Grade 11 Low Alloy steel tube (of S&T HX) design for shell design pressure at 500 degC - ASME BP

[VeeEng]

Hi All,

I came across a case where shell side design pressure of a S&T Heat exchanger is 40 bar at 500 deg C. MOC for entire heat exchanger is Gr11 LAS. When considering design of tubes, external pressure calculation is at 500 degC. For this case,
1) Going by ASME Sec VIII Div 1, external pressure chart is not available above ~ 482 degC.
2) Going by ASME Sec VIII Div 2 , part 4, Table 4.4.1 restricts usage above ~ 425 degC

Is there a way in which this can be designed using Part 5 of ASME Sec VIII Div 2? Is there any temperature limitation when "protection against buckling" is performed ?

Thanks in advance !!

Regards

VeeEng

 

[TGS4]

Buckling in Part 5 must be performed below the creep regime. That does not seem to be the case for this situation.

 

[MJCronin]

Vee

IMHO, 500C (932F) is a nice round number probably specified by someone who believes that pressure vessel quality materials are available for ANY temperature they can imagine .. (perhaps an MBA) Of course, there are limits to the rules of ASME Sec VIII and you exceed them.

Any chance to adjust the 500C design temperature ?

At this temperature, I believe that you must use the rules of the ASME (or equivalent) Section I boiler code and possibly consider a non-Shell and Tube configuration for your heat exchanger

MJCronin
Sr. Process Engineer

 

[VeeEng]

Hi TGS4 and MJCronin,

Thank you for your valuable insights.

Shell side design temperature of 500C is a transient case(480 C otherwise). Maximum expected time of 500C is less than 100 hours in the entire lifetime of exchanger.

TGS4 - Is there a way in code to ensure protection against buckling in creep regime? I understand that it should be checked per API 579 creep buckling method.

MJCronin - I will definitely try to explore the option suggested by you.

Thank You

Regards
VeeEng

 

[TGS4]

There is a Code Case coming regarding short term excursions into the creep regime. This would be perfectly suited for your situation.

Let me check into the status of that and I will advise.

 

[VeeEng]

Hi TGS4,

Thank You

Regards
VeeEng

 

[NRP99]

VeeEng

For SA 387 Gr 11 class 1 or 2 material (Assuming your LAS Gr 11 material is SA 387), ASME Sec II Part D, Table 5A, Note T7 suggest that the creep temperature starts from 500deg C.

Its confusing when you say in first post that design temperature is 500deg C and then in second post you say excursion at 500deg C. If your design temperature is in creep regime but operating is not then vessel will not experience creep or failure mode will never be creep.

Take a look at thread794-489837.

 

[VeeEng]

Thank You NRP99.