Supplementary Requirement for SA213 Tubes

[Aodwan]

Dear All,

We have to supply the SA213-316L & TP321 U tubes for our U type exchangers, (OD 19.05 x Thk 1.65 avg mm) under ASME code.

Now client has asked to apply for “Supplementary Requirement” per SA213, S1 and S2 as per grade.

When I asked my tube maker for the same, most of them suggest it is not possible mainly S1.2 heat treatment after roll straightening.
Their argument is, after heat treatment, tube shape will not be straight. Which is why they do straightening process after heat treatment.
some of them are not recommended to doing it this because of wall thickness is thin, as S1 doesn't allow any mechanical straightening operation after stress relief annealing
so they are not confident about problems occur during installation of un straightened U-Tubes into baffles and tube sheets.

So my question is, Is it practical to perform S1 or S2 Supplementary Requirement, as we have heat treated the tubes as per table 3 of SA213 ASME Sec II-A.
I am not sure how it will affect in fabrication as tubes delivered after stress relief process .

Please advise.

 

[metengr]

Depending upon the specific service application, S1 and S2 could be pertinent. Regarding installation of stress-relieved tubes through tube support plates and tubesheets of an in-service heat exchanger, a small amount of residual stress could be inadvertently introduced because of alignment. The level of residual stress is typically low enough where problems associated with SCC are low risk. So, I would not worry about it for u-tube heat exchangers, as long as the u-bends have been properly solution annealed after bending.

 

[EdStainless]

We have supplied ubends this way in the past for 321. Fabricators hate it because the tubes are not straight and it takes much more time and labor to install them in the bundle. But if operation temp is at the low end of the sensitization range then it is worth doing.

We have never done it for 304/L or 316/L. If they are that concerned about residual stresses then specify that. Good tube makers can supply tubing with zero residual hoop tensile stress (we sell it as XLS).
If they are still concerned then they need a different alloy.

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P.E. Metallurgy, Plymouth Tube