Exclusions and Inclusions of ASME Section VIII,Div 1 - Evaporators 3

[DunLidjun]

I have a question about the exclusing and inclusion process of Section 8, Div1. If I have an evaporator that operates at <= 15 PSIG but has a U-tube operating at 30 PSIG at the bottom of the evaporator, would this fall under Section VIII, Div1?

It is excluded because in U-1(c)(2)h(1) the internal and external design pressure is below 15 PSIG, but U-1(g)(1) seems to re-include it back into Section VIII.

What is your opinion?

Thanks,

SDW

 

[SnTMan]

DunLidjun, looks to me like if your evaporator is generating steam it falls under Sec VIII, Div. 1 per UG-1(g)(1), otherwise it can be excluded under UG-1(c)(2)(h).

Your U-tube may or may not be in the scope, I can't tell.

Regards,

Mike

 

[Tomtation]

The u-tube only is a code part and needs to be code-stamped. It is the same if only one side of a shell-and-tube heat exchanger exceeds 15 psig, then only that side requires a code stamp.

 

[gr2vessels]

DunLidjun,
As noted above, the tube side is comming under ASME VIII Div 1 jurisdiction, but not the evaporator shell;- my comment is that the design condition in that case must exclude the possiblity of evaporator overpressure due to the tube(s) rupture. If not excluded, then the evaporator vessel must be designed and U stamped as per ASME VIII Div 1.
cheers,
gr2vessels

 

[MJCronin]

Dun,

In my opinion, you should establish the design pressure of the shell at 30 psig, include a relief device sized for the tube break case and certify the whole evaporator to ASME VIII.

The actual maximum operating pressure is your business.

The additional cost of ASME certification is, in most cases, minimal.

And yes, I realize that there are many who would disagree with me, but you must ask yourself...Exactly what set of rules would govern the design, inspection and testing of the component if ASME-VIII is NOT invoked ?

-MJC

 

[SnTMan]

And as always, check with the jurisdiction

Mike