Cladding on tubesheet
Cladding on tubesheet
(OP)
I recently am working on a s&T heat exch. in which both tubesheet faces are cladded. The tubes are strength welded to tubesheet. As per tema RB-7.6, te tubeside clad thk. shall be 1/8" min while the shellside clad thk. shall be 3/8" min.
The presumption is that the weld prevents the tubeside fluid to penetrate the tube-tubesheet area and cause corrosion. The question is that what can prevents the shellside fluid to penetrate the tube-tubeshhet area. In fact, what is the advantage of considering 3/8" thk. on shellside face?
Please bear in mind that the tubes are not expanded and are strength welded.
Any remark would be appreciated.
The presumption is that the weld prevents the tubeside fluid to penetrate the tube-tubesheet area and cause corrosion. The question is that what can prevents the shellside fluid to penetrate the tube-tubeshhet area. In fact, what is the advantage of considering 3/8" thk. on shellside face?
Please bear in mind that the tubes are not expanded and are strength welded.
Any remark would be appreciated.





RE: Cladding on tubesheet
1) allows machining of the shellside gasket surface without cutting thru the clad
2) allows rolling of the tubes into the clad to seal the tubehole
If your shellside process is such that the tubesheet needs cladded I would definitely roll the tubes.
Regards,
Mike
RE: Cladding on tubesheet
And then, 2. shall expanding be done without grooves, because joint are strength welded?
And finally, how to expand for full length if tubesheet is too long?
Many thanks.
RE: Cladding on tubesheet
TEMA does not require grooves for strength welded tubes, see RB- & C-7.44, does not require full depth expanding, see RCB-7.51. I don't think TEMA mandates any particluar depth of expansion other than this. However, each design must be evaluated on its particulars.
Joints in thick tubesheets can be expanded in steps, can be hydraulically or even explosively expanded, although this last is usually reserved for thick tube walls, so far as I know.
It might be possible for you to expand only a small length at the shellside to seal the hole.
Regards,
Mike
RE: Cladding on tubesheet
Dear SnTMan, thanks for your advices. It really was helpful. I mean it.
Regards.
RE: Cladding on tubesheet
RE: Cladding on tubesheet
If the tubesheet is thicker than the mandrel length, the tube is rolled in steps.
DO NOT roll past the edge of the shell side tubesheet face.
rmw
RE: Cladding on tubesheet
Corrected.
-TJ Orlowski
RE: Cladding on tubesheet
rmw
RE: Cladding on tubesheet
Because of my experience I can suggest 2 methods of cladding:
1) explosion cladding (preferable)
2) turn inserts in the threaded holes in the tube sheet en weld the cladding to it.
Before inserting the tubes, but after the exploclad, a very small undercut of the tubesheet material has to be made to avoid sucking up tube sheet material in the tube to clad weld.
The tubes are preferably rolled in a chambered tubesheet.