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Expanded length of tube(ltx) to be considered in tubesheet calculation

Expanded length of tube(ltx) to be considered in tubesheet calculation

what should be the expanded length of tubesheet (ltx) to be considered in Tubesheet calculation, for strength weld plus contact expansion (i.e. 2-3% thinning) tube to tubesheet joint?
We are working with DEC (Detail Engineering Contractor). Earlier we were considering actual length of tube to be expanded and not faced any problem However one of my colleague is suggesting to consider expanded tube length as zero (0) in calculation since it cannot be measured while I understand same can be measured and not taking advantage of expanded tube length in calculation is unnecessary increasing tubesheet thickness. Please comment.

RE: Expanded length of tube(ltx) to be considered in tubesheet calculation

In cases of strength welds the roll joint is usually taken as 0.
The weld and TS strength should be adequate for full support.

Yes, you can measure the roll depths, but when doing strength welds it is common to lightly roll tubes, just to contact and then weld. Then you go back and re-roll (avoiding both front and back edges of the tubesheet). Invariably some tubes are missed.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Expanded length of tube(ltx) to be considered in tubesheet calculation

vcagrawal18, there are a couple of (I guess) non-related issues: 1) Joint strength, as accounted for by either Appendix A or UW-20. 2) Tubesheet thickness.

I am by no means an expert on Part UHX, but spent some time slogging thru it yesterday. I don't believe the joint strength affects tubesheet thickness as such, but the expansion length appears to affect tubesheet effective properties. See UHX 11 and related UHX 12, 13 or 14 as appropriate.

Like you, I have observed small expansion depths can cause an increase in tubesheet thickness as compared to larger expansion depths.

The question is whether a contact roll can be considered as expansion under Part UHX rules. Answer is I don't know, and I don't know if anybody does. I would tend to think a contact roll would not provide the same degree of fixity between the tube and tubesheet as a full roll, but only my opinion.

You want to be on the more certain side, full expand 'em.



The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Expanded length of tube(ltx) to be considered in tubesheet calculation

Thanks for your comments.
This delay in reply is because I was on vacation smilesmile.
I understand we can conclude that for strength weld + contact expansion tube to tubesheet joint, advantage of tube expansion length shall not be considered in tubesheet thickness calculation (ltx = 0) since code is not specific in defining length of expansion (ltx).

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