ASME Code Case 2286 limitations

[McJe]

While looking into the ASME code case 2286, I was wondering if there are any limitations.

I can only find direct information about cylinders, cones, speres and formed heads. Can I presume this code case is also allowed for tubes? More detailed: is it allowed to apply this code case for heat exchanger tubes?

I'm currently evaluating PVElite (2009), and this program does not calculate heat exchanger tubes with this code case, so it seems.

If ASME allows this, I'll have to send a note to PVelite.
If ASME does not allow this, I'll have to send a note to our customer...
I'll rather like the first option... ;-)

 

[gr2vessels]

The PV Elite does calculate the minimum wall thickness for internal and external pressure, on the 'loads' screen of the tubesheet design input section. Look in the bottom of the screen, after you selected the tube and tubesheet material (obviously, you have selected and completed all the previous screens). But remember, ASME Code Case 2286 has been added as an option to PVElite.
You could also go to the Coade Forum for additional (and professional) advice from the makers of the PV Elite (refer to Coade website).
Cheers,
gr2vessels

 

[vesselfab]

I thought 2286 had been added to and assimilated into the 2007 edition.

 

[McJe]

Thanks for the answers, but I'll try to clarify some more.

I know PVElite supports CC2286, but I think it doesn't calculate tubes from heat exchangers with this code case.

For example: shell = 100bar, so if the tube side shuts down, there is an external pressure of 100 bar on the tubes.
In my calculations I'm doing right now, the tubes used are not strong enough to hold this external pressure of 100bar.
But by using code case 2286, these tubes would be strong enough (I calculated this manually).

I activated 'use code case 2286' in the PVElite options.

For external pressure on the shell or channel, this code case is used, but for my heat exchanger tubes, there is no difference noticable.

So, my question is: who is right?
Am I right, assuming that tubes from heat exchangers may be calculated with code case 2286?
Or, is PVElite right, assuming heat exchanger tubes should not be calculated with CC2286?

I find this ASME code case not unambiguous enough to assume it is allowed or not to use for heat exchanger tubes.

 

[gr2vessels]

I take your word, I'm unable to check now the PV Elite. I will come back to you with the correct answer.
Cheers,
gr2vessels

 

[jamesl]

There is scope limitation for code case 2286. Most critical limit for tubes is the slenderness KL/r<200. Most likely the tubes are outside the scope of this code case.

 

[McJe]

Thanks for the answers so far.
I checked the slenderness issue.
This could indeed be a limiting factor, depending on the interpretation of the code case.
It's not all that clear if we try to calculate U-bundle tubes with this code case.

1) the K-value in the slenderness formula isn't really applicable for U-bundles. There is no axial compression involved. The part of the code case we need for this calculation doesn't involve this value.
2) And if I want to use this formula, what values do I use?
- The complete length of the tube, and both ends fixed? (--> Not OK)
- The length between baffles, and 1 end fixed- 1 end pinned? (--> OK)

Thanks!
Jeroen.