Box Header Design

[SnTMan]

We don't normally do traditional air coolers, but we've got a couple of replacement designs on our plate now. Not that it matters much to the following, these are design to Code, no stamp, no API 661, no specs, etc. We do not have commercial air cooler design software, nor API 661.

I am curious how box headers are traditionally designed. A little googling makes me beleive Appendix 13 is used for the header itself, yes? Is a ligament efficiency used in the plug & tubesheets? If so, UG-53?

How are the nozzle openings handled? If imposing limits of reinforcement I cannot believe a UG-37 calculation will make. One of these designs has transition nozzles or swages, just makes it that much worse. Is the header considered to be self-reinforcing? How is this demonstrated?

Did a site search, found this: thread794-76357, and a few references to Nozzle-Pro. What did we do before Nozzle Pro?

Thanks in advance for any insight.

Mike

 

[MikeG7]

SnTMan, I don't know the traditional method but I've seen them designed with Appendix 13 for the box header plates with a joint efficiency factor E applied at the location of the joints only as the calcs for (appendix 13 consider various locations in the box). Further per 13-4 (g) , ligaments per UG-53 are applicable for the plates containing the ligaments. I don't have much experience on this just what I read up on and what I've come across from others.
MikeG7

 

[SnTMan]

MikeG7, everything I have seen so far concernng the header itself is as you have stated. These designs meet this easily. Don't know about the nozzles yet, but given the excess thickness that seems to exist in the header plate I am going to look at simple area replacement first.

Regards,

Mike

 

[EngAddict]

If the header is only wide enough for the nozzle then the edge of the nozzle typically sit over the tube sheet. This stiffening by the tubesheet usually negates the need for reinforcing checks. However with swaged nozzles you really need to run FEA, the opening is larger and the sides of the swaged neck go into bending, often requiring stays welded inside the neck.

The rest of the header is to Appendix 13 as you noted. Appendix 28 also covers alternative corner joint details.