, it is done all of the time.
And then people wonder why the 1" tubes were $8/ft and the 1.25" tubes are $20/ft.
When there are size limitations in the spec it is usually for a reason.

Are you the fabricator?
Contact you tubing suppliers.
And look into a code case.

The real issue with these alloys is the thickness. They are very tricky to heat treat correctly.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[XL83NL]

Could the 25 mm restriction in II-D (I use the metric version) be related to (wall)thickness?

 

[metengr]

XL83NL
Yes, it is wall thickness.

 

[mandarkardekar]

metengr

Where is it specified that 25mm is wall thickness and not tube OD ??

I have tried searching ASME IID, Sec VIII Div1...but could not locate this one.

 

[XL83NL]

@ metengr; how can that be derived?

If the OP is talking OD, I think there's not problem.