Support Lug Design for a high temperature vessel

[huangdf118]

I am working on the support lug for a high temperature vessel (Di: 84 in; L(tan to tan) 120in), Temperature 1200F. I will check both lug and ring

There is no specified procedure in ASME code. I found the samples in pressure vessel design manual (Dennis Moss). These sampples are based on seismic/wind load.

In my case, the vessel is inside room, Seismic class A. The primary concern is high temperature. The deisgn manual states "not to use ring if the teperature about 500F due to discontiuned stresses. So, I may have to use lug rather than ring.But the eccentric loads of the lugs are large. In that case how to design the lug and reinforcment pad.


If some one here has expereinces on this type of problem, could you give me your advice on the design consideration and procedure of the lug and pad.

Thanks,


DF

 

[TGS4]

You need to get expert help. It's too complicated to do for free over the internet.

Absolutely, under no circumstances, should you use a repad.

 

[oknow]

If Section VIII Div.1 is the Construction code remember UG-54(a). It is often overlooked.

 

[DriveMeNuts]

Sounds like creep design. A whole level of expertise above general pressure vessel design.

You need to consult an expert.

 

[keyen]

@TGS4: why is a repad unadvisable in this (loosely defined) scenario? Is the differential thermal stress/strain the primary concern?

thanks,
DK

 

[TGS4]

Your repad will be somewhere between cooler and much cooler than the vessel, leading to very high thermal stresses in the repad weld, leading to cracking of those welds.

Note that in ASME Section VIII, Division 2, 5.5.2.3 Step 4, the Code specifically directs the engineer to not take credit for any heat transfer across unwelded contact surfaces. Further, this aspect has a lot of history of repad cracking behind it.

 

[huangdf118]

Thank you