Re-Rating Heat Exchanger Buitl in 2000 1

[Angsi]

Equipment: Shell and Tube Heat Exchanger designed to ASME Div 1

This is a simple question. If the tubesheet of the exchanger was designed and built to TEMA in 2000, and if there is a need to re-rate and re-certify the exchanger now, will the calcs have to be based on the latest ASME VIII requirements i.e. for the tubesheets?

Thanks in advance.

 

[metengr]

Yes, if this heat exchanger operates above 15 psig pressure. See my comments below;

1. If you intend to re-rate this vessel by either decreasing the minimum design metal temperature OR increasing the design pressure, this is considered an alteration.

2. Depending on where the shell and tube heat exchanger is installed, an alteration could involve either a Jurisdiction, regulatory body that regulates pressure vessels or an Insurance company that underwrites this equipment.

3. The Code that typically governs alteration of in-service pressure retaining items is the National Board Inspection Code. Design calculations using the original code of construction rules (ASME Section VIII, Div 1) will be necessary for the alteration, and will need to be reviewed by either the Jurisdiction and/or a National Board commissioned Inspector.

If items 1-3 above are applicable, I would recommend you obtain a copy of the current Edition of the NBIC and review the section on re-rating/alteration of pressure retaining items.

 

[PVGuy]

Angsi,

The rules of UHX look cumbersome; but they are not impossible to scale. UHX contains several examples, the most recent volume (128) of The Journal of Pressure Vessel
Technology has an indepth look at the rules. Also I believe the newest edition of the Jawad and Farr Guidebook to Section VIII, Division I covers it. I do not have that edition; but I have always found their books rather helpful. Good luck.

 

[DG72]

NBIC makes it very clear that this alteration (re-rate) may be performed using the edition/addenda of the original construction or a later edition/addenda, whichever is most applicable to the work being performed. (This is very clearly stated in the interpretation section of NBIC. I don't have my book with me, but I believe the interpretation is from '95).

It is perfectly acceptable to perform the re-rate using the edition/addenda of ASME code that the original equipment was built to--this means that you may use the TEMA formula for the re-rate. On the data report (R-2 form), there is a space where you specify what edition/addenda the work is being performed to--this is where you document that the alteration is being performed using the edition/addenda of the original construction.

On the other hand, you may perform the re-rate using the latest edition/addenda of the ASME code. If you elect to re-rate using the latest edition/addenda, there have been some recent changes in ASME code (in addition to UHX tubesheets) that may cause some problems with the re-rate. ASME now requires that the pass partition rib area be considered when computing the required flange bolting.
Also, the flange rigidity requirements (formerly non-mandatory appendix S-1) have become a mandatory requirement of ASME code. These 2 new requirements may cause a problem if re-rating using the latest edition of ASME code.

Either way, it is important to understand that whichever edition/addenda you elect to choose, you must meet all requirements for that edition/addenda. You can't use some of the original and some of the latest.

Hope this helps,

Dan

 

[thermmech]

It would not be a bad thing to contact the PV regulatory body in your State/Province and ask them what do they require.