Tube to tubesheet joint

[darrenyee88]

1. Can I know what is the advantage of strength welding over seal welding for tube to tubesheet joint?

2. Is there any requirement that the tube must protrude out of the tubesheet by how manny mm?

 

[gr2vessels]

1. Special services require strength welding;- also includes fixed tubesheets with significant thermal expansion between the shell and tubes or any configuration where accidental leakage from tubes cannot be tolerated. The seal welding provides for seal between the tunesheet and tubes and is used only for additional leak tightness besides of tube expansion. The pull out resistance is provided only by the tube expansion and the seal weld cannot be accounted for any strength.
2. 3 mm is the USUAL required tube protrusion, but TEMA limits the protrusion to max half tube diameter and zero for vertical exchangers to facilitate the drainage (refer TEMA Clause RCB-7.313).

 

[darrenyee88]

Then can i know what is the difference if the tube to tubesheet is seal welded and flush with tubesheet and the other seal welded and protrude out of the tubesheet by less than 3mm

 

[Duwe6]

Degree of difficulty in making the weld. A flush weld requires a recessed fitup and takes a little more skill and more time to make. A weld of a tube that protrudes a couple of mm is easier/faster to make. There are automated GTAW - tig - welding machines that will make the latter weld fairly quickly.

Please note that the preferred method of attaching tubes to their tubesheet is still rolling them into a drilled hole that has two grooves cut into it. "If everybody does something the same way, there must be a good reason"

 

[weldstan]

The throat of the fillet weld or the depth of the groove weld should be at least the thickness of the tube for a strength weld.

 

[SnTMan]

For Sec VIII, Div 1 work see UW-20 and/or Appendix A.

Regards,

Mike

 

[MJCronin]

Process and safety considerations come into play when deciding on the tube to tubesheet joint....

Here is an excellent answer to this question:

http://hghouston.com/Resources/Disc...orumid/6/postid/2526/scope/posts/Default.aspx

MJCronin
Sr. Process Engineer

 

[EdStainless]

With thin wall tubes grooves in the tubesheet holes are detrimental. It is better to provide a controlled rough surface.
A lot of seal welds are done with automated autogenous TIG. Common tube projection is 1/2 - 1 times the wall thickness.
For example Ti condenser tubes are too soft to generate enough joint strength by just rolling, so an autogenous TIG seal weld is added. They do this to millions of tubes with 0.020" - 0.035" (0.5mm-0.9mm) wall thickness.

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Plymouth Tube