Tubesheet to Shell RT Requirements

[Brown129]

I am fairly new with the code and am getting confused with joint efficiency and radiography requirements for a heat exchanger I am designing. I have a 12" .375 wall SA312 316L shell which has a weld seam. I was going to use a UW-13.2(h) as my joint design to attach to the tubesheet. The shell would be Category A Type 1 with a 70% efficiency correct? The tubesheet would be category C type 7 per UW-12? I'm confused because I believe that UW-11(4) states that because it is larger that NPS 10 I am required to have spot radiography. That joint type says that RT is N/A. Any insight would be appreciated.

 

[SnTMan]

Brown129, this is a kind of complicated subject, it will likely take you some time to master it

Joint efficiency via RT is usually applied to butt-joints only. For example your Fig UW-13.2 corner joint, and corner joints in general, is assigned an efficiency of 1 if needed. See Table UW-12, Type 7 and Note 5. You are correct it is Cat C.

For other butt joints in the shell, joint efficiency is assigned per Table UW-12 as per the type of joint. A Type 1 joint with no RT would be E = 0.7, as you state.

UW-11(a)(4) is often the source of confusion. It provides exemptions from full RT for certain joints in a vessel that is otherwise full RT'd. This has been discussed numerous times, you might do a site search for more on it.

Shells made of pipe may be treated as seamless if the circumferential seams are spot RT'd. See UW-12(d) & (e).

Except as limited by Table UW-12, the joint category and the joint efficiency are not related.

You might also see the examples in Appendix L.

Regards,

Mike

 

[BigTank]

Taking a step back toward the more obvious: you might want to talk with someone that performs radiography. Corner joints generally don't yield good x-ray results. It's very uncommon for these types of joints to be x-rayed.

I'm sorry if that's TOO obvious, but you never know. Not everyone has the opportunity to see these types of details on the production floor.

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Fitter, happier, more productive

 

[SnTMan]

BigTank has a good point. It was some time befoe I understood that.

Regards,

Mike

 

[minibenny]

I agree with the answers above, but I just thought I'd add a couple comments.

Shells made of pipe may be treated as seamless if the circumferential seams are spot RT'd. See UW-12(d) & (e).

To add to the comment, per UW-12(d) & (e), the joint efficiency on the shell would be 1.0 if UW-11(a)(5)(b) are met (which would not be the case of the above since there are no circumferential seams to shoot), and 0.85 if UW-11(a)(5)(b) are not met.

I'm confused because I believe that UW-11(4) states that because it is larger that NPS 10 I am required to have spot radiography.

Also, Brown129, the exemption from radiography for butt-joint seams NPS 10 or smaller applies to category B and C seams in nozzle and communicating chambers only, not in the main shell course. If the shell course was NPS 10 or smaller, and there were butt-joint seams (cat. A and/or B), they would require RT also, if the heat exchanger was designed with spot or full radiography.