SA 240 304 higher vs lower allowabl 1

[DJPA1234]

Dear Team,

For one of the reactor (design temp 450°C), Catalyst support beam are required to be designed with Material of construction of SA240 TP 304.
ASME II D Gives the two row of allowable. One based on 66% yield and another higher but less than (90%) yield.
For designing of such beam under continuous loading which allowable should be used for optimum and safe design.

Thanks in advance.

 

[XL83NL]

Have you read the applicable notes for this material? Note G5 is key here.

https://www.eng-tips.com/viewthread.cfm?qid=258291

https://www.eng-tips.com/viewthread.cfm?qid=218191

https://www.eng-tips.com/viewthread.cfm?qid=158350

That should give you some clues. There are more hits for G5 in IID, but these were the first 3 Google gave.

It's up to you to decide if you need to apply note G5, or not.

 

[DriveMeNuts]

In making your decision, consider that the yield stress that ASME BPVC uses is the 0.2% proof.
According to table Y-2 of ASME III Part D:
with loading to 90% of yield the material will plastically strain 0.1%.
with loading to 69% of yield the material will plastically strain 0.02%.

 

[XL83NL]

@DriveMeNuts; some yield is totally acceptable (and safe) in certain applications. The code recognizes this, amongst others through note G5. As mentioned G5 is key here. Only the designer/OP can determine whats considered safe and optimum for his application.

 

[DriveMeNuts]

XL83NL,
The purpose of G5 is for ASME to be competitive with the European code, where the 1.0% proof stress is the basis of calculating the allowable stress.

Yielding happens in every application, even with low loading. Table Y-2 provides the Engineer with a way of finding the level of yielding to determining acceptable levels for a specific application.