Division 2-Local Failure- heat treatment to make the forming strain Zero

[Ray6]

Hi Folks,
I am using Sec VIII-Div 2-para 5.3.3.1 for protection against local failure. The design is using SA-516-GR70N plate cold rolled to a cylinder. There is a ring welded on OD of this cylinder. Since the load on ring is high, calculation shows to prevent local failure, forming strain should be zero around the welding area. The code states if "If heat treatment is performed in accordance with Part 6, the forming strain may be assumed to be zero."

The part that I need some guidance is what should be heat treated so we can assume the forming strain is zero the:

1. If I heat treat the rolled plate before welding the ring, does it make the forming strain zero?
or
2. If we heat treat the weld (post weld heat treatment) between rolled plate and ring , does it make the forming strain zero?

Let's assume other than our design doesn't require any heat treatment from part 6 and the only reason for heat treatment is to make the forming strain zero.

Thanks,

 

[r6155]

Do you want to avoid PWHT?
How much is the forming strain of the shell? See table 6-1

Regards

 

[Ray6]

@r6155: Thanks for the answer. I know how to calculate forming strain using Table 6-1.I am trying to make it zero by heat treatment. The part that I do not know is what should be heat treated to make the forming strain zero. Should the rolled plate itself to be heat treated or weld should be post weld heat treated? My understanding is that heat treatment of rolled plate (before welding the ring) will make the forming strain zero.

thanks

 

[r6155]

The heat treatment is Stress Relieving like PWHT
If forming stress is less than 5% SR is not required, depending of thickness.
The best practice is PWHT all the complete vessel.

Regards

 

[TGS4]

PWHT the entire vessel as r6155 recommended. Anything less than a full PWHT and you risk introducing additional residual stresses elsewhere.

I am having a difficult time envisioning a situation where a ring on a cylinder could lead to a local failure situation. What additional details can you share?

 

forming strain zero
is an oxymoron.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[r6155]

Very good comment with oxymoron !!
But ASME VIII div 2 5.3.3.1 says "………the forming strain MAY BE ASSUMED to be zero”

Regards

 

That's not the only awkward wording to be found in the Code.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Ray6]

Thank you guys.