Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
(OP)
Does anyone know of or have a rule of thumb for what the cutoff Temperature and/or Pressure for expansion(by rolling) tubes into tubesheets is? Any literature to reference would also help apart from the valuable years of experience all you fellow engineers may have in the industry.
Also when would it be recommended to roll and weld the tube-to-tubesheet joints?
Anything helps! Thanks!
Also when would it be recommended to roll and weld the tube-to-tubesheet joints?
Anything helps! Thanks!





RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
Thank you for your response.
I have heard anecdotally and read in some heat exchanger literature that expanding and welding the tubes to the tubesheet is not uncommon. With that being said, the designer also has to decide whether the expansion is going to take place before welding or after the welding is complete. In short, the literature does not give any suggestions as to when to use this method, they do state that with experience one will learn these things. That is why I am asking for any suggestions that anyone may have in regards to this topic.
Thanks again for your response.
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
Yes, you are correct sir. Although I would like to say that I am assuming that welding either before or after expanding would only be a seal weld and not a full strength weld. Like you said if it is a full strength weld there is no need for post-weld expansion.
My question is when would it be recommended to stop expansion and (a.)move on to seal welding and expansion or (b.)strength welding?
Thanks.
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
The tubes should at least be expanded to contact near the back of the tubesheet.
The real issues when selecting is what joint strength can be generated. In high strength materials and thick tubesheets you can generate rolled joints that are as strong as the tubes. As alloys get softer (usually non-ferrous), have lower modulus (again, usually nonferrous), and tubesheets get thinner joint strengths can become problematic.
You see seal welding used in cases where joint strength is marginal (thin walled Ti tubes in Ti tubesheets) as well as the more traditional applications where leaks are fatal (acid coolers).
Tube expansion is a science unto it self. Roller expanders come in different styles, and then there is hydraulic expansion.
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Plymouth Tube
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
In your experience have you ever dealt with any heat exchangers that handle hydrogen(~75 mol%) at pressure in the 2000+ psi range and temperatures up to 800°F?
I ask this because I have a couple of BEU type Heat Exchangers, and I am trying to choose between strength welding alone, which will take care of the leak tightness, or seal-welding with rolled expansion, in this case I think it would be better to do post-weld expansion, any thoughts? I feel as if we should full strength weld, but from what I just read it seems like they might fail and that would be detrimental. Any comments that you may have will help. Thanks in advance.
RE: Rule of Thumb for cutoff Temp./Press of expansion(by rolling) in Tube-to-Tubesheet Joints
With fairly thick tube sheets.
I would think that the best practice would be to:
1. light contact roll near face of tube sheet (within 1/8", but no closer, everything must be clean and dry)
2. Autogenous seal weld (semi-sutomatic)
3. Perform weld QA, PT and/or leak test.
4. Full roll expand in steps, starting 1/2" behind the weld (you don't want to stress the welds) and working to within 1/4" of the back sheet of the tube face.
The expansions should be qualified by mack-up testing prior to fabrication.
The rolling should all be done using torque limits.
This approach lets you use tight pitch tube spacings and address both concerns (strength and sealing).
Since the weld rolled joints should provide both strength and seal, the welds are just backup.
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Plymouth Tube